/*

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 * All rights reserved.

 *

 * This source code is licensed under both the BSD-style license (found in the

 * LICENSE file in the root directory of this source tree) and the GPLv2 (found

 * in the COPYING file in the root directory of this source tree).

 * You may select, at your option, one of the above-listed licenses.

 */

/**

 * This fuzz target performs a zstd round-trip test (compress & decompress),

 * compares the result with the original, and calls abort() on corruption.

 */

#include <stddef.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include "common/cpu.h"

#include "compress/hist.h"

#include "common/huf.h"

#include "fuzz_helpers.h"

#include "fuzz_data_producer.h"

#include "common/bits.h"

static size_t adjustTableLog(size_t tableLog, size_t maxSymbol)

{

    size_t const alphabetSize = maxSymbol + 1;

    size_t minTableLog = ZSTD_highbit32(alphabetSize) + 1;

    if ((alphabetSize & (alphabetSize - 1)) != 0) {

        ++minTableLog;

    }

    assert(minTableLog <= 9);

    if (tableLog < minTableLog)

        return minTableLog;

    else

        return tableLog;

}

int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)

{

    FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);

    /* Select random parameters: #streams, X1 or X2 decoding, bmi2 */

    int const streams = FUZZ_dataProducer_int32Range(producer, 0, 1);

    int const symbols = FUZZ_dataProducer_int32Range(producer, 0, 1);

    int const flags = 0

        | (ZSTD_cpuid_bmi2(ZSTD_cpuid()) && FUZZ_dataProducer_int32Range(producer, 0, 1) ? HUF_flags_bmi2 : 0)

        | (FUZZ_dataProducer_int32Range(producer, 0, 1) ? HUF_flags_optimalDepth : 0)

        | (FUZZ_dataProducer_int32Range(producer, 0, 1) ? HUF_flags_preferRepeat : 0)

        | (FUZZ_dataProducer_int32Range(producer, 0, 1) ? HUF_flags_suspectUncompressible : 0)

        | (FUZZ_dataProducer_int32Range(producer, 0, 1) ? HUF_flags_disableAsm : 0)

        | (FUZZ_dataProducer_int32Range(producer, 0, 1) ? HUF_flags_disableFast : 0);

    /* Select a random cBufSize - it may be too small */

    size_t const cBufSize = FUZZ_dataProducer_uint32Range(producer, 0, 4 * size);

    /* Select a random tableLog - we'll adjust it up later */

    size_t tableLog = FUZZ_dataProducer_uint32Range(producer, 1, 12);

    size_t const kMaxSize = 256 * 1024;

    size = FUZZ_dataProducer_remainingBytes(producer);

    if (size > kMaxSize)

        size = kMaxSize;

    if (size <= 1) {

        FUZZ_dataProducer_free(producer);

        return 0;

    }

    uint32_t maxSymbol = 255;

    U32 count[256];

    size_t const mostFrequent = HIST_count(count, &maxSymbol, src, size);

    FUZZ_ZASSERT(mostFrequent);

    if (mostFrequent == size) {

        /* RLE */

        FUZZ_dataProducer_free(producer);

        return 0;

    }

    FUZZ_ASSERT(maxSymbol <= 255);

    tableLog = adjustTableLog(tableLog, maxSymbol);

    size_t const wkspSize = HUF_WORKSPACE_SIZE;

    void* wksp = FUZZ_malloc(wkspSize);

    void* rBuf = FUZZ_malloc(size);

    void* cBuf = FUZZ_malloc(cBufSize);

    HUF_CElt* ct = (HUF_CElt*)FUZZ_malloc(HUF_CTABLE_SIZE(maxSymbol));

    HUF_DTable* dt = (HUF_DTable*)FUZZ_malloc(HUF_DTABLE_SIZE(tableLog) * sizeof(HUF_DTable));

    dt[0] = tableLog * 0x01000001;

    tableLog = HUF_optimalTableLog(tableLog, size, maxSymbol, wksp, wkspSize, ct, count, flags);

    FUZZ_ASSERT(tableLog <= 12);

    tableLog = HUF_buildCTable_wksp(ct, count, maxSymbol, tableLog, wksp, wkspSize);

    FUZZ_ZASSERT(tableLog);

    size_t const tableSize = HUF_writeCTable_wksp(cBuf, cBufSize, ct, maxSymbol, tableLog, wksp, wkspSize);

    if (ERR_isError(tableSize)) {

        /* Errors on uncompressible data or cBufSize too small */

        goto _out;

    }

    FUZZ_ZASSERT(tableSize);

    if (symbols == 0) {

        FUZZ_ZASSERT(HUF_readDTableX1_wksp(dt, cBuf, tableSize, wksp, wkspSize, flags));

    } else {

        size_t const ret = HUF_readDTableX2_wksp(dt, cBuf, tableSize, wksp, wkspSize, flags);

        if (ERR_getErrorCode(ret) == ZSTD_error_tableLog_tooLarge) {

            FUZZ_ZASSERT(HUF_readDTableX1_wksp(dt, cBuf, tableSize, wksp, wkspSize, flags));

        } else {

            FUZZ_ZASSERT(ret);

        }

    }

    size_t cSize;

    size_t rSize;

    if (streams == 0) {

        cSize = HUF_compress1X_usingCTable(cBuf, cBufSize, src, size, ct, flags);

        FUZZ_ZASSERT(cSize);

        if (cSize != 0)

            rSize = HUF_decompress1X_usingDTable(rBuf, size, cBuf, cSize, dt, flags);

    } else {

        cSize = HUF_compress4X_usingCTable(cBuf, cBufSize, src, size, ct, flags);

        FUZZ_ZASSERT(cSize);

        if (cSize != 0)

            rSize = HUF_decompress4X_usingDTable(rBuf, size, cBuf, cSize, dt, flags);

    }

    if (cSize != 0) {

        FUZZ_ZASSERT(rSize);

        FUZZ_ASSERT_MSG(rSize == size, "Incorrect regenerated size");

        FUZZ_ASSERT_MSG(!FUZZ_memcmp(src, rBuf, size), "Corruption!");

    }

_out:

    free(rBuf);

    free(cBuf);

    free(ct);

    free(dt);

    free(wksp);

    FUZZ_dataProducer_free(producer);

    return 0;

}