Fix failure of reading zero-byte files on Drive via StreamReader.

chrome/browser/chromeos/drive/drive_file_stream_reader.cc

Index: chrome/browser/chromeos/drive/drive_file_stream_reader.cc
diff --git a/chrome/browser/chromeos/drive/drive_file_stream_reader.cc b/chrome/browser/chromeos/drive/drive_file_stream_reader.cc
index 4a5530fed586ac4612851e83dd35f89a310901ba..fd84ec3983b47389ff15ed233ace2a9b03c36960 100644
--- a/chrome/browser/chromeos/drive/drive_file_stream_reader.cc
+++ b/chrome/browser/chromeos/drive/drive_file_stream_reader.cc
@@ -339,7 +339,7 @@ int DriveFileStreamReader::Read(net::IOBuffer* buffer, int buffer_length,
 }
 
 void DriveFileStreamReader::InitializeAfterGetFileContentInitialized(
-    const net::HttpByteRange& in_byte_range,
+    const net::HttpByteRange& byte_range,
     const InitializeCompletionCallback& callback,
     FileError error,
     scoped_ptr<ResourceEntry> entry,
@@ -353,8 +353,14 @@ void DriveFileStreamReader::InitializeAfterGetFileContentInitialized(
   }
   DCHECK(entry);
 
-  net::HttpByteRange byte_range = in_byte_range;
-  if (!byte_range.ComputeBounds(entry->file_info().size())) {
+  // Note: both boundary of |byte_range| are inclusive.
+  // Convert it to half-exclusive range with missing bounds filled.

[hashimoto, 2013/12/19 08:53:40]

Is it OK to ignore suffix byte range?

[kinaba, 2013/12/20 03:57:55]

Good catch. Recovered the support for suffix range by
delegating the impl to HttpByteRange except for the corner case.

+  const int64 range_start = byte_range.HasFirstBytePosition() ?
+      byte_range.first_byte_position() : 0;
+  const int64 range_end = byte_range.HasLastBytePosition() ?
+      byte_range.last_byte_position() + 1 : entry->file_info().size();
+
+  if (range_start > range_end || entry->file_info().size() < range_end) {
     // If |byte_range| is invalid (e.g. out of bounds), return with an error.
     // At the same time, we cancel the in-flight downloading operation if
     // needed and and invalidate weak pointers so that we won't
@@ -367,17 +373,12 @@ void DriveFileStreamReader::InitializeAfterGetFileContentInitialized(
     return;
   }
 
-  // Note: both boundary of |byte_range| are inclusive.
-  int64 range_length =
-      byte_range.last_byte_position() - byte_range.first_byte_position() + 1;
-  DCHECK_GE(range_length, 0);
-
   if (local_cache_file_path.empty()) {
     // The file is not cached, and being downloaded.
     DCHECK(!ui_cancel_download_closure.is_null());
     reader_proxy_.reset(
         new internal::NetworkReaderProxy(
-            byte_range.first_byte_position(), range_length,
+            range_start, range_end - range_start,
             base::Bind(&RunTaskOnUIThread, ui_cancel_download_closure)));
     callback.Run(net::OK, entry.Pass());
     return;
@@ -389,11 +390,11 @@ void DriveFileStreamReader::InitializeAfterGetFileContentInitialized(
   util::LocalFileReader* file_reader_ptr = file_reader.get();
   file_reader_ptr->Open(
       local_cache_file_path,
-      byte_range.first_byte_position(),
+      range_start,
       base::Bind(
           &DriveFileStreamReader::InitializeAfterLocalFileOpen,
           weak_ptr_factory_.GetWeakPtr(),
-          range_length,
+          range_end - range_start,
           callback,
           base::Passed(&entry),
           base::Passed(&file_reader)));