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67 lines
2.3 KiB
67 lines
2.3 KiB
3 years ago
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/**
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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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const randomBytes = size => {
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const bytes = new Array(size)
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for (let 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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const byteArrayToBase64 = uint8 => {
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const lookup = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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const extraBytes = uint8.length % 3 // if we have 1 byte left, pad 2 bytes
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let output = ''
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let temp
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const tripletToBase64 = num => lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F]
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// go through the array every three bytes, we'll deal with trailing stuff later
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for (let 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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if (extraBytes === 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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} else if (extraBytes === 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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}
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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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const uid = len => byteArrayToBase64(randomBytes(Math.ceil(Math.max(8, len * 2)))).replace(/[+/]/g, '').slice(0, len)
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module.exports.uid = uid
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