Revert of mojo filesystem: Simplify full file reading/writing.

components/filesystem/file_impl.cc

 // Copyright 2015 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 "components/filesystem/file_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <limits>
 #include <utility>
@@ skipping 76 matching lines @@
   if (num_bytes_read < 0) {
     callback.Run(FileError::FAILED, mojo::Array<uint8_t>());
     return;
   }
 
   DCHECK_LE(static_cast<size_t>(num_bytes_read), num_bytes_to_read);
   bytes_read.resize(static_cast<size_t>(num_bytes_read));
   callback.Run(FileError::OK, std::move(bytes_read));
 }
 
+void FileImpl::ReadEntireFile(const ReadEntireFileCallback& callback) {
+  if (!file_.IsValid()) {
+    callback.Run(GetError(file_), mojo::Array<uint8_t>());
+    return;
+  }
+
+  // Seek to the front of the file.
+  if (file_.Seek(base::File::FROM_BEGIN, 0) == -1) {
+    callback.Run(FileError::FAILED, mojo::Array<uint8_t>());
+    return;
+  }
+
+  std::string contents;
+  const int kBufferSize = 1 << 16;
+  scoped_ptr<char[]> buf(new char[kBufferSize]);
+  size_t len;
+  while ((len = file_.ReadAtCurrentPos(buf.get(), kBufferSize)) > 0)
+    contents.append(buf.get(), len);
+
+  callback.Run(FileError::OK, mojo::Array<uint8_t>::From(contents));
+}
+
 // TODO(vtl): Move the implementation to a thread pool.
 void FileImpl::Write(mojo::Array<uint8_t> bytes_to_write,
                      int64_t offset,
                      Whence whence,
                      const WriteCallback& callback) {
   DCHECK(!bytes_to_write.is_null());
   if (!file_.IsValid()) {
     callback.Run(GetError(file_), 0);
     return;
   }
@@ skipping 207 matching lines @@
       new_file.TakePlatformFile(), &mojo_handle);
   if (create_result != MOJO_RESULT_OK) {
     callback.Run(FileError::FAILED, ScopedHandle());
     return;
   }
 
   callback.Run(FileError::OK, ScopedHandle(mojo::Handle(mojo_handle)));
 }
 
 }  // namespace filesystem