/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2023 Robert Clausecker
 */

#include <sys/cdefs.h>

#include <dlfcn.h>
#include <limits.h>
#include <string.h>

#include <atf-c.h>

static void *(*memrchr_fn)(const void *, int, size_t);

ATF_TC_WITHOUT_HEAD(null);
ATF_TC_BODY(null, tc)
{
        ATF_CHECK_EQ(memrchr_fn(NULL, 42, 0), NULL);
}

ATF_TC_WITHOUT_HEAD(not_found);
ATF_TC_BODY(not_found, tc)
{
        size_t i, j;
        char buf[1+15+64+1]; /* offset [0..15] + 64 buffer bytes + sentinels */

        buf[0] = 'X';
        memset(buf + 1, '-', sizeof(buf) - 1);

        for (i = 0; i < 16; i++)
                for (j = 0; j < 64; j++) {
                        buf[i + j + 1] = 'X';
                        ATF_CHECK_EQ(memrchr_fn(buf + i + 1, 'X', j), NULL);
                        buf[i + j + 1] = '-';
                }
}

static void
do_found_test(char buf[], size_t len, size_t first, size_t second)
{
        /* invariant: first <= second */

        buf[first] = 'X';
        buf[second] = 'X';
        ATF_CHECK_EQ(memrchr_fn(buf, 'X', len), buf + second);
        buf[first] = '-';
        buf[second] = '-';
}

ATF_TC_WITHOUT_HEAD(found);
ATF_TC_BODY(found, tc)
{
        size_t i, j, k, l;
        char buf[1+15+64+1];

        buf[0] = 'X';
        memset(buf + 1, '-', sizeof(buf) - 1);

        for (i = 0; i < 16; i++)
                for (j = 0; j < 64; j++)
                        for (k = 0; k < j; k++)
                                for (l = 0; l <= k; l++) {
                                        buf[i + j + 1] = 'X';
                                        do_found_test(buf + i + 1, j, l, k);
                                        buf[i + j + 1] = '-';
                                }
}

/* check that the right character is found */
static void
do_values_test(unsigned char buf[], size_t len, size_t i, int c)
{
        /* sentinels */
        buf[-1] = c;
        buf[len] = c;
        memset(buf, c + 1, len);

        if (i < len) {
                buf[i] = c;
                ATF_CHECK_EQ(memrchr_fn(buf, c, len), buf + i);
        } else
                ATF_CHECK_EQ(memrchr_fn(buf, c, len), NULL);
}

ATF_TC_WITHOUT_HEAD(values);
ATF_TC_BODY(values, tc)
{
        size_t i, j, k;
        int c;
        unsigned char buf[1+15+64+1];

        for (i = 0; i < 16; i++)
                for (j = 0; j < 64; j++)
                        for (k = 0; k <= j; k++)
                                for (c = 0; c <= UCHAR_MAX; c++)
                                        do_values_test(buf + i + 1, j, k, c);
}

ATF_TP_ADD_TCS(tp)
{
        void *dl_handle;

        dl_handle = dlopen(NULL, RTLD_LAZY);
        memrchr_fn = dlsym(dl_handle, "test_memrchr");
        if (memrchr_fn == NULL)
                memrchr_fn = memrchr;

        ATF_TP_ADD_TC(tp, null);
        ATF_TP_ADD_TC(tp, not_found);
        ATF_TP_ADD_TC(tp, found);
        ATF_TP_ADD_TC(tp, values);

        return (atf_no_error());
}