1 files changed, 190 insertions, 0 deletions
diff --git a/src/js/lz4.js b/src/js/lz4.js
new file mode 100644
index 0000000..608cdd8
--- /dev/null
+++ b/src/js/lz4.js
@@ -0,0 +1,190 @@
+/*******************************************************************************
+
+    uBlock Origin - a comprehensive, efficient content blocker
+    Copyright (C) 2018-present Raymond Hill
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see {http://www.gnu.org/licenses/}.
+
+    Home: https://github.com/gorhill/uBlock
+*/
+
+/* global lz4BlockCodec */
+
+'use strict';
+
+/******************************************************************************/
+
+import µb from './background.js';
+
+/*******************************************************************************
+
+    Experimental support for storage compression.
+
+    For background information on the topic, see:
+    https://github.com/uBlockOrigin/uBlock-issues/issues/141#issuecomment-407737186
+
+**/
+
+/******************************************************************************/
+
+let promisedInstance;
+let textEncoder, textDecoder;
+let ttlCount = 0;
+let ttlDelay = 60000;
+
+const init = function() {
+    ttlDelay = µb.hiddenSettings.autoUpdateAssetFetchPeriod * 2 * 1000;
+    if ( promisedInstance === undefined ) {
+        let flavor;
+        if ( µb.hiddenSettings.disableWebAssembly === true ) {
+            flavor = 'js';
+        }
+        promisedInstance = lz4BlockCodec.createInstance(flavor);
+    }
+    return promisedInstance;
+};
+
+// We can't shrink memory usage of lz4 codec instances, and in the
+// current case memory usage can grow to a significant amount given
+// that a single contiguous memory buffer is required to accommodate
+// both input and output data. Thus a time-to-live implementation
+// which will cause the wasm instance to be forgotten after enough
+// time elapse without the instance being used.
+
+const destroy = function() {
+    //if ( lz4CodecInstance !== undefined ) {
+    //    console.info(
+    //        'uBO: freeing lz4-block-codec instance (%s KB)',
+    //        lz4CodecInstance.bytesInUse() >>> 10
+    //    );
+    //}
+    promisedInstance = undefined;
+    textEncoder = textDecoder = undefined;
+    ttlCount = 0;
+};
+
+const ttlTimer = vAPI.defer.create(destroy);
+
+const ttlManage = function(count) {
+    ttlTimer.off();
+    ttlCount += count;
+    if ( ttlCount > 0 ) { return; }
+    ttlTimer.on(ttlDelay);
+};
+
+const encodeValue = function(lz4CodecInstance, dataIn) {
+    if ( !lz4CodecInstance ) { return; }
+    //let t0 = window.performance.now();
+    if ( textEncoder === undefined ) {
+        textEncoder = new TextEncoder();
+    }
+    const inputArray = textEncoder.encode(dataIn);
+    const inputSize = inputArray.byteLength;
+    const outputArray = lz4CodecInstance.encodeBlock(inputArray, 8);
+    if ( outputArray instanceof Uint8Array === false ) { return; }
+    outputArray[0] = 0x18;
+    outputArray[1] = 0x4D;
+    outputArray[2] = 0x22;
+    outputArray[3] = 0x04;
+    outputArray[4] = (inputSize >>>  0) & 0xFF;
+    outputArray[5] = (inputSize >>>  8) & 0xFF;
+    outputArray[6] = (inputSize >>> 16) & 0xFF;
+    outputArray[7] = (inputSize >>> 24) & 0xFF;
+    //console.info(
+    //    'uBO: [%s] compressed %d KB => %d KB (%s%%) in %s ms',
+    //    inputArray.byteLength >> 10,
+    //    outputArray.byteLength >> 10,
+    //    (outputArray.byteLength / inputArray.byteLength * 100).toFixed(0),
+    //    (window.performance.now() - t0).toFixed(1)
+    //);
+    return outputArray;
+};
+
+const decodeValue = function(lz4CodecInstance, inputArray) {
+    if ( !lz4CodecInstance ) { return; }
+    //let t0 = window.performance.now();
+    if (
+        inputArray[0] !== 0x18 || inputArray[1] !== 0x4D ||
+        inputArray[2] !== 0x22 || inputArray[3] !== 0x04
+    ) {
+        console.error('decodeValue: invalid input array');
+        return;
+    }
+    const outputSize = 
+        (inputArray[4] <<  0) | (inputArray[5] <<  8) |
+        (inputArray[6] << 16) | (inputArray[7] << 24);
+    const outputArray = lz4CodecInstance.decodeBlock(inputArray, 8, outputSize);
+    if ( outputArray instanceof Uint8Array === false ) { return; }
+    if ( textDecoder === undefined ) {
+        textDecoder = new TextDecoder();
+    }
+    const s = textDecoder.decode(outputArray);
+    //console.info(
+    //    'uBO: [%s] decompressed %d KB => %d KB (%s%%) in %s ms',
+    //    inputArray.byteLength >>> 10,
+    //    outputSize >>> 10,
+    //    (inputArray.byteLength / outputSize * 100).toFixed(0),
+    //    (window.performance.now() - t0).toFixed(1)
+    //);
+    return s;
+};
+
+const lz4Codec = {
+    // Arguments:
+    //   dataIn: must be a string
+    // Returns:
+    //   A Uint8Array, or the input string as is if compression is not
+    //   possible.
+    encode: async function(dataIn, serialize = undefined) {
+        if ( typeof dataIn !== 'string' || dataIn.length < 4096 ) {
+            return dataIn;
+        }
+        ttlManage(1);
+        const lz4CodecInstance = await init();
+        let dataOut = encodeValue(lz4CodecInstance, dataIn);
+        ttlManage(-1);
+        if ( serialize instanceof Function ) {
+            dataOut = await serialize(dataOut);
+        }
+        return dataOut || dataIn;
+    },
+    // Arguments:
+    //   dataIn: must be a Uint8Array
+    // Returns:
+    //   A string, or the input argument as is if decompression is not
+    //   possible.
+    decode: async function(dataIn, deserialize = undefined) {
+        if ( deserialize instanceof Function ) {
+            dataIn = await deserialize(dataIn);
+        }
+        if ( dataIn instanceof Uint8Array === false ) {
+            return dataIn;
+        }
+        ttlManage(1);
+        const lz4CodecInstance = await init();
+        const dataOut = decodeValue(lz4CodecInstance, dataIn);
+        ttlManage(-1);
+        return dataOut || dataIn;
+    },
+    relinquish: function() {
+        ttlDelay = 1;
+        ttlManage(0);
+    },
+};
+
+/******************************************************************************/
+
+export default lz4Codec;
+
+/******************************************************************************/