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 base::RefCountedThreadSafe<FileStreamMd5Digester> {
+ public:
+  typedef base::Callback<void(const std::string&)> ResultCallback;
+
+  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:
+  // Private for RefCountedThreadSafe.
+  ~FileStreamMd5Digester();
+
+  // 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.
+  static const int kBufferSize_ = 512 * 1024;  // 512 kB.

[mtomasz, 2015/02/02 23:47:08]

nit: Yeah, I'd suggest to move it to an anonymous namespace in .cc file. We
always do that and try to make headers as small as possible (because we already
have tons of them). We usually move everything what's possible from private
section to anonymous namespace.

[Ben Kwa, 2015/02/03 16:32:19]

Done.

+  scoped_ptr<storage::FileStreamReader> reader_;
+  ResultCallback callback_;
+  scoped_refptr<net::IOBuffer> buffer_;
+  base::MD5Context md5_context_;
+
+  friend class base::RefCountedThreadSafe<FileStreamMd5Digester>;
+  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_