feat(perf): speed up construction of bbjs Frs

AztecProtocol · Feb 9, 2025 · 18151df · 18151df
1 parent 4526059
commit 18151df
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Showing 2 changed files with 20 additions and 11 deletions.
diff --git a/barretenberg/ts/src/bigint-array/index.ts b/barretenberg/ts/src/bigint-array/index.ts
@@ -10,12 +10,20 @@ export function toBigIntBE(bytes: Uint8Array) {
   return bigint;
 }
 
-export function toBufferBE(value: bigint, byteLength = 32) {
-  const bytes = new Uint8Array(byteLength);
-  const view = new DataView(bytes.buffer);
-  for (let i = 0; i < byteLength; i++) {
-    view.setUint8(byteLength - i - 1, Number(value & BigInt(0xff)));
-    value >>= BigInt(8);
-  }
-  return bytes;
+export function bufToBigIntBE(buf: Buffer) {
+  return (
+    (buf.readBigInt64BE(0) << 192n) +
+    (buf.readBigInt64BE(8) << 128n) +
+    (buf.readBigInt64BE(16) << 64n) +
+    buf.readBigInt64BE(24)
+  );
+}
+
+export function toBufferBE(value: bigint, byteLength = 32): Buffer {
+  const buf = Buffer.alloc(byteLength);
+  buf.writeBigUInt64BE(value >> 192n, 0);
+  buf.writeBigUInt64BE((value >> 128n) & 0xffffffffffffffffn, 8);
+  buf.writeBigUInt64BE((value >> 64n) & 0xffffffffffffffffn, 16);
+  buf.writeBigUInt64BE(value & 0xffffffffffffffffn, 24);
+  return buf;
 }
diff --git a/barretenberg/ts/src/types/fields.ts b/barretenberg/ts/src/types/fields.ts
@@ -1,5 +1,5 @@
 import { randomBytes } from '../random/index.js';
-import { toBigIntBE, toBufferBE } from '../bigint-array/index.js';
+import { bufToBigIntBE, toBigIntBE, toBufferBE } from '../bigint-array/index.js';
 import { BufferReader, uint8ArrayToHexString } from '../serialize/index.js';
 
 // TODO(#4189): Replace with implementation in yarn-project/foundation/src/fields/fields.ts
@@ -15,9 +15,10 @@ export class Fr {
   static SIZE_IN_BYTES = 32;
   value: Uint8Array;
 
-  constructor(value: Uint8Array | bigint) {
+  constructor(value: Uint8Array | bigint | Buffer) {
     // We convert buffer value to bigint to be able to check it fits within modulus
-    const valueBigInt = typeof value === 'bigint' ? value : toBigIntBE(value);
+    const valueBigInt =
+      typeof value === 'bigint' ? value : value instanceof Buffer ? bufToBigIntBE(value) : toBigIntBE(value);
 
     if (valueBigInt > Fr.MAX_VALUE) {
       throw new Error(`Value 0x${valueBigInt.toString(16)} is greater or equal to field modulus.`);