27 lines
807 B
JavaScript
27 lines
807 B
JavaScript
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'use strict'
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var crypto = require('crypto')
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var isInt = function (n) {
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return Number(n) === n && n % 1 === 0
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}
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var isValid = function (input) {
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var type = typeof input
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if (type === 'number' && isNaN(input)) return false
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return type === 'number' || type === 'string' || Buffer.isBuffer(input)
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}
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var toNumber = function (buf) {
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return buf.readUInt16BE(0) * 0xffffffff + buf.readUInt32BE(2)
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}
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module.exports = function (input, max) {
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if (max === undefined) max = Infinity
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if ((!isInt(max) && max !== Infinity) || max <= 0) throw new Error('max must be positive integer')
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if (!isValid(input)) throw new Error('Input must be a string, buffer or a number')
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if (typeof input === 'number') input = input.toString()
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return toNumber(crypto.createHash('sha1').update(input).digest()) % max
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}
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