sandboxed-api/oss-internship-2020/libarchive/ld_preload_example/minitar_main.cc

// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// clang-format off
/*-
 * This is a compact "tar" program whose primary goal is small size.
 * Statically linked, it can be very small indeed.  This serves a number
 * of goals:
 *   o a testbed for libarchive (to check for link pollution),
 *   o a useful tool for space-constrained systems (boot floppies, etc),
 *   o a place to experiment with new implementation ideas for bsdtar,
 *   o a small program to demonstrate libarchive usage.
 *
 * Use the following macros to suppress features:
 *   NO_BZIP2 - Implies NO_BZIP2_CREATE and NO_BZIP2_EXTRACT
 *   NO_BZIP2_CREATE - Suppress bzip2 compression support.
 *   NO_BZIP2_EXTRACT - Suppress bzip2 auto-detection and decompression.
 *   NO_COMPRESS - Implies NO_COMPRESS_CREATE and NO_COMPRESS_EXTRACT
 *   NO_COMPRESS_CREATE - Suppress compress(1) compression support
 *   NO_COMPRESS_EXTRACT - Suppress compress(1) auto-detect and decompression.
 *   NO_CREATE - Suppress all archive creation support.
 *   NO_CPIO_EXTRACT - Suppress auto-detect and dearchiving of cpio archives.
 *   NO_GZIP - Implies NO_GZIP_CREATE and NO_GZIP_EXTRACT
 *   NO_GZIP_CREATE - Suppress gzip compression support.
 *   NO_GZIP_EXTRACT - Suppress gzip auto-detection and decompression.
 *   NO_LOOKUP - Try to avoid getpw/getgr routines, which can be very large
 *   NO_TAR_EXTRACT - Suppress tar extraction
 *
 * With all of the above macros defined (except NO_TAR_EXTRACT), you
 * get a very small program that can recognize and extract essentially
 * any uncompressed tar archive.  On FreeBSD 5.1, this minimal program
 * is under 64k, statically linked, which compares rather favorably to
 *         main(){printf("hello, world");}
 * which is over 60k statically linked on the same operating system.
 * Without any of the above macros, you get a static executable of
 * about 180k with a lot of very sophisticated modern features.
 * Obviously, it's trivial to add support for ISO, Zip, mtree,
 * lzma/xz, etc.  Just fill in the appropriate setup calls.
 */

#include "minitar.h"  // NOLINT(build/include)

/*
 * NO_CREATE implies NO_BZIP2_CREATE and NO_GZIP_CREATE and NO_COMPRESS_CREATE.
 */
#ifdef NO_CREATE
#undef NO_BZIP2_CREATE
#define NO_BZIP2_CREATE
#undef NO_COMPRESS_CREATE
#define NO_COMPRESS_CREATE
#undef NO_GZIP_CREATE
#define NO_GZIP_CREATE
#endif

/*
 * The combination of NO_BZIP2_CREATE and NO_BZIP2_EXTRACT is
 * equivalent to NO_BZIP2.
 */
#ifdef NO_BZIP2_CREATE
#ifdef NO_BZIP2_EXTRACT
#undef NO_BZIP2
#define NO_BZIP2
#endif
#endif

#ifdef NO_BZIP2
#undef NO_BZIP2_EXTRACT
#define NO_BZIP2_EXTRACT
#undef NO_BZIP2_CREATE
#define NO_BZIP2_CREATE
#endif

/*
 * The combination of NO_COMPRESS_CREATE and NO_COMPRESS_EXTRACT is
 * equivalent to NO_COMPRESS.
 */
#ifdef NO_COMPRESS_CREATE
#ifdef NO_COMPRESS_EXTRACT
#undef NO_COMPRESS
#define NO_COMPRESS
#endif
#endif

#ifdef NO_COMPRESS
#undef NO_COMPRESS_EXTRACT
#define NO_COMPRESS_EXTRACT
#undef NO_COMPRESS_CREATE
#define NO_COMPRESS_CREATE
#endif

/*
 * The combination of NO_GZIP_CREATE and NO_GZIP_EXTRACT is
 * equivalent to NO_GZIP.
 */
#ifdef NO_GZIP_CREATE
#ifdef NO_GZIP_EXTRACT
#undef NO_GZIP
#define NO_GZIP
#endif
#endif

#ifdef NO_GZIP
#undef NO_GZIP_EXTRACT
#define NO_GZIP_EXTRACT
#undef NO_GZIP_CREATE
#define NO_GZIP_CREATE
#endif

int main(int unused_argc, const char** argv) {
  const char* filename = nullptr;
  int compress;
  int flags;
  int mode;
  int opt;

  mode = 'x';
  int verbose = 0;
  compress = '\0';
  flags = ARCHIVE_EXTRACT_TIME;

  /* Among other sins, getopt(3) pulls in printf(3). */
  while (*++argv != nullptr && **argv == '-') {
    const char* p = *argv + 1;

    while ((opt = *p++) != '\0') {
      switch (opt) {
#ifndef NO_CREATE
        case 'c':
          mode = opt;
          break;
#endif
        case 'f':
          if (*p != '\0')
            filename = p;
          else
            filename = *++argv;
          p += strlen(p);
          break;
#ifndef NO_BZIP2_CREATE
        case 'j':
          compress = opt;
          break;
#endif
        case 'p':
          flags |= ARCHIVE_EXTRACT_PERM;
          flags |= ARCHIVE_EXTRACT_ACL;
          flags |= ARCHIVE_EXTRACT_FFLAGS;
          break;
        case 't':
          mode = opt;
          break;
        case 'v':
          verbose++;
          break;
        case 'x':
          mode = opt;
          break;
#ifndef NO_BZIP2_CREATE
        case 'y':
          compress = opt;
          break;
#endif
#ifndef NO_COMPRESS_CREATE
        case 'Z':
          compress = opt;
          break;
#endif
#ifndef NO_GZIP_CREATE
        case 'z':
          compress = opt;
          break;
#endif
        default:
          usage();
      }
    }
  }

  switch (mode) {
#ifndef NO_CREATE
    case 'c':
      create(filename, compress, argv, verbose);
      break;
#endif
    case 't':
      extract(filename, 0, flags, verbose);
      break;
    case 'x':
      extract(filename, 1, flags, verbose);
      break;
  }

  return (0);
}

// clang-format on