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Change lookback to ring buffer

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This commit is contained in:
Eric MacDonald
2021-08-07 14:52:09 -04:00
parent 3da637dfb0
commit 6a286d6851
1 changed files with 9 additions and 6 deletions
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15
zefie_wtvp_minisrv/WTVLzpf.js
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@@ -18,6 +18,7 @@ class WTVLzpf extends EventEmitter {
total_compressed = 0;
chunk_size = 65535;
flag_table = new Uint16Array(0x1000)
ring_buffer = new Uint8Array(0x2000)
compressed_data = null;
nomatchEncode = [
@@ -285,6 +286,7 @@ class WTVLzpf extends EventEmitter {
this.current_literal = 0;
this.total_compressed = 0;
this.compressed_offset = 0;
this.ring_buffer.fill(0x00, 0, 0x2000)
this.flag_table.fill(0xFFFF, 0, 0x1000);
this.compressed_data = (length > 0) ? null : Buffer.alloc(length);
}
@@ -349,16 +351,17 @@ class WTVLzpf extends EventEmitter {
var code = -1;
var byte = uncompressed_data.readUInt8(i);
this.ring_buffer[i & 0x1FFF] = byte;
if(match_index > 0) {
if (byte != uncompressed_data.readUInt8(flag) || match_index > 0x0127) {
if (byte != this.ring_buffer[flag] || match_index > 0x0127) {
code_length = this.matchEncode[match_index][1];
code = this.matchEncode[match_index][0];
match_index = 0;
type_index = 3;
} else {
match_index++;
flag++;
match_index = (match_index + 1) & 0x1FFF;
flag = (flag + 1) & 0x1FFF;
sum = (sum + byte) & 0xFFFF;
working_data = ((working_data * 0x0100) + byte) & 0xFFFFFFFF;
i++;
@@ -369,7 +372,7 @@ class WTVLzpf extends EventEmitter {
if (i >= 3) {
flags_index = (working_data >>> 0x0B ^ working_data) & 0x0FFF;
flag = this.flag_table[flags_index];
this.flag_table[flags_index] = i;
this.flag_table[flags_index] = i & 0x1FFF;
} else {
type_index++;
}
@@ -377,9 +380,9 @@ class WTVLzpf extends EventEmitter {
if (flag == 0xFFFF) {
code_length = this.nomatchEncode[byte][1];
code = this.nomatchEncode[byte][0] << 0x10;
} else if (byte == uncompressed_data.readUInt8(flag)) {
} else if (byte == this.ring_buffer[flag]) {
match_index = 1;
flag++;
flag = (flag + 1) & 0x1FFF;
type_index = 4;
} else {
code_length = this.nomatchEncode[byte][1] + 1;