gold/compressed_output.cc

   1 // compressed_output.cc -- manage compressed output sections for gold
   2
   3 // Copyright 2007 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 "compressed_output.h"
  31
  32 namespace gold
  33 {
  34
  35 // Compress UNCOMPRESSED_DATA of size UNCOMPRESSED_SIZE.  Returns true
  36 // if it successfully compressed, false if it failed for any reason
  37 // (including not having zlib support in the library).  If it returns
  38 // true, it allocates memory for the compressed data using new, and
  39 // sets *COMPRESSED_DATA and *COMPRESSED_SIZE to appropriate values.
  40
  41 #ifdef HAVE_ZLIB_H
  42
  43 static bool
  44 zlib_compress(const char* uncompressed_data, unsigned long uncompressed_size,
  45               char** compressed_data, unsigned long* compressed_size)
  46 {
  47   *compressed_size = uncompressed_size + uncompressed_size / 1000 + 128;
  48   *compressed_data = new char[*compressed_size];
  49
  50   int compress_level;
  51   if (parameters->optimization_level() >= 1)
  52     compress_level = 9;
  53   else
  54     compress_level = 1;
  55
  56   int rc = compress2(reinterpret_cast<Bytef*>(*compressed_data),
  57                      compressed_size,
  58                      reinterpret_cast<const Bytef*>(uncompressed_data),
  59                      uncompressed_size,
  60                      compress_level);
  61   if (rc == Z_OK)
  62     return true;
  63   else
  64     {
  65       delete[] *compressed_data;
  66       *compressed_data = NULL;
  67       return false;
  68     }
  69 }
  70
  71 #else // !defined(HAVE_ZLIB_H)
  72
  73 static bool
  74 zlib_compress(const char*, unsigned long, char**, unsigned long*)
  75 {
  76   return false;
  77 }
  78
  79 #endif // !defined(HAVE_ZLIB_H)
  80
  81 // After compressing an output section, we rename it from foo to
  82 // foo.zlib.nnnn, where nnnn is the uncompressed size of the section.
  83
  84 static std::string
  85 zlib_compressed_suffix(unsigned long uncompressed_size)
  86 {
  87   char size_string[64];
  88   snprintf(size_string, sizeof(size_string), "%lu", uncompressed_size);
  89   return std::string(".zlib.") + size_string;
  90 }
  91
  92 // Class Output_compressed_section.
  93
  94 // Set the final data size of a compressed section.  This is where
  95 // we actually compress the section data.
  96
  97 void
  98 Output_compressed_section::set_final_data_size()
  99 {
 100   off_t uncompressed_size = this->postprocessing_buffer_size();
 101
 102   // (Try to) compress the data.
 103   unsigned long compressed_size;
 104   unsigned char* u_uncompressed_data = this->postprocessing_buffer();
 105   char* uncompressed_data = reinterpret_cast<char*>(u_uncompressed_data);
 106
 107   // At this point the contents of all regular input sections will
 108   // have been copied into the postprocessing buffer, and relocations
 109   // will have been applied.  Now we need to copy in the contents of
 110   // anything other than a regular input section.
 111   this->write_to_postprocessing_buffer();
 112
 113   bool success = false;
 114   if (this->options_->zlib_compress_debug_sections())
 115     success = zlib_compress(uncompressed_data, uncompressed_size,
 116                             &this->data_, &compressed_size);
 117   if (success)
 118     {
 119       std::string suffix(zlib_compressed_suffix(uncompressed_size));
 120       this->new_section_name_ = std::string(this->name()) + suffix;
 121       this->set_name(this->new_section_name_.c_str());
 122       this->set_data_size(compressed_size);
 123     }
 124   else
 125     {
 126       gold_warning(_("not compressing section data: zlib error"));
 127       gold_assert(this->data_ == NULL);
 128       this->set_data_size(uncompressed_size);
 129     }
 130 }
 131
 132 // Write out a compressed section.  If we couldn't compress, we just
 133 // write it out as normal, uncompressed data.
 134
 135 void
 136 Output_compressed_section::do_write(Output_file* of)
 137 {
 138   off_t offset = this->offset();
 139   off_t data_size = this->data_size();
 140   unsigned char* view = of->get_output_view(offset, data_size);
 141   if (this->data_ == NULL)
 142     memcpy(view, this->postprocessing_buffer(), data_size);
 143   else
 144     memcpy(view, this->data_, data_size);
 145   of->write_output_view(offset, data_size, view);
 146 }
 147
 148 } // End namespace gold.