Signal-Desktop/ts/textsecure/StringView.ts

102 lines
2.8 KiB
TypeScript

// Copyright 2020 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
/* eslint-disable no-bitwise */
/* eslint-disable no-nested-ternary */
const StringView = {
/*
* These functions from the Mozilla Developer Network
* and have been placed in the public domain.
* https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding
* https://developer.mozilla.org/en-US/docs/MDN/About#Copyrights_and_licenses
*/
// prettier-ignore
b64ToUint6(nChr: number): number {
return nChr > 64 && nChr < 91
? nChr - 65
: nChr > 96 && nChr < 123
? nChr - 71
: nChr > 47 && nChr < 58
? nChr + 4
: nChr === 43
? 62
: nChr === 47
? 63
: 0;
},
base64ToBytes(sBase64: string, nBlocksSize: number): ArrayBuffer {
const sB64Enc = sBase64.replace(/[^A-Za-z0-9+/]/g, '');
const nInLen = sB64Enc.length;
const nOutLen = nBlocksSize
? Math.ceil(((nInLen * 3 + 1) >> 2) / nBlocksSize) * nBlocksSize
: (nInLen * 3 + 1) >> 2;
const aBBytes = new ArrayBuffer(nOutLen);
const taBytes = new Uint8Array(aBBytes);
let nMod3;
let nMod4;
let nOutIdx = 0;
let nInIdx = 0;
for (let nUint24 = 0; nInIdx < nInLen; nInIdx += 1) {
nMod4 = nInIdx & 3;
nUint24 |=
StringView.b64ToUint6(sB64Enc.charCodeAt(nInIdx)) << (18 - 6 * nMod4);
if (nMod4 === 3 || nInLen - nInIdx === 1) {
for (
nMod3 = 0;
nMod3 < 3 && nOutIdx < nOutLen;
nMod3 += 1, nOutIdx += 1
) {
taBytes[nOutIdx] = (nUint24 >>> ((16 >>> nMod3) & 24)) & 255;
}
nUint24 = 0;
}
}
return aBBytes;
},
// prettier-ignore
uint6ToB64(nUint6: number): number {
return nUint6 < 26
? nUint6 + 65
: nUint6 < 52
? nUint6 + 71
: nUint6 < 62
? nUint6 - 4
: nUint6 === 62
? 43
: nUint6 === 63
? 47
: 65;
},
bytesToBase64(aBytes: Uint8Array): string {
let nMod3;
let sB64Enc = '';
let nUint24 = 0;
const nLen = aBytes.length;
for (let nIdx = 0; nIdx < nLen; nIdx += 1) {
nMod3 = nIdx % 3;
if (nIdx > 0 && ((nIdx * 4) / 3) % 76 === 0) {
sB64Enc += '\r\n';
}
nUint24 |= aBytes[nIdx] << ((16 >>> nMod3) & 24);
if (nMod3 === 2 || aBytes.length - nIdx === 1) {
sB64Enc += String.fromCharCode(
StringView.uint6ToB64((nUint24 >>> 18) & 63),
StringView.uint6ToB64((nUint24 >>> 12) & 63),
StringView.uint6ToB64((nUint24 >>> 6) & 63),
StringView.uint6ToB64(nUint24 & 63)
);
nUint24 = 0;
}
}
return sB64Enc.replace(/A(?=A$|$)/g, '=');
},
};
export default StringView;