reuse global Uint8Array

bench.ts

@@ -7,6 +7,7 @@ import { hash as jsHashV3 } from "./js/v3.ts";
 import { hash as jsHashV4 } from "./js/v4.ts";
 import { hash as jsHashV5 } from "./js/v5.ts";
 import { hash as jsHashV6 } from "./js/v6.ts";
+import { hash as jsHashV7 } from "./js/v7.ts";
 import { hash as latestHash } from "./js/latest.ts";
 
 // Share the same input buffer across benchmars.
@@ -55,4 +56,5 @@ bench("Js#04", jsHashV3);
 bench("Js#05", jsHashV4);
 bench("Js#06", jsHashV5);
 bench("Js#07", jsHashV6);
-bench("Js#08", latestHash);
+bench("Js#08", jsHashV7);
+bench("Js#09", latestHash);

js/latest.ts

@@ -246,16 +246,28 @@ function readLittleEndianWordsFull(
   }
 }
 
+// Pre-allocate and reuse when possible.
+const blockWords = new Uint32Array(16) as W16;
+let cvStack: Uint32Array | null = null;
+
+function getCvStack(maxDepth: number) {
+  const depth = Math.max(maxDepth, 10);
+  const length = depth * 8;
+  if (cvStack == null || cvStack.length < length) {
+    cvStack = new Uint32Array(length);
+  }
+  return cvStack;
+}
+
 export function hash(input: Uint8Array): Uint8Array {
   const flags = 0;
   const keyWords = IV;
+  const out = new Uint32Array(8);
 
   // The hasher state.
-  const blockWords = new Uint32Array(16) as W16;
-  const maxCvDepth = Math.log2(1 + (input.length >> 10)) + 1;
-  const cvStack = new Uint32Array(maxCvDepth << 3);
+  const maxCvDepth = Math.log2(1 + Math.ceil(input.length / 1024)) + 1;
+  const cvStack = getCvStack(maxCvDepth);
   let cvStackPos = 0;
-
   let chunkCounter = 0;
   let offset = 0;
 
@@ -346,7 +358,7 @@ export function hash(input: Uint8Array): Uint8Array {
       0,
       blockWords,
       0,
-      blockWords,
+      out,
       0,
       true,
       0,
@@ -394,7 +406,7 @@ export function hash(input: Uint8Array): Uint8Array {
       0,
       cvStack,
       cvStackPos,
-      blockWords,
+      out,
       0,
       true,
       0,
@@ -403,5 +415,5 @@ export function hash(input: Uint8Array): Uint8Array {
     );
   }
 
-  return new Uint8Array(blockWords.buffer, 0, 32);
+  return new Uint8Array(out.buffer, 0, 32);
 }