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

base/platform_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/scoped_temp_dir.h"
 #include "base/platform_file.h"
 #include "base/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 193 matching lines @@
     EXPECT_EQ(data_to_write[i], data_read_2[i]);
   for (int i = kTestDataSize; i < kOffsetBeyondEndOfFile; i++)
     EXPECT_EQ(0, data_read_2[i]);
   for (int i = kOffsetBeyondEndOfFile; i < file_size; i++)
     EXPECT_EQ(data_to_write[i - kOffsetBeyondEndOfFile], data_read_2[i]);
 
   // Close the file handle to allow the temp directory to be deleted.
   base::ClosePlatformFile(file);
 }
 
+TEST(PlatformFile, AppendPlatformFile) {
+  base::ScopedTempDir temp_dir;
+  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
+  FilePath file_path = temp_dir.path().AppendASCII("append_file");
+  base::PlatformFile file = base::CreatePlatformFile(
+      file_path,
+      base::PLATFORM_FILE_CREATE | base::PLATFORM_FILE_APPEND,
+      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,

[jar (doing other things), 2013/06/05 16:39:21]

Yes... this is exactly what I was asking for.

nit: Can you similarly adjust the other calls in this file (such as on line
272-275, where they put one arg on multiple lines for no reason without extra
indent, and put multiple args on one line).  This way the file will have a
consistent approach (for future changes).

+      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());
   FilePath file_path = temp_dir.path().AppendASCII("truncate_file");
   base::PlatformFile file = base::CreatePlatformFile(
       file_path,
       base::PLATFORM_FILE_CREATE |
       base::PLATFORM_FILE_READ |
       base::PLATFORM_FILE_WRITE,
       NULL, NULL);
@@ skipping 104 matching lines @@
   EXPECT_EQ(info.last_modified.ToInternalValue(),
             new_last_modified.ToInternalValue());
 #endif
 
   EXPECT_EQ(info.creation_time.ToInternalValue(),
             creation_time.ToInternalValue());
 
   // Close the file handle to allow the temp directory to be deleted.
   base::ClosePlatformFile(file);
 }