From Craig Silverstein: Add support for compressing .debug_str section.

gold/compressed_output.h

@@ -0,0 +1,137 @@
+// compressed_output.h -- compressed output sections for gold  -*- C++ -*-
+
+// Copyright 2007 Free Software Foundation, Inc.
+// Written by Ian Lance Taylor <iant@google.com>.
+
+// This file is part of gold.
+
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+// MA 02110-1301, USA.
+
+// We support compressing .debug_* sections on output.  (And,
+// potentially one day, other sections.)  This is a form of
+// relaxation.  This file adds support for merging and emitting the
+// compressed sections.
+
+#ifndef GOLD_COMPRESSED_OUTPUT_H
+#define GOLD_COMPRESSED_OUTPUT_H
+
+#include <string>
+#include <vector>
+
+#include "output.h"
+#include "merge.h"
+
+namespace gold
+{
+
+class General_options;
+
+// This is used for compressing a section before emitting it in the
+// output file.  This only works for unloaded sections, since it
+// assumes the final section contents are available at
+// set_final_data_size() time.  For loaded sections (those that end up
+// in segments), this is not true; relocations are applied after
+// set_final_data_size() is called.  However, for unloaded sections,
+// we can -- and do -- postpone calling finalize_data_size() until
+// after relocations are applies.
+
+class Output_compressed_section_data : public Output_section_data
+{
+ public:
+  Output_compressed_section_data(uint64_t addralign,
+                                 const General_options& options)
+    : Output_section_data(addralign), options_(options), data_(NULL)
+  { }
+
+ protected:
+  // Add an input section.
+  bool
+  do_add_input_section(Relobj* object, unsigned int shndx);
+
+  // Set the final data size.
+  void
+  set_final_data_size();
+
+  // Change the name of the output section to reflect it's compressed.
+  const char*
+  do_modified_output_section_name(const char* name);
+
+  // Write the data to the file.
+  void
+  do_write(Output_file*);
+
+ private:
+  struct Object_entry
+  {
+    Relobj* object;
+    unsigned int shndx;
+    const unsigned char* contents;
+    off_t length;
+
+    Object_entry(Relobj* o, unsigned int s)
+      : object(o), shndx(s), contents(NULL), length(0)
+    { }
+  };
+
+  const General_options& options_;
+  std::vector<Object_entry> objects_;
+  char* data_;
+  std::string new_section_name_;
+};
+
+// This is a special case for when the output section is a string
+// section and does not have any relocations to apply to it.
+
+template<typename Char_type>
+class Output_compressed_string : public Output_merge_string<Char_type>
+{
+ public:
+  Output_compressed_string(uint64_t addralign,
+                           const General_options& options)
+    : Output_merge_string<Char_type>(addralign),
+      options_(options), compressed_data_(NULL)
+  { }
+
+  ~Output_compressed_string()
+  { delete[] compressed_data_; }
+
+ protected:
+  // Add an input section.
+  bool
+  do_add_input_section(Relobj* object, unsigned int shndx);
+
+  // Set the final data size.  Also compresses the buffer.
+  void
+  set_final_data_size();
+
+  // Change the name of the output section to reflect it's compressed.
+  const char*
+  do_modified_output_section_name(const char* name);
+
+  // Write the data to the file.
+  void
+  do_write(Output_file*);
+
+ private:
+  const General_options& options_;
+  char* compressed_data_;
+  // This is just a buffer to store the section name in "permanent" storage.
+  std::string new_section_name_;
+};
+
+} // End namespace gold.
+
+#endif // !defined(GOLD_COMPRESSED_OUTPUT_H)