130 lines
2.7 KiB
JavaScript
Vendored
130 lines
2.7 KiB
JavaScript
Vendored
var hpack = require('../hpack');
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var utils = hpack.utils;
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var huffman = hpack.huffman.encode;
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var assert = utils.assert;
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var WBuf = require('wbuf');
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function Encoder() {
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this.buffer = new WBuf();
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this.word = 0;
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this.bitOffset = 0;
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}
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module.exports = Encoder;
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Encoder.create = function create() {
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return new Encoder();
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};
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Encoder.prototype.render = function render() {
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return this.buffer.render();
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};
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Encoder.prototype.encodeBit = function encodeBit(bit) {
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var octet;
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this.word <<= 1;
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this.word |= bit;
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this.bitOffset++;
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if (this.bitOffset === 8) {
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this.buffer.writeUInt8(this.word);
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this.word = 0;
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this.bitOffset = 0;
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}
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};
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Encoder.prototype.encodeBits = function encodeBits(bits, len) {
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var left = bits;
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var leftLen = len;
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while (leftLen > 0) {
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var avail = Math.min(leftLen, 8 - this.bitOffset);
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var toWrite = left >>> (leftLen - avail);
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if (avail === 8) {
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this.buffer.writeUInt8(toWrite);
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} else {
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this.word <<= avail;
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this.word |= toWrite;
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this.bitOffset += avail;
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if (this.bitOffset === 8) {
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this.buffer.writeUInt8(this.word);
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this.word = 0;
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this.bitOffset = 0;
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}
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}
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leftLen -= avail;
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left &= (1 << leftLen) - 1;
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}
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};
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// Just for testing
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Encoder.prototype.skipBits = function skipBits(num) {
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this.bitOffset += num;
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this.buffer.skip(this.bitOffset >> 3);
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this.bitOffset &= 0x7;
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};
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Encoder.prototype.encodeInt = function encodeInt(num) {
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var prefix = 8 - this.bitOffset;
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// We are going to end up octet-aligned
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this.bitOffset = 0;
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var max = (1 << prefix) - 1;
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// Fast case - int fits into the prefix
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if (num < max) {
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this.buffer.writeUInt8((this.word << prefix) | num);
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return octet;
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}
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var left = num - max;
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this.buffer.writeUInt8((this.word << prefix) | max);
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do {
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var octet = left & 0x7f;
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left >>= 7;
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if (left !== 0)
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octet |= 0x80;
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this.buffer.writeUInt8(octet);
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} while (left !== 0);
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};
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Encoder.prototype.encodeStr = function encodeStr(value, isHuffman) {
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this.encodeBit(isHuffman ? 1 : 0);
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if (!isHuffman) {
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this.buffer.reserve(value.length + 1);
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this.encodeInt(value.length);
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for (var i = 0; i < value.length; i++)
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this.buffer.writeUInt8(value[i]);
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return;
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}
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var codes = [];
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var len = 0;
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var pad = 0;
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for (var i = 0; i < value.length; i++) {
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var code = huffman[value[i]];
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codes.push(code);
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len += code[0];
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}
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if (len % 8 !== 0)
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pad = 8 - (len % 8);
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len += pad;
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this.buffer.reserve((len / 8) + 1);
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this.encodeInt(len / 8);
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for (var i = 0; i < codes.length; i++) {
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var code = codes[i];
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this.encodeBits(code[1], code[0]);
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}
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// Append padding
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this.encodeBits(0xff >>> (8 - pad), pad);
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};
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