Merge the two buffer list implementations

runtime/bin/buffer_list.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * Utility class that holds a number of byte buffers and can deliver
+ * the bytes either one by one or in chunks.
+ */
+class _BufferList {
+  _BufferList() {
+    clear();
+  }
+
+  /**
+   * Adds a new buffer to the list possibly with an offset of the
+   * first byte of interest. The offset can only be specified if the
+   * buffer list is empty.
+   */
+  void add(List<int> buffer, [int offset = 0]) {
+    assert(offset == 0 || _buffers.isEmpty());
+    _buffers.addLast(buffer);
+    _length += buffer.length;
+    if (offset != 0) _index = offset;
+  }
+
+  /**
+   * Returns the first buffer from the list. This returns the whole
+   * buffer and does not remove the buffer from the list. Use
+   * [index] to determine the index of the first byte in the buffer.
+   */
+  List<int> get first() => _buffers.first();
+
+  /* Returns the current index of the next byte. This will always be
+   * an index into the first buffer as when the index is advanced past
+   * the end of a buffer it is removed from the list.
+   */
+  int get index() =>  _index;
+
+  /**
+   * Peek at the next available byte.
+   */
+  int peek() => _buffers.first()[_index];
+
+  /*
+   * Returns the next available byte removing it from the buffers.
+   */
+  int next() {
+    int value = _buffers.first()[_index++];
+    _length--;
+    if (_index == _buffers.first().length) {
+      _buffers.removeFirst();
+      _index = 0;
+    }
+    return value;
+  }
+
+  /**
+   * Remove a number of bytes from the buffer list. Currently the
+   * number of bytes to remove must be confined to the first buffer.
+   */
+  void removeBytes(int count) {
+    int firstRemaining = first.length - _index;
+    assert(count <= firstRemaining);
+    if (count == firstRemaining) {
+      _buffers.removeFirst();
+      _index = 0;
+    } else {
+      _index += count;
+    }
+    _length -= count;
+  }
+
+
+  /**
+   * Returns the total number of bytes remaining in the buffers.
+   */
+  int get length() => _length;
+
+  /**
+   * Returns whether the buffer list is empty that is has no bytes
+   * available.
+   */
+  bool isEmpty() => _buffers.isEmpty();
+
+  /**
+   * Clears the content of the buffer list.
+   */
+  void clear() {
+    _index = 0;
+    _length = 0;
+    _buffers = new Queue();
+  }
+
+  int _length;  // Total number of bytes remaining in the buffers.
+  Queue<List<int>> _buffers;  // List of data buffers.
+  int _index;  // Index of the next byte in the first buffer.
+}