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Use JS Map instead of JS object for the huffman code tables. Seems to be a pretty good performance improvement on Chrome, Safari, Firefox.

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This commit is contained in:
Jeff Schiller 2021-12-12 00:32:28 -08:00
parent 4496948aaf
commit 843caf4e61
3 changed files with 63 additions and 9 deletions
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15
archive/unzip.js
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@ -251,17 +251,14 @@ function getHuffmanCodes(bitLengths) {
} }
// Step 3: Assign numerical values to all codes // Step 3: Assign numerical values to all codes
const table = {}; const table = new Map();
let tableLength = 0;
for (let n = 0; n < numLengths; ++n) { for (let n = 0; n < numLengths; ++n) {
const len = bitLengths[n]; const len = bitLengths[n];
if (len != 0) { if (len != 0) {
table[next_code[len]] = { length: len, symbol: n }; //, bitstring: binaryValueToString(next_code[len],len) }; table.set(next_code[len], { length: len, symbol: n }); //, bitstring: binaryValueToString(next_code[len],len) };
tableLength++;
next_code[len]++; next_code[len]++;
} }
} }
table.maxLength = tableLength;
return table; return table;
} }
@ -317,7 +314,6 @@ function getFixedDistanceTable() {
function decodeSymbol(bstream, hcTable) { function decodeSymbol(bstream, hcTable) {
let code = 0; let code = 0;
let len = 0; let len = 0;
let match = false;
// loop until we match // loop until we match
for (; ;) { for (; ;) {
@ -327,16 +323,16 @@ function decodeSymbol(bstream, hcTable) {
++len; ++len;
// check against Huffman Code table and break if found // check against Huffman Code table and break if found
if (hcTable.hasOwnProperty(code) && hcTable[code].length == len) { if (hcTable.has(code) && hcTable.get(code).length == len) {
break; break;
} }
if (len > hcTable.maxLength) { if (len > hcTable.maxLength) {
err(`Bit stream out of sync, didn't find a Huffman Code, length was ${len} ` + err(`Bit stream out of sync, didn't find a Huffman Code, length was ${len} ` +
`and table only max code length of ${hcTable.maxLength}`); `and table only max code length of ${hcTable.length}`);
break; break;
} }
} }
return hcTable[code].symbol; return hcTable.get(code).symbol;
} }
@ -710,6 +706,7 @@ onmessage = function (event) {
bytestream = new bitjs.io.ByteStream(bytes); bytestream = new bitjs.io.ByteStream(bytes);
} else { } else {
bytestream.push(bytes); bytestream.push(bytes);
// TODO: Shouldn't this return here if it's not waiting?
} }
if (unarchiveState === UnarchiveState.NOT_STARTED) { if (unarchiveState === UnarchiveState.NOT_STARTED) {

13
tests/zipper-test.html Normal file
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@ -0,0 +1,13 @@
<!DOCTYPE html>
<html>
<head>
<script src="zipper-test.js" type="module"></script>
</head>
<body>
<div>
<input id="zip-tester" type="file" multiple>
<span id="archive-uploader-label">Select a bunch of zip files</span>
</div>
<div id="result"></div>
</body>
</html>

44
tests/zipper-test.js Normal file
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@ -0,0 +1,44 @@
import { UnarchiveEventType, Unzipper } from '../archive/archive.js';
const result = document.querySelector('#result');
const fileInputEl = document.querySelector('#zip-tester');
async function getFiles(fileChangeEvt) {
result.innerHTML = `Starting to load files`;
const files = fileChangeEvt.target.files;
const buffers = [];
for (const file of files) {
buffers.push(await new Promise((resolve, reject) => {
const fr = new FileReader();
fr.onload = () => {
resolve(new Uint8Array(fr.result));
};
fr.readAsArrayBuffer(file);
}));
}
result.innerHTML = `Loaded files`;
let fileNum = 0;
const INC = 100 / files.length;
const start = performance.now();
for (const b of buffers) {
await new Promise((resolve, reject) => {
const unzipper = new Unzipper(b.buffer, { pathToBitJS: '../' });
unzipper.addEventListener(UnarchiveEventType.FINISH, () => {
fileNum++;
resolve();
});
result.innerHTML = `Unzipping file ${fileNum} / ${files.length}`;
unzipper.start();
});
}
const end = performance.now();
result.innerHTML = `Unzipping took ${end - start}ms`;
}
fileInputEl.addEventListener('change', getFiles, false);