Use memory mapped file in courgette_tool

courgette/courgette_tool.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 39 matching lines @@
   vfprintf(stderr, format, args);
   fprintf(stderr, "\n");
   va_end(args);
   exit(1);
 }
 
 // A file reader that calls Problem() on failure.
 class BufferedFileReader {
  public:
   BufferedFileReader(const base::FilePath& file_name, const char* kind) {
-    int64_t file_size = 0;
-    if (!base::GetFileSize(file_name, &file_size))
-      Problem("Can't read %s file.", kind);
-    buffer_.reserve(static_cast<size_t>(file_size));
-    if (!base::ReadFileToString(file_name, &buffer_))
+    if (!buffer_.Initialize(file_name))
       Problem("Can't read %s file.", kind);
   }
-  const uint8_t* data() {
-    return reinterpret_cast<const uint8_t*>(buffer_.data());
-  }
-  size_t length() { return buffer_.length(); }
+  const uint8_t* data() const { return buffer_.data(); }
+  size_t length() const { return buffer_.length(); }
 
  private:
-  std::string buffer_;
+  base::MemoryMappedFile buffer_;
 };
 
 void WriteSinkToFile(const courgette::SinkStream *sink,
                      const base::FilePath& output_file) {
   int count =
       base::WriteFile(output_file,
                            reinterpret_cast<const char*>(sink->Buffer()),
                            static_cast<int>(sink->Length()));
   if (count == -1)
     Problem("Can't write output.");
@@ skipping 432 matching lines @@
         UsageProblem("-gen1[au] <old_file> <new_file> <patch_files_root>");
       DisassembleAdjustDiff(values[0], values[1], values[2],
                             cmd_spread_1_adjusted);
     } else {
       UsageProblem("No operation specified");
     }
   }
 
   return 0;
 }