Write NULL as "" so readString() always returns a non-NULL string.

include/core/SkWriter32.h

 
 /*
  * Copyright 2008 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkWriter32_DEFINED
@@ skipping 150 matching lines @@
 
     /**
      *  Write size bytes from src, and pad to 4 byte alignment with zeroes.
      */
     void writePad(const void* src, size_t size);
 
     /**
      *  Writes a string to the writer, which can be retrieved with
      *  SkReader32::readString().
      *  The length can be specified, or if -1 is passed, it will be computed by
-     *  calling strlen(). The length must be < 0xFFFF
+     *  calling strlen(). The length must be < max size_t.
+     *
+     *  If you write NULL, it will be read as "".
      */
     void writeString(const char* str, size_t len = (size_t)-1);
 
     /**
      *  Computes the size (aligned to multiple of 4) need to write the string
      *  in a call to writeString(). If the length is not specified, it will be
      *  computed by calling strlen().
      */
     static size_t WriteStringSize(const char* str, size_t len = (size_t)-1);
 
@@ skipping 108 matching lines @@
 
 private:
     union {
         void*   fPtrAlignment;
         double  fDoubleAlignment;
         char    fStorage[SIZE];
     } fData;
 };
 
 #endif