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

net/base/file_stream_posix.cc

 // 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.
 
 // For 64-bit file access (off_t = off64_t, lseek64, etc).
 #define _FILE_OFFSET_BITS 64
 
 #include "net/base/file_stream.h"
 
 #include <sys/types.h>
@@ skipping 136 matching lines @@
     ssize_t res = read(file_, buf, static_cast<size_t>(buf_len));
     if (res == static_cast<ssize_t>(-1)) {
       if (errno == EINTR)
         continue;
       return MapErrorCode(errno);
     }
     return static_cast<int>(res);
   }
 }
 
+int FileStream::ReadUntilComplete(char *buf, int buf_len) {
+  int to_read = buf_len;
+  int bytes_total = 0;
+
+  do {
+    int bytes_read = Read(buf, to_read, NULL);
+    if (bytes_read <= 0) {
+      if (bytes_total == 0)
+        return bytes_read;
+
+      return bytes_total;
+    }
+
+    bytes_total += bytes_read;
+    buf += bytes_read;
+    to_read -= bytes_read;
+  } while (bytes_total < buf_len);
+
+  return bytes_total;
+}
+
 // TODO(deanm): async.
 int FileStream::Write(
     const char* buf, int buf_len, CompletionCallback* callback) {
 
   // read(..., 0) will return 0, which indicates end-of-file.
   DCHECK(buf_len > 0 && buf_len <= SSIZE_MAX);
 
   if (!IsOpen())
     return ERR_UNEXPECTED;
 
   int total_bytes_written = 0;
   size_t len = static_cast<size_t>(buf_len);
   while (total_bytes_written < buf_len) {
     ssize_t res = write(file_, buf, len);
     if (res == static_cast<ssize_t>(-1)) {
       if (errno == EINTR)
         continue;
       return MapErrorCode(errno);
     }
     total_bytes_written += res;
     buf += res;
     len -= res;
   }
   return total_bytes_written;
 }
 
 }  // namespace net