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var Buffer = require('safe-buffer').Buffer
// prototype class for hash functions
function Hash (blockSize, finalSize) {
this._block = Buffer.alloc(blockSize)
this._finalSize = finalSize
this._blockSize = blockSize
this._len = 0
}
Hash.prototype.update = function (data, enc) {
if (typeof data === 'string') {
enc = enc || 'utf8'
data = Buffer.from(data, enc)
}
var block = this._block
var blockSize = this._blockSize
var length = data.length
var accum = this._len
for (var offset = 0; offset < length;) {
var assigned = accum % blockSize
var remainder = Math.min(length - offset, blockSize - assigned)
for (var i = 0; i < remainder; i++) {
block[assigned + i] = data[offset + i]
}
accum += remainder
offset += remainder
if ((accum % blockSize) === 0) {
this._update(block)
}
}
this._len += length
return this
}
Hash.prototype.digest = function (enc) {
var rem = this._len % this._blockSize
this._block[rem] = 0x80
// zero (rem + 1) trailing bits, where (rem + 1) is the smallest
// non-negative solution to the equation (length + 1 + (rem + 1)) === finalSize mod blockSize
this._block.fill(0, rem + 1)
if (rem >= this._finalSize) {
this._update(this._block)
this._block.fill(0)
}
var bits = this._len * 8
// uint32
if (bits <= 0xffffffff) {
this._block.writeUInt32BE(bits, this._blockSize - 4)
// uint64
} else {
var lowBits = (bits & 0xffffffff) >>> 0
var highBits = (bits - lowBits) / 0x100000000
this._block.writeUInt32BE(highBits, this._blockSize - 8)
this._block.writeUInt32BE(lowBits, this._blockSize - 4)
}
this._update(this._block)
var hash = this._hash()
return enc ? hash.toString(enc) : hash
}
Hash.prototype._update = function () {
throw new Error('_update must be implemented by subclass')
}
module.exports = Hash
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