tx: add tbsHash method.

lib/bcoin/block.js

@@ -437,7 +437,8 @@ Block.prototype.postVerify = function postVerify() {
     // BIP30 - Ensure there are no duplicate txids
     if (this.chain.index[tx.hash('hex')]) {
       // Blocks 91842 and 91880 created duplicate
-      // txids by carefully crafting the coinbases.
+      // txids by using the same exact output script
+      // and extraNonce.
       this.chain.emit('debug', 'Block is overwriting txids: %s', this.rhash);
       if (!(network.type === 'main' && (height === 91842 || height === 91880)))
         return false;

lib/bcoin/miner.js

@@ -205,8 +205,17 @@ Miner.prototype.createBlock = function createBlock(tx) {
       index: 0xffffffff
     },
     script: [
+      // Height (required in v2+ blocks)
       new bn(this.last.height + 1).toArray().reverse(),
+      // extraNonce - incremented when
+      // the nonce overflows.
       [],
+      // Add a nonce to ensure we don't
+      // collide with a previous coinbase
+      // of ours.
+      utils.nonce().toArray(),
+      // Let the world know this little
+      // miner succeeded.
       utils.ascii2array(this.msg || 'mined by bcoin')
     ],
     seq: 0xffffffff

lib/bcoin/tx.js

@@ -653,6 +653,62 @@ TX.prototype.signatureHash = function signatureHash(index, s, type) {
   return hash;
 };
 
+TX.prototype.tbsHash = function tbsHash(enc) {
+  var copy = this.clone();
+  var i, j, input, s, raw, redeem, m;
+
+  if (this.isCoinbase())
+    return this.hash(enc);
+
+  if (this._tbsHash) {
+    return enc === 'hex'
+      ? utils.toHex(this._tbsHash)
+      : this._tbsHash.slice();
+  }
+
+  for (i = 0; i < copy.inputs.length; i++) {
+    input = copy.inputs[i];
+    input.out.tx = this.inputs[i].out.tx;
+    assert(input.out.tx);
+
+    s = input.script;
+    redeem = input.out.tx.getSubscript(input.out.index);
+
+    if (bcoin.script.isScripthash(redeem)) {
+      raw = s[s.length - 1];
+      assert(Array.isArray(raw) && raw.length);
+      redeem = bcoin.script.subscript(bcoin.script.decode(raw));
+    } else {
+      raw = null;
+    }
+
+    if (bcoin.script.isPubkey(redeem)) {
+      input.script = [[]];
+    } else if (bcoin.script.isPubkeyhash(redeem)) {
+      assert(Array.isArray(s[1]) && s[1].length);
+      input.script = [[], s[1]];
+    } else if (bcoin.script.isMultisig(redeem)) {
+      m = s[0];
+      if (Array.isArray(m))
+        m = m[0];
+      input.script = [[]];
+      for (i = 0; i < m; i++)
+        input.script.push([]);
+    } else {
+      input.script = [];
+    }
+
+    if (raw)
+      input.script.push(raw);
+  }
+
+  this._tbsHash = utils.dsha256(copy.render(true));
+
+  return enc === 'hex'
+    ? utils.toHex(this._tbsHash)
+    : this._tbsHash.slice();
+};
+
 TX.prototype.verify = function verify(index, force, flags) {
   // Valid if included in block
   if (!force && this.ts !== 0)
@@ -1202,7 +1258,7 @@ TX.prototype.__defineGetter__('fee', function() {
 });
 
 TX.prototype.__defineGetter__('value', function() {
-  return this.funds('in');
+  return this.funds('out');
 });
 
 TX.prototype.__defineGetter__('height', function() {