/*

Copyright (c) 2008, 2010, 2014-2019, Arvid Norberg

Copyright (c) 2017, 2019, Alden Torres

All rights reserved.

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions

are met:

    * Redistributions of source code must retain the above copyright

      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright

      notice, this list of conditions and the following disclaimer in

      the documentation and/or other materials provided with the distribution.

    * Neither the name of the author nor the names of its

      contributors may be used to endorse or promote products derived

      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

*/

#include "libtorrent/assert.hpp"

#include "libtorrent/puff.hpp"

#include "libtorrent/gzip.hpp"

#include <string>

namespace {

  enum

  {

    FTEXT = 0x01,

    FHCRC = 0x02,

    FEXTRA = 0x04,

    FNAME = 0x08,

    FCOMMENT = 0x10,

    FRESERVED = 0xe0,

    GZIP_MAGIC0 = 0x1f,

    GZIP_MAGIC1 = 0x8b

  };

}

namespace libtorrent {

  struct gzip_error_category final : boost::system::error_category

  {

    const char* name() const BOOST_SYSTEM_NOEXCEPT override;

    std::string message(int ev) const override;

    boost::system::error_condition default_error_condition(int ev) const BOOST_SYSTEM_NOEXCEPT override

    { return {ev, *this}; }

  };

  const char* gzip_error_category::name() const BOOST_SYSTEM_NOEXCEPT

  {

    return "gzip error";

  }

  std::string gzip_error_category::message(int ev) const

  {

    static char const* msgs[] =

    {

      "no error",

      "invalid gzip header",

      "inflated data too large",

      "available inflate data did not terminate",

      "output space exhausted before completing inflate",

      "invalid block type (type == 3)",

      "stored block length did not match one's complement",

      "dynamic block code description: too many length or distance codes",

      "dynamic block code description: code lengths codes incomplete",

      "dynamic block code description: repeat lengths with no first length",

      "dynamic block code description: repeat more than specified lengths",

      "dynamic block code description: invalid literal/length code lengths",

      "dynamic block code description: invalid distance code lengths",

      "invalid literal/length or distance code in fixed or dynamic block",

      "distance is too far back in fixed or dynamic block",

      "unknown gzip error",

    };

    if (ev < 0 || ev >= int(sizeof(msgs)/sizeof(msgs[0])))

      return "Unknown error";

    return msgs[ev];

  }

  boost::system::error_category& gzip_category()

  {

    static gzip_error_category category;

    return category;

  }

  namespace gzip_errors

  {

    boost::system::error_code make_error_code(error_code_enum e)

    {

      return {e, gzip_category()};

    }

  }

namespace {

  // returns -1 if gzip header is invalid or the header size in bytes

  int gzip_header(span<char const> const in)

  {

    // The zip header cannot be shorter than 10 bytes

    if (in.size() < 10) return -1;

    span<unsigned char const> buffer(

      reinterpret_cast<const unsigned char*>(in.data()), in.size());

    // gzip is defined in https://tools.ietf.org/html/rfc1952

    // check the magic header of gzip

    if ((buffer[0] != GZIP_MAGIC0) || (buffer[1] != GZIP_MAGIC1)) return -1;

    int const method = buffer[2];

    int const flags = buffer[3];

    // check for reserved flag and make sure it's compressed with the correct method

    // we only support deflate

    if (method != 8 || (flags & FRESERVED) != 0) return -1;

    // skip time, xflags, OS code. The first 10 bytes of the header:

    // +---+---+---+---+---+---+---+---+---+---+

    // |ID1|ID2|CM |FLG|     MTIME     |XFL|OS | (more-->)

    // +---+---+---+---+---+---+---+---+---+---+

    buffer = buffer.subspan(10);

    if (flags & FEXTRA)

    {

      if (buffer.size() < 2) return -1;

      auto const extra_len = (buffer[1] << 8) | buffer[0];

      if (buffer.size() < extra_len + 2) return -1;

      buffer = buffer.subspan(extra_len + 2);

    }

    if (flags & FNAME)

    {

      if (buffer.empty()) return -1;

      while (buffer[0] != 0)

      {

        buffer = buffer.subspan(1);

        if (buffer.empty()) return -1;

      }

      buffer = buffer.subspan(1);

    }

    if (flags & FCOMMENT)

    {

      if (buffer.empty()) return -1;

      while (buffer[0] != 0)

      {

        buffer = buffer.subspan(1);

        if (buffer.empty()) return -1;

      }

      buffer = buffer.subspan(1);

    }

    if (flags & FHCRC)

    {

      if (buffer.size() < 2) return -1;

      buffer = buffer.subspan(2);

    }

    return static_cast<int>(in.size() - buffer.size());

  }

  } // anonymous namespace

  void inflate_gzip(span<char const> in

    , std::vector<char>& buffer

    , int maximum_size

    , error_code& ec)

  {

    ec.clear();

    TORRENT_ASSERT(maximum_size > 0);

    int const header_len = gzip_header(in);

    if (header_len < 0)

    {

      ec = gzip_errors::invalid_gzip_header;

      return;

    }

    // start off with 4 kilobytes and grow

    // if needed

    unsigned long destlen = 4096;

    int ret = 0;

    in = in.subspan(header_len);

    unsigned long srclen = std::uint32_t(in.size());

    do

    {

      try

      {

        buffer.resize(destlen);

      }

      catch (std::exception const&)

      {

        ec = errors::no_memory;

        return;

      }

      ret = puff(reinterpret_cast<unsigned char*>(buffer.data())

        , &destlen

        , reinterpret_cast<const unsigned char*>(in.data())

        , &srclen);

      // if the destination buffer wasn't large enough, double its

      // size and try again. Unless it's already at its max, in which

      // case we fail

      if (ret == 1) // 1:  output space exhausted before completing inflate

      {

        if (destlen == std::uint32_t(maximum_size))

        {

          ec = gzip_errors::inflated_data_too_large;

          return;

        }

        destlen *= 2;

        if (destlen > std::uint32_t(maximum_size))

          destlen = std::uint32_t(maximum_size);

      }

    } while (ret == 1);

    if (ret != 0)

    {

      switch (ret)

      {

        case   2: ec = gzip_errors::data_did_not_terminate; return;

        case   1: ec = gzip_errors::space_exhausted; return;

        case  -1: ec = gzip_errors::invalid_block_type; return;

        case  -2: ec = gzip_errors::invalid_stored_block_length; return;

        case  -3: ec = gzip_errors::too_many_length_or_distance_codes; return;

        case  -4: ec = gzip_errors::code_lengths_codes_incomplete; return;

        case  -5: ec = gzip_errors::repeat_lengths_with_no_first_length; return;

        case  -6: ec = gzip_errors::repeat_more_than_specified_lengths; return;

        case  -7: ec = gzip_errors::invalid_literal_length_code_lengths; return;

        case  -8: ec = gzip_errors::invalid_distance_code_lengths; return;

        case  -9: ec = gzip_errors::invalid_literal_code_in_block; return;

        case -10: ec = gzip_errors::distance_too_far_back_in_block; return;

        default: ec = gzip_errors::unknown_gzip_error; return;

      }

    }

    if (destlen > buffer.size())

    {

      ec = gzip_errors::unknown_gzip_error;

      return;

    }

    buffer.resize(destlen);

  }

}