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/*******************************************************************************
uBlock Origin - a comprehensive, efficient content blocker
Copyright (C) 2014-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
*/
'use strict';
/******************************************************************************/
// Custom base64 codecs. These codecs are meant to encode/decode typed arrays
// to/from strings.
// https://github.com/uBlockOrigin/uBlock-issues/issues/461
// Provide a fallback encoding for Chromium 59 and less by issuing a plain
// JSON string. The fallback can be removed once min supported version is
// above 59.
// TODO: rename µBlock.base64 to µBlock.SparseBase64, now that
// µBlock.DenseBase64 has been introduced.
// TODO: Should no longer need to test presence of TextEncoder/TextDecoder.
const valToDigit = new Uint8Array(64);
const digitToVal = new Uint8Array(128);
{
const chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz@%';
for ( let i = 0, n = chars.length; i < n; i++ ) {
const c = chars.charCodeAt(i);
valToDigit[i] = c;
digitToVal[c] = i;
}
}
// The dense base64 codec is best for typed buffers which values are
// more random. For example, buffer contents as a result of compression
// contain less repetitive values and thus the content is more
// random-looking.
// TODO: Investigate that in Firefox, creating a new Uint8Array from the
// ArrayBuffer fails, the content of the resulting Uint8Array is
// non-sensical. WASM-related?
export const denseBase64 = {
magic: 'DenseBase64_1',
encode: function(input) {
const m = input.length % 3;
const n = input.length - m;
let outputLength = n / 3 * 4;
if ( m !== 0 ) {
outputLength += m + 1;
}
const output = new Uint8Array(outputLength);
let j = 0;
for ( let i = 0; i < n; i += 3) {
const i1 = input[i+0];
const i2 = input[i+1];
const i3 = input[i+2];
output[j+0] = valToDigit[ i1 >>> 2];
output[j+1] = valToDigit[i1 << 4 & 0b110000 | i2 >>> 4];
output[j+2] = valToDigit[i2 << 2 & 0b111100 | i3 >>> 6];
output[j+3] = valToDigit[i3 & 0b111111 ];
j += 4;
}
if ( m !== 0 ) {
const i1 = input[n];
output[j+0] = valToDigit[i1 >>> 2];
if ( m === 1 ) { // 1 value
output[j+1] = valToDigit[i1 << 4 & 0b110000];
} else { // 2 values
const i2 = input[n+1];
output[j+1] = valToDigit[i1 << 4 & 0b110000 | i2 >>> 4];
output[j+2] = valToDigit[i2 << 2 & 0b111100 ];
}
}
const textDecoder = new TextDecoder();
const b64str = textDecoder.decode(output);
return this.magic + b64str;
},
decode: function(instr, arrbuf) {
if ( instr.startsWith(this.magic) === false ) {
throw new Error('Invalid µBlock.denseBase64 encoding');
}
const outputLength = this.decodeSize(instr);
const outbuf = arrbuf instanceof ArrayBuffer === false
? new Uint8Array(outputLength)
: new Uint8Array(arrbuf);
const inputLength = instr.length - this.magic.length;
let i = this.magic.length;
let j = 0;
const m = inputLength & 3;
const n = i + inputLength - m;
while ( i < n ) {
const i1 = digitToVal[instr.charCodeAt(i+0)];
const i2 = digitToVal[instr.charCodeAt(i+1)];
const i3 = digitToVal[instr.charCodeAt(i+2)];
const i4 = digitToVal[instr.charCodeAt(i+3)];
i += 4;
outbuf[j+0] = i1 << 2 | i2 >>> 4;
outbuf[j+1] = i2 << 4 & 0b11110000 | i3 >>> 2;
outbuf[j+2] = i3 << 6 & 0b11000000 | i4;
j += 3;
}
if ( m !== 0 ) {
const i1 = digitToVal[instr.charCodeAt(i+0)];
const i2 = digitToVal[instr.charCodeAt(i+1)];
outbuf[j+0] = i1 << 2 | i2 >>> 4;
if ( m === 3 ) {
const i3 = digitToVal[instr.charCodeAt(i+2)];
outbuf[j+1] = i2 << 4 & 0b11110000 | i3 >>> 2;
}
}
return outbuf;
},
decodeSize: function(instr) {
if ( instr.startsWith(this.magic) === false ) { return 0; }
const inputLength = instr.length - this.magic.length;
const m = inputLength & 3;
const n = inputLength - m;
let outputLength = (n >>> 2) * 3;
if ( m !== 0 ) {
outputLength += m - 1;
}
return outputLength;
},
};
/******************************************************************************/
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