Adds truncate to FileStream.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/39301

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@11245 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 73 insertions, 0 deletions

diff --git a/net/base/file_stream.h b/net/base/file_stream.h
index 28b40e7..9447c07 100644
--- a/net/base/file_stream.h
+++ b/net/base/file_stream.h
@@ -109,6 +109,11 @@ class FileStream {
   // You can pass NULL as the callback for synchronous I/O.
   int Write(const char* buf, int buf_len, CompletionCallback* callback);
 
+  // Truncates the file to be |bytes| length. This is only valid for writable
+  // files. After truncation the file stream is positioned at |bytes|. The new
+  // position is retured, or a value < 0 on error.
+  int64 Truncate(int64 bytes);
+
  private:
   class AsyncContext;
   friend class AsyncContext;
diff --git a/net/base/file_stream_posix.cc b/net/base/file_stream_posix.cc
index 34f7889..d7f4811 100644
--- a/net/base/file_stream_posix.cc
+++ b/net/base/file_stream_posix.cc
@@ -201,4 +201,21 @@ int FileStream::Write(
   return total_bytes_written;
 }
 
+int64 FileStream::Truncate(int64 bytes) {
+  if (!IsOpen())
+    return ERR_UNEXPECTED;
+
+  // We better be open for reading.
+  DCHECK(open_flags_ & base::PLATFORM_FILE_WRITE);
+
+  // Seek to the position to truncate from.
+  int64 seek_position = Seek(FROM_BEGIN, bytes);
+  if (seek_position != bytes)
+    return ERR_UNEXPECTED;
+
+  // And truncate the file.
+  int result = ftruncate(file_, bytes);
+  return result == 0 ? seek_position : MapErrorCode(errno);
+}
+
 }  // namespace net
diff --git a/net/base/file_stream_unittest.cc b/net/base/file_stream_unittest.cc
index 318eb93..966b9ff 100644
--- a/net/base/file_stream_unittest.cc
+++ b/net/base/file_stream_unittest.cc
@@ -406,4 +406,31 @@ TEST_F(FileStreamTest, BasicReadWrite) {
   EXPECT_EQ(kTestDataSize * 2, file_size);
 }
 
+// Tests truncating a file.
+TEST_F(FileStreamTest, Truncate) {
+  int flags = base::PLATFORM_FILE_CREATE_ALWAYS | base::PLATFORM_FILE_WRITE;
+
+  net::FileStream write_stream;
+  ASSERT_EQ(net::OK, write_stream.Open(temp_file_path(), flags));
+
+  // Write some data to the file.
+  const char test_data[] = "0123456789";
+  write_stream.Write(test_data, arraysize(test_data), NULL);
+
+  // Truncate the file.
+  ASSERT_EQ(4, write_stream.Truncate(4));
+
+  // Write again.
+  write_stream.Write(test_data, 4, NULL);
+
+  // Close the stream.
+  write_stream.Close();
+
+  // Read in the contents and make sure we get back what we expected.
+  std::string read_contents;
+  file_util::ReadFileToString(temp_file_path(), &read_contents);
+
+  ASSERT_TRUE(read_contents == "01230123");
+}
+
 // TODO(erikkay): more READ_WRITE tests?
diff --git a/net/base/file_stream_win.cc b/net/base/file_stream_win.cc
index 0a6c201..93a3fd9 100644
--- a/net/base/file_stream_win.cc
+++ b/net/base/file_stream_win.cc
@@ -287,4 +287,28 @@ int FileStream::Write(
   return rv;
 }
 
+int64 FileStream::Truncate(int64 bytes) {
+  if (!IsOpen())
+    return ERR_UNEXPECTED;
+
+  // We better be open for reading.
+  DCHECK(open_flags_ & base::PLATFORM_FILE_WRITE);
+
+  // Seek to the position to truncate from.
+  int64 seek_position = Seek(FROM_BEGIN, bytes);
+  if (seek_position != bytes)
+    return ERR_UNEXPECTED;
+
+  // And truncate the file.
+  BOOL result = SetEndOfFile(file_);
+  if (!result) {
+    DWORD error = GetLastError();
+    LOG(WARNING) << "SetEndOfFile failed: " << error;
+    return MapErrorCode(error);
+  }
+
+  // Success.
+  return seek_position;
+}
+
 }  // namespace net