#include <stdio.h>

#include <assert.h>

#include "zbuild.h"

#ifdef ZLIB_COMPAT

#  include "zlib.h"

#else

#  include "zlib-ng.h"

#endif

static const uint8_t *data;

static size_t dataLen;

static void check_compress_level(uint8_t *compr, z_uintmax_t comprLen,

                                 uint8_t *uncompr, z_uintmax_t uncomprLen,

                                 int level) {

    PREFIX(compress2)(compr, &comprLen, data, dataLen, level);

    PREFIX(uncompress)(uncompr, &uncomprLen, compr, comprLen);

    /* Make sure compress + uncompress gives back the input data. */

    assert(dataLen == uncomprLen);

    assert(0 == memcmp(data, uncompr, dataLen));

}

#define put_byte(s, i, c) {s[i] = (unsigned char)(c);}

static void write_zlib_header(uint8_t *s) {

    unsigned level_flags = 0; /* compression level (0..3) */

    unsigned w_bits = 8; /* window size log2(w_size) (8..16) */

    unsigned int header = (Z_DEFLATED + ((w_bits-8)<<4)) << 8;

    header |= (level_flags << 6);

    header += 31 - (header % 31);

    /* s is guaranteed to be longer than 2 bytes. */

    put_byte(s, 0, (header >> 8));

    put_byte(s, 1, (header & 0xff));

}

static void check_decompress(uint8_t *compr, z_uintmax_t comprLen) {

    /* We need to write a valid zlib header of size two bytes. Copy the input data

       in a larger buffer. Do not modify the input data to avoid libFuzzer error:

       fuzz target overwrites its const input. */

    size_t copyLen = dataLen + 2;

    uint8_t *copy = (uint8_t *)malloc(copyLen);

    memcpy(copy + 2, data, dataLen);

    write_zlib_header(copy);

    PREFIX(uncompress)(compr, &comprLen, copy, (z_uintmax_t)copyLen);

    free(copy);

}

int LLVMFuzzerTestOneInput(const uint8_t *d, size_t size) {

    /* compressBound does not provide enough space for low compression levels. */

    z_size_t comprLen = 100 + 2 * PREFIX(compressBound)(size);

    z_size_t uncomprLen = (z_size_t)size;

    uint8_t *compr, *uncompr;

    /* Discard inputs larger than 1Mb. */

    static size_t kMaxSize = 1024 * 1024;

    if (size < 1 || size > kMaxSize)

        return 0;

    data = d;

    dataLen = size;

    compr = (uint8_t *)calloc(1, comprLen);

    uncompr = (uint8_t *)calloc(1, uncomprLen);

    check_compress_level(compr, comprLen, uncompr, uncomprLen, 1);

    check_compress_level(compr, comprLen, uncompr, uncomprLen, 3);

    check_compress_level(compr, comprLen, uncompr, uncomprLen, 6);

    check_compress_level(compr, comprLen, uncompr, uncomprLen, 7);

    check_decompress(compr, comprLen);

    free(compr);

    free(uncompr);

    /* This function must return 0. */

    return 0;

}