primitives: add serialized offset and only for block reader/writer

lib/primitives/block.js

@@ -645,7 +645,7 @@ class Block extends AbstractBlock {
     let witness = 0;
 
     for (let i = 0; i < count; i++) {
-      const tx = TX.fromReader(br);
+      const tx = TX.fromReader(br, true);
       witness += tx._witness;
       this.txs.push(tx);
     }
@@ -738,7 +738,7 @@ class Block extends AbstractBlock {
     bw.writeVarint(this.txs.length);
 
     for (const tx of this.txs)
-      tx.toWriter(bw);
+      tx.toWriter(bw, true);
 
     return bw;
   }

lib/primitives/tx.js

@@ -58,6 +58,7 @@ class TX {
 
     this._raw = null;
     this._offset = -1;
+    this._block = false;
     this._size = -1;
     this._witness = -1;
     this._sigops = -1;
@@ -159,6 +160,7 @@ class TX {
     this._raw = null;
     this._size = -1;
     this._offset = -1;
+    this._block = false;
     this._witness = -1;
     this._sigops = -1;
 
@@ -247,15 +249,21 @@ class TX {
   /**
    * Write the transaction to a buffer writer.
    * @param {BufferWriter} bw
+   * @param {Boolean} block
    */
 
-  toWriter(bw) {
+  toWriter(bw, block) {
     if (this.mutable) {
       if (this.hasWitness())
         return this.writeWitness(bw);
       return this.writeNormal(bw);
     }
 
+    if (block) {
+      this._offset = bw.offset;
+      this._block = true;
+    }
+
     bw.writeBytes(this.toRaw());
 
     return bw;
@@ -320,7 +328,7 @@ class TX {
    */
 
   getPosition() {
-    assert(this._offset >= 0, 'Position not available.');
+    assert(this._block && this._offset > 80, 'Position not available.');
 
     return {
       offset: this._offset,
@@ -2243,11 +2251,12 @@ class TX {
   /**
    * Instantiate a transaction from a buffer reader.
    * @param {BufferReader} br
+   * @param {Boolean} block
    * @returns {TX}
    */
 
-  static fromReader(br) {
-    return new this().fromReader(br);
+  static fromReader(br, block) {
+    return new this().fromReader(br, block);
   }
 
   /**
@@ -2264,11 +2273,12 @@ class TX {
    * Inject properties from buffer reader.
    * @private
    * @param {BufferReader} br
+   * @param {Boolean} block
    */
 
-  fromReader(br) {
+  fromReader(br, block) {
     if (hasWitnessBytes(br))
-      return this.fromWitnessReader(br);
+      return this.fromWitnessReader(br, block);
 
     const start = br.start();
 
@@ -2286,9 +2296,13 @@ class TX {
 
     this.locktime = br.readU32();
 
+    if (block) {
+      this._offset = start;
+      this._block = true;
+    }
+
     if (!this.mutable) {
       this._raw = br.endData();
-      this._offset = start;
       this._size = this._raw.length;
       this._witness = 0;
     } else {
@@ -2303,9 +2317,10 @@ class TX {
    * buffer reader (witness serialization).
    * @private
    * @param {BufferReader} br
+   * @param {Boolean} block
    */
 
-  fromWitnessReader(br) {
+  fromWitnessReader(br, block) {
     const start = br.start();
 
     this.version = br.readU32();
@@ -2354,10 +2369,14 @@ class TX {
 
     this.locktime = br.readU32();
 
+    if (block) {
+      this._offset = start;
+      this._block = true;
+    }
+
     if (!this.mutable && hasWitness) {
       this._raw = br.endData();
       this._size = this._raw.length;
-      this._offset = start;
       this._witness = witness;
     } else {
       br.end();

test/block-test.js

@@ -405,7 +405,46 @@ describe('Block', function() {
     }
   });
 
-  it('should deserialize with offset positions for txs (witness)', () => {
+  it('should serialize with offset positions for txs (witness)', () => {
+    const [block] = block482683.getBlock();
+
+    const expected = [
+      {offset: 81, size: 217},
+      {offset: 298, size: 815},
+      {offset: 1113, size: 192},
+      {offset: 1305, size: 259},
+      {offset: 1564, size: 223},
+      {offset: 1787, size: 1223},
+      {offset: 3010, size: 486},
+      {offset: 3496, size: 665},
+      {offset: 4161, size: 3176},
+      {offset: 7337, size: 225},
+      {offset: 7562, size: 1223},
+      {offset: 8785, size: 503}
+    ];
+
+    assert.equal(expected.length, block.txs.length);
+    assert.equal(block.getSize(), expected.reduce((a, b) => a + b.size, 81));
+
+    // Reset the offset for all transactions, and clear
+    // any cached values for the block.
+    block.refresh(true);
+    for (let i = 0; i < block.txs.length; i++)
+      assert.equal(block.txs[i]._offset, -1);
+
+    // Serialize the block, as done before saving to disk.
+    const raw = block.toRaw();
+    assert(raw);
+
+    for (let i = 0; i < block.txs.length; i++) {
+      const {offset, size} = block.txs[i].getPosition();
+
+      assert.strictEqual(offset, expected[i].offset);
+      assert.strictEqual(size, expected[i].size);
+    }
+  });
+
+  it('should deserialize with offset positions for txs', () => {
     const [block] = block300025.getBlock();
 
     assert.equal(block.txs.length, 461);