gold/compressed_output.h

   1 // compressed_output.h -- compressed output sections for gold  -*- C++ -*-
   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 // We support compressing .debug_* sections on output.  (And,
  24 // potentially one day, other sections.)  This is a form of
  25 // relaxation.  This file adds support for merging and emitting the
  26 // compressed sections.
  27
  28 #ifndef GOLD_COMPRESSED_OUTPUT_H
  29 #define GOLD_COMPRESSED_OUTPUT_H
  30
  31 #include <string>
  32 #include <vector>
  33
  34 #include "output.h"
  35 #include "merge.h"
  36
  37 namespace gold
  38 {
  39
  40 class General_options;
  41
  42 // This is used for compressing a section before emitting it in the
  43 // output file.  This only works for unloaded sections, since it
  44 // assumes the final section contents are available at
  45 // set_final_data_size() time.  For loaded sections (those that end up
  46 // in segments), this is not true; relocations are applied after
  47 // set_final_data_size() is called.  However, for unloaded sections,
  48 // we can -- and do -- postpone calling finalize_data_size() until
  49 // after relocations are applies.
  50
  51 class Output_compressed_section_data : public Output_section_data
  52 {
  53  public:
  54   Output_compressed_section_data(uint64_t addralign,
  55                                  const General_options& options)
  56     : Output_section_data(addralign), options_(options), data_(NULL)
  57   { }
  58
  59  protected:
  60   // Add an input section.
  61   bool
  62   do_add_input_section(Relobj* object, unsigned int shndx);
  63
  64   // Set the final data size.
  65   void
  66   set_final_data_size();
  67
  68   // Change the name of the output section to reflect it's compressed.
  69   const char*
  70   do_modified_output_section_name(const char* name);
  71
  72   // Write the data to the file.
  73   void
  74   do_write(Output_file*);
  75
  76  private:
  77   struct Object_entry
  78   {
  79     Relobj* object;
  80     unsigned int shndx;
  81     const unsigned char* contents;
  82     off_t length;
  83
  84     Object_entry(Relobj* o, unsigned int s)
  85       : object(o), shndx(s), contents(NULL), length(0)
  86     { }
  87   };
  88
  89   const General_options& options_;
  90   std::vector<Object_entry> objects_;
  91   char* data_;
  92   std::string new_section_name_;
  93 };
  94
  95 // This is a special case for when the output section is a string
  96 // section and does not have any relocations to apply to it.
  97
  98 template<typename Char_type>
  99 class Output_compressed_string : public Output_merge_string<Char_type>
 100 {
 101  public:
 102   Output_compressed_string(uint64_t addralign,
 103                            const General_options& options)
 104     : Output_merge_string<Char_type>(addralign),
 105       options_(options), compressed_data_(NULL)
 106   { }
 107
 108   ~Output_compressed_string()
 109   { delete[] compressed_data_; }
 110
 111  protected:
 112   // Add an input section.
 113   bool
 114   do_add_input_section(Relobj* object, unsigned int shndx);
 115
 116   // Set the final data size.  Also compresses the buffer.
 117   void
 118   set_final_data_size();
 119
 120   // Change the name of the output section to reflect it's compressed.
 121   const char*
 122   do_modified_output_section_name(const char* name);
 123
 124   // Write the data to the file.
 125   void
 126   do_write(Output_file*);
 127
 128  private:
 129   const General_options& options_;
 130   char* compressed_data_;
 131   // This is just a buffer to store the section name in "permanent" storage.
 132   std::string new_section_name_;
 133 };
 134
 135 } // End namespace gold.
 136
 137 #endif // !defined(GOLD_COMPRESSED_OUTPUT_H)