Base: WritePlatformFile now retries the operation if

base/platform_file_posix.cc

 // Copyright (c) 2011 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.
 
 #include "base/platform_file.h"
 
 #include <fcntl.h>
 #include <errno.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ skipping 137 matching lines @@
 
 int ReadPlatformFile(PlatformFile file, int64 offset, char* data, int size) {
   if (file < 0)
     return -1;
 
   return HANDLE_EINTR(pread(file, data, size, offset));
 }
 
 int WritePlatformFile(PlatformFile file, int64 offset,
                       const char* data, int size) {
-  if (file < 0)
+  if (file < 0 || size < 0)
     return -1;
 
-  return HANDLE_EINTR(pwrite(file, data, size, offset));
+  int bytes_written = 0;
+  int rv = -1;
+  while (bytes_written < size) {
+    rv = HANDLE_EINTR(pwrite(file, data + bytes_written,
+                             size - bytes_written, offset + bytes_written));
+
+    if (rv <= 0)
+      break;
+
+    bytes_written += rv;
+  }
+
+  return bytes_written ? bytes_written : (size ? rv : 0);

[Scott Hess - ex-Googler, 2011/08/25 21:05:23]

If !bytes_written && !size, then rv<=0, so I think you don't need the latter
conditional operator.

[rvargas (doing something else), 2011/08/25 21:28:06]

I want to return 0 instead of -1 (rv) if !size, and at the same time return the
same error that pwrite returns if there is a failure (not force a -1)

[Scott Hess - ex-Googler, 2011/08/25 21:33:01]

This means that the code changes to always return 0 for size==0, whereas before
it would only return 0 for size==0 if the 0-sized write was successful.  This
might matter if, for instance, someone is testing if the file is writable, but
not writing anything to it.  They should be repremanded, though.

Actually, I just noticed that the current code doesn't even call pwrite() when
size==0.  If this is the right thing to do, you could just handle it before the
loop.

[rvargas (doing something else), 2011/08/25 21:37:50]

No, that's not what I meant... fixing it.

 }
 
 bool TruncatePlatformFile(PlatformFile file, int64 length) {
   return ((file >= 0) && !HANDLE_EINTR(ftruncate(file, length)));
 }
 
 bool FlushPlatformFile(PlatformFile file) {
   return !HANDLE_EINTR(fsync(file));
 }
 
@@ skipping 19 matching lines @@
   info->is_directory = S_ISDIR(file_info.st_mode);
   info->is_symbolic_link = S_ISLNK(file_info.st_mode);
   info->size = file_info.st_size;
   info->last_modified = base::Time::FromTimeT(file_info.st_mtime);
   info->last_accessed = base::Time::FromTimeT(file_info.st_atime);
   info->creation_time = base::Time::FromTimeT(file_info.st_ctime);
   return true;
 }
 
 }  // namespace base