[Blob] BlobReader class & tests, and removal of all redundant reading.

storage/browser/blob/upload_blob_element_reader.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 "storage/browser/blob/upload_blob_element_reader.h"
+
+#include "net/base/net_errors.h"
+#include "storage/browser/blob/blob_data_handle.h"
+#include "storage/browser/blob/blob_reader.h"
+
+namespace storage {
+
+UploadBlobElementReader::UploadBlobElementReader(
+    scoped_ptr<storage::BlobReader> reader,
+    scoped_ptr<BlobDataHandle> handle)
+    : reader_(reader.Pass()), handle_(handle.Pass()) {}
+
+UploadBlobElementReader::~UploadBlobElementReader() {}
+
+const UploadBlobElementReader*
+UploadBlobElementReader::AsUploadBlobElementReaderForTests() const {
+  return this;
+}
+
+int UploadBlobElementReader::Init(const net::CompletionCallback& callback) {
+  BlobReader::Status status = reader_->CalculateSize(callback);
+  switch (status) {
+    case BlobReader::Status::NET_ERROR:
+      return reader_->net_error();
+    case BlobReader::Status::PENDING_IO:
+      return net::ERR_IO_PENDING;
+    case BlobReader::Status::DONE:
+      return net::OK;
+  }
+  NOTREACHED();
+  return net::ERR_FAILED;
+}
+
+uint64_t UploadBlobElementReader::GetContentLength() const {
+  return reader_->total_size();
+}
+
+uint64_t UploadBlobElementReader::BytesRemaining() const {
+  return reader_->remaining_bytes();
+}
+
+bool UploadBlobElementReader::IsInMemory() const {
+  return reader_->IsInMemory();
+}
+
+int UploadBlobElementReader::Read(net::IOBuffer* buf,
+                                  int buf_length,
+                                  const net::CompletionCallback& callback) {
+  int length = 0;
+  BlobReader::Status status = reader_->Read(buf, buf_length, &length, callback);
+  switch (status) {
+    case BlobReader::Status::NET_ERROR:
+      return reader_->net_error();
+    case BlobReader::Status::PENDING_IO:
+      return net::ERR_IO_PENDING;
+    case BlobReader::Status::DONE:
+      return length;
+  }
+  NOTREACHED();
+  return net::ERR_FAILED;
+}
+
+const std::string& UploadBlobElementReader::uuid() const {
+  return handle_->uuid();
+}
+
+}  // namespace storage