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base.ts
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base.ts
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function getLengths(b64: string): [number, number] {
const len: number = b64.length;
// if (len % 4 > 0) {
// throw new TypeError("Invalid string. Length must be a multiple of 4");
// }
// Trim off extra bytes after placeholder bytes are found
// See: https://github.com/beatgammit/base64-js/issues/42
let validLen: number = b64.indexOf("=");
if (validLen === -1) {
validLen = len;
}
const placeHoldersLen: number = validLen === len ? 0 : 4 - (validLen % 4);
return [validLen, placeHoldersLen];
}
export function init(
lookup: string[],
revLookup: number[],
urlsafe: boolean = false,
) {
function _byteLength(validLen: number, placeHoldersLen: number): number {
return Math.floor(((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen);
}
function tripletToBase64(num: number): string {
return (
lookup[(num >> 18) & 0x3f] +
lookup[(num >> 12) & 0x3f] +
lookup[(num >> 6) & 0x3f] +
lookup[num & 0x3f]
);
}
function encodeChunk(buf: Uint8Array, start: number, end: number): string {
const out: string[] = new Array((end - start) / 3);
for (let i: number = start, curTriplet: number = 0; i < end; i += 3) {
out[curTriplet++] = tripletToBase64(
(buf[i] << 16) + (buf[i + 1] << 8) + buf[i + 2],
);
}
return out.join("");
}
return {
// base64 is 4/3 + up to two characters of the original data
byteLength(b64: string): number {
return _byteLength.apply(null, getLengths(b64));
},
toUint8Array(b64: string): Uint8Array {
const [validLen, placeHoldersLen]: number[] = getLengths(b64);
const buf = new Uint8Array(_byteLength(validLen, placeHoldersLen));
// If there are placeholders, only get up to the last complete 4 chars
const len: number = placeHoldersLen ? validLen - 4 : validLen;
let tmp: number;
let curByte: number = 0;
let i: number;
for (i = 0; i < len; i += 4) {
tmp = (revLookup[b64.charCodeAt(i)] << 18) |
(revLookup[b64.charCodeAt(i + 1)] << 12) |
(revLookup[b64.charCodeAt(i + 2)] << 6) |
revLookup[b64.charCodeAt(i + 3)];
buf[curByte++] = (tmp >> 16) & 0xff;
buf[curByte++] = (tmp >> 8) & 0xff;
buf[curByte++] = tmp & 0xff;
}
if (placeHoldersLen === 2) {
tmp = (revLookup[b64.charCodeAt(i)] << 2) |
(revLookup[b64.charCodeAt(i + 1)] >> 4);
buf[curByte++] = tmp & 0xff;
} else if (placeHoldersLen === 1) {
tmp = (revLookup[b64.charCodeAt(i)] << 10) |
(revLookup[b64.charCodeAt(i + 1)] << 4) |
(revLookup[b64.charCodeAt(i + 2)] >> 2);
buf[curByte++] = (tmp >> 8) & 0xff;
buf[curByte++] = tmp & 0xff;
}
return buf;
},
fromUint8Array(buf: Uint8Array): string {
const maxChunkLength: number = 16383; // Must be multiple of 3
const len: number = buf.length;
const extraBytes: number = len % 3; // If we have 1 byte left, pad 2 bytes
const len2: number = len - extraBytes;
const parts: string[] = new Array(
Math.ceil(len2 / maxChunkLength) + (extraBytes ? 1 : 0),
);
let curChunk: number = 0;
let chunkEnd: number;
// Go through the array every three bytes, we'll deal with trailing stuff later
for (let i: number = 0; i < len2; i += maxChunkLength) {
chunkEnd = i + maxChunkLength;
parts[curChunk++] = encodeChunk(
buf,
i,
chunkEnd > len2 ? len2 : chunkEnd,
);
}
let tmp: number;
// Pad the end with zeros, but make sure to not forget the extra bytes
if (extraBytes === 1) {
tmp = buf[len2];
parts[curChunk] = lookup[tmp >> 2] + lookup[(tmp << 4) & 0x3f];
if (!urlsafe) parts[curChunk] += "==";
} else if (extraBytes === 2) {
tmp = (buf[len2] << 8) | (buf[len2 + 1] & 0xff);
parts[curChunk] = lookup[tmp >> 10] +
lookup[(tmp >> 4) & 0x3f] +
lookup[(tmp << 2) & 0x3f];
if (!urlsafe) parts[curChunk] += "=";
}
return parts.join("");
},
};
}