70 lines
1.7 KiB
JavaScript
70 lines
1.7 KiB
JavaScript
// prototype class for hash functions
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function Hash (blockSize, finalSize) {
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this._block = new Buffer(blockSize)
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this._finalSize = finalSize
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this._blockSize = blockSize
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this._len = 0
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this._s = 0
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}
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Hash.prototype.update = function (data, enc) {
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if (typeof data === 'string') {
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enc = enc || 'utf8'
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data = new Buffer(data, enc)
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}
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var l = this._len += data.length
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var s = this._s || 0
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var f = 0
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var buffer = this._block
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while (s < l) {
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var t = Math.min(data.length, f + this._blockSize - (s % this._blockSize))
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var ch = (t - f)
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for (var i = 0; i < ch; i++) {
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buffer[(s % this._blockSize) + i] = data[i + f]
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}
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s += ch
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f += ch
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if ((s % this._blockSize) === 0) {
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this._update(buffer)
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}
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}
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this._s = s
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return this
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}
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Hash.prototype.digest = function (enc) {
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// Suppose the length of the message M, in bits, is l
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var l = this._len * 8
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// Append the bit 1 to the end of the message
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this._block[this._len % this._blockSize] = 0x80
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// and then k zero bits, where k is the smallest non-negative solution to the equation (l + 1 + k) === finalSize mod blockSize
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this._block.fill(0, this._len % this._blockSize + 1)
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if (l % (this._blockSize * 8) >= this._finalSize * 8) {
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this._update(this._block)
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this._block.fill(0)
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}
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// to this append the block which is equal to the number l written in binary
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// TODO: handle case where l is > Math.pow(2, 29)
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this._block.writeInt32BE(l, this._blockSize - 4)
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var hash = this._update(this._block) || this._hash()
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return enc ? hash.toString(enc) : hash
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}
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Hash.prototype._update = function () {
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throw new Error('_update must be implemented by subclass')
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}
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module.exports = Hash
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