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update: compression system: make asynchronous

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zefie
2021-08-06 16:20:44 -04:00
parent ad16a04c55
commit 3da637dfb0
2 changed files with 44 additions and 17 deletions
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38
zefie_wtvp_minisrv/WTVLzpf.js
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@@ -1,3 +1,5 @@
var EventEmitter = require('events').EventEmitter;
/**
* Pure-JS implementation of WebTV's LZPF compression
*
@@ -7,12 +9,14 @@
* By: Eric MacDonald (eMac)
*/
class WTVLzpf {
// Note: currentlty doesn't offer streaming support but this is good enough to meet perf demands at the scale we're at.
class WTVLzpf extends EventEmitter {
// Note: currentlty doesn't offer optimal streaming support but this is good enough to meet perf demands at the scale we're at.
current_length = 0
current_literal = 0
compressed_offset = 0
total_compressed = 0;
chunk_size = 65535;
flag_table = new Uint16Array(0x1000)
compressed_data = null;
@@ -261,23 +265,28 @@ class WTVLzpf {
/**
* Initialize the Lzpf class.
*
* @param chunk_size {Number} Set the size of the compressed data chunks to fire off with 'data' event. (suggested betweet 2048 and 65535);
* @returns {undefined}
*/
constructor() {
constructor(chunk_size = 0) {
super(); // for extended class
if (chunk_size > 0) this.chunk_size = chunk_size;
this.clear();
}
/**
* Sets starting values for the compression algorithm.
*
* @param length {Number} size of compressed data Buffer to allocate
* @returns {undefined}
*/
clear() {
clear(length = 0) {
this.current_length = 0;
this.current_literal = 0;
this.total_compressed = 0;
this.compressed_offset = 0;
this.flag_table.fill(0xFFFF, 0, 0x1000);
this.compressed_data = null;
this.compressed_data = (length > 0) ? null : Buffer.alloc(length);
}
/**
@@ -288,7 +297,7 @@ class WTVLzpf {
*
* @returns {undefined}
*/
EncodeLiteral(code_length, code) {
async EncodeLiteral(code_length, code) {
// Using >>> to stick with unsigned integers without making a mess with casting.
this.current_literal |= code >>> (this.current_length & 0x1F);
@@ -310,9 +319,8 @@ class WTVLzpf {
*
* @returns {Buffer} Lzpf compression data
*/
Compress(uncompressed_data) {
async Compress(uncompressed_data) {
this.clear();
if (uncompressed_data.words) {
// if its a wordArray convert it to a Buffer
@@ -326,7 +334,8 @@ class WTVLzpf {
}
var uncompressed_len = uncompressed_data.byteLength;
this.compressed_data = new Buffer.alloc(uncompressed_len);
this.clear(uncompressed_len);
this.compressed_data = new Buffer.alloc((uncompressed_len >= this.chunk_size) ? this.chunk_size : uncompressed_len);
var i = 0;
var sum = 0;
@@ -385,6 +394,11 @@ class WTVLzpf {
if (code_length > 0) {
this.EncodeLiteral(code_length, code);
}
if (this.compressed_offset == this.chunk_size) {
this.total_compressed += this.compressed_offset;
this.emit('data', this.compressed_data, this.compressed_offset, (this.total_compressed - this.compressed_offset), false);
this.compressed_offset = 0;
}
}
// Finish up. This would normally be in an Lzpf_Finish method.
@@ -415,11 +429,9 @@ class WTVLzpf {
this.compressed_offset = this.compressed_data.writeUInt8(this.current_literal >>> 0x18, this.compressed_offset);
this.compressed_offset = this.compressed_data.writeUInt8(0x20, this.compressed_offset);
var output_buffer = new Buffer.alloc(this.compressed_offset);
this.compressed_data.copy(output_buffer, 0, 0, this.compressed_offset)
this.compressed_data = null;
this.total_compressed += this.compressed_offset;
return output_buffer;
this.emit('data', this.compressed_data, this.compressed_offset, (this.total_compressed - this.compressed_offset), this.total_compressed);
}
}