Files.app: Implement md5 hashing over file streams.

chrome/browser/drive/drive_api_util.h

 // 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.
 
 #ifndef CHROME_BROWSER_DRIVE_DRIVE_API_UTIL_H_
 #define CHROME_BROWSER_DRIVE_DRIVE_API_UTIL_H_
 
 #include <string>
 
+#include "base/md5.h"
 #include "base/memory/scoped_ptr.h"
 #include "google_apis/drive/drive_api_error_codes.h"
 #include "google_apis/drive/drive_common_callbacks.h"
 
 class GURL;
 
 namespace base {
 class FilePath;
 class Value;
 }  // namespace base
 
 namespace google_apis {
 class ChangeList;
 class ChangeResource;
 class FileList;
 class FileResource;
 class ResourceEntry;
 }  // namespace google_apis
 
+namespace net {
+class IOBuffer;
+}  // namespace net
+
+namespace storage {
+class FileStreamReader;
+}  // namespace storage
+
 namespace drive {
 namespace util {
 
 // Google Apps MIME types:
 const char kGoogleDocumentMimeType[] = "application/vnd.google-apps.document";
 const char kGoogleDrawingMimeType[] = "application/vnd.google-apps.drawing";
 const char kGooglePresentationMimeType[] =
     "application/vnd.google-apps.presentation";
 const char kGoogleSpreadsheetMimeType[] =
     "application/vnd.google-apps.spreadsheet";
@@ skipping 18 matching lines @@
 std::string TranslateQuery(const std::string& original_query);
 
 // If |resource_id| is in the old resource ID format used by WAPI, converts it
 // into the new format.
 std::string CanonicalizeResourceId(const std::string& resource_id);
 
 // Returns the (base-16 encoded) MD5 digest of the file content at |file_path|,
 // or an empty string if an error is found.
 std::string GetMd5Digest(const base::FilePath& file_path);
 
+// Computes the (base-16 encoded) MD5 digest of data extracted from a file
+// stream.
+class FileStreamMd5Digester {
+ public:
+  typedef base::Callback<void(const std::string&)> ResultCallback;
+
+  FileStreamMd5Digester();
+  ~FileStreamMd5Digester();
+
+  // Computes an MD5 digest of data read from the given |streamReader|.  The
+  // work occurs asynchronously, and the resulting hash is returned via the
+  // |callback|.  If an error occurs, |callback| is called with an empty string.
+  // Only one stream can be processed at a time by each digester.  Do not call
+  // GetMd5Digest before the results of a previous call have been returned.
+  void GetMd5Digest(scoped_ptr<storage::FileStreamReader> stream_reader,
+                    const ResultCallback& callback);
+
+ private:
+  // Kicks off a read of the next chunk from the stream.
+  void ReadNextChunk();
+  // Handles the incoming chunk of data from a stream read.
+  void OnChunkRead(int result);
+
+  // Maximum chunk size for read operations.
+  scoped_ptr<storage::FileStreamReader> reader_;
+  ResultCallback callback_;
+  scoped_refptr<net::IOBuffer> buffer_;
+  base::MD5Context md5_context_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileStreamMd5Digester);
+};
+
 // Returns preferred file extension for hosted documents which have given mime
 // type.
 std::string GetHostedDocumentExtension(const std::string& mime_type);
 
 // Returns true if the given mime type is corresponding to one of known hosted
 // document types.
 bool IsKnownHostedDocumentMimeType(const std::string& mime_type);
 
 // Returns true if the given file path has an extension corresponding to one of
 // hosted document types.
 bool HasHostedDocumentExtension(const base::FilePath& path);
 
 }  // namespace util
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_DRIVE_DRIVE_API_UTIL_H_