Added new ReadFileToString API with a max_size argument

base/file_util.cc

Index: base/file_util.cc
diff --git a/base/file_util.cc b/base/file_util.cc
index e44f713cdb31828010ad9be92739a3d021dc4685..e0bc02d772960a891b8987b14e6c42f8bb726e25 100644
--- a/base/file_util.cc
+++ b/base/file_util.cc
@@ -126,7 +126,9 @@ bool TextContentsEqual(const FilePath& filename1, const FilePath& filename2) {
   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");
@@ -136,7 +138,18 @@ bool ReadFileToString(const FilePath& path, std::string* contents) {
 
   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);
   }
@@ -145,6 +158,16 @@ bool ReadFileToString(const FilePath& path, std::string* contents) {
   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);