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>
@@ skipping 108 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) {
+static bool ReadFileToStringImpl(const FilePath& path,
+                                 std::string* contents,
+                                 size_t maxsize) {
   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;
+
+  // Many files supplied in path have incorrect size (proc files, streams etc)
+  // hence the file is read sequentially as opposed to one-shot read.
   while ((len = fread(buf, 1, sizeof(buf), file)) > 0) {
+    if ((maxsize - size) < len) {
+      if (contents)
+        contents->clear();
+      CloseFile(file);
+      return false;
+    }
+    size += len;
     if (contents)
       contents->append(buf, len);
   }
   CloseFile(file);
 
   return true;
 }
 
+bool ReadFileToString(const FilePath& path,
+                      std::string* contents,
+                      size_t maxsize) {
+  return ReadFileToStringImpl(path, contents, maxsize);
+}
+
+bool ReadFileToString(const FilePath& path, std::string* contents) {
+  return ReadFileToStringImpl(path, contents, ~(size_t)0);

[Andrew T Wilson (Slow), 2014/02/11 10:27:12]

Can you use SIZE_MAX here instead of ~0?

I'm OK with having a separate ReadFileToStringImpl but you should do one of the
following:

1) Wrap it in an anonymous namespace (since it's not intended to be exported
from this file).

2) Move it into ReadFileToString(path, contents, maxsize) itself, and have
ReadFileToString(path, contents) just call the 3-parameter version of the
function.

[kaliamoorthi, 2014/02/11 16:29:16]

Changed to std::numeric_limits<size_t>::max() as discussed. Chose option 2 and
removed ReadFileToStringImpl.

+}
+
 bool IsDirectoryEmpty(const FilePath& dir_path) {
   FileEnumerator files(dir_path, false,
       FileEnumerator::FILES | FileEnumerator::DIRECTORIES);
   if (files.Next().empty())
     return true;
   return false;
 }
 
 FILE* CreateAndOpenTemporaryFile(FilePath* path) {
   FilePath directory;
@@ skipping 82 matching lines @@
     if (!PathExists(new_path) &&
         (!have_suffix || !PathExists(FilePath(new_path.value() + suffix)))) {
       return count;
     }
   }
 
   return -1;
 }
 
 }  // namespace file_util