var Buffer = require('safe-buffer').Buffer
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// prototype class for hash functions
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function Hash (blockSize, finalSize) {
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this._block = Buffer.alloc(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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}
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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 = Buffer.from(data, enc)
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}
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var block = this._block
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var blockSize = this._blockSize
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var length = data.length
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var accum = this._len
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for (var offset = 0; offset < length;) {
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var assigned = accum % blockSize
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var remainder = Math.min(length - offset, blockSize - assigned)
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for (var i = 0; i < remainder; i++) {
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block[assigned + i] = data[offset + i]
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}
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accum += remainder
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offset += remainder
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if ((accum % blockSize) === 0) {
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this._update(block)
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}
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}
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this._len += length
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return this
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}
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Hash.prototype.digest = function (enc) {
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var rem = this._len % this._blockSize
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this._block[rem] = 0x80
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// zero (rem + 1) trailing bits, where (rem + 1) is the smallest
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// non-negative solution to the equation (length + 1 + (rem + 1)) === finalSize mod blockSize
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this._block.fill(0, rem + 1)
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if (rem >= this._finalSize) {
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this._update(this._block)
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this._block.fill(0)
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}
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var bits = this._len * 8
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// uint32
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if (bits <= 0xffffffff) {
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this._block.writeUInt32BE(bits, this._blockSize - 4)
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// uint64
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} else {
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var lowBits = (bits & 0xffffffff) >>> 0
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var highBits = (bits - lowBits) / 0x100000000
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this._block.writeUInt32BE(highBits, this._blockSize - 8)
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this._block.writeUInt32BE(lowBits, this._blockSize - 4)
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}
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this._update(this._block)
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var hash = 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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