grab block height from the coinbase script.

lib/bcoin/block.js

@@ -14,6 +14,7 @@ var constants = bcoin.protocol.constants;
 
 function Block(data, subtype) {
   var self = this;
+  var tx;
 
   if (!(this instanceof Block))
     return new Block(data, subtype);
@@ -57,6 +58,13 @@ function Block(data, subtype) {
       tx.ts = tx.ts || self.ts;
       return tx;
     });
+
+    if (this.version >= 2) {
+      tx = this.txs[0];
+      if (tx && tx.inputs[0] && +tx.inputs[0].out.hash === 0)
+        this._height = bcoin.script.coinbase(tx.inputs[0].script);
+    }
+
     this.invalid = !this._checkBlock();
   }
 

lib/bcoin/script.js

@@ -1138,6 +1138,20 @@ script.isScripthashInput = function isScripthashInput(s, redeem) {
   return keys;
 };
 
+script.coinbase = function coinbase(s) {
+  var base = s._raw || script.encode(s);
+  var len = Math.min(base[0], base.length);
+  var height = 0;
+  var i, b;
+
+  for (i = 0; i < len; i++) {
+    b = base[i + 1] & 0xff;
+    height |= b << (8 * i);
+  }
+
+  return height;
+};
+
 // https://github.com/bitcoin/bips/blob/master/bip-0066.mediawiki
 /**
  * A canonical signature exists of: <30> <total len> <02> <len R> <R> <02> <len S> <S> <hashtype>