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January 1, 2013 08:02
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how to generate minecraft hex digests
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var crypto = require('crypto'); | |
var assert = require('assert'); | |
function mcHexDigest(str) { | |
var hash = new Buffer(crypto.createHash('sha1').update(str).digest(), 'binary'); | |
// check for negative hashes | |
var negative = hash.readInt8(0) < 0; | |
if (negative) performTwosCompliment(hash); | |
var digest = hash.toString('hex'); | |
// trim leading zeroes | |
digest = digest.replace(/^0+/g, ''); | |
if (negative) digest = '-' + digest; | |
return digest; | |
} | |
function performTwosCompliment(buffer) { | |
var carry = true; | |
var i, newByte, value; | |
for (i = buffer.length - 1; i >= 0; --i) { | |
value = buffer.readUInt8(i); | |
newByte = ~value & 0xff; | |
if (carry) { | |
carry = newByte === 0xff; | |
buffer.writeUInt8(newByte + 1, i); | |
} else { | |
buffer.writeUInt8(newByte, i); | |
} | |
} | |
} | |
assert.strictEqual(mcHexDigest('Notch'), "4ed1f46bbe04bc756bcb17c0c7ce3e4632f06a48"); | |
assert.strictEqual(mcHexDigest('jeb_'), "-7c9d5b0044c130109a5d7b5fb5c317c02b4e28c1"); | |
assert.strictEqual(mcHexDigest('simon'), "88e16a1019277b15d58faf0541e11910eb756f6"); |
This is much simpler using modern javascript:
function hexDigest(text) {
const hash = crypto.createHash("sha1")
.update(text)
.digest()
return BigInt.asIntN( // performs two's compliment
160, // hash size in bits
hash.reduce( // convert buffer to bigint using reduce
(a, x) =>
a << 8n | // bit-shift the accumulator 8 bits (one byte) to the left
BigInt(x), // fill lower byte just freed up by bit-shifting using bitwise or-operator
0n // start with accumulator value of 0
)
).toString(16) // display the result with base 16 (hex)
}
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Replying to timvandam
I smell ECMAscript... delicious!