Replace NULL with nullptr or null in webrtc/audio/ and common_audio/.

webrtc/common_audio/ring_buffer.h

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 13 matching lines @@
 
 typedef struct RingBuffer {
   size_t read_pos;
   size_t write_pos;
   size_t element_count;
   size_t element_size;
   enum Wrap rw_wrap;
   char* data;
 } RingBuffer;
 
-// Creates and initializes the buffer. Returns NULL on failure.
+// Creates and initializes the buffer. Returns null on failure.
 RingBuffer* WebRtc_CreateBuffer(size_t element_count, size_t element_size);
 void WebRtc_InitBuffer(RingBuffer* handle);
 void WebRtc_FreeBuffer(void* handle);
 
 // Reads data from the buffer. The |data_ptr| will point to the address where
 // it is located. If all |element_count| data are feasible to read without
 // buffer wrap around |data_ptr| will point to the location in the buffer.
 // Otherwise, the data will be copied to |data| (memory allocation done by the
 // user) and |data_ptr| points to the address of |data|. |data_ptr| is only
 // guaranteed to be valid until the next call to WebRtc_WriteBuffer().
 //
-// To force a copying to |data|, pass a NULL |data_ptr|.
+// To force a copying to |data|, pass a null |data_ptr|.
 //
 // Returns number of elements read.
 size_t WebRtc_ReadBuffer(RingBuffer* handle,
                          void** data_ptr,
                          void* data,
                          size_t element_count);
 
 // Writes |data| to buffer and returns the number of elements written.
 size_t WebRtc_WriteBuffer(RingBuffer* handle, const void* data,
                           size_t element_count);
 
 // Moves the buffer read position and returns the number of elements moved.
 // Positive |element_count| moves the read position towards the write position,
 // that is, flushing the buffer. Negative |element_count| moves the read
 // position away from the the write position, that is, stuffing the buffer.
 // Returns number of elements moved.
 int WebRtc_MoveReadPtr(RingBuffer* handle, int element_count);
 
 // Returns number of available elements to read.
 size_t WebRtc_available_read(const RingBuffer* handle);
 
 // Returns number of available elements for write.
 size_t WebRtc_available_write(const RingBuffer* handle);
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif  // WEBRTC_COMMON_AUDIO_RING_BUFFER_H_