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..243d8e7885b63d01224e0a86f033f6f2398d97e3 100644
--- a/base/file_util.cc
+++ b/base/file_util.cc
@@ -10,6 +10,7 @@
 #include <stdio.h>
 
 #include <fstream>
+#include <limits>
 
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
@@ -126,7 +127,11 @@ bool TextContentsEqual(const FilePath& filename1, const FilePath& filename2) {
   return true;
 }
 
-bool ReadFileToString(const FilePath& path, std::string* contents) {
+bool ReadFileToString(const FilePath& path,
+                      std::string* contents,
+                      size_t max_size) {
+  if(contents)

[Andrew T Wilson (Slow), 2014/02/17 14:38:22]

Two things:

1) space before the open paren.
2) this is changing the behavior of ReadFileToString(), which in its current
incarnation appends to the current value of contents, and never clears it. Are
we sure that nobody depends on the current implementation?

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

I have fixed 1 in a new patch.

+    contents->clear();
   if (path.ReferencesParent())
     return false;
   FILE* file = OpenFile(path, "rb");
@@ -136,13 +141,29 @@ bool ReadFileToString(const FilePath& path, std::string* contents) {
 
   char buf[1 << 16];
   size_t len;
+  size_t size = 0;
+  bool return_var = true;

[Andrew T Wilson (Slow), 2014/02/17 14:38:22]

Change this name to something like "read_status".

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

Done.

+
+  // 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)
+      contents->append(buf, std::min(len, max_size - size));
+
+    if ((max_size - size) < len) {
+      return_var = false;
+      break;
+    }
+
+    size += len;
   }
   CloseFile(file);
 
-  return true;
+  return return_var;
+}
+
+bool ReadFileToString(const FilePath& path, std::string* contents) {
+  return ReadFileToString(path, contents, std::numeric_limits<size_t>::max());
 }
 
 bool IsDirectoryEmpty(const FilePath& dir_path) {