feat: add function computeMastRoot()

Author: motorina0

src/merkle.d.ts

@@ -1,2 +1,3 @@
 /// <reference types="node" />
 export declare function fastMerkleRoot(values: Buffer[], digestFn: (b: Buffer) => Buffer): Buffer;
+export declare function computeMastRoot(scripts: any): Buffer;

src/merkle.js

@@ -1,6 +1,13 @@
 'use strict';
 Object.defineProperty(exports, '__esModule', { value: true });
-exports.fastMerkleRoot = void 0;
+exports.computeMastRoot = exports.fastMerkleRoot = void 0;
+const buffer_1 = require('buffer');
+const bcrypto = require('./crypto');
+// todo: use varuint-bitcoin??
+const varuint = require('bip174/src/lib/converter/varint');
+const TAP_LEAF_TAG = buffer_1.Buffer.from('TapLeaf', 'utf8');
+const TAP_BRANCH_TAG = buffer_1.Buffer.from('TapBranch', 'utf8');
+const LEAF_VERSION_TAPSCRIPT = 0xc0;
 function fastMerkleRoot(values, digestFn) {
   if (!Array.isArray(values)) throw TypeError('Expected values Array');
   if (typeof digestFn !== 'function')
@@ -20,3 +27,40 @@ function fastMerkleRoot(values, digestFn) {
   return results[0];
 }
 exports.fastMerkleRoot = fastMerkleRoot;
+// todo: solve any[]
+function computeMastRoot(scripts) {
+  if (scripts.length === 1) {
+    const script = scripts[0];
+    if (Array.isArray(script)) {
+      return computeMastRoot(script);
+    }
+    script.version = script.version || LEAF_VERSION_TAPSCRIPT;
+    if ((script.version & 1) !== 0) throw new Error('Invalid script version'); // todo typedef error
+    // todo: if (script.output)scheck is bytes
+    const scriptOutput = buffer_1.Buffer.from(script.output, 'hex');
+    return bcrypto.taggedHash(
+      TAP_LEAF_TAG,
+      buffer_1.Buffer.concat([
+        buffer_1.Buffer.from([script.version]),
+        serializeScript(scriptOutput),
+      ]),
+    );
+  }
+  // todo: this is a binary tree, use zero an one index
+  const half = Math.trunc(scripts.length / 2);
+  let leftHash = computeMastRoot(scripts.slice(0, half));
+  let rightHash = computeMastRoot(scripts.slice(half));
+  if (leftHash.compare(rightHash) === 1)
+    [leftHash, rightHash] = [rightHash, leftHash];
+  return bcrypto.taggedHash(
+    TAP_BRANCH_TAG,
+    buffer_1.Buffer.concat([leftHash, rightHash]),
+  );
+}
+exports.computeMastRoot = computeMastRoot;
+function serializeScript(s) {
+  const varintLen = varuint.encodingLength(s.length);
+  const buffer = buffer_1.Buffer.allocUnsafe(varintLen); // better
+  varuint.encode(s.length, buffer);
+  return buffer_1.Buffer.concat([buffer, s]);
+}

ts_src/merkle.ts

@@ -1,3 +1,14 @@
+import { Buffer as NBuffer } from 'buffer';
+import * as bcrypto from './crypto';
+// todo: use varuint-bitcoin??
+import * as varuint from 'bip174/src/lib/converter/varint';
+
+
+const TAP_LEAF_TAG = NBuffer.from('TapLeaf', 'utf8');
+const TAP_BRANCH_TAG = NBuffer.from('TapBranch', 'utf8');
+const LEAF_VERSION_TAPSCRIPT = 0xc0
+
+
 export function fastMerkleRoot(
   values: Buffer[],
   digestFn: (b: Buffer) => Buffer,
@@ -25,3 +36,32 @@ export function fastMerkleRoot(
 
   return results[0];
 }
+
+// todo: solve any[]
+export function computeMastRoot(scripts: any): Buffer {
+  if (scripts.length === 1) {
+      const script = scripts[0]
+      if (Array.isArray(script)) {
+          return computeMastRoot(script)
+      }
+      script.version = script.version || LEAF_VERSION_TAPSCRIPT
+      if ((script.version & 1) !== 0) throw new Error("Invalid script version") // todo typedef error
+      // todo: if (script.output)scheck is bytes
+      const scriptOutput = NBuffer.from(script.output, 'hex')
+      return bcrypto.taggedHash(TAP_LEAF_TAG, NBuffer.concat([NBuffer.from([script.version]), serializeScript(scriptOutput)]))
+  }
+  // todo: this is a binary tree, use zero an one index
+  const half = Math.trunc(scripts.length / 2)
+  let leftHash = computeMastRoot(scripts.slice(0, half))
+  let rightHash = computeMastRoot(scripts.slice(half))
+
+  if (leftHash.compare(rightHash) === 1) [leftHash, rightHash] = [rightHash, leftHash]
+  return bcrypto.taggedHash(TAP_BRANCH_TAG, NBuffer.concat([leftHash, rightHash]))
+}
+
+function serializeScript(s: Buffer) {
+  const varintLen = varuint.encodingLength(s.length);
+  const buffer = NBuffer.allocUnsafe(varintLen); // better
+  varuint.encode(s.length, buffer);
+  return NBuffer.concat([buffer, s])
+}