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This commit is contained in:
Eric MacDonald
2021-09-08 21:53:20 -04:00
parent fda7e0c1b5
commit a18c832754
1 changed files with 20 additions and 20 deletions
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40
zefie_wtvp_minisrv/WTVLzpf.js
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@@ -22,12 +22,12 @@ class WTVLzpf {
current_length = 0;
current_literal = 0;
flag = 0xFFFF;
ring_bufer_index = 0xFFFF;
working_data = 0;
match_index = 0;
type_index = 0;
checksum = 0;
flag_table = new Uint16Array(0x1000)
hash_table = new Uint16Array(0x1000)
ring_buffer = new Uint8Array(0x2000)
encoded_data = [];
@@ -141,10 +141,10 @@ class WTVLzpf {
*
* When we find a byte match in the ring buffer we use this dictionary to encode the length of the matched bytes.
*
* - These are intentionally 32-bit. The leftmost bit is 1 in each of these to tell the decoder to use match decoding.
* - LZP flag bits are used to encode the position where the matched bytes start.
* - These are intentionally 32-bit. The leftmost flag bit is 1 in each of these to tell the decoder to use match decoding.
* - LZP hash bits are used to encode the position where the matched bytes start.
* - We're allowed to match up to 298 bytes before we can't encode more (we need an entry in this dictionary for each byte more).
* - We can reach for matches 65KB behind the current LZ cursor (65KB is the ring buffer size and highest a 16-bit flag can reach).
* - We can reach for matches 65KB behind the current LZ cursor (65KB is the ring buffer size and highest a 16-bit hash can reach).
**/
matchEncode = [
/* [MATCH CODE, MATCH CODE BIT LENGTH] */
@@ -318,14 +318,14 @@ class WTVLzpf {
clear() {
this.current_length = 0;
this.current_literal = 0;
this.flag = 0xFFFF;
this.ring_bufer_index = 0xFFFF;
this.working_data = 0;
this.match_index = 0;
this.type_index = 0;
this.checksum = 0;
this.filler_byte = 0x20
this.ring_buffer.fill(this.filler_byte, 0, 0x2000)
this.flag_table.fill(0xFFFF, 0, 0x1000);
this.hash_table.fill(0xFFFF, 0, 0x1000);
this.encoded_data = [];
}
@@ -384,7 +384,7 @@ class WTVLzpf {
var uncompressed_len = unencoded_data.byteLength;
var i = 0;
var flags_index = 0;
var hash_index = 0;
while (i < uncompressed_len) {
var code_length = -1;
var code = -1;
@@ -393,35 +393,35 @@ class WTVLzpf {
this.ring_buffer[i & 0x1FFF] = byte;
if (this.match_index > 0) {
if (byte != this.ring_buffer[this.flag] || this.match_index > 0x0127) {
if (byte != this.ring_buffer[this.ring_bufer_index] || 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.ring_bufer_index = (this.ring_bufer_index + 1) & 0x1FFF;
this.checksum = (this.checksum + byte) & 0xFFFF;
this.working_data = ((this.working_data * 0x0100) + byte) & 0xFFFFFFFF;
i++;
}
} else {
this.flag = 0xFFFF;
this.ring_bufer_index = 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;
hash_index = (this.working_data >>> 0x0B ^ this.working_data) & 0x0FFF;
this.ring_bufer_index = this.hash_table[hash_index];
this.hash_table[hash_index] = i & 0x1FFF;
} else {
this.type_index++;
}
if (this.flag == 0xFFFF) {
if (this.ring_bufer_index == 0xFFFF) {
code_length = this.nomatchEncode[byte][1];
code = this.nomatchEncode[byte][0] << 0x10;
} else if (byte == this.ring_buffer[this.flag] && compress_data) {
} else if (byte == this.ring_buffer[this.ring_bufer_index] && compress_data) {
this.match_index = 1;
this.flag = (this.flag + 1) & 0x1FFF;
this.ring_bufer_index = (this.ring_bufer_index + 1) & 0x1FFF;
this.type_index = 4;
} else {
code_length = this.nomatchEncode[byte][1] + 1;
@@ -459,9 +459,9 @@ class WTVLzpf {
this.EncodeLiteral(code_length, code);
}
var flags_index = (this.working_data >>> 0x0B ^ this.working_data) & 0x0FFF;
var flag = this.flag_table[flags_index];
if (flag == 0xFFFF) {
var hash_index = (this.working_data >>> 0x0B ^ this.working_data) & 0x0FFF;
var ring_bufer_index = this.hash_table[hash_index];
if (ring_bufer_index == 0xFFFF) {
this.EncodeLiteral(0x10, 0x00990000);
} else {
this.EncodeLiteral(0x11, 0x004c8000);