/*
 * test-ringbuf.c - unit tests for C ring buffer implementation.
 *
 * Written in 2011 by Drew Hess <dhess-src@bothan.net>.
 *
 * To the extent possible under law, the author(s) have dedicated all
 * copyright and related and neighboring rights to this software to
 * the public domain worldwide. This software is distributed without
 * any warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication
 * along with this software. If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.
 */

#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <signal.h>
#include <assert.h>
#include "ringbuf.h"

/*
 * Fill a buffer with a test pattern.
 */
void *
fill_buffer(void *buf, size_t buf_size, const char *test_pattern)
{
    size_t pattern_size = strlen(test_pattern);
    size_t nblocks = buf_size / pattern_size;
    uint8_t *p = buf;
    size_t n;
    for (n = 0; n != nblocks; ++n, p += pattern_size)
        memcpy(p, (const void *) test_pattern, pattern_size);
    memcpy(p, (const void *) test_pattern, buf_size % pattern_size);
    
    return buf;
}

int rdfd = -1;
int wrfd = -1;
char rd_template[] = "/tmp/tmpXXXXXXringbuf";
char wr_template[] = "/tmp/tmpXXXXXXringbuf-wr";

void
cleanup()
{
    if (rdfd != -1) {
        close(rdfd);
        unlink(rd_template);
    }
    if (wrfd != -1) {
        close(wrfd);
        unlink(wr_template);
    }
}

void
sigabort(int unused)
{
    cleanup();
    exit(1);
}

#define START_NEW_TEST(test_num) \
    fprintf(stderr, "Test %d...", (++test_num));

#define END_TEST(test_num) \
    fprintf(stderr, "pass.\n");

/* Default size for these tests. */
#define RINGBUF_SIZE 4096

int
main(int argc, char **argv)
{
    if (atexit(cleanup) == -1) {
        fprintf(stderr, "Can't install atexit handler, exiting.\n");
        exit(98);
    }
    
    /*
     * catch SIGABRT when asserts fail for proper test file
     * cleanup.
     */
    struct sigaction sa, osa;
    sa.sa_handler = sigabort;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    if (sigaction(SIGABRT, &sa, &osa) == -1) {
        fprintf(stderr, "Can't install SIGABRT handler, exiting.\n");
        exit(99);
    }

    ringbuf_t rb1 = ringbuf_new(RINGBUF_SIZE - 1);

    int test_num = 0;

    /*
     * N.B.: these tests check both the ringbuf_t interface *and* a
     * particular implementation. They are not black-box tests. If you
     * make changes to the ringbuf_t implementation, some of these
     * tests may break.
     */
    
    /* We use the base pointer for some implementation testing. */
       
    const uint8_t *rb1_base = ringbuf_head(rb1);

    /* Initial conditions */
    START_NEW_TEST(test_num);
    assert(ringbuf_buffer_size(rb1) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    END_TEST(test_num);

    /* freeing a ring buffer sets the pointer to 0 */
    START_NEW_TEST(test_num);
    ringbuf_free(&rb1);
    assert(!rb1);
    END_TEST(test_num);

    /* Different sizes */
    rb1 = ringbuf_new(24);
    rb1_base = ringbuf_head(rb1);

    START_NEW_TEST(test_num);
    assert(ringbuf_buffer_size(rb1) == 25);
    assert(ringbuf_capacity(rb1) == 24);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    ringbuf_free(&rb1);
    assert(!rb1);
    END_TEST(test_num);

    rb1 = ringbuf_new(RINGBUF_SIZE - 1);
    rb1_base = ringbuf_head(rb1);

    /* ringbuf_reset tests */
    START_NEW_TEST(test_num);
    ringbuf_memset(rb1, 1, 8);
    ringbuf_reset(rb1);
    assert(ringbuf_buffer_size(rb1) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1)); /* overflow */
    ringbuf_reset(rb1);
    assert(ringbuf_buffer_size(rb1) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    END_TEST(test_num);

    /* ringbuf_memset with zero count */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 1, 0) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    END_TEST(test_num);

    uint8_t *buf = malloc(RINGBUF_SIZE * 2);
    memset(buf, 57, RINGBUF_SIZE);
    memset(buf + RINGBUF_SIZE, 58, RINGBUF_SIZE);
    
    /* ringbuf_memset a few bytes of data */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, 7) == 7);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 7);
    assert(ringbuf_bytes_used(rb1) == 7);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), 7) == 0);
    END_TEST(test_num);

    /* ringbuf_memset full capacity */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);
    
    /* ringbuf_memset, twice */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, 7) == 7);
    assert(ringbuf_memset(rb1, 57, 15) == 15);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb1) == 7 + 15);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - (7 + 15));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), 7 + 15) == 0);
    END_TEST(test_num);

    /* ringbuf_memset, twice (to full capacity) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, RINGBUF_SIZE - 2) == RINGBUF_SIZE - 2);
    assert(ringbuf_memset(rb1, 57, 1) == 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_memset, overflow by 1 byte */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, RINGBUF_SIZE) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_memset, twice (overflow by 1 byte on 2nd copy) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(ringbuf_memset(rb1, 57, 1) == 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /*
     * ringbuf_memset, attempt to overflow by 2 bytes, but
     * ringbuf_memset will stop at 1 byte overflow (length clamping,
     * see ringbuf_memset documentation).
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, RINGBUF_SIZE + 1) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base);
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);
    
    /*
     * ringbuf_memset, twice, overflowing both times.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(ringbuf_memset(rb1, 57, RINGBUF_SIZE) == RINGBUF_SIZE);
    assert(ringbuf_memset(rb1, 58, RINGBUF_SIZE) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base);
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + RINGBUF_SIZE, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /*
     * The length of test_pattern should not fit naturally into
     * RINGBUF_SIZE, or else it won't be possible to detect proper
     * wrapping of the head pointer.
     */
    const char test_pattern[] = "abcdefghijk";
    assert((strlen(test_pattern) % RINGBUF_SIZE) != 0);
    fill_buffer(buf, RINGBUF_SIZE * 2, test_pattern);

    /* ringbuf_memcpy_into with zero count */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 0) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_memcpy_into a few bytes of data */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, strlen(test_pattern)) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - strlen(test_pattern));
    assert(ringbuf_bytes_used(rb1) == strlen(test_pattern));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp(test_pattern, ringbuf_tail(rb1), strlen(test_pattern)) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_memcpy_into full capacity */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, RINGBUF_SIZE - 1) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);
    
    /* ringbuf_memcpy_into, twice */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, strlen(test_pattern)) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + strlen(test_pattern), strlen(test_pattern) - 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - (2 * strlen(test_pattern) - 1));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), 2 * strlen(test_pattern) - 1) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_memcpy_into, twice (to full capacity) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 2) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + RINGBUF_SIZE - 2, 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_into, overflow by 1 byte */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_into, twice (overflow by 1 byte on 2nd copy) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + RINGBUF_SIZE - 1, 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_into, overflow by 2 bytes (will wrap) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(ringbuf_tail(rb1) == rb1_base + 2);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 2, RINGBUF_SIZE - 2) == 0);
    assert(strncmp((const char *) rb1_base, (const char *) buf + RINGBUF_SIZE, 1) == 0);
    END_TEST(test_num);

    rdfd = mkstemps(rd_template, strlen("ringbuf"));
    assert(rdfd != -1);
    assert(write(rdfd, buf, RINGBUF_SIZE * 2) == RINGBUF_SIZE * 2);
    
    /* ringbuf_read with zero count */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, 0) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(*(char *)ringbuf_head(rb1) == '\1');
    assert(lseek(rdfd, 0, SEEK_CUR) == 0);
    END_TEST(test_num);

    /* ringbuf_read a few bytes of data */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, strlen(test_pattern)) == strlen(test_pattern));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - strlen(test_pattern));
    assert(ringbuf_bytes_used(rb1) == strlen(test_pattern));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp(test_pattern, ringbuf_tail(rb1), strlen(test_pattern)) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_read full capacity */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, RINGBUF_SIZE - 1) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);
    
    /* ringbuf_read, twice */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, strlen(test_pattern)) == strlen(test_pattern));
    assert(ringbuf_read(rdfd, rb1, strlen(test_pattern) - 1) == strlen(test_pattern) - 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - (2 * strlen(test_pattern) - 1));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), 2 * strlen(test_pattern) - 1) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_read, twice (to full capacity) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 2) == RINGBUF_SIZE - 2);
    assert(ringbuf_read(rdfd, rb1, 1) == 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) buf, ringbuf_tail(rb1), RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_read, overflow by 1 byte */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE) == RINGBUF_SIZE);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_read, twice (overflow by 1 byte on 2nd copy) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(ringbuf_read(rdfd, rb1, 1) == 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_read, try to overflow by 2 bytes; will return a short count */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE + 1) == RINGBUF_SIZE); /* short count */
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    /* head should point to the beginning of the buffer */
    assert(ringbuf_head(rb1) == rb1_base);
    /* tail should have bumped forward by 1 byte */
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    uint8_t *dst = malloc(RINGBUF_SIZE * 2);
    
    /* ringbuf_memcpy_from with zero count, empty ring buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    assert(ringbuf_memcpy_from(dst, rb1, 0) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE * 2) == 0);
    END_TEST(test_num);

    /*
     * The length of test_pattern2 should not fit naturally into
     * RINGBUF_SIZE, or else it won't be possible to detect proper
     * wrapping of the head pointer.
     */
    const char test_pattern2[] = "0123456789A";
    assert((strlen(test_pattern2) % RINGBUF_SIZE) != 0);
    uint8_t *buf2 = malloc(RINGBUF_SIZE * 2);
    fill_buffer(buf2, RINGBUF_SIZE * 2, test_pattern2);

    /* ringbuf_memcpy_from with zero count, non-empty ring buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, test_pattern2, strlen(test_pattern2));
    assert(ringbuf_memcpy_from(dst, rb1, 0) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - strlen(test_pattern2));
    assert(ringbuf_bytes_used(rb1) == strlen(test_pattern2));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE * 2) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_from a few bytes of data */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, test_pattern2, strlen(test_pattern2));
    assert(ringbuf_memcpy_from(dst, rb1, 3) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - (strlen(test_pattern2) - 3));
    assert(ringbuf_bytes_used(rb1) == strlen(test_pattern2) - 3);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 3);
    assert(ringbuf_head(rb1) == (uint8_t *) ringbuf_tail(rb1) + (strlen(test_pattern2) - 3));
    assert(strncmp((const char *) dst, test_pattern2, 3) == 0);
    assert(strncmp((const char *) dst + 3, (const char *) buf + 3, RINGBUF_SIZE * 2 - 3) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_from full capacity */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, RINGBUF_SIZE - 1);
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 1) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(strncmp((const char *) dst, (const char *) buf2, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf + RINGBUF_SIZE - 1, RINGBUF_SIZE + 1) == 0);
    END_TEST(test_num);
    
    /* ringbuf_memcpy_from, twice */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, 13);
    assert(ringbuf_memcpy_from(dst, rb1, 9) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_from((uint8_t *) dst + 9, rb1, 4) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 13);
    assert(strncmp((const char *) dst, (const char *) buf2, 13) == 0);
    assert(strncmp((const char *) dst + 13, (const char *) buf + 13, RINGBUF_SIZE * 2 - 13) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_from, twice (full capacity) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, RINGBUF_SIZE - 1);
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 2) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_from(dst + RINGBUF_SIZE - 2, rb1, 1) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(strncmp((const char *) dst, (const char *) buf2, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf + RINGBUF_SIZE - 1, RINGBUF_SIZE * 2 - (RINGBUF_SIZE -1)) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_from, attempt to underflow */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, 15);
    assert(ringbuf_memcpy_from(dst, rb1, 16) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 15);
    assert(ringbuf_bytes_used(rb1) == 15);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_head(rb1) == rb1_base + 15);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE * 2) == 0);
    END_TEST(test_num);
    
    /* ringbuf_memcpy_from, attempt to underflow on 2nd call */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, 15);
    assert(ringbuf_memcpy_from(dst, rb1, 14) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_from(dst + 14, rb1, 2) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 1);
    assert(ringbuf_bytes_used(rb1) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 14);
    assert(ringbuf_head(rb1) == rb1_base + 15);
    assert(strncmp((const char *) dst, (const char *) buf2, 14) == 0);
    assert(strncmp((const char *) dst + 14, (const char *) buf + 14, RINGBUF_SIZE * 2 - 14) == 0);
    END_TEST(test_num);
    
    wrfd = mkstemps(wr_template, strlen("ringbuf-wr"));
    assert(wrfd != -1);

    /* ringbuf_write with zero count, empty ring buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(ringbuf_write(wrfd, rb1, 0) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    /* should return 0 (EOF) */
    assert(read(wrfd, dst, 10) == 0);
    END_TEST(test_num);

    /* ringbuf_write with zero count, non-empty ring buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    ringbuf_memcpy_into(rb1, test_pattern2, strlen(test_pattern2));
    assert(ringbuf_write(wrfd, rb1, 0) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - strlen(test_pattern2));
    assert(ringbuf_bytes_used(rb1) == strlen(test_pattern2));
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    /* should return 0 (EOF) */
    assert(read(wrfd, dst, 10) == 0);
    END_TEST(test_num);

    /* ringbuf_write a few bytes of data */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, test_pattern2, strlen(test_pattern2));
    assert(ringbuf_write(wrfd, rb1, 3) == 3);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - (strlen(test_pattern2) - 3));
    assert(ringbuf_bytes_used(rb1) == strlen(test_pattern2) - 3);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 3);
    assert(ringbuf_head(rb1) == (uint8_t *) ringbuf_tail(rb1) + (strlen(test_pattern2) - 3));
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 4) == 3);
    assert(read(wrfd, dst + 3, 1) == 0);
    assert(strncmp((const char *) dst, test_pattern2, 3) == 0);
    assert(strncmp((const char *) dst + 3, (const char *) buf + 3, RINGBUF_SIZE * 2 - 3) == 0);
    END_TEST(test_num);

    /* ringbuf_write full capacity */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, RINGBUF_SIZE - 1);
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE) == RINGBUF_SIZE - 1);
    assert(read(wrfd, dst + RINGBUF_SIZE - 1, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf2, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf + RINGBUF_SIZE - 1, RINGBUF_SIZE + 1) == 0);
    END_TEST(test_num);

    /* ringbuf_write, twice */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, 13);
    assert(ringbuf_write(wrfd, rb1, 9) == 9);
    assert(ringbuf_write(wrfd, rb1, 4) == 4);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 13);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 14) == 13);
    assert(read(wrfd, dst + 13, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf2, 13) == 0);
    assert(strncmp((const char *) dst + 13, (const char *) buf + 13, RINGBUF_SIZE * 2 - 13) == 0);
    END_TEST(test_num);

    /* ringbuf_write, twice (full capacity) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, RINGBUF_SIZE - 1);
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 2) == RINGBUF_SIZE - 2);
    assert(ringbuf_write(wrfd, rb1, 1) == 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(read(wrfd, dst + RINGBUF_SIZE - 1, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf2, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf + RINGBUF_SIZE - 1, RINGBUF_SIZE * 2 - (RINGBUF_SIZE -1)) == 0);
    END_TEST(test_num);

    /* ringbuf_write, attempt to underflow */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, 15);
    assert(ringbuf_write(wrfd, rb1, 16) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 15);
    assert(ringbuf_bytes_used(rb1) == 15);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_head(rb1) == rb1_base + 15);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE * 2) == 0);
    END_TEST(test_num);
    
    /* ringbuf_write, attempt to underflow on 2nd call */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern);
    ringbuf_memcpy_into(rb1, buf2, 15);
    assert(ringbuf_write(wrfd, rb1, 14) == 14);
    assert(ringbuf_write(wrfd, rb1, 2) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 1);
    assert(ringbuf_bytes_used(rb1) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 14);
    assert(ringbuf_head(rb1) == rb1_base + 15);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 15) == 14);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf2, 1) == 0);
    assert(strncmp((const char *) dst + 14, (const char *) buf + 14, RINGBUF_SIZE * 2 - 14) == 0);
    END_TEST(test_num);
    
    /* ringbuf_read followed by ringbuf_write */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 11) == 11);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, 11) == 0);
    assert(strncmp((const char *) dst + 11, (const char *) buf2 + 11, RINGBUF_SIZE * 2 - 11) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_read followed by partial ringbuf_write */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    ringbuf_reset(rb1);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 7) == 7);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 4);
    assert(ringbuf_bytes_used(rb1) == 4);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 11) == 7);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, 7) == 0);
    assert(strncmp((const char *) dst + 7, (const char *) buf2 + 7, RINGBUF_SIZE * 2 - 7) == 0);
    assert(ringbuf_tail(rb1) == rb1_base + 7);
    assert(ringbuf_head(rb1) == rb1_base + 11);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /*
     * ringbuf_read, ringbuf_write, then ringbuf_read to just before
     * the end of contiguous buffer, but don't wrap
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11 - 1) == RINGBUF_SIZE - 11 - 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 11);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 11 - 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 11);
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 11) == 11);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, 11) == 0);
    assert(strncmp((const char *) dst + 11, (const char *) buf2 + 11, RINGBUF_SIZE * 2 - 11) == 0);
    END_TEST(test_num);

    /*
     * ringbuf_read, ringbuf_write, then ringbuf_read to the end of
     * the contiguous buffer, which should cause the head pointer to
     * wrap.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11) == RINGBUF_SIZE - 11);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 10);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 11);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 11);
    assert(ringbuf_head(rb1) == rb1_base);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, 11) == 11);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, 11) == 0);
    assert(strncmp((const char *) dst + 11, (const char *) buf2 + 11, RINGBUF_SIZE * 2 - 11) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except the 2nd ringbuf_read attempts to
     * read 1 beyond the end of the contiguous buffer. Because
     * ringbuf_read only calls read(2) at most once, it should return
     * a short count (short by one byte), since wrapping around and
     * continuing to fill the ring buffer would require 2 read(2)
     * calls. For good measure, follow it up with a ringbuf_write that
     * causes the tail pointer to stop just short of wrapping, which
     * tests behavior when the ring buffer's head pointer is less than
     * its tail pointer.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* should return a short count! */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11 + 1) == RINGBUF_SIZE - 11);
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 12) == RINGBUF_SIZE - 12);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 2);
    assert(ringbuf_bytes_used(rb1) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(ringbuf_head(rb1) == rb1_base);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf2 + RINGBUF_SIZE - 1, RINGBUF_SIZE * 2 - (RINGBUF_SIZE - 1)) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except when the 2nd ringbuf_read returns
     * a short count, do another.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* should return a short count! */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11 + 1) == RINGBUF_SIZE - 11);
    assert(ringbuf_read(rdfd, rb1, 1) == 1);
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 12) == RINGBUF_SIZE - 12);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 3);
    assert(ringbuf_bytes_used(rb1) == 2);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf2 + RINGBUF_SIZE - 1, RINGBUF_SIZE * 2 - (RINGBUF_SIZE - 1)) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except the 2nd ringbuf_write causes the
     * tail pointer to wrap (just).
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* should return a short count! */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11 + 1) == RINGBUF_SIZE - 11);
    assert(ringbuf_read(rdfd, rb1, 1) == 1);
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 11) == RINGBUF_SIZE - 11);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 2);
    assert(ringbuf_bytes_used(rb1) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE) == RINGBUF_SIZE);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE, (const char *) buf2 + RINGBUF_SIZE, RINGBUF_SIZE) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except the 2nd ringbuf_write returns a
     * short count.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* should return a short count! */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11 + 1) == RINGBUF_SIZE - 11);
    assert(ringbuf_read(rdfd, rb1, 1) == 1);
    /* should return a short count! */
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 10) == RINGBUF_SIZE - 11);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 2);
    assert(ringbuf_bytes_used(rb1) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE) == RINGBUF_SIZE);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE, (const char *) buf2 + RINGBUF_SIZE, RINGBUF_SIZE) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except do a 3rd ringbuf_write after the
     * 2nd returns the short count.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* should return a short count! */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11 + 1) == RINGBUF_SIZE - 11);
    assert(ringbuf_read(rdfd, rb1, 1) == 1);
    /* should return a short count! */
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 10) == RINGBUF_SIZE - 11);
    assert(ringbuf_write(wrfd, rb1, 1) == 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(read(wrfd, dst, RINGBUF_SIZE + 1) == RINGBUF_SIZE + 1);
    assert(read(wrfd, dst, 1) == 0);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE + 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE + 1, (const char *) buf2 + RINGBUF_SIZE + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /* ringbuf_memcpy_into followed by ringbuf_memcpy_from */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(strncmp((const char *) dst, (const char *) buf, 11) == 0);
    assert(strncmp((const char *) dst + 11, (const char *) buf2 + 11, RINGBUF_SIZE * 2 - 11) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_memcpy_into followed by partial ringbuf_memcpy_from */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 7) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 4);
    assert(ringbuf_bytes_used(rb1) == 4);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(strncmp((const char *) dst, (const char *) buf, 7) == 0);
    assert(strncmp((const char *) dst + 7, (const char *) buf2 + 7, RINGBUF_SIZE * 2 - 7) == 0);
    assert(ringbuf_tail(rb1) == rb1_base + 7);
    assert(ringbuf_head(rb1) == rb1_base + 11);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /*
     * ringbuf_memcpy_into, ringbuf_memcpy_from, then
     * ringbuf_memcpy_into to just before the end of contiguous
     * buffer, but don't wrap
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11 - 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 11);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 11 - 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 11);
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(strncmp((const char *) dst, (const char *) buf, 11) == 0);
    assert(strncmp((const char *) dst + 11, (const char *) buf2 + 11, RINGBUF_SIZE * 2 - 11) == 0);
    END_TEST(test_num);

    /*
     * ringbuf_memcpy_into, ringbuf_memcpy_from, then
     * ringbuf_memcpy_into to the end of the contiguous buffer, which
     * should cause the head pointer to wrap.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 10);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 11);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 11);
    assert(ringbuf_head(rb1) == rb1_base);
    assert(strncmp((const char *) dst, (const char *) buf, 11) == 0);
    assert(strncmp((const char *) dst + 11, (const char *) buf2 + 11, RINGBUF_SIZE * 2 - 11) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except the 2nd ringbuf_memcpy_into reads
     * 1 beyond the end of the contiguous buffer, which causes it to
     * wrap and do a 2nd memcpy from the start of the contiguous
     * buffer. For good measure, follow it up with a ringbuf_write
     * that causes the tail pointer to stop just short of wrapping,
     * which tests behavior when the ring buffer's head pointer is
     * less than its tail pointer.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11 + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst + 11, rb1, RINGBUF_SIZE - 12) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 3);
    assert(ringbuf_bytes_used(rb1) == 2);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE - 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE - 1, (const char *) buf2 + RINGBUF_SIZE - 1, RINGBUF_SIZE * 2 - (RINGBUF_SIZE - 1)) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except the 2nd ringbuf_write causes the
     * tail pointer to wrap (just).
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11 + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst + 11, rb1, RINGBUF_SIZE - 11) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 2);
    assert(ringbuf_bytes_used(rb1) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE, (const char *) buf2 + RINGBUF_SIZE, RINGBUF_SIZE) == 0);
    END_TEST(test_num);

    /*
     * Same as previous test, except the 2nd ringbuf_write performs 2
     * memcpy's, the 2nd of which starts from the beginning of the
     * contiguous buffer after the wrap.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11 + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst + 11, rb1, RINGBUF_SIZE - 11 + 1) == ringbuf_tail(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(strncmp((const char *) dst, (const char *) buf, RINGBUF_SIZE + 1) == 0);
    assert(strncmp((const char *) dst + RINGBUF_SIZE + 1, (const char *) buf2 + RINGBUF_SIZE + 1, RINGBUF_SIZE - 1) == 0);
    END_TEST(test_num);

    /*
     * Overflow with ringbuf_read when tail pointer is > head
     * pointer. Should bump tail pointer to head + 1.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* wrap head */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11) == RINGBUF_SIZE - 11);
    /* overflow */
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base + 11);
    assert(ringbuf_tail(rb1) == rb1_base + 12);
    END_TEST(test_num);

    /*
     * Overflow with ringbuf_read when tail pointer is > head pointer,
     * and tail pointer is at the end of the contiguous buffer. Should
     * wrap tail pointer to beginning of contiguous buffer.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ftruncate(wrfd, 0) == 0);
    assert(lseek(wrfd, 0, SEEK_SET) == 0);
    assert(lseek(rdfd, 0, SEEK_SET) == 0);
    assert(ringbuf_read(rdfd, rb1, 11) == 11);
    assert(ringbuf_write(wrfd, rb1, 11) == 11);
    /* wrap head */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 11) == RINGBUF_SIZE - 11);
    /* write until tail points to end of contiguous buffer */
    assert(ringbuf_write(wrfd, rb1, RINGBUF_SIZE - 12) == RINGBUF_SIZE - 12);
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    /* overflow */
    assert(ringbuf_read(rdfd, rb1, RINGBUF_SIZE - 1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(ringbuf_tail(rb1) == rb1_base);
    END_TEST(test_num);

    /*
     * Overflow with ringbuf_memcpy_into when tail pointer is > head
     * pointer. Should bump tail pointer to head + 1.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    /* wrap head */
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11) == ringbuf_head(rb1));
    /* overflow */
    assert(ringbuf_memcpy_into(rb1, buf + RINGBUF_SIZE, 11) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base + 11);
    assert(ringbuf_tail(rb1) == rb1_base + 12);
    END_TEST(test_num);

    /*
     * Overflow with ringbuf_memcpy_into when tail pointer is > head
     * pointer, and tail pointer is at the end of the contiguous
     * buffer. Should wrap tail pointer to beginning of contiguous
     * buffer.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    fill_buffer(dst, RINGBUF_SIZE * 2, test_pattern2);
    assert(ringbuf_memcpy_into(rb1, buf, 11) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 11) == ringbuf_tail(rb1));
    /* wrap head */
    assert(ringbuf_memcpy_into(rb1, buf + 11, RINGBUF_SIZE - 11) == ringbuf_head(rb1));
    /* copy from until tail points to end of contiguous buffer */
    assert(ringbuf_memcpy_from(dst + 11, rb1, RINGBUF_SIZE - 12) == ringbuf_tail(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 1);
    /* overflow */
    assert(ringbuf_memcpy_into(rb1, buf + RINGBUF_SIZE, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(ringbuf_tail(rb1) == rb1_base);
    END_TEST(test_num);

    ringbuf_t rb2 = ringbuf_new(RINGBUF_SIZE - 1);
    const uint8_t *rb2_base = ringbuf_head(rb2);
    
    /* ringbuf_copy with zero count, empty buffers */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_copy(rb1, rb2, 0) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb2) == ringbuf_head(rb2));
    assert(ringbuf_head(rb1) == rb1_base);
    assert(ringbuf_head(rb2) == rb2_base);
    END_TEST(test_num);

    /* ringbuf_copy with zero count, empty src */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_copy(rb1, rb2, 0) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 2);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == 2);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == ringbuf_head(rb2));
    assert(ringbuf_head(rb1) == rb1_base + 2);
    assert(ringbuf_head(rb2) == rb2_base);
    END_TEST(test_num);

    /* ringbuf_copy with zero count, empty dst */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb2, buf, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 0) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2) - 2);
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(ringbuf_bytes_used(rb2) == 2);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(ringbuf_is_empty(rb1));
    assert(!ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == ringbuf_head(rb1));
    assert(ringbuf_tail(rb2) == rb2_base);
    assert(ringbuf_head(rb1) == rb1_base);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    END_TEST(test_num);

    /* ringbuf_copy with zero count */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_into(rb2, buf2, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 0) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 2);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2) - 2);
    assert(ringbuf_bytes_used(rb1) == 2);
    assert(ringbuf_bytes_used(rb2) == 2);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(!ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == rb2_base);
    assert(ringbuf_head(rb1) == rb1_base + 2);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    END_TEST(test_num);

    /* ringbuf_copy full contents of rb2 into rb1 (initially empty) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb2, buf2, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 2) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 2);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == 2);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == rb2_base + 2);
    assert(ringbuf_head(rb1) == rb1_base + 2);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf2, 2) == 0);
    END_TEST(test_num);

    /* ringbuf_copy full contents of rb2 into rb1 (latter initially
     * has 3 bytes) */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, 3) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_into(rb2, buf2, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 2) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 5);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == 5);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == rb2_base + 2);
    assert(ringbuf_head(rb1) == rb1_base + 5);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf, 3) == 0);
    assert(strncmp((const char *) ringbuf_tail(rb1) + 3, (const char *) buf2, 2) == 0);
    END_TEST(test_num);

    /* ringbuf_copy, wrap head of dst */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    /* make sure rb1 doesn't overflow on later ringbuf_copy */
    assert(ringbuf_memcpy_from(dst, rb1, 1) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb2, buf2, 1) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 1) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base + 1);
    assert(ringbuf_tail(rb2) == rb2_base + 1);
    assert(ringbuf_head(rb1) == rb1_base);
    assert(ringbuf_head(rb2) == rb2_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 1, RINGBUF_SIZE - 2) == 0);
    assert(strncmp((const char *) ringbuf_tail(rb1) + RINGBUF_SIZE - 2, (const char *) buf2, 1) == 0);
    END_TEST(test_num);

    /* ringbuf_copy, wrap head of dst and continue copying into start
     * of contiguous buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    /* make sure rb1 doesn't overflow on later ringbuf_copy */
    assert(ringbuf_memcpy_from(dst, rb1, 2) == ringbuf_tail(rb1));
    assert(ringbuf_memcpy_into(rb2, buf2, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 2) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base + 2);
    assert(ringbuf_tail(rb2) == rb2_base + 2);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 2, RINGBUF_SIZE - 3) == 0);
    /* last position in contiguous buffer */
    assert(strncmp((const char *) ringbuf_tail(rb1) + RINGBUF_SIZE - 3, (const char *) buf2, 1) == 0);
    /* start of contiguous buffer (from copy wrap) */
    assert(strncmp((const char *) rb1_base, (const char *) buf2 + 1, 1) == 0);
    END_TEST(test_num);

    /* ringbuf_copy, wrap tail of src */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb2, buf2, RINGBUF_SIZE - 1) == ringbuf_head(rb2));
    assert(ringbuf_head(rb2) == rb2_base + RINGBUF_SIZE - 1);
    assert(ringbuf_memcpy_from(dst, rb2, RINGBUF_SIZE - 3) == ringbuf_tail(rb2));
    assert(ringbuf_tail(rb2) == rb2_base + RINGBUF_SIZE - 3);
    assert(ringbuf_memcpy_into(rb2, (uint8_t *) buf2 + RINGBUF_SIZE - 1, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 3) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 1 - 3);
    assert(ringbuf_bytes_free(rb2) == RINGBUF_SIZE - 1 - 1);
    assert(ringbuf_bytes_used(rb1) == 3);
    assert(ringbuf_bytes_used(rb2) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(!ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == rb2_base);
    assert(ringbuf_head(rb1) == rb1_base + 3);
    assert(ringbuf_head(rb2) == rb2_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf2 + RINGBUF_SIZE - 3, 3) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_copy, wrap tail of src and continue copying from start
     * of contiguous buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb2, buf2, RINGBUF_SIZE - 1) == ringbuf_head(rb2));
    assert(ringbuf_head(rb2) == rb2_base + RINGBUF_SIZE - 1);
    assert(ringbuf_memcpy_from(dst, rb2, RINGBUF_SIZE - 3) == ringbuf_tail(rb2));
    assert(ringbuf_tail(rb2) == rb2_base + RINGBUF_SIZE - 3);
    assert(ringbuf_memcpy_into(rb2, buf2 + RINGBUF_SIZE - 1, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 4) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 1 - 4);
    assert(ringbuf_bytes_free(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb1) == 4);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == rb2_base + 1);
    assert(ringbuf_head(rb1) == rb1_base + 4);
    assert(ringbuf_head(rb2) == rb2_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf2 + RINGBUF_SIZE - 3, 4) == 0);
    assert(*(char *)ringbuf_head(rb1) == '\1');
    END_TEST(test_num);

    /* ringbuf_copy, wrap tail of src and head of dst simultaneously,
     * then continue copying from start of contiguous buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb2, buf2, RINGBUF_SIZE - 1) == ringbuf_head(rb2));
    assert(ringbuf_head(rb2) == rb2_base + RINGBUF_SIZE - 1);
    assert(ringbuf_memcpy_from(dst, rb2, RINGBUF_SIZE - 3) == ringbuf_tail(rb2));
    assert(ringbuf_tail(rb2) == rb2_base + RINGBUF_SIZE - 3);
    assert(ringbuf_memcpy_into(rb2, buf2 + RINGBUF_SIZE - 1, 2) == ringbuf_head(rb2));
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 3) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 3);
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 3) == ringbuf_tail(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 3);
    assert(ringbuf_copy(rb1, rb2, 4) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 1 - 4);
    assert(ringbuf_bytes_free(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb1) == 4);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 3);
    assert(ringbuf_tail(rb2) == rb2_base + 1);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(ringbuf_head(rb2) == rb2_base + 1);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf2 + RINGBUF_SIZE - 3, 3) == 0);
    assert(strncmp((const char *) rb1_base, (const char *) buf2 + RINGBUF_SIZE, 1) == 0);
    END_TEST(test_num);

    /* ringbuf_copy, force 3 separate memcpy's: up to end of src, then
     * up to end of dst, then copy remaining bytes. */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb2, buf2, RINGBUF_SIZE - 1) == ringbuf_head(rb2));
    assert(ringbuf_head(rb2) == rb2_base + RINGBUF_SIZE - 1);
    assert(ringbuf_memcpy_from(dst, rb2, RINGBUF_SIZE - 2) == ringbuf_tail(rb2));
    assert(ringbuf_tail(rb2) == rb2_base + RINGBUF_SIZE - 2);
    assert(ringbuf_memcpy_into(rb2, buf2 + RINGBUF_SIZE - 1, 5) == ringbuf_head(rb2));
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 3) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 3);
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 4);
    assert(ringbuf_copy(rb1, rb2, 5) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == RINGBUF_SIZE - 1 - 6);
    assert(ringbuf_bytes_free(rb2) == RINGBUF_SIZE - 1 - 1);
    assert(ringbuf_bytes_used(rb1) == 6);
    assert(ringbuf_bytes_used(rb2) == 1);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(!ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base + RINGBUF_SIZE - 4);
    assert(ringbuf_tail(rb2) == rb2_base + 3);
    assert(ringbuf_head(rb1) == rb1_base + 2);
    assert(ringbuf_head(rb2) == rb2_base + 4);
    /* one byte from buf */
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + RINGBUF_SIZE - 4, 1) == 0);
    /* 5 bytes from buf2, 3 at end of contiguous buffer and 2 after the wrap */
    assert(strncmp((const char *) ringbuf_tail(rb1) + 1, (const char *) buf2 + RINGBUF_SIZE - 2, 3) == 0);
    assert(strncmp((const char *) rb1_base, (const char *) buf2 + RINGBUF_SIZE - 2 + 3, 2) == 0);
    END_TEST(test_num);

    /* ringbuf_copy overflow */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_head(rb1) == rb1_base + RINGBUF_SIZE - 1);
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_memcpy_into(rb2, buf2, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 2) == ringbuf_head(rb1));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == 0);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2));
    assert(ringbuf_bytes_used(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_used(rb2) == 0);
    assert(ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base + 2);
    assert(ringbuf_tail(rb2) == rb2_base + 2);
    assert(ringbuf_head(rb1) == rb1_base + 1);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    assert(strncmp(ringbuf_tail(rb1), (const char *) buf + 2, RINGBUF_SIZE - 1 - 2) == 0);
    assert(strncmp((const char *) ringbuf_tail(rb1) + RINGBUF_SIZE - 1 - 2, (const char *) buf2, 1) == 0);
    assert(strncmp((const char *) rb1_base, (const char *) buf2 + 1, 1) == 0);
    END_TEST(test_num);

    /* ringbuf_copy attempted underflow */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_reset(rb2);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb2, 2, ringbuf_buffer_size(rb2));
    ringbuf_reset(rb2);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_into(rb2, buf2, 2) == ringbuf_head(rb2));
    assert(ringbuf_copy(rb1, rb2, 3) == 0);
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb2) == RINGBUF_SIZE - 1);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1) - 2);
    assert(ringbuf_bytes_free(rb2) == ringbuf_capacity(rb2) - 2);
    assert(ringbuf_bytes_used(rb1) == 2);
    assert(ringbuf_bytes_used(rb2) == 2);
    assert(!ringbuf_is_full(rb1));
    assert(!ringbuf_is_full(rb2));
    assert(!ringbuf_is_empty(rb1));
    assert(!ringbuf_is_empty(rb2));
    assert(ringbuf_tail(rb1) == rb1_base);
    assert(ringbuf_tail(rb2) == rb2_base);
    assert(ringbuf_head(rb1) == rb1_base + 2);
    assert(ringbuf_head(rb2) == rb2_base + 2);
    END_TEST(test_num);

    /* ringbuf_copy, different capacities, overflow 2nd */
    START_NEW_TEST(test_num);
    ringbuf_t rb3 = ringbuf_new(8);
    const uint8_t *rb3_base = ringbuf_head(rb3);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    ringbuf_memset(rb3, 3, ringbuf_buffer_size(rb3));
    ringbuf_reset(rb3);
    assert(ringbuf_memcpy_into(rb1, buf, 10) == ringbuf_head(rb1));
    assert(ringbuf_copy(rb3, rb1, 10) == ringbuf_head(rb3));
    assert(ringbuf_capacity(rb1) == RINGBUF_SIZE - 1);
    assert(ringbuf_capacity(rb3) == 8);
    assert(ringbuf_bytes_free(rb1) == ringbuf_capacity(rb1));
    assert(ringbuf_bytes_free(rb3) == 0);
    assert(ringbuf_bytes_used(rb1) == 0);
    assert(ringbuf_bytes_used(rb3) == 8);
    assert(!ringbuf_is_full(rb1));
    assert(ringbuf_is_full(rb3));
    assert(ringbuf_is_empty(rb1));
    assert(!ringbuf_is_empty(rb3));
    assert(ringbuf_tail(rb1) == rb1_base + 10);
    assert(ringbuf_tail(rb3) == rb3_base + 2);
    assert(ringbuf_head(rb1) == rb1_base + 10);
    assert(ringbuf_head(rb3) == rb3_base + 1);
    assert(strncmp(ringbuf_tail(rb3), (const char *) buf + 2, 7) == 0);
    assert(strncmp((const char *) rb3_base, (const char *) buf + 9, 1) == 0);
    ringbuf_free(&rb3);
    END_TEST(test_num);

    /* ringbuf_findchr */

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_findchr(rb1, 'a', 0) == 0);
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'a', 0) == 0);
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'a', 1) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'b', 0) == 1);
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'b', 1) == 1);
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'b', 2) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 2) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 1, 0) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, strlen(test_pattern) + 1) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'a', 1) == strlen(test_pattern));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, strlen(test_pattern) + 1) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'a', strlen(test_pattern)) == strlen(test_pattern));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, strlen(test_pattern) + 1) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'a', strlen(test_pattern) + 1) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, (strlen(test_pattern) * 2) - 1) == ringbuf_head(rb1));
    assert(ringbuf_findchr(rb1, 'a', strlen(test_pattern) + 1) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 3) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 1) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'a', 0) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 3) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 1) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'b', 0) == 0);
    END_TEST(test_num);

    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, 3) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, 2) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'b', 0) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    /* find 'd' in last byte of contiguous buffer */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE - 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'd', 0) == 3);
    END_TEST(test_num);

    /*
     * Find just before wrap with offset 1.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'd', 1) == 1);
    END_TEST(test_num);

    /*
     * Miss the 'd' at the end due to offset 2.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'd', 2) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    /*
     * should *not* find 'a' in the first byte of the contiguous
     * buffer when head wraps.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 1 byte */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'a', 0) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);

    /*
     * Should find 'e' at first byte of contiguous buffer (i.e.,
     * should wrap during search).
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'e', 0) == 2);
    END_TEST(test_num);

    /*
     * Should find 'e' at first byte, with offset 1.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'e', 1) == 2);
    END_TEST(test_num);
    
    /*
     * Search begins at first byte due to offset 2, should find 'e'.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'e', 2) == 2);
    END_TEST(test_num);
    
    /*
     * Miss the 'e' at first byte due to offset 3.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 4) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'e', 3) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);
    
    /*
     * Should *not* find the 'c' left over from overwritten contents
     * (where head is currently pointing).
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 1) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'c', 0) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);
    
    /*
     * Should *not* find the 'd' left over from overwritten contents.
     */
    START_NEW_TEST(test_num);
    ringbuf_reset(rb1);
    ringbuf_memset(rb1, 1, ringbuf_buffer_size(rb1));
    ringbuf_reset(rb1);
    /* head will wrap around and overflow by 2 bytes */
    assert(ringbuf_memcpy_into(rb1, buf, RINGBUF_SIZE + 1) == ringbuf_head(rb1));
    assert(ringbuf_memcpy_from(dst, rb1, RINGBUF_SIZE - 1) == ringbuf_tail(rb1));
    assert(ringbuf_findchr(rb1, 'd', 1) == ringbuf_bytes_used(rb1));
    END_TEST(test_num);
    
    ringbuf_free(&rb1);
    ringbuf_free(&rb2);
    free(buf);
    free(buf2);
    free(dst);
    return 0;
}