Files.app: Implement md5 hashing over file streams.

chrome/browser/drive/drive_api_util.cc

Index: chrome/browser/drive/drive_api_util.cc
diff --git a/chrome/browser/drive/drive_api_util.cc b/chrome/browser/drive/drive_api_util.cc
index 064f4a2d8740af5dc150982e12f84a2570fe56ca..0b02e2ace41f9b23fa32617fdd8896b4920d237b 100644
--- a/chrome/browser/drive/drive_api_util.cc
+++ b/chrome/browser/drive/drive_api_util.cc
@@ -16,6 +16,9 @@
 #include "base/values.h"
 #include "google_apis/drive/drive_api_parser.h"
 #include "net/base/escape.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "storage/browser/blob/file_stream_reader.h"
 #include "third_party/re2/re2/re2.h"
 #include "url/gurl.h"
 
@@ -163,6 +166,54 @@ std::string GetMd5Digest(const base::FilePath& file_path) {
   return MD5DigestToBase16(digest);
 }
 
+FileStreamMd5Digester::FileStreamMd5Digester()
+    : buffer_(new net::IOBuffer(kBufferSize_)) {
+}
+
+FileStreamMd5Digester::~FileStreamMd5Digester() {
+}
+
+void FileStreamMd5Digester::GetMd5Digest(
+    scoped_ptr<storage::FileStreamReader> stream_reader,
+    const ResultCallback& callback) {
+  reader_ = stream_reader.Pass();
+  callback_ = callback;
+  base::MD5Init(&md5_context_);
+
+  // Start the read/hash.
+  ReadNextChunk();
+}
+
+void FileStreamMd5Digester::ReadNextChunk() {
+  const int result =
+      reader_->Read(buffer_.get(), kBufferSize_,
+                    base::Bind(&FileStreamMd5Digester::OnChunkRead, this));
+  if (result != net::ERR_IO_PENDING) {
+    OnChunkRead(result);
+  }
+}
+
+void FileStreamMd5Digester::OnChunkRead(int result) {
+  if (result < 0) {
+    // Error - just return empty string.
+    callback_.Run("");
+    return;
+  } else if (result == 0) {
+    // EOF.
+    base::MD5Digest digest;
+    base::MD5Final(&digest, &md5_context_);
+    std::string result = MD5DigestToBase16(digest);
+    callback_.Run(result);
+    return;
+  }
+
+  // Read data and digest it.
+  base::MD5Update(&md5_context_, base::StringPiece(buffer_->data(), result));
+
+  // Kick off the next read.
+  ReadNextChunk();

[mtomasz, 2015/02/02 23:47:07]

For large files we will keep the IO thread busy for number of seconds. IIRC this
thread is shared with IPC. While occupying IO thread is not as bad as UI, it may
cause unresponsiveness of the browser. Please check with huge files if browser
is still responsive. IIf it's fine, then let's go with the current solution. If
it's not, then we may want to use a blocking thread pool.

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

Will investigate this today and update with what I find.

+}
+
 std::string GetHostedDocumentExtension(const std::string& mime_type) {
   for (size_t i = 0; i < arraysize(kHostedDocumentKinds); ++i) {
     if (mime_type == kHostedDocumentKinds[i].mime_type)