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![Peter von der Ahé](/assets/img/avatar_default.png)
Change-Id: Ie436375c78496366accf0ba82938e54cbe30b143 Reviewed-on: https://dart-review.googlesource.com/3001 Commit-Queue: Peter von der Ahé <ahe@google.com> Reviewed-by: Lasse R.H. Nielsen <lrn@google.com> Reviewed-by: Vyacheslav Egorov <vegorov@google.com> Reviewed-by: Johnni Winther <johnniwinther@google.com>
197 lines
5.6 KiB
Dart
197 lines
5.6 KiB
Dart
// Copyright (c) 2012, 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 "core_patch.dart";
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@patch
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class StringBuffer {
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static const int _BUFFER_SIZE = 64;
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static const int _PARTS_TO_COMPACT = 128;
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static const int _PARTS_TO_COMPACT_SIZE_LIMIT = _PARTS_TO_COMPACT * 8;
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/**
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* When strings are written to the string buffer, we add them to a
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* list of string parts.
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*/
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List<String> _parts;
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/**
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* Total number of code units in the string parts. Does not include
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* the code units added to the buffer.
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*/
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int _partsCodeUnits = 0;
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/**
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* To preserve memory, we sometimes compact the parts. This combines
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* several smaller parts into a single larger part to cut down on the
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* cost that comes from the per-object memory overhead. We keep track
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* of the last index where we ended our compaction and the number of
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* code units added since the last compaction.
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*/
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int _partsCompactionIndex = 0;
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int _partsCodeUnitsSinceCompaction = 0;
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/**
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* The buffer is used to build up a string from code units. It is
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* used when writing short strings or individual char codes to the
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* buffer. The buffer is allocated on demand.
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*/
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Uint16List _buffer;
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int _bufferPosition = 0;
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/**
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* Collects the approximate maximal magnitude of the code units added
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* to the buffer.
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*
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* The value of each added code unit is or'ed with this variable, so the
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* most significant bit set in any code unit is also set in this value.
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* If below 256, the string in the buffer is a Latin-1 string.
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*/
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int _bufferCodeUnitMagnitude = 0;
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/// Creates the string buffer with an initial content.
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@patch
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StringBuffer([Object content = ""]) {
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write(content);
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}
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@patch
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int get length => _partsCodeUnits + _bufferPosition;
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@patch
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void write(Object obj) {
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String str = '$obj';
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if (str.isEmpty) return;
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_consumeBuffer();
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_addPart(str);
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}
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@patch
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void writeCharCode(int charCode) {
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if (charCode <= 0xFFFF) {
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if (charCode < 0) {
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throw new RangeError.range(charCode, 0, 0x10FFFF);
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}
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_ensureCapacity(1);
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_buffer[_bufferPosition++] = charCode;
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_bufferCodeUnitMagnitude |= charCode;
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} else {
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if (charCode > 0x10FFFF) {
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throw new RangeError.range(charCode, 0, 0x10FFFF);
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}
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_ensureCapacity(2);
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int bits = charCode - 0x10000;
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_buffer[_bufferPosition++] = 0xD800 | (bits >> 10);
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_buffer[_bufferPosition++] = 0xDC00 | (bits & 0x3FF);
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_bufferCodeUnitMagnitude |= 0xFFFF;
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}
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}
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@patch
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void writeAll(Iterable objects, [String separator = ""]) {
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Iterator iterator = objects.iterator;
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if (!iterator.moveNext()) return;
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if (separator.isEmpty) {
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do {
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write(iterator.current);
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} while (iterator.moveNext());
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} else {
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write(iterator.current);
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while (iterator.moveNext()) {
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write(separator);
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write(iterator.current);
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}
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}
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}
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@patch
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void writeln([Object obj = ""]) {
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write(obj);
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write("\n");
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}
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/** Makes the buffer empty. */
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@patch
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void clear() {
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_parts = null;
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_partsCodeUnits = _bufferPosition = _bufferCodeUnitMagnitude = 0;
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}
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/** Returns the contents of buffer as a string. */
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@patch
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String toString() {
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_consumeBuffer();
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return (_partsCodeUnits == 0)
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? ""
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: _StringBase._concatRange(_parts, 0, _parts.length);
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}
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/** Ensures that the buffer has enough capacity to add n code units. */
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void _ensureCapacity(int n) {
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if (_buffer == null) {
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_buffer = new Uint16List(_BUFFER_SIZE);
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} else if (_bufferPosition + n > _buffer.length) {
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_consumeBuffer();
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}
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}
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/**
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* Consumes the content of the buffer by turning it into a string
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* and adding it as a part. After calling this the buffer position
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* will be reset to zero.
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*/
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void _consumeBuffer() {
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if (_bufferPosition == 0) return;
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bool isLatin1 = _bufferCodeUnitMagnitude <= 0xFF;
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String str = _create(_buffer, _bufferPosition, isLatin1);
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_bufferPosition = _bufferCodeUnitMagnitude = 0;
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_addPart(str);
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}
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/**
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* Adds a new part to this string buffer and keeps track of how
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* many code units are contained in the parts.
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*/
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void _addPart(String str) {
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int length = str.length;
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_partsCodeUnits += length;
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_partsCodeUnitsSinceCompaction += length;
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if (_parts == null) {
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// Empirically this is a good capacity to minimize total bytes allocated.
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_parts = new _GrowableList.withCapacity(10)..add(str);
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} else {
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_parts.add(str);
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int partsSinceCompaction = _parts.length - _partsCompactionIndex;
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if (partsSinceCompaction == _PARTS_TO_COMPACT) {
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_compact();
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}
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}
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}
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/**
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* Compacts the last N parts if their average size allows us to save a
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* lot of memory by turning them all into a single part.
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*/
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void _compact() {
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if (_partsCodeUnitsSinceCompaction < _PARTS_TO_COMPACT_SIZE_LIMIT) {
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String compacted = _StringBase._concatRange(
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_parts,
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_partsCompactionIndex, // Start
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_partsCompactionIndex + _PARTS_TO_COMPACT // End
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);
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_parts.length = _parts.length - _PARTS_TO_COMPACT;
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_parts.add(compacted);
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}
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_partsCodeUnitsSinceCompaction = 0;
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_partsCompactionIndex = _parts.length;
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}
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/**
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* Create a [String] from the UFT-16 code units in buffer.
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*/
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static String _create(Uint16List buffer, int length, bool isLatin1)
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native "StringBuffer_createStringFromUint16Array";
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}
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