gold/compressed_output.cc

   1 // compressed_output.cc -- manage compressed output sections for gold
   2
   3 // Copyright 2007, 2008 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #ifdef HAVE_ZLIB_H
  26 #include <zlib.h>
  27 #endif
  28
  29 #include "parameters.h"
  30 #include "options.h"
  31 #include "compressed_output.h"
  32
  33 namespace gold
  34 {
  35
  36 // Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns true
  37 // if it successfully compressed, false if it failed for any reason
  38 // (including not having zlib support in the library).  If it returns
  39 // true, it allocates memory for the compressed data using new, and
  40 // sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
  41 // It also writes a header before COMPRESSED_DATA: 4 bytes saying
  42 // "ZLIB", and 8 bytes indicating the uncompressed size, in big-endian
  43 // order.
  44
  45 #ifdef HAVE_ZLIB_H
  46
  47 static bool
  48 zlib_compress(const unsigned char* uncompressed_data,
  49               unsigned long uncompressed_size,
  50               unsigned char** compressed_data,
  51               unsigned long* compressed_size)
  52 {
  53   const int header_size = 12;
  54   *compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
  55   *compressed_data = new unsigned char[*compressed_size + header_size];
  56
  57   int compress_level;
  58   if (parameters->options().optimize() >= 1)
  59     compress_level = 9;
  60   else
  61     compress_level = 1;
  62
  63   int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data) + header_size,
  64                      compressed_size,
  65                      reinterpret_cast<const Bytef*>(uncompressed_data),
  66                      uncompressed_size,
  67                      compress_level);
  68   if (rc == Z_OK)
  69     {
  70       memcpy(*compressed_data, "ZLIB", 4);
  71       elfcpp::Swap_unaligned<64, true>::writeval(*compressed_data + 4,
  72                                                  uncompressed_size);
  73       *compressed_size += header_size;
  74       return true;
  75     }
  76   else
  77     {
  78       delete[] *compressed_data;
  79       *compressed_data = NULL;
  80       return false;
  81     }
  82 }
  83
  84 #else // !defined(HAVE_ZLIB_H)
  85
  86 static bool
  87 zlib_compress(const unsigned char*, unsigned long,
  88               unsigned char**, unsigned long*)
  89 {
  90   return false;
  91 }
  92
  93 #endif // !defined(HAVE_ZLIB_H)
  94
  95 // Class Output_compressed_section.
  96
  97 // Set the final data size of a compressed section.  This is where
  98 // we actually compress the section data.
  99
 100 void
 101 Output_compressed_section::set_final_data_size()
 102 {
 103   off_t uncompressed_size = this->postprocessing_buffer_size();
 104
 105   // (Try to) compress the data.
 106   unsigned long compressed_size;
 107   unsigned char* uncompressed_data = this->postprocessing_buffer();
 108
 109   // At this point the contents of all regular input sections will
 110   // have been copied into the postprocessing buffer, and relocations
 111   // will have been applied.  Now we need to copy in the contents of
 112   // anything other than a regular input section.
 113   this->write_to_postprocessing_buffer();
 114
 115   bool success = false;
 116   if (strcmp(this->options_->compress_debug_sections(), "zlib") == 0)
 117     success = zlib_compress(uncompressed_data, uncompressed_size,
 118                             &this->data_, &compressed_size);
 119   if (success)
 120     {
 121       // This converts .debug_foo to .zdebug_foo
 122       this->new_section_name_ = std::string(".z") + (this->name() + 1);
 123       this->set_name(this->new_section_name_.c_str());
 124       this->set_data_size(compressed_size);
 125     }
 126   else
 127     {
 128       gold_warning(_("not compressing section data: zlib error"));
 129       gold_assert(this->data_ == NULL);
 130       this->set_data_size(uncompressed_size);
 131     }
 132 }
 133
 134 // Write out a compressed section.  If we couldn't compress, we just
 135 // write it out as normal, uncompressed data.
 136
 137 void
 138 Output_compressed_section::do_write(Output_file* of)
 139 {
 140   off_t offset = this->offset();
 141   off_t data_size = this->data_size();
 142   unsigned char* view = of->get_output_view(offset, data_size);
 143   if (this->data_ == NULL)
 144     memcpy(view, this->postprocessing_buffer(), data_size);
 145   else
 146     memcpy(view, this->data_, data_size);
 147   of->write_output_view(offset, data_size, view);
 148 }
 149
 150 } // End namespace gold.