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// compressed_output.cc -- manage compressed debug sections for gold

// Copyright 2007, 2008, 2010 Free Software Foundation, Inc.

// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation; either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

// MA 02110-1301, USA.

#include "gold.h"

#ifdef HAVE_ZLIB_H

#include <zlib.h>

#endif

#include "parameters.h"

#include "options.h"

#include "compressed_output.h"

namespace gold

{

#ifdef HAVE_ZLIB_H

// Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns true

// if it successfully compressed, false if it failed for any reason

// (including not having zlib support in the library).  If it returns

// true, it allocates memory for the compressed data using new, and

// sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.

// It also writes a header before COMPRESSED_DATA: 4 bytes saying

// "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian

// order.

static bool

zlib_compress(const unsigned char* uncompressed_data,

              unsigned long uncompressed_size,

              unsigned char** compressed_data,

              unsigned long* compressed_size)

{

  const int header_size = 12;

  *compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;

  *compressed_data = new unsigned char[*compressed_size + header_size];

  int compress_level;

  if (parameters->options().optimize() >= 1)

    compress_level = 9;

  else

    compress_level = 1;

  int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,

                     compressed_size,

                     reinterpret_cast<const Bytef*>(uncompressed_data),

                     uncompressed_size,

                     compress_level);

  if (rc == Z_OK)

    {

      memcpy(*compressed_data, "ZLIB", 4);

      elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,

                                                 uncompressed_size);

      *compressed_size += header_size;

      return true;

    }

  else

    {

      delete[] *compressed_data;

      *compressed_data = NULL;

      return false;

    }

}

// Decompress COMPRESSED_DATA of size COMPRESSED_SIZE, into a buffer

// UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns TRUE if it

// decompressed successfully, false if it failed.  The buffer, of

// appropriate size, is provided by the caller, and is typically part

// of the memory-mapped output file.

static bool

zlib_decompress(const unsigned char* compressed_data,

                unsigned long compressed_size,

                unsigned char* uncompressed_data,

                unsigned long uncompressed_size)

{

  z_stream strm;

  int rc;

  /* It is possible the section consists of several compressed

     buffers concatenated together, so we uncompress in a loop.  */

  strm.zalloc = NULL;

  strm.zfree = NULL;

  strm.opaque = NULL;

  strm.avail_in = compressed_size;

  strm.next_in = const_cast<Bytef*>(compressed_data);

  strm.avail_out = uncompressed_size;

  rc = inflateInit(&strm);

  while (strm.avail_in > 0)

    {

      if (rc != Z_OK)

        return false;

      strm.next_out = ((Bytef*) uncompressed_data

                       + (uncompressed_size - strm.avail_out));

      rc = inflate(&strm, Z_FINISH);

      if (rc != Z_STREAM_END)

        return false;

      rc = inflateReset(&strm);

    }

  rc = inflateEnd(&strm);

  if (rc != Z_OK || strm.avail_out != 0)

    return false;

  return true;

}

#else // !defined(HAVE_ZLIB_H)

static bool

zlib_compress(const unsigned char*, unsigned long,

              unsigned char**, unsigned long*)

{

  return false;

}

static bool

zlib_decompress(const unsigned char*, unsigned long,

                unsigned char*, unsigned long)

{

  return false;

}

#endif // !defined(HAVE_ZLIB_H)

// Read the compression header of a compressed debug section and return

// the uncompressed size.

uint64_t

get_uncompressed_size(const unsigned char* compressed_data,

                      section_size_type compressed_size)

{

  const unsigned int zlib_header_size = 12;

  /* Verify the compression header.  Currently, we support only zlib

     compression, so it should be "ZLIB" followed by the uncompressed

     section size, 8 bytes in big-endian order.  */

  if (compressed_size >= zlib_header_size

      && strncmp(reinterpret_cast<const char*>(compressed_data),

                 "ZLIB", 4) == 0)

    return elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);

  return -1ULL;

}

// Decompress a compressed debug section directly into the output file.

bool

decompress_input_section(const unsigned char* compressed_data,

                         unsigned long compressed_size,

                         unsigned char* uncompressed_data,

                         unsigned long uncompressed_size)

{

  const unsigned int zlib_header_size = 12;

  /* Verify the compression header.  Currently, we support only zlib

     compression, so it should be "ZLIB" followed by the uncompressed

     section size, 8 bytes in big-endian order.  */

  if (compressed_size >= zlib_header_size

      && strncmp(reinterpret_cast<const char*>(compressed_data),

                 "ZLIB", 4) == 0)

    {

      unsigned long uncompressed_size_check =

          elfcpp::Swap_unaligned<64, true>::readval(compressed_data + 4);

      gold_assert(uncompressed_size_check == uncompressed_size);

      return zlib_decompress(compressed_data + zlib_header_size,

                             compressed_size - zlib_header_size,

                             uncompressed_data,

                             uncompressed_size);

    }

  return false;

}

// Class Output_compressed_section.

// Set the final data size of a compressed section.  This is where

// we actually compress the section data.

void

Output_compressed_section::set_final_data_size()

{

  off_t uncompressed_size = this->postprocessing_buffer_size();

  // (Try to) compress the data.

  unsigned long compressed_size;

  unsigned char* uncompressed_data = this->postprocessing_buffer();

  // At this point the contents of all regular input sections will

  // have been copied into the postprocessing buffer, and relocations

  // will have been applied.  Now we need to copy in the contents of

  // anything other than a regular input section.

  this->write_to_postprocessing_buffer();

  bool success = false;

  if (strcmp(this->options_->compress_debug_sections(), "zlib") == 0)

    success = zlib_compress(uncompressed_data, uncompressed_size,

                            &this->data_, &compressed_size);

  if (success)

    {

      // This converts .debug_foo to .zdebug_foo

      this->new_section_name_ = std::string(".z") + (this->name() + 1);

      this->set_name(this->new_section_name_.c_str());

      this->set_data_size(compressed_size);

    }

  else

    {

      gold_warning(_("not compressing section data: zlib error"));

      gold_assert(this->data_ == NULL);

      this->set_data_size(uncompressed_size);

    }

}

// Write out a compressed section.  If we couldn't compress, we just

// write it out as normal, uncompressed data.

void

Output_compressed_section::do_write(Output_file* of)

{

  off_t offset = this->offset();

  off_t data_size = this->data_size();

  unsigned char* view = of->get_output_view(offset, data_size);

  if (this->data_ == NULL)

    memcpy(view, this->postprocessing_buffer(), data_size);

  else

    memcpy(view, this->data_, data_size);

  of->write_output_view(offset, data_size, view);

}

} // End namespace gold.