refactor(sdk-coin-sol): address code review feedback on constants and offsets

Author: Copilot

modules/sdk-coin-sol/src/lib/confidentialMintBuilder.ts

@@ -2,7 +2,7 @@ import { BaseCoin as CoinConfig } from '@bitgo/statics';
 import { BuildTransactionError, TransactionType } from '@bitgo/sdk-core';
 import { Transaction } from './transaction';
 import { TransactionBuilder } from './transactionBuilder';
-import { InstructionBuilderTypes } from './constants';
+import { INSTRUCTIONS_SYSVAR_ADDRESS, InstructionBuilderTypes } from './constants';
 import {
   ConfidentialMint,
   ConfigureConfidentialTransferAccount,
@@ -184,8 +184,7 @@ export class ConfidentialMintBuilder extends TransactionBuilder {
           mintAddress: this._configureParams.mintAddress,
           authorityAddress: this._configureParams.authorityAddress,
           instructionsSysvarOrContextStateAddress:
-            this._configureParams.instructionsSysvarOrContextStateAddress ||
-            'Sysvar1nstructions1111111111111111111111111',
+            this._configureParams.instructionsSysvarOrContextStateAddress || INSTRUCTIONS_SYSVAR_ADDRESS,
           decryptableZeroBalance: this._configureParams.decryptableZeroBalance,
           maximumPendingBalanceCreditCounter: this._configureParams.maximumPendingBalanceCreditCounter,
           proofInstructionOffset: this._configureParams.proofInstructionOffset ?? 0,
@@ -196,7 +195,7 @@ export class ConfidentialMintBuilder extends TransactionBuilder {
     if (this._mintParams) {
       const params = this._mintParams;
       const recordOwner = params.recordAccountOwnerAddress || params.contextStateAuthorityAddress;
-      const space = Math.ceil(Buffer.from(params.rangeRecordData, 'hex').length / 2) * 2;
+      const space = Buffer.from(params.rangeRecordData, 'hex').length;
 
       instructions.push({
         type: InstructionBuilderTypes.CreateRecordAccount,

modules/sdk-coin-sol/src/lib/constants.ts

@@ -35,6 +35,9 @@ export const JITO_STAKE_POOL_RESERVE_ACCOUNT_TESTNET = 'rrWBQqRqBXYZw3CmPCCcjFxQ
 export const JITO_MANAGER_FEE_ACCOUNT = 'feeeFLLsam6xZJFc6UQFrHqkvVt4jfmVvi2BRLkUZ4i';
 export const JITO_MANAGER_FEE_ACCOUNT_TESTNET = 'DH7tmjoQ5zjqcgfYJU22JqmXhP5EY1tkbYpgVWUS2oNo';
 
+/** Solana Instructions sysvar address. Used by Token-2022 extension instructions that verify proofs in-tx. */
+export const INSTRUCTIONS_SYSVAR_ADDRESS = 'Sysvar1nstructions1111111111111111111111111';
+
 // Sdk instructions, mainly to check decoded types.
 export enum ValidInstructionTypesEnum {
   AdvanceNonceAccount = 'AdvanceNonceAccount',

modules/sdk-coin-sol/src/lib/solInstructionFactory.ts

@@ -27,7 +27,7 @@ import {
 import assert from 'assert';
 import BigNumber from 'bignumber.js';
 import { struct, u8, blob } from '@solana/buffer-layout';
-import { InstructionBuilderTypes, MEMO_PROGRAM_PK } from './constants';
+import { INSTRUCTIONS_SYSVAR_ADDRESS, InstructionBuilderTypes, MEMO_PROGRAM_PK } from './constants';
 import {
   AtaClose,
   AtaInit,
@@ -850,7 +850,7 @@ function configureConfidentialTransferAccountInstruction(
     { pubkey: new PublicKey(tokenAddress), isSigner: false, isWritable: true },
     { pubkey: new PublicKey(mintAddress), isSigner: false, isWritable: false },
     {
-      pubkey: new PublicKey(instructionsSysvarOrContextStateAddress || 'Sysvar1nstructions1111111111111111111111111'),
+      pubkey: new PublicKey(instructionsSysvarOrContextStateAddress || INSTRUCTIONS_SYSVAR_ADDRESS),
       isSigner: false,
       isWritable: false,
     },
@@ -1004,6 +1004,8 @@ function writeRecordDataInstruction(data: WriteRecordData): TransactionInstructi
   assert(recordData, 'Missing data param');
 
   const dataBuffer = Buffer.from(recordData, 'hex');
+  const offsetBuffer = Buffer.alloc(4);
+  offsetBuffer.writeUInt32LE(offset, 0);
   return [
     new TransactionInstruction({
       keys: [
@@ -1013,7 +1015,7 @@ function writeRecordDataInstruction(data: WriteRecordData): TransactionInstructi
           : []),
       ],
       programId: new PublicKey(recordAccountOwnerAddress || ZK_ELGAMAL_PROOF_PROGRAM_ID),
-      data: Buffer.concat([Buffer.from([1]), Buffer.from(new Uint32Array([offset]).buffer), dataBuffer]),
+      data: Buffer.concat([Buffer.from([1]), offsetBuffer, dataBuffer]),
     }),
   ];
 }