Add support for loading pak files from arbitrary file regions.

base/files/file_unittest.cc

 // Copyright (c) 2012 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 "base/file_util.h"
 #include "base/files/file.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 254 matching lines @@
 
 TEST(FileTest, Length) {
   base::ScopedTempDir temp_dir;
   ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
   FilePath file_path = temp_dir.path().AppendASCII("truncate_file");
   File file(file_path,
             base::File::FLAG_CREATE | base::File::FLAG_READ |
                 base::File::FLAG_WRITE);
   ASSERT_TRUE(file.IsValid());
   EXPECT_EQ(0, file.GetLength());
+  EXPECT_EQ(0, base::File::Region(file).offset);
+  EXPECT_EQ(0, base::File::Region(file).size);
 
   // Write "test" to the file.
   char data_to_write[] = "test";
   int kTestDataSize = 4;
   int bytes_written = file.Write(0, data_to_write, kTestDataSize);
   EXPECT_EQ(kTestDataSize, bytes_written);
 
   // Extend the file.
   const int kExtendedFileLength = 10;
   int64 file_size = 0;
   EXPECT_TRUE(file.SetLength(kExtendedFileLength));
   EXPECT_EQ(kExtendedFileLength, file.GetLength());
   EXPECT_TRUE(GetFileSize(file_path, &file_size));
   EXPECT_EQ(kExtendedFileLength, file_size);
+  EXPECT_EQ(0, base::File::Region(file).offset);
+  EXPECT_EQ(kExtendedFileLength, base::File::Region(file).size);
 
   // Make sure the file was zero-padded.
   char data_read[32];
   int bytes_read = file.Read(0, data_read, static_cast<int>(file_size));
   EXPECT_EQ(file_size, bytes_read);
   for (int i = 0; i < kTestDataSize; i++)
     EXPECT_EQ(data_to_write[i], data_read[i]);
   for (int i = kTestDataSize; i < file_size; i++)
     EXPECT_EQ(0, data_read[i]);
 
   // Truncate the file.
   const int kTruncatedFileLength = 2;
   EXPECT_TRUE(file.SetLength(kTruncatedFileLength));
   EXPECT_EQ(kTruncatedFileLength, file.GetLength());
   EXPECT_TRUE(GetFileSize(file_path, &file_size));
   EXPECT_EQ(kTruncatedFileLength, file_size);
+  EXPECT_EQ(0, base::File::Region(file).offset);
+  EXPECT_EQ(kTruncatedFileLength, base::File::Region(file).size);
 
   // Make sure the file was truncated.
   bytes_read = file.Read(0, data_read, kTestDataSize);
   EXPECT_EQ(file_size, bytes_read);
   for (int i = 0; i < file_size; i++)
     EXPECT_EQ(data_to_write[i], data_read[i]);
 }
 
 // Flakily fails: http://crbug.com/86494
 #if defined(OS_ANDROID)
@@ skipping 144 matching lines @@
                    NULL));
   ASSERT_TRUE(dir.IsValid());
 
   base::File::Info info;
   EXPECT_TRUE(dir.GetInfo(&info));
   EXPECT_TRUE(info.is_directory);
   EXPECT_FALSE(info.is_symbolic_link);
   EXPECT_EQ(0, info.size);
 }
 #endif  // defined(OS_WIN)