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 "compressed_output.h"
  30 #include "parameters.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_data.
  93
  94 // Add an input section.  In this case, we just keep track of the sections.
  95
  96 bool
  97 Output_compressed_section_data::do_add_input_section(Relobj* obj,
  98                                                      unsigned int shndx)
  99 {
 100   this->objects_.push_back(Object_entry(obj, shndx));
 101   return true;
 102 }
 103
 104 // Set the final data size of a compressed section.  This is where
 105 // we actually compress the section data.
 106
 107 void
 108 Output_compressed_section_data::set_final_data_size()
 109 {
 110   // FIXME: assert that relocations have already been applied.
 111
 112   off_t uncompressed_size = 0;
 113   for (std::vector<Object_entry>::iterator it = this->objects_.begin();
 114        it != this->objects_.end();
 115        ++it)
 116     {
 117       it->contents
 118         = it->object->section_contents(it->shndx, &it->length, false);
 119       uncompressed_size += it->length;
 120     }
 121
 122   // (Try to) compress the data.
 123   unsigned long compressed_size;
 124   char* uncompressed_data = new char[uncompressed_size];
 125   off_t pos = 0;
 126   for (std::vector<Object_entry>::const_iterator it = this->objects_.begin();
 127        it != this->objects_.end();
 128        ++it)
 129     {
 130       memcpy(uncompressed_data + pos,
 131              reinterpret_cast<const char*>(it->contents),
 132              it->length);
 133       pos += it->length;
 134     }
 135
 136   bool success = false;
 137   if (options_.zlib_compress_debug_sections())
 138     success = zlib_compress(uncompressed_data, uncompressed_size,
 139                             &this->data_, &compressed_size);
 140   if (success)
 141     {
 142       delete[] uncompressed_data;
 143       this->set_data_size(compressed_size);
 144       this->new_section_name_ = zlib_compressed_suffix(uncompressed_size);
 145     }
 146   else
 147     {
 148       gold_warning(_("Not compressing section data: zlib error"));
 149       gold_assert(this->data_ == NULL);
 150       this->data_ = uncompressed_data;
 151       this->set_data_size(uncompressed_size);
 152     }
 153 }
 154
 155 // Change the name of the output section to reflect it's compressed.
 156 // The layout routines call into this right before finalizing the
 157 // shstrtab.
 158
 159 const char*
 160 Output_compressed_section_data::do_modified_output_section_name(
 161   const char* name)
 162 {
 163   // This mean we never compressed the data.
 164   if (this->new_section_name_.empty())
 165     return NULL;
 166   this->new_section_name_ = std::string(name) + this->new_section_name_;
 167   return this->new_section_name_.c_str();
 168 }
 169
 170 // Write out a compressed section.  If we couldn't compress, we just
 171 // write it out as normal, uncompressed data.
 172
 173 void
 174 Output_compressed_section_data::do_write(Output_file* of)
 175 {
 176   unsigned char* uview = of->get_output_view(this->offset(),
 177                                              this->data_size());
 178   char* view = reinterpret_cast<char*>(uview);
 179   memcpy(view, this->data_, this->data_size());
 180   of->write_output_view(this->offset(), this->data_size(), uview);
 181 }
 182
 183 // Class Output_compressed_string.
 184
 185 // Add an input section.  We don't do anything special here.
 186
 187 template<typename Char_type>
 188 bool
 189 Output_compressed_string<Char_type>::do_add_input_section(Relobj* object,
 190                                                           unsigned int shndx)
 191 {
 192   return Output_merge_string<Char_type>::do_add_input_section(object, shndx);
 193 }
 194
 195 // Set the final data size of a compressed section.  This is where
 196 // we actually compress the section data.
 197
 198 template<typename Char_type>
 199 void
 200 Output_compressed_string<Char_type>::set_final_data_size()
 201 {
 202   // First let the superclass finalize all its data, then write it to
 203   // a buffer.
 204   unsigned long uncompressed_size = this->finalize_merged_data();
 205   char* uncompressed_data = new char[uncompressed_size];
 206   this->stringpool_to_buffer(uncompressed_data, uncompressed_size);
 207
 208   // (Try to) compress the data.
 209   unsigned long compressed_size;
 210   if (options_.zlib_compress_debug_sections()
 211       && zlib_compress(uncompressed_data, uncompressed_size,
 212                        &this->compressed_data_, &compressed_size))
 213     {
 214       this->set_data_size(compressed_size);
 215       // Save some memory.
 216       this->clear_stringpool();
 217       // We will be renaming the section to name.zlib.uncompressed_size.
 218       this->new_section_name_ = zlib_compressed_suffix(uncompressed_size);
 219     }
 220   else
 221     {
 222       this->compressed_data_ = NULL;
 223       this->set_data_size(uncompressed_size);
 224     }
 225
 226   delete[] uncompressed_data;
 227 }
 228
 229 // Change the name of the output section to reflect it's compressed.
 230 // The layout routines call into this right before finalizing the
 231 // shstrtab.
 232
 233 template<typename Char_type>
 234 const char*
 235 Output_compressed_string<Char_type>::do_modified_output_section_name(
 236   const char* name)
 237 {
 238   // This mean we never compressed the data
 239   if (this->new_section_name_.empty())
 240     return NULL;
 241   this->new_section_name_ = std::string(name) + this->new_section_name_;
 242   return this->new_section_name_.c_str();
 243 }
 244
 245 // Write out a compressed string section.  If we couldn't compress,
 246 // we just write out the normal string section.
 247
 248 template<typename Char_type>
 249 void
 250 Output_compressed_string<Char_type>::do_write(Output_file* of)
 251 {
 252   if (this->compressed_data_ == NULL)
 253     Output_merge_string<Char_type>::do_write(of);
 254   else
 255     {
 256       unsigned char* uview = of->get_output_view(this->offset(),
 257                                                  this->data_size());
 258       char* view = reinterpret_cast<char*>(uview);
 259       memcpy(view, this->compressed_data_, this->data_size());
 260       of->write_output_view(this->offset(), this->data_size(), uview);
 261     }
 262 }
 263
 264 // Instantiate the templates we need.
 265
 266 template
 267 class Output_compressed_string<char>;
 268
 269 template
 270 class Output_compressed_string<uint16_t>;
 271
 272 template
 273 class Output_compressed_string<uint32_t>;
 274
 275 } // End namespace gold.