Resize IPC input buffer to fit the next message.

base/pickle.h

 // 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.
 
 #ifndef BASE_PICKLE_H_
 #define BASE_PICKLE_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 253 matching lines @@
   // Resize the capacity, note that the input value should not include the size
   // of the header.
   void Resize(size_t new_capacity);
 
   // Find the end of the pickled data that starts at range_start.  Returns NULL
   // if the entire Pickle is not found in the given data range.
   static const char* FindNext(size_t header_size,
                               const char* range_start,
                               const char* range_end);
 
+  // Parse pickle header and return total size of the pickle. Data range
+  // doesn't need to contain entire pickle.
+  // Returns true if pickle header was found and parsed. Callers must check
+  // returned |pickle_size| for sanity (against maximum message size, etc).
+  // NOTE: when function successfully parses a header, but encounters an
+  // overflow during pickle size calculation, it sets |pickle_size| to the
+  // maximum size_t value and returns true.
+  static bool PeekNext(size_t header_size,
+                       const char* range_start,
+                       const char* range_end,
+                       size_t* pickle_size);
+
   // The allocation granularity of the payload.
   static const int kPayloadUnit;
 
  private:
   friend class PickleIterator;
 
   Header* header_;
   size_t header_size_;  // Supports extra data between header and payload.
   // Allocation size of payload (or -1 if allocation is const). Note: this
   // doesn't count the header.
   size_t capacity_after_header_;
   // The offset at which we will write the next field. Note: this doesn't count
   // the header.
   size_t write_offset_;
 
   // Just like WriteBytes, but with a compile-time size, for performance.
   template<size_t length> void BASE_EXPORT WriteBytesStatic(const void* data);
 
   // Writes a POD by copying its bytes.
   template <typename T> bool WritePOD(const T& data) {
     WriteBytesStatic<sizeof(data)>(&data);
     return true;
   }
   inline void WriteBytesCommon(const void* data, size_t length);
 
   FRIEND_TEST_ALL_PREFIXES(PickleTest, DeepCopyResize);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, Resize);
+  FRIEND_TEST_ALL_PREFIXES(PickleTest, PeekNext);
+  FRIEND_TEST_ALL_PREFIXES(PickleTest, PeekNextOverflow);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNext);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextWithIncompleteHeader);
   FRIEND_TEST_ALL_PREFIXES(PickleTest, FindNextOverflow);
 };
 
 }  // namespace base
 
 #endif  // BASE_PICKLE_H_