[fsp] Add support for truncating files.

chrome/browser/chromeos/file_system_provider/fileapi/provider_async_file_util.cc

 // Copyright 2014 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 "chrome/browser/chromeos/file_system_provider/fileapi/provider_async_file_util.h"
 
 #include "base/callback.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 195 matching lines @@
 }
 
 // Routes the response of CopyEntry to a callback of MoveLocalFile() on the
 // IO thread.
 void OnMoveEntry(const fileapi::AsyncFileUtil::StatusCallback& callback,
                  base::File::Error result) {
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE, base::Bind(callback, result));
 }
 
+// Executes Truncate on the UI thread.
+void TruncateOnUIThread(
+    scoped_ptr<fileapi::FileSystemOperationContext> context,
+    const fileapi::FileSystemURL& url,
+    int64 length,
+    const fileapi::AsyncFileUtil::StatusCallback& callback) {
+  util::FileSystemURLParser parser(url);
+  if (!parser.Parse()) {
+    callback.Run(base::File::FILE_ERROR_INVALID_OPERATION);
+    return;
+  }
+
+  parser.file_system()->Truncate(parser.file_path(), length, callback);
+}
+
+// Routes the response of Truncate back to the IO thread.
+void OnTruncate(const fileapi::AsyncFileUtil::StatusCallback& callback,
+                base::File::Error result) {
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE, base::Bind(callback, result));
+}
+
 }  // namespace
 
 ProviderAsyncFileUtil::ProviderAsyncFileUtil() {}
 
 ProviderAsyncFileUtil::~ProviderAsyncFileUtil() {}
 
 void ProviderAsyncFileUtil::CreateOrOpen(
     scoped_ptr<fileapi::FileSystemOperationContext> context,
     const fileapi::FileSystemURL& url,
     int file_flags,
@@ skipping 79 matching lines @@
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   callback.Run(base::File::FILE_ERROR_ACCESS_DENIED);
 }
 
 void ProviderAsyncFileUtil::Truncate(
     scoped_ptr<fileapi::FileSystemOperationContext> context,
     const fileapi::FileSystemURL& url,
     int64 length,
     const StatusCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  callback.Run(base::File::FILE_ERROR_ACCESS_DENIED);
+  BrowserThread::PostTask(BrowserThread::UI,
+                          FROM_HERE,
+                          base::Bind(&TruncateOnUIThread,
+                                     base::Passed(&context),
+                                     url,
+                                     length,
+                                     base::Bind(&OnTruncate, callback)));
 }
 
 void ProviderAsyncFileUtil::CopyFileLocal(
     scoped_ptr<fileapi::FileSystemOperationContext> context,
     const fileapi::FileSystemURL& src_url,
     const fileapi::FileSystemURL& dest_url,
     CopyOrMoveOption option,
     const CopyFileProgressCallback& progress_callback,
     const StatusCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
@@ skipping 85 matching lines @@
   NOTIMPLEMENTED();
   callback.Run(base::File::FILE_ERROR_INVALID_OPERATION,
                base::File::Info(),
                base::FilePath(),
                scoped_refptr<webkit_blob::ShareableFileReference>());
 }
 
 }  // namespace internal
 }  // namespace file_system_provider
 }  // namespace chromeos