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47 lines
1.2 KiB
47 lines
1.2 KiB
/** |
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* Secure random string generator with custom alphabet. |
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* |
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* Alphabet must contain 256 symbols or less. Otherwise, the generator |
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* will not be secure. |
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* |
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* @param {generator} random The random bytess generator. |
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* @param {string} alphabet Symbols to be used in new random string. |
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* @param {size} size The number of symbols in new random string. |
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* |
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* @return {string} Random string. |
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* |
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* @example |
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* var format = require('nanoid/format') |
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* |
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* function random (size) { |
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* var result = [] |
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* for (var i = 0; i < size; i++) result.push(randomByte()) |
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* return result |
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* } |
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* |
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* format(random, "abcdef", 5) //=> "fbaef" |
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* |
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* @name format |
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*/ |
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module.exports = function (random, alphabet, size) { |
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var mask = (2 << Math.log(alphabet.length - 1) / Math.LN2) - 1 |
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var step = Math.ceil(1.6 * mask * size / alphabet.length) |
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var id = '' |
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while (true) { |
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var bytes = random(step) |
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for (var i = 0; i < step; i++) { |
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var byte = bytes[i] & mask |
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if (alphabet[byte]) { |
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id += alphabet[byte] |
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if (id.length === size) return id |
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} |
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} |
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} |
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} |
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/** |
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* @callback generator |
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* @param {number} bytes The number of bytes to generate. |
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* @return {number[]} Random bytes. |
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*/
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