more default function args; default Interp flags

- Use default function arguments of ES6/ES2015 available in Node 6.1 in more
  places. I went through every library class and replaced all obvious
  roundabout uses of default arguments with real default arguments.

- Replace Interp default flags = 0 with more reasonable defaults, particularly
  P2SH and CHECKLOCKTIMEVERIFY. When using this code in a real full node, you
  need to specify flags manually because which flags to use depends on context.
  But when using the interpreter casually to build and test transactions, it is
  better to use all the flags. The only major flag that is not yet active is
  CHECKSEQUENCEVERIFY - we should enable that flag by default once it gets
  activated. It's worth noting however that whether that flag is used or not
  depends on the version of the transaction.

lib/bip-39.js

@@ -235,14 +235,12 @@ let inject = function (deps) {
      * Convert a mnemonic to a seed. Does not check for validity of the mnemonic -
      * for that, you should manually run check() first.
      */
-    mnemonic2Seed (passphrase) {
+    mnemonic2Seed (passphrase = '') {
       let mnemonic = this.mnemonic
       if (!this.check()) {
         throw new Error('Mnemonic does not pass the check - was the mnemonic typed incorrectly? Are there extra spaces?')
       }
-      if (passphrase === undefined) {
-        passphrase = ''
-      } else if (typeof passphrase !== 'string') {
+      if (typeof passphrase !== 'string') {
         throw new Error('passphrase must be a string or undefined')
       }
       mnemonic = mnemonic.normalize('NFKD')

lib/bn.js

@@ -86,8 +86,8 @@ let inject = function (deps) {
     return this
   }
 
-  BN.fromBuffer = function (buf, opts) {
-    if (opts !== undefined && opts.endian === 'little') {
+  BN.fromBuffer = function (buf, opts = {endian: 'big'}) {
+    if (opts.endian === 'little') {
       buf = reverseBuf(buf)
     }
     let hex = buf.toString('hex')
@@ -102,9 +102,9 @@ let inject = function (deps) {
     return this
   }
 
-  BN.prototype.toBuffer = function (opts) {
+  BN.prototype.toBuffer = function (opts = {size: undefined, endian: 'big'}) {
     let buf
-    if (opts && opts.size) {
+    if (opts.size) {
       let hex = this.toString(16, 2)
       let natlen = hex.length / 2
       buf = new Buffer(hex, 'hex')
@@ -128,7 +128,7 @@ let inject = function (deps) {
       buf = new Buffer(hex, 'hex')
     }
 
-    if (opts !== undefined && opts.endian === 'little') {
+    if (opts.endian === 'little') {
       buf = reverseBuf(buf)
     }
     let longzero = new Buffer([0])
@@ -142,16 +142,12 @@ let inject = function (deps) {
    * Signed magnitude buffer. Most significant bit represents sign (0 = positive,
    * 1 = negative).
    */
-  BN.prototype.fromSm = function (buf, opts) {
+  BN.prototype.fromSm = function (buf, opts = {endian: 'big'}) {
     if (buf.length === 0) {
       this.fromBuffer(new Buffer([0]))
     }
 
-    let endian = 'big'
-    if (opts) {
-      endian = opts.endian
-    }
-
+    let endian = opts.endian
     if (endian === 'little') {
       buf = reverseBuf(buf)
     }
@@ -166,11 +162,8 @@ let inject = function (deps) {
     return this
   }
 
-  BN.prototype.toSm = function (opts) {
-    let endian = 'big'
-    if (opts) {
-      endian = opts.endian
-    }
+  BN.prototype.toSm = function (opts = {endian: 'big'}) {
+    let endian = opts.endian
 
     let buf
     if (this.cmp(0) === -1) {
@@ -202,13 +195,13 @@ let inject = function (deps) {
    * Produce a BN from the "bits" value in a blockheader. Analagous to Bitcoin
    * Core's uint256 SetCompact method. bits is assumed to be UInt32.
    */
-  BN.prototype.fromBits = function (bits, opts) {
+  BN.prototype.fromBits = function (bits, opts = {strict: false}) {
     // To performed bitwise operations in javascript, we need to convert to a
     // signed 32 bit value.
     let buf = new Buffer(4)
     buf.writeUInt32BE(bits, 0)
     bits = buf.readInt32BE(0)
-    if (opts && opts.strict && (bits & 0x00800000)) {
+    if (opts.strict && (bits & 0x00800000)) {
       throw new Error('negative bit set')
     }
     let nsize = bits >> 24

lib/br.js

@@ -32,19 +32,13 @@ let inject = function (deps) {
       return this.pos >= this.buf.length
     }
 
-    read (len) {
-      if (len === undefined) {
-        len = this.buf.length
-      }
+    read (len = this.buf.length) {
       let buf = this.buf.slice(this.pos, this.pos + len)
       this.pos = this.pos + len
       return buf
     }
 
-    readReverse (len) {
-      if (len === undefined) {
-        len = this.buf.length
-      }
+    readReverse (len = this.buf.length) {
       let buf = this.buf.slice(this.pos, this.pos + len)
       this.pos = this.pos + len
       let buf2 = new Buffer(buf.length)

lib/interp.js

@@ -44,7 +44,7 @@ let inject = function (deps) {
   let TxIn = deps.TxIn
 
   class Interp extends Struct {
-    constructor (script, tx, nIn, stack = [], altStack = [], pc = 0, pBeginCodeHash = 0, nOpCount = 0, ifStack = [], errStr = '', flags = 0) {
+    constructor (script, tx, nIn, stack = [], altStack = [], pc = 0, pBeginCodeHash = 0, nOpCount = 0, ifStack = [], errStr = '', flags = Interp.defaultFlags) {
       super({script, tx, nIn, stack, altStack, pc, pBeginCodeHash, nOpCount, ifStack, errStr, flags})
     }
 
@@ -56,7 +56,7 @@ let inject = function (deps) {
       this.nOpCount = 0
       this.ifStack = []
       this.errStr = ''
-      this.flags = 0
+      this.flags = Interp.defaultFlags
       return this
     }
 
@@ -1527,6 +1527,12 @@ let inject = function (deps) {
   // See Bip112 for details
   Interp.SCRIPT_VERIFY_CHECKSEQUENCEVERIFY = (1 << 10)
 
+  // These are the things we wish to verify by default. At the time of writing,
+  // P2SH and CHECKLOCKTIMEVERIFY are both active, but CHECKSEQUENCEVERIFY is
+  // not.
+  Interp.defaultFlags = Interp.SCRIPT_VERIFY_P2SH | Interp.SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY
+  // Interp.defaultFlags = Interp.SCRIPT_VERIFY_P2SH | Interp.SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY | Interp.SCRIPT_VERIFY_CHECKSEQUENCEVERIFY
+
   return Interp
 }
 

lib/script.js

@@ -332,11 +332,11 @@ let inject = function (deps) {
      * defaults to true. If sort is true, the pubKeys are sorted
      * lexicographically.
     */
-    fromPubKeys (m, pubKeys, sort) {
+    fromPubKeys (m, pubKeys, sort = true) {
       if (typeof m !== 'number') {
         throw new Error('m must be a number')
       }
-      if (sort === true || sort === undefined) {
+      if (sort === true) {
         pubKeys = Script.sortPubKeys(pubKeys)
       }
       this.writeOpCode(m + OpCode.OP_1 - 1)

lib/struct.js

@@ -147,8 +147,7 @@ let inject = function (deps) {
         throw new Error('buf must be a buffer')
       }
       let br = new Br(buf)
-      let args = [br].concat(rest)
-      return this.fromBr.apply(this, args)
+      return this.fromBr(br, ...rest)
     }
 
     static fromBuffer (...rest) {
@@ -160,8 +159,7 @@ let inject = function (deps) {
         throw new Error('buf must be a buffer')
       }
       let br = new Br(buf)
-      let args = [br].concat(rest)
-      return this.asyncFromBr.apply(this, args)
+      return this.asyncFromBr(br, ...rest)
     }
 
     static asyncFromBuffer (buf, ...rest) {

test/interp.js

@@ -21,7 +21,7 @@ describe('Interp', function () {
     interp.nOpCount.should.equal(0)
     interp.ifStack.length.should.equal(0)
     interp.errStr.should.equal('')
-    interp.flags.should.equal(0)
+    interp.flags.should.equal(Interp.defaultFlags)
     interp = new Interp()
     ;(interp instanceof Interp).should.equal(true)
     interp.stack.length.should.equal(0)
@@ -31,7 +31,7 @@ describe('Interp', function () {
     interp.nOpCount.should.equal(0)
     interp.ifStack.length.should.equal(0)
     interp.errStr.should.equal('')
-    interp.flags.should.equal(0)
+    interp.flags.should.equal(Interp.defaultFlags)
   })
 
   describe('#fromJson', function () {