Refactor PickleIterator.

base/pickle.h

Index: base/pickle.h
===================================================================
--- base/pickle.h	(revision 271871)
+++ base/pickle.h	(working copy)
@@ -20,7 +20,7 @@
 // while the PickleIterator object is in use.
 class BASE_EXPORT PickleIterator {
  public:
-  PickleIterator() : read_ptr_(NULL), read_end_ptr_(NULL) {}
+  PickleIterator() : payload_ptr_(NULL), read_index_(0), end_index_(0) {}
   explicit PickleIterator(const Pickle& pickle);
 
   // Methods for reading the payload of the Pickle. To read from the start of
@@ -63,6 +63,9 @@
   template <typename Type>
   inline bool ReadBuiltinType(Type* result);
 
+  // Advance read_index_ but do not allow it to exceed end_index_.
+  inline void Advance(size_t size);
+
   // Get read pointer for Type and advance read pointer.
   template<typename Type>
   inline const char* GetReadPointerAndAdvance();
@@ -77,8 +80,9 @@
                                               size_t size_element);
 
   // Pointers to the Pickle data.
-  const char* read_ptr_;
-  const char* read_end_ptr_;
+  const char* payload_ptr_;
+  size_t read_index_;
+  size_t end_index_;
 
   FRIEND_TEST_ALL_PREFIXES(PickleTest, GetReadPointerAndAdvance);
 };
@@ -277,7 +281,9 @@
   }
 
   // The payload is the pickle data immediately following the header.
-  size_t payload_size() const { return header_->payload_size; }
+  size_t payload_size() const {
+    return header_ ? header_->payload_size : 0;
+  }
 
   const char* payload() const {
     return reinterpret_cast<const char*>(header_) + header_size_;