Support read/write memory-mapped files.

base/files/memory_mapped_file_unittest.cc

Index: base/files/memory_mapped_file_unittest.cc
diff --git a/base/files/memory_mapped_file_unittest.cc b/base/files/memory_mapped_file_unittest.cc
index 396ab72fbcb91a71795704747d130f6f0fb569cb..4f2b4dbb1c89c2c5f3566004bfde449a64cfc127 100644
--- a/base/files/memory_mapped_file_unittest.cc
+++ b/base/files/memory_mapped_file_unittest.cc
@@ -170,6 +170,74 @@ TEST_F(MemoryMappedFileTest, MapLargePartialRegionInTheMiddle) {
   ASSERT_TRUE(CheckBufferContents(map.data(), kPartialSize, kOffset));
 }
 
+TEST_F(MemoryMappedFileTest, WriteableFile) {
+  const size_t kFileSize = 127;
+  CreateTemporaryTestFile(kFileSize);
+
+  {
+    MemoryMappedFile map;
+    map.Initialize(temp_file_path(), MemoryMappedFile::READ_WRITE);
+    ASSERT_EQ(kFileSize, map.length());
+    ASSERT_TRUE(map.data() != NULL);

[danakj, 2016/04/25 21:26:17]

nullptr

[bcwhite, 2016/04/26 00:08:46]

Done here and elsewhere in file.

+    EXPECT_TRUE(map.IsValid());
+    ASSERT_TRUE(CheckBufferContents(map.data(), kFileSize, 0));
+
+    uint8_t* bytes = map.data();
+    bytes[0] = 'B';
+    bytes[1] = 'a';
+    bytes[2] = 'r';
+    bytes[kFileSize - 1] = '!';
+    EXPECT_FALSE(CheckBufferContents(map.data(), kFileSize, 0));
+    EXPECT_TRUE(CheckBufferContents(map.data() + 3, kFileSize - 4, 3));
+  }
+
+  int64_t file_size;
+  ASSERT_TRUE(GetFileSize(temp_file_path(), &file_size));
+  EXPECT_EQ(static_cast<int64_t>(kFileSize), file_size);
+
+  std::string contents;
+  ASSERT_TRUE(ReadFileToString(temp_file_path(), &contents));
+  EXPECT_EQ("Bar", contents.substr(0, 3));
+  EXPECT_EQ("!", contents.substr(kFileSize - 1, 1));
+}
+
+TEST_F(MemoryMappedFileTest, ExtendableFile) {
+  const size_t kFileSize = 127;
+  const size_t kFileExtend = 100;
+  CreateTemporaryTestFile(kFileSize);
+
+  {
+    File file(temp_file_path(),
+              File::FLAG_OPEN | File::FLAG_READ | File::FLAG_WRITE);
+    MemoryMappedFile::Region region = {0, kFileSize + kFileExtend};
+    MemoryMappedFile map;
+    map.Initialize(std::move(file), region,
+                   MemoryMappedFile::READ_WRITE_EXTEND);
+    EXPECT_EQ(kFileSize + kFileExtend, map.length());
+    ASSERT_TRUE(map.data() != NULL);

[danakj, 2016/04/25 21:26:17]

nullptr

[bcwhite, 2016/04/26 00:08:46]

Done.

+    EXPECT_TRUE(map.IsValid());
+    ASSERT_TRUE(CheckBufferContents(map.data(), kFileSize, 0));
+
+    uint8_t* bytes = map.data();
+    EXPECT_EQ(0, bytes[kFileSize + 0]);
+    EXPECT_EQ(0, bytes[kFileSize + 1]);
+    EXPECT_EQ(0, bytes[kFileSize + 2]);
+    bytes[kFileSize + 0] = 'B';
+    bytes[kFileSize + 1] = 'A';
+    bytes[kFileSize + 2] = 'Z';
+    EXPECT_TRUE(CheckBufferContents(map.data(), kFileSize, 0));
+  }
+
+  int64_t file_size;
+  ASSERT_TRUE(GetFileSize(temp_file_path(), &file_size));
+  EXPECT_LE(static_cast<int64_t>(kFileSize + 3), file_size);
+  EXPECT_GE(static_cast<int64_t>(kFileSize + kFileExtend), file_size);
+
+  std::string contents;
+  ASSERT_TRUE(ReadFileToString(temp_file_path(), &contents));
+  EXPECT_EQ("BAZ", contents.substr(kFileSize, 3));
+}
+
 }  // namespace
 
 }  // namespace base