// Copyright 2022 The Wuffs Authors.

//

// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or

// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license

// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your

// option. This file may not be copied, modified, or distributed

// except according to those terms.

//

// SPDX-License-Identifier: Apache-2.0 OR MIT

// ----------------

// Silence the nested slash-star warning for the next comment's command line.

#pragma clang diagnostic push

#pragma clang diagnostic ignored "-Wcomment"

/*

This fuzzer (the fuzz function) is typically run indirectly, by a framework

such as https://github.com/google/oss-fuzz calling LLVMFuzzerTestOneInput.

When working on the fuzz implementation, or as a coherence check, defining

WUFFS_CONFIG__FUZZLIB_MAIN will let you manually run fuzz over a set of files:

gcc -DWUFFS_CONFIG__FUZZLIB_MAIN bzip2_fuzzer.c

./a.out ../../../test/data/*.bzip2

rm -f ./a.out

It should print "PASS", amongst other information, and exit(0).

*/

#pragma clang diagnostic pop

// Wuffs ships as a "single file C library" or "header file library" as per

// https://github.com/nothings/stb/blob/master/docs/stb_howto.txt

//

// To use that single file as a "foo.c"-like implementation, instead of a

// "foo.h"-like header, #define WUFFS_IMPLEMENTATION before #include'ing or

// compiling it.

#define WUFFS_IMPLEMENTATION

#if defined(WUFFS_CONFIG__FUZZLIB_MAIN)

// Defining the WUFFS_CONFIG__STATIC_FUNCTIONS macro is optional, but when

// combined with WUFFS_IMPLEMENTATION, it demonstrates making all of Wuffs'

// functions have static storage.

//

// This can help the compiler ignore or discard unused code, which can produce

// faster compiles and smaller binaries. Other motivations are discussed in the

// "ALLOW STATIC IMPLEMENTATION" section of

// https://raw.githubusercontent.com/nothings/stb/master/docs/stb_howto.txt

#define WUFFS_CONFIG__STATIC_FUNCTIONS

#endif  // defined(WUFFS_CONFIG__FUZZLIB_MAIN)

// Defining the WUFFS_CONFIG__MODULE* macros are optional, but it lets users of

// release/c/etc.c choose which parts of Wuffs to build. That file contains the

// entire Wuffs standard library, implementing a variety of codecs and file

// formats. Without this macro definition, an optimizing compiler or linker may

// very well discard Wuffs code for unused codecs, but listing the Wuffs

// modules we use makes that process explicit. Preprocessing means that such

// code simply isn't compiled.

#define WUFFS_CONFIG__MODULES

#define WUFFS_CONFIG__MODULE__BASE

#define WUFFS_CONFIG__MODULE__BZIP2

// If building this program in an environment that doesn't easily accommodate

// relative includes, you can use the script/inline-c-relative-includes.go

// program to generate a stand-alone C file.

#include "../../../release/c/wuffs-unsupported-snapshot.c"

#include "../fuzzlib/fuzzlib.c"

// 64 KiB.

#define DST_BUFFER_ARRAY_SIZE 65536

// Wuffs allows either statically or dynamically allocated work buffers. This

// program exercises static allocation.

#define WORK_BUFFER_ARRAY_SIZE \

  WUFFS_BZIP2__DECODER_WORKBUF_LEN_MAX_INCL_WORST_CASE

#if WORK_BUFFER_ARRAY_SIZE > 0

uint8_t g_work_buffer_array[WORK_BUFFER_ARRAY_SIZE];

#else

// Not all C/C++ compilers support 0-length arrays.

uint8_t g_work_buffer_array[1];

#endif

const char*  //

fuzz(wuffs_base__io_buffer* src, uint64_t hash) {

  wuffs_bzip2__decoder dec;

  wuffs_base__status status = wuffs_bzip2__decoder__initialize(

      &dec, sizeof dec, WUFFS_VERSION,

      (hash & 1) ? WUFFS_INITIALIZE__LEAVE_INTERNAL_BUFFERS_UNINITIALIZED : 0);

  if (!wuffs_base__status__is_ok(&status)) {

    return wuffs_base__status__message(&status);

  }

  // Ignore the checksum for 99.99%-ish of all input. When fuzzers generate

  // random input, the checkum is very unlikely to match. Still, it's useful to

  // verify that checksumming does not lead to e.g. buffer overflows.

  wuffs_bzip2__decoder__set_quirk(&dec, WUFFS_BASE__QUIRK_IGNORE_CHECKSUM,

                                  hash & 0xFFFE);

  static uint8_t dst_buffer[DST_BUFFER_ARRAY_SIZE];

  wuffs_base__io_buffer dst =

      wuffs_base__ptr_u8__writer(&dst_buffer[0], DST_BUFFER_ARRAY_SIZE);

  while (true) {

    dst.meta.wi = 0;

    status = wuffs_bzip2__decoder__transform_io(

        &dec, &dst, src,

        wuffs_base__make_slice_u8(g_work_buffer_array, WORK_BUFFER_ARRAY_SIZE));

    if (status.repr != wuffs_base__suspension__short_write) {

      break;

    }

    if (dst.meta.wi == 0) {

      fprintf(stderr, "wuffs_bzip2__decoder__transform_io made no progress\n");

      intentional_segfault();

    }

  }

  return wuffs_base__status__message(&status);

}