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Optimise memory usage while computing Murmur2

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comp500 2019-12-23 16:31:36 +00:00
parent 432bb4e25f
commit a0da889a02
1 changed files with 24 additions and 9 deletions
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33
src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.kt
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@ -10,7 +10,7 @@ class Murmur2Hasher : IHasher {
val tempBuffer = Buffer()
override val hash: Hash by lazy(LazyThreadSafetyMode.NONE) {
val data = computeNormalizedArray(internalBuffer.readByteArray())
val data = internalBuffer.readByteArray()
Murmur2Hash(Murmur2Lib.hash32(data, data.size, 1))
}
@ -19,27 +19,42 @@ class Murmur2Hasher : IHasher {
val out = delegate.read(tempBuffer, byteCount)
if (out > -1) {
sink.write(tempBuffer.clone(), out)
internalBuffer.write(tempBuffer, out)
computeNormalizedBufferFaster(tempBuffer, internalBuffer)
}
return out
}
// Credit to https://github.com/modmuss50/CAV2/blob/master/murmur.go
private fun computeNormalizedArray(input: ByteArray): ByteArray {
val output = ByteArray(input.size)
// private fun computeNormalizedArray(input: ByteArray): ByteArray {
// val output = ByteArray(input.size)
// var index = 0
// for (b in input) {
// when (b) {
// 9.toByte(), 10.toByte(), 13.toByte(), 32.toByte() -> {}
// else -> {
// output[index] = b
// index++
// }
// }
// }
// val outputTrimmed = ByteArray(index)
// System.arraycopy(output, 0, outputTrimmed, 0, index)
// return outputTrimmed
// }
private fun computeNormalizedBufferFaster(input: Buffer, output: Buffer) {
var index = 0
for (b in input) {
val arr = input.readByteArray()
for (b in arr) {
when (b) {
9.toByte(), 10.toByte(), 13.toByte(), 32.toByte() -> {}
else -> {
output[index] = b
arr[index] = b
index++
}
}
}
val outputTrimmed = ByteArray(index)
System.arraycopy(output, 0, outputTrimmed, 0, index)
return outputTrimmed
output.write(arr, 0, index)
}
}