Add an "append flag" to base::PlatformFile.

base/platform_file_unittest.cc

Index: base/platform_file_unittest.cc
diff --git a/base/platform_file_unittest.cc b/base/platform_file_unittest.cc
index 748387610f0436ca3ee90147e81dd3cc2482e114..203e28446c217cb28072ae1fbcd8402126bf2439 100644
--- a/base/platform_file_unittest.cc
+++ b/base/platform_file_unittest.cc
@@ -211,6 +211,59 @@ TEST(PlatformFile, ReadWritePlatformFile) {
   base::ClosePlatformFile(file);
 }
 
+TEST(PlatformFile, AppendPlatformFile) {
+  base::ScopedTempDir temp_dir;
+  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
+  FilePath file_path = temp_dir.path().AppendASCII("read_write_file");
+  base::PlatformFile file = base::CreatePlatformFile(
+      file_path,
+      base::PLATFORM_FILE_CREATE |
+      base::PLATFORM_FILE_READ |
+      base::PLATFORM_FILE_WRITE,
+      NULL, NULL);
+  EXPECT_NE(base::kInvalidPlatformFileValue, file);
+
+  char data_to_write[] = "test";
+  const int kTestDataSize = 4;
+
+  // Write 0 bytes to the file.
+  int bytes_written = WriteFully(file, 0, data_to_write, 0);
+  EXPECT_EQ(0, bytes_written);
+
+  // Write "test" to the file.
+  bytes_written = WriteFully(file, 0, data_to_write, kTestDataSize);
+  EXPECT_EQ(kTestDataSize, bytes_written);
+
+  base::ClosePlatformFile(file);
+  file = base::CreatePlatformFile(
+      file_path,
+      base::PLATFORM_FILE_OPEN |
+      base::PLATFORM_FILE_READ |
+      base::PLATFORM_FILE_APPEND,
+      NULL, NULL);
+  EXPECT_NE(base::kInvalidPlatformFileValue, file);
+  if (file == base::kInvalidPlatformFileValue) {
+    printf("errno: %d\n", errno);
+  }
+
+  char append_data_to_write[] = "78";
+  const int kAppendDataSize = 2;
+
+  // Append "test" to the file.
+  bytes_written = WriteFully(file, 0, append_data_to_write, kAppendDataSize);
+  EXPECT_EQ(2, bytes_written);
+
+  // Read the entire file
+  char data_read_1[32];
+  int bytes_read = ReadFully(file, 0, data_read_1,
+                             kTestDataSize + kAppendDataSize);
+  EXPECT_EQ(6, bytes_read);
+
+  // Close the file handle to allow the temp directory to be deleted.
+  base::ClosePlatformFile(file);
+}
+
+
 TEST(PlatformFile, TruncatePlatformFile) {
   base::ScopedTempDir temp_dir;
   ASSERT_TRUE(temp_dir.CreateUniqueTempDir());