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