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34 lines
983 B
34 lines
983 B
var crypto = require('crypto')
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, fs = require('fs')
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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 crypto.randomBytes(Math.ceil(Math.max(8, len * 2)))
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.toString('base64')
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.replace(/[+\/]/g, '')
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.slice(0, len);
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}
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/**
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* Callback signature: err
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*/
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function ensureFileDoesntExist (file, callback) {
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fs.exists(file, function (exists) {
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if (!exists) { return callback(null); }
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fs.unlink(file, function (err) { return callback(err); });
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});
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}
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module.exports.uid = uid;
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module.exports.ensureFileDoesntExist = ensureFileDoesntExist;
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