/*

 * 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 attempts to decompress the fuzzed data with the simple

 * decompression function to ensure the decompressor never crashes.

 */

#define ZSTD_STATIC_LINKING_ONLY

#include <stddef.h>

#include <stdlib.h>

#include <stdio.h>

#include "fuzz_helpers.h"

#include "zstd.h"

#include "fuzz_data_producer.h"

static ZSTD_DStream *dstream = NULL;

uint32_t seed;

static ZSTD_outBuffer makeOutBuffer(FUZZ_dataProducer_t *producer, void* buf, size_t bufSize)

{

  ZSTD_outBuffer buffer = { buf, 0, 0 };

  if (FUZZ_dataProducer_empty(producer)) {

    buffer.size = bufSize;

  } else {

    buffer.size = (FUZZ_dataProducer_uint32Range(producer, 0, bufSize));

  }

  FUZZ_ASSERT(buffer.size <= bufSize);

  if (buffer.size == 0) {

    buffer.dst = NULL;

  }

  return buffer;

}

static ZSTD_inBuffer makeInBuffer(const uint8_t **src, size_t *size,

                                  FUZZ_dataProducer_t *producer)

{

  ZSTD_inBuffer buffer = { *src, 0, 0 };

  FUZZ_ASSERT(*size > 0);

  if (FUZZ_dataProducer_empty(producer)) {

    buffer.size = *size;

  } else {

    buffer.size = (FUZZ_dataProducer_uint32Range(producer, 0, *size));

  }

  FUZZ_ASSERT(buffer.size <= *size);

  *src += buffer.size;

  *size -= buffer.size;

  if (buffer.size == 0) {

    buffer.src = NULL;

  }

  return buffer;

}

int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)

{

    /* Give a random portion of src data to the producer, to use for

    parameter generation. The rest will be used for (de)compression */

    FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);

    int stableOutBuffer;

    ZSTD_outBuffer out;

    void* buf;

    size_t bufSize;

    size = FUZZ_dataProducer_reserveDataPrefix(producer);

    bufSize = MAX(10 * size, ZSTD_BLOCKSIZE_MAX);

    /* Allocate all buffers and contexts if not already allocated */

    buf = FUZZ_malloc(bufSize);

    if (!dstream) {

        dstream = ZSTD_createDStream();

        FUZZ_ASSERT(dstream);

    } else {

        FUZZ_ZASSERT(ZSTD_DCtx_reset(dstream, ZSTD_reset_session_only));

    }

    stableOutBuffer = FUZZ_dataProducer_uint32Range(producer, 0, 10) == 5;

    if (stableOutBuffer) {

      FUZZ_ZASSERT(ZSTD_DCtx_setParameter(dstream, ZSTD_d_stableOutBuffer, 1));

      out.dst = buf;

      out.size = bufSize;

      out.pos = 0;

    } else {

      out = makeOutBuffer(producer, buf, bufSize);

    }

    while (size > 0) {

        ZSTD_inBuffer in = makeInBuffer(&src, &size, producer);

        do {

            size_t const rc = ZSTD_decompressStream(dstream, &out, &in);

            if (ZSTD_isError(rc)) goto error;

            if (out.pos == out.size) {

                if (stableOutBuffer) goto error;

                out = makeOutBuffer(producer, buf, bufSize);

            }

        } while (in.pos != in.size);

    }

error:

#ifndef STATEFUL_FUZZING

    ZSTD_freeDStream(dstream); dstream = NULL;

#endif

    FUZZ_dataProducer_free(producer);

    free(buf);

    return 0;

}