Clone transaction data more efficiently

Author: lukechilds

src/bufferutils.js

@@ -41,6 +41,12 @@ function reverseBuffer(buffer) {
   return buffer;
 }
 exports.reverseBuffer = reverseBuffer;
+function cloneBuffer(buffer) {
+  const clone = Buffer.alloc(buffer.length);
+  buffer.copy(clone);
+  return buffer;
+}
+exports.cloneBuffer = cloneBuffer;
 /**
  * Helper class for serialization of bitcoin data types into a pre-allocated buffer.
  */

src/psbt.js

@@ -104,10 +104,23 @@ class Psbt {
     return this.__CACHE.__TX.locktime;
   }
   get txInputs() {
-    return deepClone(this.__CACHE.__TX.ins);
+    return this.__CACHE.__TX.ins.map(input => {
+      return {
+        hash: bufferutils_1.cloneBuffer(input.hash),
+        index: input.index,
+        script: bufferutils_1.cloneBuffer(input.script),
+        sequence: input.sequence,
+        witness: input.witness.map(buffer => bufferutils_1.cloneBuffer(buffer)),
+      };
+    });
   }
   get txOutputs() {
-    return deepClone(this.__CACHE.__TX.outs);
+    return this.__CACHE.__TX.outs.map(output => {
+      return {
+        script: bufferutils_1.cloneBuffer(output.script),
+        value: output.value,
+      };
+    });
   }
   combine(...those) {
     this.data.combine(...those.map(o => o.data));
@@ -591,11 +604,6 @@ class PsbtTransaction {
     return this.tx.toBuffer();
   }
 }
-function deepClone(obj) {
-  return JSON.parse(JSON.stringify(obj), (_, value) =>
-    value.type === 'Buffer' ? Buffer.from(value.data) : value,
-  );
-}
 function canFinalize(input, script, scriptType) {
   switch (scriptType) {
     case 'pubkey':

ts_src/bufferutils.ts

@@ -48,6 +48,12 @@ export function reverseBuffer(buffer: Buffer): Buffer {
   return buffer;
 }
 
+export function cloneBuffer(buffer: Buffer): Buffer {
+  const clone = Buffer.alloc(buffer.length);
+  buffer.copy(clone);
+  return buffer;
+}
+
 /**
  * Helper class for serialization of bitcoin data types into a pre-allocated buffer.
  */

ts_src/psbt.ts

@@ -14,7 +14,7 @@ import {
 } from 'bip174/src/lib/interfaces';
 import { checkForInput } from 'bip174/src/lib/utils';
 import { toOutputScript } from './address';
-import { reverseBuffer } from './bufferutils';
+import { cloneBuffer, reverseBuffer } from './bufferutils';
 import { hash160 } from './crypto';
 import {
   fromPublicKey as ecPairFromPublicKey,
@@ -24,7 +24,7 @@ import {
 import { bitcoin as btcNetwork, Network } from './networks';
 import * as payments from './payments';
 import * as bscript from './script';
-import { Output, Transaction } from './transaction';
+import { Input, Output, Transaction } from './transaction';
 
 /**
  * These are the default arguments for a Psbt instance.
@@ -137,12 +137,25 @@ export class Psbt {
     return this.__CACHE.__TX.locktime;
   }
 
-  get txInputs(): TransactionInput[] {
-    return deepClone(this.__CACHE.__TX.ins);
+  get txInputs(): Input[] {
+    return this.__CACHE.__TX.ins.map(input => {
+      return {
+        hash: cloneBuffer(input.hash),
+        index: input.index,
+        script: cloneBuffer(input.script),
+        sequence: input.sequence,
+        witness: input.witness.map(buffer => cloneBuffer(buffer)),
+      };
+    });
   }
 
-  get txOutputs(): TransactionInput[] {
-    return deepClone(this.__CACHE.__TX.outs);
+  get txOutputs(): Output[] {
+    return this.__CACHE.__TX.outs.map(output => {
+      return {
+        script: cloneBuffer(output.script),
+        value: output.value,
+      };
+    });
   }
 
   combine(...those: Psbt[]): this {
@@ -773,12 +786,6 @@ class PsbtTransaction implements ITransaction {
   }
 }
 
-function deepClone(obj: any): any {
-  return JSON.parse(JSON.stringify(obj), (_, value) =>
-    value.type === 'Buffer' ? Buffer.from(value.data) : value,
-  );
-}
-
 function canFinalize(
   input: PsbtInput,
   script: Buffer,

types/bufferutils.d.ts

@@ -1,6 +1,7 @@
 export declare function readUInt64LE(buffer: Buffer, offset: number): number;
 export declare function writeUInt64LE(buffer: Buffer, value: number, offset: number): number;
 export declare function reverseBuffer(buffer: Buffer): Buffer;
+export declare function cloneBuffer(buffer: Buffer): Buffer;
 /**
  * Helper class for serialization of bitcoin data types into a pre-allocated buffer.
  */

types/psbt.d.ts

@@ -2,7 +2,7 @@ import { Psbt as PsbtBase } from 'bip174';
 import { KeyValue, PsbtGlobalUpdate, PsbtInput, PsbtInputUpdate, PsbtOutput, PsbtOutputUpdate, TransactionInput } from 'bip174/src/lib/interfaces';
 import { Signer, SignerAsync } from './ecpair';
 import { Network } from './networks';
-import { Transaction } from './transaction';
+import { Input, Output, Transaction } from './transaction';
 /**
  * Psbt class can parse and generate a PSBT binary based off of the BIP174.
  * There are 6 roles that this class fulfills. (Explained in BIP174)
@@ -46,8 +46,8 @@ export declare class Psbt {
     readonly inputCount: number;
     readonly txVersion: number;
     readonly txLocktime: number;
-    readonly txInputs: TransactionInput[];
-    readonly txOutputs: TransactionInput[];
+    readonly txInputs: Input[];
+    readonly txOutputs: Output[];
     combine(...those: Psbt[]): this;
     clone(): Psbt;
     setMaximumFeeRate(satoshiPerByte: number): void;