Added new ReadFileToString API with a max_size argument

base/file_util.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"
 
 #if defined(OS_WIN)
 #include <io.h>
 #endif
 #include <stdio.h>
 
 #include <fstream>
+#include <limits>
 
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 
 namespace base {
@@ skipping 96 matching lines @@
     else if (end2 + 1 < line2.length())
       line2.erase(end2 + 1);
 
     if (line1 != line2)
       return false;
   } while (!file1.eof() || !file2.eof());
 
   return true;
 }
 
-bool ReadFileToString(const FilePath& path, std::string* contents) {
+bool ReadFileToString(const FilePath& path,
+                      std::string* contents,
+                      size_t max_size) {
+  if (contents)
+    contents->clear();
   if (path.ReferencesParent())
     return false;
   FILE* file = OpenFile(path, "rb");
   if (!file) {
     return false;
   }
 
   char buf[1 << 16];
   size_t len;
+  size_t size = 0;
+  bool read_status = true;
+
+  // Many files supplied in |path| have incorrect size (proc files etc).
+  // Hence, the file is read sequentially as opposed to a one-shot read.
   while ((len = fread(buf, 1, sizeof(buf), file)) > 0) {
-    if (contents)
-      contents->append(buf, len);
+    if (contents && (max_size - size) > 0)

[brettw, 2014/02/18 05:24:33]

Does the max_size - size check do anything? These are both unsigned types so the
result can't be negative (I think this is OK based on your logic, but please
double-check that's what you expected). But then this is just a check != 0. But
there's no problem appending 0 bytes. I think I'd find it clearer if this wasn't
here and we just did if (contents) ...

[kaliamoorthi, 2014/02/18 11:50:50]

Done.

+      contents->append(buf, std::min(len, max_size - size));
+
+    if ((max_size - size) < len) {
+      read_status = false;
+      break;
+    }
+
+    size += len;
   }
   CloseFile(file);
 
-  return true;
+  return read_status;
+}
+
+bool ReadFileToString(const FilePath& path, std::string* contents) {
+  return ReadFileToString(path, contents, std::numeric_limits<size_t>::max());
 }
 
 bool IsDirectoryEmpty(const FilePath& dir_path) {
   FileEnumerator files(dir_path, false,
       FileEnumerator::FILES | FileEnumerator::DIRECTORIES);
   if (files.Next().empty())
     return true;
   return false;
 }
 
@@ skipping 84 matching lines @@
     if (!PathExists(new_path) &&
         (!have_suffix || !PathExists(FilePath(new_path.value() + suffix)))) {
       return count;
     }
   }
 
   return -1;
 }
 
 }  // namespace file_util