/*

 * gzip_decompress.c - decompress with a gzip wrapper

 *

 * Copyright 2016 Eric Biggers

 *

 * Permission is hereby granted, free of charge, to any person

 * obtaining a copy of this software and associated documentation

 * files (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use,

 * copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following

 * conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 */

#include "lib_common.h"

#include "gzip_constants.h"

LIBDEFLATEAPI enum libdeflate_result

libdeflate_gzip_decompress_ex(struct libdeflate_decompressor *d,

            const void *in, size_t in_nbytes,

            void *out, size_t out_nbytes_avail,

            size_t *actual_in_nbytes_ret,

            size_t *actual_out_nbytes_ret)

{

  const u8 *in_next = in;

  const u8 * const in_end = in_next + in_nbytes;

  u8 flg;

  size_t actual_in_nbytes;

  size_t actual_out_nbytes;

  enum libdeflate_result result;

  if (in_nbytes < GZIP_MIN_OVERHEAD)

    return LIBDEFLATE_BAD_DATA;

  /* ID1 */

  if (*in_next++ != GZIP_ID1)

    return LIBDEFLATE_BAD_DATA;

  /* ID2 */

  if (*in_next++ != GZIP_ID2)

    return LIBDEFLATE_BAD_DATA;

  /* CM */

  if (*in_next++ != GZIP_CM_DEFLATE)

    return LIBDEFLATE_BAD_DATA;

  flg = *in_next++;

  /* MTIME */

  in_next += 4;

  /* XFL */

  in_next += 1;

  /* OS */

  in_next += 1;

  if (flg & GZIP_FRESERVED)

    return LIBDEFLATE_BAD_DATA;

  /* Extra field */

  if (flg & GZIP_FEXTRA) {

    u16 xlen = get_unaligned_le16(in_next);

    in_next += 2;

    if (in_end - in_next < (u32)xlen + GZIP_FOOTER_SIZE)

      return LIBDEFLATE_BAD_DATA;

    in_next += xlen;

  }

  /* Original file name (zero terminated) */

  if (flg & GZIP_FNAME) {

    while (*in_next++ != 0 && in_next != in_end)

      ;

    if (in_end - in_next < GZIP_FOOTER_SIZE)

      return LIBDEFLATE_BAD_DATA;

  }

  /* File comment (zero terminated) */

  if (flg & GZIP_FCOMMENT) {

    while (*in_next++ != 0 && in_next != in_end)

      ;

    if (in_end - in_next < GZIP_FOOTER_SIZE)

      return LIBDEFLATE_BAD_DATA;

  }

  /* CRC16 for gzip header */

  if (flg & GZIP_FHCRC) {

    in_next += 2;

    if (in_end - in_next < GZIP_FOOTER_SIZE)

      return LIBDEFLATE_BAD_DATA;

  }

  /* Compressed data  */

  result = libdeflate_deflate_decompress_ex(d, in_next,

          in_end - GZIP_FOOTER_SIZE - in_next,

          out, out_nbytes_avail,

          &actual_in_nbytes,

          actual_out_nbytes_ret);

  if (result != LIBDEFLATE_SUCCESS)

    return result;

  if (actual_out_nbytes_ret)

    actual_out_nbytes = *actual_out_nbytes_ret;

  else

    actual_out_nbytes = out_nbytes_avail;

  in_next += actual_in_nbytes;

  /* CRC32 */

  if (libdeflate_crc32(0, out, actual_out_nbytes) !=

      get_unaligned_le32(in_next))

    return LIBDEFLATE_BAD_DATA;

  in_next += 4;

  /* ISIZE */

  if ((u32)actual_out_nbytes != get_unaligned_le32(in_next))

    return LIBDEFLATE_BAD_DATA;

  in_next += 4;

  if (actual_in_nbytes_ret)

    *actual_in_nbytes_ret = in_next - (u8 *)in;

  return LIBDEFLATE_SUCCESS;

}

LIBDEFLATEAPI enum libdeflate_result

libdeflate_gzip_decompress(struct libdeflate_decompressor *d,

         const void *in, size_t in_nbytes,

         void *out, size_t out_nbytes_avail,

         size_t *actual_out_nbytes_ret)

{

  return libdeflate_gzip_decompress_ex(d, in, in_nbytes,

               out, out_nbytes_avail,

               NULL, actual_out_nbytes_ret);

}