From b37e39abca9feab06989d13b35f3eb1d72268392 Mon Sep 17 00:00:00 2001
From: "Ryan X. Charles" <ryanxcharles@gmail.com>
Date: Tue, 23 Sep 2014 21:28:03 -0700
Subject: [PATCH] Script().writeXX convenience methods

Script().writeOp('OP_CHECKMULTISIG'), or...
Script().writeOp(174), or...
Script().writeBuffer([push data buffer]), or...
Script().write([op string, number, or push data buffer])

These convenience methods let you easily write a script.
---
 lib/script.js  | 42 ++++++++++++++++++++++++++++++++++++++++++
 test/script.js | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/lib/script.js b/lib/script.js
index 461109321..63376b27e 100644
--- a/lib/script.js
+++ b/lib/script.js
@@ -234,4 +234,46 @@ Script.prototype.isScripthashIn = function() {
   }
 };
 
+Script.prototype.write = function(obj) {
+  if (typeof obj === 'string')
+    this.writeOp(obj);
+  else if (typeof obj === 'number')
+    this.writeOp(obj);
+  else if (Buffer.isBuffer(obj))
+    this.writeBuffer(obj);
+  else if (typeof obj === 'object')
+    this.chunks.push(obj);
+  else
+    throw new Error('Invalid script chunk');
+  return this;
+};
+
+Script.prototype.writeOp = function(str) {
+  if (typeof str === 'number')
+    this.chunks.push(str);
+  else
+    this.chunks.push(Opcode(str).toNumber());
+  return this;
+};
+
+Script.prototype.writeBuffer = function(buf) {
+  var opcodenum;
+  var len = buf.length;
+  if (buf.length > 0 && buf.length < Opcode.map.OP_PUSHDATA1) {
+    opcodenum = buf.length;
+  } else if (buf.length < Math.pow(2, 8)) {
+    opcodenum = Opcode.map.OP_PUSHDATA1;
+  } else if (buf.length < Math.pow(2, 16)) {
+    opcodenum = Opcode.map.OP_PUSHDATA2;
+  } else if (buf.length < Math.pow(2, 32)) {
+    opcodenum = Opcode.map.OP_PUSHDATA4;
+  }
+  this.chunks.push({
+    buf: buf,
+    len: len,
+    opcodenum: opcodenum
+  });
+  return this;
+};
+
 module.exports = Script;
diff --git a/test/script.js b/test/script.js
index 4aed785f7..83f1b148e 100644
--- a/test/script.js
+++ b/test/script.js
@@ -265,4 +265,44 @@ describe('Script', function() {
 
   });
 
+  describe('#writeOp', function() {
+
+    it('should write these ops', function() {
+      Script().writeOp('OP_CHECKMULTISIG').toString().should.equal('OP_CHECKMULTISIG');
+      Script().writeOp(Opcode.map.OP_CHECKMULTISIG).toString().should.equal('OP_CHECKMULTISIG');
+    });
+
+  });
+
+  describe('#writeBuffer', function() {
+    
+    it('should write these push data', function() {
+      var buf = new Buffer(1);
+      buf.fill(0);
+      Script().writeBuffer(buf).toString().should.equal('1 0x00');
+      buf = new Buffer(255);
+      buf.fill(0);
+      Script().writeBuffer(buf).toString().should.equal('OP_PUSHDATA1 255 0x' + buf.toString('hex'));
+      buf = new Buffer(256);
+      buf.fill(0);
+      Script().writeBuffer(buf).toString().should.equal('OP_PUSHDATA2 256 0x' + buf.toString('hex'));
+      buf = new Buffer(Math.pow(2, 16));
+      buf.fill(0);
+      Script().writeBuffer(buf).toString().should.equal('OP_PUSHDATA4 ' + Math.pow(2, 16) + ' 0x' + buf.toString('hex'));
+    });
+
+  });
+
+  describe('#write', function() {
+
+    it('should write both pushdata and non-pushdata chunks', function() {
+      Script().write('OP_CHECKMULTISIG').toString().should.equal('OP_CHECKMULTISIG');
+      Script().write(Opcode.map.OP_CHECKMULTISIG).toString().should.equal('OP_CHECKMULTISIG');
+      var buf = new Buffer(1);
+      buf.fill(0);
+      Script().write(buf).toString().should.equal('1 0x00');
+    });
+
+  });
+
 });