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80 lines
2.5 KiB
JavaScript
80 lines
2.5 KiB
JavaScript
8 months ago
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"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.SlipDecoder = void 0;
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const stream_1 = require("stream");
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/**
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* A transform stream that decodes slip encoded data.
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* @extends Transform
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*
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* Runs in O(n) time, stripping out slip encoding and emitting decoded data. Optionally custom slip escape and delimiters can be provided.
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*/
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class SlipDecoder extends stream_1.Transform {
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constructor(options = {}) {
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super(options);
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const { START, ESC = 0xdb, END = 0xc0, ESC_START, ESC_END = 0xdc, ESC_ESC = 0xdd } = options;
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this.opts = {
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START,
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ESC,
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END,
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ESC_START,
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ESC_END,
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ESC_ESC,
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};
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this.buffer = Buffer.alloc(0);
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this.escape = false;
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this.start = false;
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}
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_transform(chunk, encoding, cb) {
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for (let ndx = 0; ndx < chunk.length; ndx++) {
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let byte = chunk[ndx];
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if (byte === this.opts.START) {
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this.start = true;
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continue;
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}
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else if (undefined == this.opts.START) {
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this.start = true;
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}
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if (this.escape) {
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if (byte === this.opts.ESC_START && this.opts.START) {
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byte = this.opts.START;
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}
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else if (byte === this.opts.ESC_ESC) {
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byte = this.opts.ESC;
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}
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else if (byte === this.opts.ESC_END) {
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byte = this.opts.END;
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}
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else {
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this.escape = false;
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this.push(this.buffer);
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this.buffer = Buffer.alloc(0);
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}
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}
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else {
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if (byte === this.opts.ESC) {
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this.escape = true;
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continue;
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}
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if (byte === this.opts.END) {
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this.push(this.buffer);
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this.buffer = Buffer.alloc(0);
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this.escape = false;
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this.start = false;
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continue;
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}
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}
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this.escape = false;
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if (this.start) {
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this.buffer = Buffer.concat([this.buffer, Buffer.from([byte])]);
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}
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}
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cb();
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}
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_flush(cb) {
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this.push(this.buffer);
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this.buffer = Buffer.alloc(0);
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cb();
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}
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}
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exports.SlipDecoder = SlipDecoder;
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