refactor: use buffer-layout to clean up buffer encoding

web3.js/src/transaction.js

@@ -1,9 +1,11 @@
 // @flow
 
 import assert from 'assert';
+import * as BufferLayout from 'buffer-layout';
 import nacl from 'tweetnacl';
 import bs58 from 'bs58';
 
+import * as Layout from './layout';
 import type {Account} from './account';
 import type {PublicKey} from './publickey';
 
@@ -54,7 +56,7 @@ export class Transaction {
   /**
    * Program Id to execute
    */
-  programId: ?PublicKey;
+  programId: PublicKey;
 
   /**
    * A recent transaction id.  Must be populated by the caller
@@ -79,53 +81,46 @@ export class Transaction {
    * @private
    */
   _getSignData(): Buffer {
-    const {lastId} = this;
+    const {lastId, keys, programId, userdata} = this;
     if (!lastId) {
       throw new Error('Transaction lastId required');
     }
 
-    // Start with a Buffer that should be large enough to fit any Transaction
-    const transactionData = Buffer.alloc(2048);
+    const signDataLayout = BufferLayout.struct([
+      BufferLayout.ns64('keysLength'),
+      BufferLayout.seq(
+        Layout.publicKey('key'),
+        keys.length,
+        'keys'
+      ),
+      Layout.publicKey('programId'),
+      Layout.publicKey('lastId'),
+      BufferLayout.ns64('fee'),
+      BufferLayout.ns64('userdataLength'),
+      BufferLayout.blob(userdata.length, 'userdata'),
+    ]);
 
-    let pos = 0;
+    let signData = Buffer.alloc(2048);
+    let length = signDataLayout.encode(
+      {
+        keysLength: keys.length,
+        keys: keys.map((key) => key.toBuffer()),
+        programId: programId.toBuffer(),
+        lastId: Buffer.from(bs58.decode(lastId)),
+        fee: 0,
+        userdataLength: userdata.length,
+        userdata,
+      },
+      signData
+    );
 
-    // serialize `this.keys`
-    transactionData.writeUInt32LE(this.keys.length, pos);  // u64
-    pos += 8;
-    for (let key of this.keys) {
-      const keyBytes = key.toBuffer();
-      keyBytes.copy(transactionData, pos);
-      pos += 32;
+    if (userdata.length === 0) {
+      // If userdata is empty, strip the 64bit 'userdataLength' field from
+      // the end of signData
+      length -= 8;
     }
-
-    // serialize `this.programId`
-    if (this.programId) {
-      const keyBytes = this.programId.toBuffer();
-      keyBytes.copy(transactionData, pos);
-    }
-    pos += 32;
-
-    // serialize `this.lastId`
-    {
-      const lastIdBytes = Buffer.from(bs58.decode(lastId));
-      assert(lastIdBytes.length === 32);
-      lastIdBytes.copy(transactionData, pos);
-      pos += 32;
-    }
-
-    // serialize `this.fee`
-    transactionData.writeUInt32LE(this.fee, pos);        // u64
-    pos += 8;
-
-    // serialize `this.userdata`
-    if (this.userdata.length > 0) {
-      transactionData.writeUInt32LE(this.userdata.length, pos);  // u64
-      pos += 8;
-      this.userdata.copy(transactionData, pos);
-      pos += this.userdata.length;
-    }
-
-    return transactionData.slice(0, pos);
+    signData = signData.slice(0, length);
+    return signData;
   }
 
   /**
@@ -134,8 +129,8 @@ export class Transaction {
    * The Transaction must be assigned a valid `lastId` before invoking this method
    */
   sign(from: Account) {
-    const transactionData = this._getSignData();
-    this.signature = nacl.sign.detached(transactionData, from.secretKey);
+    const signData = this._getSignData();
+    this.signature = nacl.sign.detached(signData, from.secretKey);
     assert(this.signature.length === 64);
   }
 
@@ -150,13 +145,13 @@ export class Transaction {
       throw new Error('Transaction has not been signed');
     }
 
-    const transactionData = this._getSignData();
+    const signData = this._getSignData();
     const wireTransaction = Buffer.alloc(
-      signature.length + transactionData.length
+      signature.length + signData.length
     );
 
     Buffer.from(signature).copy(wireTransaction, 0);
-    transactionData.copy(wireTransaction, signature.length);
+    signData.copy(wireTransaction, signature.length);
     return wireTransaction;
   }
 }