more fee estimation.

lib/bcoin/tx.js

@@ -626,71 +626,88 @@ TX.prototype.isCoinbase = function isCoinbase() {
 };
 
 TX.prototype.maxSize = function maxSize() {
-  // Create copy with 0-script inputs
   var copy = this.clone();
-  var size;
+  var i, input, total, size, s, m, n;
 
-  copy.inputs.forEach(function(input) {
-    input.script = [];
-  });
+  // Create copy with 0-script inputs
+  for (i = 0; i < copy.inputs.length; i++)
+    copy.inputs[i].script = [];
 
-  size = copy.render().length;
+  total = copy.render().length;
 
   // Add size for signatures and public keys
-  copy.inputs.forEach(function(input, i) {
-    var s, m, n;
+  for (i = 0; i < copy.inputs.length; i++) {
+    input = copy.inputs[i];
+    size = 0;
 
     // Get the previous output's subscript
     s = input.out.tx.getSubscript(input.out.index);
 
     if (bcoin.script.isPubkey(s)) {
-      // Signature + len
-      size += 74;
-      return;
-    }
-
-    if (bcoin.script.isPubkeyhash(s)) {
-      // Signature + len
-      size += 74;
-      // Pub key + len
-      size += 34;
-      return;
-    }
-
-    if (bcoin.script.isMultisig(s)) {
-      // Multisig
-      // Empty byte
-      size += 1;
-      // Signature + len
+      // P2PK
+      // OP_PUSHDATA0 [signature]
+      size += 1 + 73;
+    } else if (bcoin.script.isPubkeyhash(s)) {
+      // P2PKH
+      // OP_PUSHDATA0 [signature]
+      size += 1 + 73;
+      // OP_PUSHDATA0 [key]
+      size += 1 + 65;
+    } else if (bcoin.script.isMultisig(s)) {
+      // Bare Multisig
+      // Get the previous m value:
       m = s[0];
-      // If using pushdata instead of OP_1-16:
       if (Array.isArray(m))
         m = m[0] || 0;
       assert(m >= 1 && m <= 3);
-      size += 74 * m;
-      return;
+      // OP_0
+      size += 1;
+      // OP_PUSHDATA0 [signature] ...
+      size += (1 + 73) * m;
+    } else if (bcoin.script.isScripthash(s)) {
+      // P2SH Multisig
+      // This technically won't work well for other
+      // kinds of P2SH. It will also over-estimate
+      // the fee by a lot (at least 10000 satoshis
+      // since we don't have access to the m and n
+      // values), which will be recalculated later.
+      // If fee turns out to be smaller later, we
+      // simply add more of the fee to the change
+      // output.
+      // m value
+      m = 15;
+      // n value
+      n = 15;
+      // OP_0
+      size += 1;
+      // OP_PUSHDATA0 [signature] ...
+      size += (1 + 73) * m;
+      // OP_PUSHDATA2 [redeem]
+      size += 3;
+      // m value
+      size += 1;
+      // OP_PUSHDATA0 [key] ...
+      size += (1 + 65) * n;
+      // n value
+      size += 1;
+      // OP_CHECKMULTISIG
+      size += 1;
     }
 
-    if (bcoin.script.isScripthash(s)) {
-      // Multisig
-      // Empty byte
-      size += 1;
-      // Signature + len
-      size += 74 * 15;
-      // Redeem script
-      // m byte
-      size += 1;
-      // 1 byte length + 65 byte pubkey
-      size += 66 * 15;
-      // n byte
-      size += 1;
-      // checkmultisig byte
-      size += 1;
-      return;
-    }
-  }, this);
+    // Byte for varint size of input script
+    if (size < 0xfd)
+      size += 0;
+    else if (size <= 0xffff)
+      size += 2;
+    else if (size <= 0xffffffff)
+      size += 4;
+    else
+      size += 8;
 
-  return size;
+    total += size;
+  }
+
+  return total;
 };
 
 TX.prototype.getUnspent = function getUnspent(unspent) {