71 lines
1.9 KiB
JavaScript
71 lines
1.9 KiB
JavaScript
'use strict'
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const { createInflateRaw, Z_DEFAULT_WINDOWBITS } = require('node:zlib')
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const { isValidClientWindowBits } = require('./util')
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const tail = Buffer.from([0x00, 0x00, 0xff, 0xff])
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const kBuffer = Symbol('kBuffer')
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const kLength = Symbol('kLength')
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class PerMessageDeflate {
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/** @type {import('node:zlib').InflateRaw} */
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#inflate
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#options = {}
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constructor (extensions) {
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this.#options.serverNoContextTakeover = extensions.has('server_no_context_takeover')
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this.#options.serverMaxWindowBits = extensions.get('server_max_window_bits')
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}
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decompress (chunk, fin, callback) {
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// An endpoint uses the following algorithm to decompress a message.
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// 1. Append 4 octets of 0x00 0x00 0xff 0xff to the tail end of the
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// payload of the message.
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// 2. Decompress the resulting data using DEFLATE.
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if (!this.#inflate) {
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let windowBits = Z_DEFAULT_WINDOWBITS
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if (this.#options.serverMaxWindowBits) { // empty values default to Z_DEFAULT_WINDOWBITS
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if (!isValidClientWindowBits(this.#options.serverMaxWindowBits)) {
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callback(new Error('Invalid server_max_window_bits'))
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return
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}
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windowBits = Number.parseInt(this.#options.serverMaxWindowBits)
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}
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this.#inflate = createInflateRaw({ windowBits })
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this.#inflate[kBuffer] = []
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this.#inflate[kLength] = 0
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this.#inflate.on('data', (data) => {
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this.#inflate[kBuffer].push(data)
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this.#inflate[kLength] += data.length
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})
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this.#inflate.on('error', (err) => {
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this.#inflate = null
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callback(err)
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})
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}
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this.#inflate.write(chunk)
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if (fin) {
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this.#inflate.write(tail)
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}
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this.#inflate.flush(() => {
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const full = Buffer.concat(this.#inflate[kBuffer], this.#inflate[kLength])
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this.#inflate[kBuffer].length = 0
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this.#inflate[kLength] = 0
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callback(null, full)
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})
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}
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}
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module.exports = { PerMessageDeflate }
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