From a0da889a02b6bc715ca57537c3f5d261c69de185 Mon Sep 17 00:00:00 2001
From: comp500 <comp500@users.noreply.github.com>
Date: Mon, 23 Dec 2019 16:31:36 +0000
Subject: [PATCH] Optimise memory usage while computing Murmur2

---
 .../installer/metadata/hash/Murmur2Hasher.kt  | 33 ++++++++++++++-----
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.kt b/src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.kt
index 1beffb2..d061acf 100644
--- a/src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.kt
+++ b/src/main/kotlin/link/infra/packwiz/installer/metadata/hash/Murmur2Hasher.kt
@@ -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)
 		}
 
 	}