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 static bool
  42 zlib_compress(const char* uncompressed_data, unsigned long uncompressed_size,
  43               char** compressed_data, unsigned long* compressed_size)
  44 {
  45 #ifndef HAVE_ZLIB_H
  46   return false;
  47 #else
  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 #endif  // #ifdef HAVE_ZLIB_H
  71 }
  72
  73 // After compressing an output section, we rename it from foo to
  74 // foo.zlib.nnnn, where nnnn is the uncompressed size of the section.
  75
  76 static std::string
  77 zlib_compressed_suffix(unsigned long uncompressed_size)
  78 {
  79   char size_string[64];
  80   snprintf(size_string, sizeof(size_string), "%lu", uncompressed_size);
  81   return std::string(".zlib.") + size_string;
  82 }
  83
  84 // Class Output_compressed_section_data.
  85
  86 // Add an input section.  In this case, we just keep track of the sections.
  87
  88 bool
  89 Output_compressed_section_data::do_add_input_section(Relobj* obj,
  90                                                      unsigned int shndx)
  91 {
  92   this->objects_.push_back(Object_entry(obj, shndx));
  93   return true;
  94 }
  95
  96 // Set the final data size of a compressed section.  This is where
  97 // we actually compress the section data.
  98
  99 void
 100 Output_compressed_section_data::set_final_data_size()
 101 {
 102   // FIXME: assert that relocations have already been applied.
 103
 104   off_t uncompressed_size = 0;
 105   for (std::vector<Object_entry>::iterator it = this->objects_.begin();
 106        it != this->objects_.end();
 107        ++it)
 108     {
 109       it->contents
 110         = it->object->section_contents(it->shndx, &it->length, false);
 111       uncompressed_size += it->length;
 112     }
 113
 114   // (Try to) compress the data.
 115   unsigned long compressed_size;
 116   char* uncompressed_data = new char[uncompressed_size];
 117   off_t pos = 0;
 118   for (std::vector<Object_entry>::const_iterator it = this->objects_.begin();
 119        it != this->objects_.end();
 120        ++it)
 121     {
 122       memcpy(uncompressed_data + pos,
 123              reinterpret_cast<const char*>(it->contents),
 124              it->length);
 125       pos += it->length;
 126     }
 127
 128   bool success = false;
 129   if (options_.zlib_compress_debug_sections())
 130     success = zlib_compress(uncompressed_data, uncompressed_size,
 131                             &this->data_, &compressed_size);
 132   if (success)
 133     {
 134       delete[] uncompressed_data;
 135       this->set_data_size(compressed_size);
 136       this->new_section_name_ = zlib_compressed_suffix(uncompressed_size);
 137     }
 138   else
 139     {
 140       gold_warning(_("Not compressing section data: zlib error"));
 141       gold_assert(this->data_ == NULL);
 142       this->data_ = uncompressed_data;
 143       this->set_data_size(uncompressed_size);
 144     }
 145 }
 146
 147 // Change the name of the output section to reflect it's compressed.
 148 // The layout routines call into this right before finalizing the
 149 // shstrtab.
 150
 151 const char*
 152 Output_compressed_section_data::do_modified_output_section_name(
 153   const char* name)
 154 {
 155   // This mean we never compressed the data.
 156   if (this->new_section_name_.empty())
 157     return NULL;
 158   this->new_section_name_ = std::string(name) + this->new_section_name_;
 159   return this->new_section_name_.c_str();
 160 }
 161
 162 // Write out a compressed section.  If we couldn't compress, we just
 163 // write it out as normal, uncompressed data.
 164
 165 void
 166 Output_compressed_section_data::do_write(Output_file* of)
 167 {
 168   unsigned char* uview = of->get_output_view(this->offset(),
 169                                              this->data_size());
 170   char* view = reinterpret_cast<char*>(uview);
 171   memcpy(view, this->data_, this->data_size());
 172   of->write_output_view(this->offset(), this->data_size(), uview);
 173 }
 174
 175 // Class Output_compressed_string.
 176
 177 // Add an input section.  We don't do anything special here.
 178
 179 template<typename Char_type>
 180 bool
 181 Output_compressed_string<Char_type>::do_add_input_section(Relobj* object,
 182                                                           unsigned int shndx)
 183 {
 184   return Output_merge_string<Char_type>::do_add_input_section(object, shndx);
 185 }
 186
 187 // Set the final data size of a compressed section.  This is where
 188 // we actually compress the section data.
 189
 190 template<typename Char_type>
 191 void
 192 Output_compressed_string<Char_type>::set_final_data_size()
 193 {
 194   // First let the superclass finalize all its data, then write it to
 195   // a buffer.
 196   unsigned long uncompressed_size = this->finalize_merged_data();
 197   char* uncompressed_data = new char[uncompressed_size];
 198   this->stringpool_to_buffer(uncompressed_data, uncompressed_size);
 199
 200   // (Try to) compress the data.
 201   unsigned long compressed_size;
 202   if (options_.zlib_compress_debug_sections()
 203       && zlib_compress(uncompressed_data, uncompressed_size,
 204                        &this->compressed_data_, &compressed_size))
 205     {
 206       this->set_data_size(compressed_size);
 207       // Save some memory.
 208       this->clear_stringpool();
 209       // We will be renaming the section to name.zlib.uncompressed_size.
 210       this->new_section_name_ = zlib_compressed_suffix(uncompressed_size);
 211     }
 212   else
 213     {
 214       this->compressed_data_ = NULL;
 215       this->set_data_size(uncompressed_size);
 216     }
 217
 218   delete[] uncompressed_data;
 219 }
 220
 221 // Change the name of the output section to reflect it's compressed.
 222 // The layout routines call into this right before finalizing the
 223 // shstrtab.
 224
 225 template<typename Char_type>
 226 const char*
 227 Output_compressed_string<Char_type>::do_modified_output_section_name(
 228   const char* name)
 229 {
 230   // This mean we never compressed the data
 231   if (this->new_section_name_.empty())
 232     return NULL;
 233   this->new_section_name_ = std::string(name) + this->new_section_name_;
 234   return this->new_section_name_.c_str();
 235 }
 236
 237 // Write out a compressed string section.  If we couldn't compress,
 238 // we just write out the normal string section.
 239
 240 template<typename Char_type>
 241 void
 242 Output_compressed_string<Char_type>::do_write(Output_file* of)
 243 {
 244   if (this->compressed_data_ == NULL)
 245     Output_merge_string<Char_type>::do_write(of);
 246   else
 247     {
 248       unsigned char* uview = of->get_output_view(this->offset(),
 249                                                  this->data_size());
 250       char* view = reinterpret_cast<char*>(uview);
 251       memcpy(view, this->compressed_data_, this->data_size());
 252       of->write_output_view(this->offset(), this->data_size(), uview);
 253     }
 254 }
 255
 256 // Instantiate the templates we need.
 257
 258 template
 259 class Output_compressed_string<char>;
 260
 261 template
 262 class Output_compressed_string<uint16_t>;
 263
 264 template
 265 class Output_compressed_string<uint32_t>;
 266
 267 } // End namespace gold.