Make AudioVector::operator[] inline and modify index calculation

webrtc/modules/audio_coding/neteq/audio_vector.h

 /*
  *  Copyright (c) 2012 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.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_AUDIO_VECTOR_H_
 #define WEBRTC_MODULES_AUDIO_CODING_NETEQ_AUDIO_VECTOR_H_
 
 #include <string.h>  // Access to size_t.
 #include <memory>
 
+#include "webrtc/base/checks.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
 class AudioVector {
  public:
   // Creates an empty AudioVector.
   AudioVector();
 
@@ skipping 76 matching lines @@
   // region.
   virtual void CrossFade(const AudioVector& append_this, size_t fade_length);
 
   // Returns the number of elements in this AudioVector.
   virtual size_t Size() const;
 
   // Returns true if this AudioVector is empty.
   virtual bool Empty() const;
 
   // Accesses and modifies an element of AudioVector.
-  const int16_t& operator[](size_t index) const;
-  int16_t& operator[](size_t index);
+  inline const int16_t& operator[](size_t index) const {
+    return array_[WrapIndex(index, begin_index_, capacity_)];
+  }
+
+  inline int16_t& operator[](size_t index) {
+    return array_[WrapIndex(index, begin_index_, capacity_)];
+  }
 
  private:
   static const size_t kDefaultInitialSize = 10;
 
+  // This method is used by the [] operators to calculate an index within the
+  // capacity of the array, but without using the modulo operation (%).
+  static inline size_t WrapIndex(size_t index,
+                                 size_t begin_index,
+                                 size_t capacity) {
+    RTC_DCHECK_GE(begin_index + index, index);  // Check for overflow.
+    const size_t ix = begin_index + index >= capacity
+                          ? begin_index + index - capacity
+                          : begin_index + index;
+    RTC_DCHECK_LT(ix, capacity);
+    return ix;
+  }
+
   void Reserve(size_t n);
 
   void InsertByPushBack(const int16_t* insert_this, size_t length,
                         size_t position);
 
   void InsertByPushFront(const int16_t* insert_this, size_t length,
                          size_t position);
 
   void InsertZerosByPushBack(size_t length, size_t position);
 
   void InsertZerosByPushFront(size_t length, size_t position);
 
   std::unique_ptr<int16_t[]> array_;
 
   size_t capacity_;  // Allocated number of samples in the array.
 
   // The index of the first sample in |array_|, except when
   // |begin_index_ == end_index_|, which indicates an empty buffer.
   size_t begin_index_;
 
   // The index of the sample after the last sample in |array_|.
   size_t end_index_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioVector);
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_AUDIO_VECTOR_H_