helene
Version:
Real-time Web Apps for Node.js
63 lines • 2.38 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.uid = uid;
function randomBytes(size) {
const bytes = new Array(size);
let r;
for (let i = 0, r; i < size; i++) {
if ((i & 0x03) == 0)
r = Math.random() * 0x100000000;
bytes[i] = (r >>> ((i & 0x03) << 3)) & 0xff;
}
return bytes;
}
/**
* Taken from the base64-js module
* https://github.com/beatgammit/base64-js/
*/
function byteArrayToBase64(uint8) {
const lookup = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', extraBytes = uint8.length % 3; // if we have 1 byte left, pad 2 bytes
let output = '', temp, length, i;
function tripletToBase64(num) {
return (lookup[(num >> 18) & 0x3f] +
lookup[(num >> 12) & 0x3f] +
lookup[(num >> 6) & 0x3f] +
lookup[num & 0x3f]);
}
// go through the array every three bytes, we'll deal with trailing stuff later
for (i = 0, length = uint8.length - extraBytes; i < length; i += 3) {
temp = (uint8[i] << 16) + (uint8[i + 1] << 8) + uint8[i + 2];
output += tripletToBase64(temp);
}
// pad the end with zeros, but make sure to not forget the extra bytes
switch (extraBytes) {
case 1:
temp = uint8[uint8.length - 1];
output += lookup[temp >> 2];
output += lookup[(temp << 4) & 0x3f];
output += '==';
break;
case 2:
temp = (uint8[uint8.length - 2] << 8) + uint8[uint8.length - 1];
output += lookup[temp >> 10];
output += lookup[(temp >> 4) & 0x3f];
output += lookup[(temp << 2) & 0x3f];
output += '=';
break;
}
return output;
}
/**
* Return a random alphanumerical string of length len
* There is a very small probability (less than 1/1,000,000) for the length to be less than len
* (il the base64 conversion yields too many pluses and slashes) but
* that's not an issue here
* The probability of a collision is tiny (need 3*10^12 documents to have one chance in a million of a collision)
* See http://en.wikipedia.org/wiki/Birthday_problem
*/
function uid(len) {
return byteArrayToBase64(randomBytes(Math.ceil(Math.max(8, len * 2))))
.replace(/[+/]/g, '')
.slice(0, len);
}
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