zefie/minisrv
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

'Working' Lzpf stream compression

Browse Source
This commit is contained in:
Eric MacDonald
2021-08-07 16:10:40 -04:00
parent eb6fc5f89a
commit e6958fb2c3
1 changed files with 75 additions and 71 deletions
Download Patch File Download Diff File Expand all files Collapse all files

146
zefie_wtvp_minisrv/WTVLzpf.js
View File

@@ -12,8 +12,9 @@ var EventEmitter = require('events').EventEmitter;
class WTVLzpf {
// 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
current_length = 0;
current_literal = 0;
flag = 0xFFFF;
working_data = 0;
match_index = 0;
type_index = 0;
@@ -281,6 +282,7 @@ class WTVLzpf {
clear() {
this.current_length = 0;
this.current_literal = 0;
this.flag = 0xFFFF;
this.working_data = 0;
this.match_index = 0;
this.type_index = 0;
@@ -340,6 +342,73 @@ class WTVLzpf {
* @returns {Buffer} Lzpf compression data
*/
CompressBlock(uncompressed_data) {
this.compressed_data = [];
if (uncompressed_data.words) {
uncompressed_data = new Buffer.from(wtvsec.wordArrayToUint8Array(uncompressed_data));
} else if (!uncompressed_data.byteLength) {
// otherwise if its not already a Buffer, convert it to one
uncompressed_data = new Buffer.from(uncompressed_data);
}
var uncompressed_len = uncompressed_data.length;
var i = 0;
var flags_index = 0;
while (i < uncompressed_len) {
var code_length = -1;
var code = -1;
var byte = uncompressed_data.readUInt8(i);
this.ring_buffer[i & 0x1FFF] = byte;
if (this.match_index > 0) {
if (byte != this.ring_buffer[this.flag] || this.match_index > 0x0127) {
code_length = this.matchEncode[this.match_index][1];
code = this.matchEncode[this.match_index][0];
this.match_index = 0;
this.type_index = 3;
} else {
this.match_index = (this.match_index + 1) & 0x1FFF;
this.flag = (this.flag + 1) & 0x1FFF;
this.checksum = (this.checksum + byte) & 0xFFFF;
this.working_data = ((this.working_data * 0x0100) + byte) & 0xFFFFFFFF;
i++;
}
} else {
this.flag = 0xFFFF;
if (i >= 3) {
flags_index = (this.working_data >>> 0x0B ^ this.working_data) & 0x0FFF;
this.flag = this.flag_table[flags_index];
this.flag_table[flags_index] = i & 0x1FFF;
} else {
this.type_index++;
}
if (this.flag == 0xFFFF) {
code_length = this.nomatchEncode[byte][1];
code = this.nomatchEncode[byte][0] << 0x10;
} else if (byte == this.ring_buffer[this.flag]) {
this.match_index = 1;
this.flag = (this.flag + 1) & 0x1FFF;
this.type_index = 4;
} else {
code_length = this.nomatchEncode[byte][1] + 1;
code = this.nomatchEncode[byte][0] << 0x0F;
}
this.checksum = (this.checksum + byte) & 0xFFFF;
this.working_data = ((this.working_data * 0x0100) + byte) & 0xFFFFFFFF;
i++;
}
if (code_length > 0) {
this.EncodeLiteral(code_length, code);
}
}
return Buffer.from(this.compressed_data);
}
/**
@@ -349,7 +418,7 @@ class WTVLzpf {
*
* @returns {Buffer} Lzpf compression data
*/
Finalize() {
Finish() {
var code_length = -1
var code = -1
@@ -390,74 +459,9 @@ class WTVLzpf {
* @returns {Buffer} Lzpf compression data
*/
Compress(uncompressed_data) {
this.clear();
if (uncompressed_data.words) {
uncompressed_data = new Buffer.from(wtvsec.wordArrayToUint8Array(uncompressed_data));
} else if (!uncompressed_data.byteLength) {
// otherwise if its not already a Buffer, convert it to one
uncompressed_data = new Buffer.from(uncompressed_data);
}
var uncompressed_len = uncompressed_data.length;
var i = 0;
var flag = 0xFFFF;
var flags_index = 0;
while(i < uncompressed_len) {
var code_length = -1;
var code = -1;
var byte = uncompressed_data.readUInt8(i);
this.ring_buffer[i & 0x1FFF] = byte;
if (this.match_index > 0) {
if (byte != this.ring_buffer[flag] || this.match_index > 0x0127) {
code_length = this.matchEncode[this.match_index][1];
code = this.matchEncode[this.match_index][0];
this.match_index = 0;
this.type_index = 3;
} else {
this.match_index = (this.match_index + 1) & 0x1FFF;
flag = (flag + 1) & 0x1FFF;
this.checksum = (this.checksum + byte) & 0xFFFF;
this.working_data = ((this.working_data * 0x0100) + byte) & 0xFFFFFFFF;
i++;
}
} else {
flag = 0xFFFF;
if (i >= 3) {
flags_index = (this.working_data >>> 0x0B ^ this.working_data) & 0x0FFF;
flag = this.flag_table[flags_index];
this.flag_table[flags_index] = i & 0x1FFF;
} else {
this.type_index++;
}
if (flag == 0xFFFF) {
code_length = this.nomatchEncode[byte][1];
code = this.nomatchEncode[byte][0] << 0x10;
} else if (byte == this.ring_buffer[flag]) {
this.match_index = 1;
flag = (flag + 1) & 0x1FFF;
this.type_index = 4;
} else {
code_length = this.nomatchEncode[byte][1] + 1;
code = this.nomatchEncode[byte][0] << 0x0F;
}
this.checksum = (this.checksum + byte) & 0xFFFF;
this.working_data = ((this.working_data * 0x0100) + byte) & 0xFFFFFFFF;
i++;
}
if (code_length > 0) {
this.EncodeLiteral(code_length, code);
}
}
this.Finalize();
this.Begin();
this.CompressBlock(uncompressed_data)
this.Finish();
return Buffer.from(this.compressed_data);
}