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78 lines
2.4 KiB
78 lines
2.4 KiB
/**
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* Specific customUtils for the browser, where we don't have access to the Crypto and Buffer modules
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*/
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/**
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* Taken from the crypto-browserify module
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* https://github.com/dominictarr/crypto-browserify
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* NOTE: Math.random() does not guarantee "cryptographic quality" but we actually don't need it
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*/
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function randomBytes (size) {
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var bytes = new Array(size);
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var r;
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for (var i = 0, r; i < size; i++) {
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if ((i & 0x03) == 0) r = Math.random() * 0x100000000;
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bytes[i] = r >>> ((i & 0x03) << 3) & 0xff;
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}
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return bytes;
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}
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/**
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* Taken from the base64-js module
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* https://github.com/beatgammit/base64-js/
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*/
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function byteArrayToBase64 (uint8) {
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var lookup = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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, extraBytes = uint8.length % 3 // if we have 1 byte left, pad 2 bytes
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, output = ""
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, temp, length, i;
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function tripletToBase64 (num) {
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return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F];
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};
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// go through the array every three bytes, we'll deal with trailing stuff later
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for (i = 0, length = uint8.length - extraBytes; i < length; i += 3) {
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temp = (uint8[i] << 16) + (uint8[i + 1] << 8) + (uint8[i + 2]);
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output += tripletToBase64(temp);
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}
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// pad the end with zeros, but make sure to not forget the extra bytes
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switch (extraBytes) {
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case 1:
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temp = uint8[uint8.length - 1];
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output += lookup[temp >> 2];
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output += lookup[(temp << 4) & 0x3F];
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output += '==';
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break;
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case 2:
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temp = (uint8[uint8.length - 2] << 8) + (uint8[uint8.length - 1]);
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output += lookup[temp >> 10];
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output += lookup[(temp >> 4) & 0x3F];
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output += lookup[(temp << 2) & 0x3F];
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output += '=';
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break;
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}
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return output;
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}
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/**
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* Return a random alphanumerical string of length len
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* There is a very small probability (less than 1/1,000,000) for the length to be less than len
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* (il the base64 conversion yields too many pluses and slashes) but
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* that's not an issue here
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* The probability of a collision is extremely small (need 3*10^12 documents to have one chance in a million of a collision)
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* See http://en.wikipedia.org/wiki/Birthday_problem
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*/
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function uid (len) {
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return byteArrayToBase64(randomBytes(Math.ceil(Math.max(8, len * 2)))).replace(/[+\/]/g, '').slice(0, len);
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}
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module.exports.uid = uid;
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