base::ReadFile() should return the number of read bytes on Windows.

base/file_util_posix.cc

 // Copyright (c) 2012 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/file_util.h"
 
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <libgen.h>
@@ skipping 633 matching lines @@
 
 FILE* OpenFile(const FilePath& filename, const char* mode) {
   ThreadRestrictions::AssertIOAllowed();
   FILE* result = NULL;
   do {
     result = fopen(filename.value().c_str(), mode);
   } while (!result && errno == EINTR);
   return result;
 }
 
-int ReadFile(const FilePath& filename, char* data, int size) {
+int ReadFile(const FilePath& filename, char* data, int max_size) {
   ThreadRestrictions::AssertIOAllowed();
   int fd = HANDLE_EINTR(open(filename.value().c_str(), O_RDONLY));
   if (fd < 0)
     return -1;
 
-  ssize_t bytes_read = HANDLE_EINTR(read(fd, data, size));
-  if (int ret = IGNORE_EINTR(close(fd)) < 0)
-    return ret;
+  ssize_t bytes_read = HANDLE_EINTR(read(fd, data, max_size));
+  if (IGNORE_EINTR(close(fd)) < 0)
+    return -1;
   return bytes_read;
 }
 
 int WriteFile(const FilePath& filename, const char* data, int size) {
   ThreadRestrictions::AssertIOAllowed();
   int fd = HANDLE_EINTR(creat(filename.value().c_str(), 0666));
   if (fd < 0)
     return -1;
 
   int bytes_written = WriteFileDescriptor(fd, data, size);
-  if (int ret = IGNORE_EINTR(close(fd)) < 0)
-    return ret;
+  if (IGNORE_EINTR(close(fd)) < 0)
+    return -1;
   return bytes_written;
 }
 
 int WriteFileDescriptor(const int fd, const char* data, int size) {
   // Allow for partial writes.
   ssize_t bytes_written_total = 0;
   for (ssize_t bytes_written_partial = 0; bytes_written_total < size;
        bytes_written_total += bytes_written_partial) {
     bytes_written_partial =
         HANDLE_EINTR(write(fd, data + bytes_written_total,
                            size - bytes_written_total));
     if (bytes_written_partial < 0)
       return -1;
   }
 
   return bytes_written_total;
 }
 
 int AppendToFile(const FilePath& filename, const char* data, int size) {
   ThreadRestrictions::AssertIOAllowed();
   int fd = HANDLE_EINTR(open(filename.value().c_str(), O_WRONLY | O_APPEND));
   if (fd < 0)
     return -1;
 
   int bytes_written = WriteFileDescriptor(fd, data, size);
-  if (int ret = IGNORE_EINTR(close(fd)) < 0)
-    return ret;
+  if (IGNORE_EINTR(close(fd)) < 0)
+    return -1;
   return bytes_written;
 }
 
 // Gets the current working directory for the process.
 bool GetCurrentDirectory(FilePath* dir) {
   // getcwd can return ENOENT, which implies it checks against the disk.
   ThreadRestrictions::AssertIOAllowed();
 
   char system_buffer[PATH_MAX] = "";
   if (!getcwd(system_buffer, sizeof(system_buffer))) {
@@ skipping 178 matching lines @@
     result = false;
   if (IGNORE_EINTR(close(outfile)) < 0)
     result = false;
 
   return result;
 }
 #endif  // !defined(OS_MACOSX)
 
 }  // namespace internal
 }  // namespace base