'use strict'
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var inherits = require('inherits')
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var Buffer = require('safe-buffer').Buffer
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var Base = require('cipher-base')
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var ZEROS = Buffer.alloc(128)
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var blocksize = 64
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function Hmac (alg, key) {
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Base.call(this, 'digest')
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if (typeof key === 'string') {
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key = Buffer.from(key)
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}
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this._alg = alg
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this._key = key
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if (key.length > blocksize) {
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key = alg(key)
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} else if (key.length < blocksize) {
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key = Buffer.concat([key, ZEROS], blocksize)
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}
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var ipad = this._ipad = Buffer.allocUnsafe(blocksize)
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var opad = this._opad = Buffer.allocUnsafe(blocksize)
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for (var i = 0; i < blocksize; i++) {
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ipad[i] = key[i] ^ 0x36
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opad[i] = key[i] ^ 0x5C
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}
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this._hash = [ipad]
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}
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inherits(Hmac, Base)
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Hmac.prototype._update = function (data) {
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this._hash.push(data)
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}
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Hmac.prototype._final = function () {
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var h = this._alg(Buffer.concat(this._hash))
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return this._alg(Buffer.concat([this._opad, h]))
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}
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module.exports = Hmac
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