Adds a new method ReadUntilComplete to FileStream which ensure that a...

net/base/file_stream.h

 // Copyright (c) 2008 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.
 
 // This file defines FileStream, a basic interface for reading and writing files
 // synchronously or asynchronously with support for seeking to an offset.
 // Note that even when used asynchronously, only one operation is supported at
 // a time.
 
 #ifndef NET_BASE_FILE_STREAM_H_
@@ skipping 63 matching lines @@
   // In the case of an asychronous read, the memory pointed to by |buf| must
   // remain valid until the callback is notified.  However, it is valid to
   // destroy or close the file stream while there is an asynchronous read in
   // progress.  That will cancel the read and allow the buffer to be freed.
   // 
   // This method should not be called if the stream was opened WRITE_ONLY.
   //
   // You can pass NULL as the callback for synchronous I/O.
   int Read(char* buf, int buf_len, CompletionCallback* callback);
 
+  // Performs the same as Read, but ensures that exactly buf_len bytes
+  // are copied into buf.  A partial read may occur, but only as a result of
+  // end-of-file or fatal error.  Returns the number of bytes copied into buf,
+  // 0 if at end-of-file and no bytes have been read into buf yet,
+  // or an error code if the operation could not be performed.
+  int ReadUntilComplete(char *buf, int buf_len);
+
   // Call this method to write data at the current stream position.  Up to
   // buf_len bytes will be written from buf. (In other words, partial writes are
   // allowed.)  Returns the number of bytes written, or an error code if the 
   // operation could not be performed.
   //
   // If opened with PLATFORM_FILE_ASYNC, then a non-null callback
   // must be passed to this method.  In asynchronous mode, if the write could
   // not complete synchronously, then ERR_IO_PENDING is returned, and the
   // callback will be notified on the current thread (via the MessageLoop) when
   // the write has completed.
@@ skipping 18 matching lines @@
 
   base::PlatformFile file_;
   int open_flags_;
 
   DISALLOW_COPY_AND_ASSIGN(FileStream);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_FILE_STREAM_H_