mirror of
https://github.com/dart-lang/sdk
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45d35b1588
The non-copying version is internally, as this is always the behaviour we want, when receiving data from the system. File-reads are also further improved, by only reading data in chunks, if initial length is 0. This is a special case where the file can be a character device. Overall improvement is around a factor of 6. BUG= R=sgjesse@google.com Review URL: https://codereview.chromium.org//218493012 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@34589 260f80e4-7a28-3924-810f-c04153c831b5
207 lines
4.7 KiB
Dart
207 lines
4.7 KiB
Dart
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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part of dart.io;
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/**
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* Builds a list of bytes, allowing bytes and lists of bytes to be added at the
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* end.
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*
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* Used to efficiently collect bytes and lists of bytes.
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*/
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abstract class BytesBuilder {
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/**
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* Construct a new empty [BytesBuilder].
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*
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* If [copy] is true, the data is always copied when added to the list. If
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* it [copy] is false, the data is only copied if needed. That means that if
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* the lists are changed after added to the [BytesBuilder], it may effect the
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* output. Default is `true`.
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*/
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factory BytesBuilder({bool copy: true}) {
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if (copy) {
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return new _CopyingBytesBuilder();
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} else {
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return new _BytesBuilder();
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}
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}
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/**
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* Appends [bytes] to the current contents of the builder.
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*
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* Each value of [bytes] will be bit-representation truncated to the range
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* 0 .. 255.
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*/
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void add(List<int> bytes);
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/**
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* Append [byte] to the current contents of the builder.
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*
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* The [byte] will be bit-representation truncated to the range 0 .. 255.
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*/
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void addByte(int byte);
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/**
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* Returns the contents of `this` and clears `this`.
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*
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* The list returned is a view of the the internal buffer, limited to the
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* [length].
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*/
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List<int> takeBytes();
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/**
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* Returns a copy of the current contents of the builder.
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*
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* Leaves the contents of the builder intact.
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*/
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List<int> toBytes();
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/**
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* The number of bytes in the builder.
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*/
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int get length;
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/**
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* Returns `true` if the buffer is empty.
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*/
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bool get isEmpty;
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/**
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* Returns `true` if the buffer is not empty.
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*/
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bool get isNotEmpty;
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/**
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* Clear the contents of the builder.
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*/
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void clear();
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}
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class _CopyingBytesBuilder implements BytesBuilder {
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// Start with 1024 bytes.
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static const int _INIT_SIZE = 1024;
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int _length = 0;
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Uint8List _buffer;
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void add(List<int> bytes) {
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int bytesLength = bytes.length;
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if (bytesLength == 0) return;
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int required = _length + bytesLength;
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if (_buffer == null) {
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int size = _pow2roundup(required);
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size = max(size, _INIT_SIZE);
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_buffer = new Uint8List(size);
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} else if (_buffer.length < required) {
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// We will create a list in the range of 2-4 times larger than
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// required.
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int size = _pow2roundup(required) * 2;
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var newBuffer = new Uint8List(size);
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newBuffer.setRange(0, _buffer.length, _buffer);
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_buffer = newBuffer;
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}
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assert(_buffer.length >= required);
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if (bytes is Uint8List) {
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_buffer.setRange(_length, required, bytes);
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} else {
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for (int i = 0; i < bytesLength; i++) {
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_buffer[_length + i] = bytes[i];
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}
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}
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_length = required;
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}
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void addByte(int byte) => add([byte]);
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List<int> takeBytes() {
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if (_buffer == null) return new Uint8List(0);
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var buffer = new Uint8List.view(_buffer.buffer, 0, _length);
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clear();
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return buffer;
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}
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List<int> toBytes() {
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if (_buffer == null) return new Uint8List(0);
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return new Uint8List.fromList(
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new Uint8List.view(_buffer.buffer, 0, _length));
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}
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int get length => _length;
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bool get isEmpty => _length == 0;
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bool get isNotEmpty => _length != 0;
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void clear() {
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_length = 0;
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_buffer = null;
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}
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int _pow2roundup(int x) {
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--x;
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x |= x >> 1;
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x |= x >> 2;
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x |= x >> 4;
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x |= x >> 8;
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x |= x >> 16;
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return x + 1;
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}
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}
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class _BytesBuilder implements BytesBuilder {
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int _length = 0;
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final List _chunks = [];
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void add(List<int> bytes) {
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if (bytes is! Uint8List) {
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bytes = new Uint8List.fromList(bytes);
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}
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_chunks.add(bytes);
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_length += bytes.length;
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}
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void addByte(int byte) => add([byte]);
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List<int> takeBytes() {
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if (_chunks.length == 0) return new Uint8List(0);
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if (_chunks.length == 1) {
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var buffer = _chunks.single;
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clear();
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return buffer;
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}
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var buffer = new Uint8List(_length);
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int offset = 0;
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for (var chunk in _chunks) {
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buffer.setRange(offset, offset + chunk.length, chunk);
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offset += chunk.length;
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}
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clear();
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return buffer;
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}
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List<int> toBytes() {
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if (_chunks.length == 0) return new Uint8List(0);
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var buffer = new Uint8List(_length);
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int offset = 0;
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for (var chunk in _chunks) {
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buffer.setRange(offset, offset + chunk.length, chunk);
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offset += chunk.length;
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}
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return buffer;
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}
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int get length => _length;
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bool get isEmpty => _length == 0;
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bool get isNotEmpty => _length != 0;
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void clear() {
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_length = 0;
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_chunks.clear();
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}
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}
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