Factor the end-of-script error handling into a function.

Use it to reduce code dpulication in the bip16 case.

In addition we export it so that that a user could run:
for !done && err == nil {
	done, err = s.Step()
}
err = s.CheckErrorCondition()

manually instead of having to run Execute().

script.go

@@ -77,6 +77,15 @@ var StackErrUnknownAddress = errors.New("non-recognised address")
 // on top of the stack is false signifying that the script has failed.
 var StackErrScriptFailed = errors.New("execute fail, fail on stack")
 
+// StackErrScriptUnfinished is returned when CheckErrorCondition is called
+// on a script that has not finished executing.
+var StackErrScriptUnfinished = errors.New("Error check when script unfinished")
+
+// StackErrEmpyStack is returned when the stack is empty at the end of
+// execution. Normal operation requires that a boolean is on top of the stack
+// when the scripts have finished executing.
+var StackErrEmptyStack = errors.New("Stack empty at end of execution")
+
 // Bip16Activation is the timestamp where BIP0016 is valid to use in the
 // blockchain.  To be used to determine if BIP0016 should be called for or not.
 // This timestamp corresponds to Sun Apr 1 00:00:00 UTC 2012.
@@ -358,8 +367,21 @@ func (s *Script) Execute() (err error) {
 			return dstr + astr
 		}))
 	}
+
+	return s.CheckErrorCondition()
+}
+
+// CheckErrorCondition returns nil if the running script has ended and was
+// successful, leaving a a true boolean on the stack. An error otherwise,
+// including if the script has not finished.
+func (s *Script) CheckErrorCondition() (err error) {
+	// Check we are actually done. if pc is past the end of script array
+	// then we have run out of scripts to run.
+	if s.scriptidx < len(s.scripts) {
+		return StackErrScriptUnfinished
+	}
 	if s.dstack.Depth() < 1 {
-		return fmt.Errorf("stack empty at end of execution")
+		return StackErrEmptyStack
 	}
 	v, err := s.dstack.PopBool()
 	if err == nil && v == false {
@@ -367,8 +389,8 @@ func (s *Script) Execute() (err error) {
 		log.Tracef("%v", func() string {
 			dis0, _ := s.DisasmScript(0)
 			dis1, _ := s.DisasmScript(1)
-			return fmt.Sprintf("script0: %s\n script1: %s",
+			return fmt.Sprintf("scripts failed: script0: %s\n"+
-				dis0, dis1)
+				"script1: %s", dis0, dis1)
 		})
 		err = StackErrScriptFailed
 	}
@@ -376,7 +398,6 @@ func (s *Script) Execute() (err error) {
 		// conditional execution stack context left active
 		err = StackErrMissingEndif
 	}
-
 	return err
 }
 
@@ -416,17 +437,18 @@ func (m *Script) Step() (done bool, err error) {
 		m.numOps = 0 // number of ops is per script.
 		m.scriptoff = 0
 		if m.scriptidx == 0 && m.bip16 {
+			m.scriptidx++
 			m.savedFirstStack = m.GetStack()
 		} else if m.scriptidx == 1 && m.bip16 {
-			// Check for successful completion of script
+			// Put us past the end for CheckErrorCondition()
-			v, err := m.dstack.PopBool()
+			m.scriptidx++
+			// We check script ran ok, if so then we pull
+			// the script out of the first stack and executre that.
+			err := m.CheckErrorCondition()
 			if err != nil {
 				return false, err
 			}
-			if v == false {
+
-				return false, StackErrScriptFailed
-			}
-			// check that first element on stack is a bool
 			script := m.savedFirstStack[len(m.savedFirstStack)-1]
 			pops, err := parseScript(script)
 			if err != nil {
@@ -436,8 +458,9 @@ func (m *Script) Step() (done bool, err error) {
 			// Set stack to be the stack from first script
 			// minus the script itself
 			m.SetStack(m.savedFirstStack[:len(m.savedFirstStack)-1])
+		} else {
+			m.scriptidx++
 		}
-		m.scriptidx++
 		// there are zero length scripts in the wild
 		if m.scriptidx < len(m.scripts) && m.scriptoff >= len(m.scripts[m.scriptidx]) {
 			m.scriptidx++

test_coverage.txt

@@ -2,137 +2,138 @@
 github.com/conformal/btcscript/stack.go		 asInt				 100.00% (18/18)
 github.com/conformal/btcscript/opcode.go	 opcodeWithin			 100.00% (13/13)
 github.com/conformal/btcscript/opcode.go	 parsedOpcode.print		 100.00% (12/12)
-github.com/conformal/btcscript/opcode.go	 parsedOpcode.bytes		 100.00% (12/12)
 github.com/conformal/btcscript/stack.go		 Stack.nipN			 100.00% (12/12)
-github.com/conformal/btcscript/opcode.go	 opcodeIf			 100.00% (11/11)
+github.com/conformal/btcscript/opcode.go	 parsedOpcode.bytes		 100.00% (12/12)
 github.com/conformal/btcscript/opcode.go	 opcodeNotIf			 100.00% (11/11)
-github.com/conformal/btcscript/opcode.go	 opcodeNumEqual			 100.00% (10/10)
+github.com/conformal/btcscript/opcode.go	 opcodeIf			 100.00% (11/11)
-github.com/conformal/btcscript/opcode.go	 opcodeBoolOr			 100.00% (10/10)
-github.com/conformal/btcscript/stack.go		 Stack.Tuck			 100.00% (10/10)
-github.com/conformal/btcscript/opcode.go	 opcodeBoolAnd			 100.00% (10/10)
 github.com/conformal/btcscript/opcode.go	 opcodeMin			 100.00% (10/10)
-github.com/conformal/btcscript/opcode.go	 opcodeGreaterThanOrEqual	 100.00% (10/10)
 github.com/conformal/btcscript/opcode.go	 opcodeLessThanOrEqual		 100.00% (10/10)
 github.com/conformal/btcscript/opcode.go	 opcodeGreaterThan		 100.00% (10/10)
+github.com/conformal/btcscript/opcode.go	 opcodeNumEqual			 100.00% (10/10)
 github.com/conformal/btcscript/opcode.go	 opcodeLessThan			 100.00% (10/10)
+github.com/conformal/btcscript/opcode.go	 opcodeGreaterThanOrEqual	 100.00% (10/10)
+github.com/conformal/btcscript/stack.go		 Stack.Tuck			 100.00% (10/10)
+github.com/conformal/btcscript/opcode.go	 opcodeBoolAnd			 100.00% (10/10)
+github.com/conformal/btcscript/opcode.go	 opcodeBoolOr			 100.00% (10/10)
 github.com/conformal/btcscript/opcode.go	 opcodeNumNotEqual		 100.00% (10/10)
 github.com/conformal/btcscript/opcode.go	 opcodeMax			 100.00% (10/10)
-github.com/conformal/btcscript/script.go	 DisasmString			 100.00% (9/9)
+github.com/conformal/btcscript/stack.go		 Stack.OverN			 100.00% (9/9)
 github.com/conformal/btcscript/stack.go		 Stack.RotN			 100.00% (9/9)
 github.com/conformal/btcscript/stack.go		 Stack.SwapN			 100.00% (9/9)
-github.com/conformal/btcscript/stack.go		 Stack.OverN			 100.00% (9/9)
+github.com/conformal/btcscript/script.go	 DisasmString			 100.00% (9/9)
-github.com/conformal/btcscript/opcode.go	 opcodeAdd			 100.00% (8/8)
-github.com/conformal/btcscript/stack.go		 Stack.DupN			 100.00% (8/8)
-github.com/conformal/btcscript/opcode.go	 opcodeSub			 100.00% (8/8)
 github.com/conformal/btcscript/opcode.go	 opcodeEqual			 100.00% (8/8)
-github.com/conformal/btcscript/opcode.go	 opcodeRoll			 100.00% (7/7)
+github.com/conformal/btcscript/stack.go		 Stack.DupN			 100.00% (8/8)
-github.com/conformal/btcscript/stack.go		 Stack.DropN			 100.00% (7/7)
+github.com/conformal/btcscript/opcode.go	 opcodeAdd			 100.00% (8/8)
+github.com/conformal/btcscript/opcode.go	 opcodeSub			 100.00% (8/8)
 github.com/conformal/btcscript/opcode.go	 opcodePick			 100.00% (7/7)
 github.com/conformal/btcscript/opcode.go	 opcodeNot			 100.00% (7/7)
+github.com/conformal/btcscript/stack.go		 Stack.DropN			 100.00% (7/7)
 github.com/conformal/btcscript/opcode.go	 opcode0NotEqual		 100.00% (7/7)
-github.com/conformal/btcscript/opcode.go	 opcodeIfDup			 100.00% (6/6)
+github.com/conformal/btcscript/opcode.go	 opcodeRoll			 100.00% (7/7)
 github.com/conformal/btcscript/opcode.go	 opcodeVerify			 100.00% (6/6)
-github.com/conformal/btcscript/opcode.go	 opcodeElse			 100.00% (6/6)
 github.com/conformal/btcscript/opcode.go	 parsedOpcode.conditional	 100.00% (6/6)
-github.com/conformal/btcscript/opcode.go	 opcode1Add			 100.00% (5/5)
+github.com/conformal/btcscript/opcode.go	 opcodeElse			 100.00% (6/6)
-github.com/conformal/btcscript/stack.go		 Stack.RollN			 100.00% (5/5)
+github.com/conformal/btcscript/opcode.go	 opcodeIfDup			 100.00% (6/6)
-github.com/conformal/btcscript/opcode.go	 opcodeRipemd160		 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeHash256			 100.00% (5/5)
 github.com/conformal/btcscript/stack.go		 Stack.PickN			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeSize			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcode1Sub			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeNegate			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeAbs			 100.00% (5/5)
-github.com/conformal/btcscript/script.go	 removeOpcodeByData		 100.00% (5/5)
-github.com/conformal/btcscript/script.go	 removeOpcode			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeSha256			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeHash160			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeToAltStack		 100.00% (5/5)
 github.com/conformal/btcscript/opcode.go	 opcodeFromAltStack		 100.00% (5/5)
-github.com/conformal/btcscript/stack.go		 Stack.PopBool			 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcode1Add			 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeCheckMultiSigVerify	 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeToAltStack		 100.00% (5/5)
-github.com/conformal/btcscript/stack.go		 Stack.PeekInt			 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeNegate			 100.00% (5/5)
-github.com/conformal/btcscript/script.go	 unparseScript			 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeRipemd160		 100.00% (5/5)
-github.com/conformal/btcscript/opcode.go	 opcodeEqualVerify		 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeHash160			 100.00% (5/5)
-github.com/conformal/btcscript/stack.go		 Stack.PeekByteArray		 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeHash256			 100.00% (5/5)
+github.com/conformal/btcscript/opcode.go	 opcode1Sub			 100.00% (5/5)
+github.com/conformal/btcscript/stack.go		 Stack.RollN			 100.00% (5/5)
+github.com/conformal/btcscript/script.go	 removeOpcodeByData		 100.00% (5/5)
+github.com/conformal/btcscript/opcode.go	 opcodeSize			 100.00% (5/5)
+github.com/conformal/btcscript/script.go	 removeOpcode			 100.00% (5/5)
+github.com/conformal/btcscript/opcode.go	 opcodeAbs			 100.00% (5/5)
+github.com/conformal/btcscript/opcode.go	 opcodeSha256			 100.00% (5/5)
 github.com/conformal/btcscript/stack.go		 Stack.PeekBool			 100.00% (4/4)
-github.com/conformal/btcscript/opcode.go	 opcodeNumEqualVerify		 100.00% (4/4)
-github.com/conformal/btcscript/stack.go		 asBool				 100.00% (4/4)
 github.com/conformal/btcscript/opcode.go	 opcodeEndif			 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeEqualVerify		 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeNumEqualVerify		 100.00% (4/4)
+github.com/conformal/btcscript/opcode.go	 opcodeCheckMultiSigVerify	 100.00% (4/4)
+github.com/conformal/btcscript/stack.go		 Stack.PopBool			 100.00% (4/4)
+github.com/conformal/btcscript/stack.go		 asBool				 100.00% (4/4)
+github.com/conformal/btcscript/stack.go		 Stack.PeekByteArray		 100.00% (4/4)
+github.com/conformal/btcscript/stack.go		 Stack.PeekInt			 100.00% (4/4)
 github.com/conformal/btcscript/stack.go		 Stack.PopInt			 100.00% (4/4)
+github.com/conformal/btcscript/script.go	 unparseScript			 100.00% (4/4)
 github.com/conformal/btcscript/script.go	 getStack			 100.00% (4/4)
-github.com/conformal/btcscript/stack.go		 fromBool			 100.00% (3/3)
+github.com/conformal/btcscript/script.go	 scriptUInt16			 100.00% (3/3)
 github.com/conformal/btcscript/script.go	 scriptUInt8			 100.00% (3/3)
+github.com/conformal/btcscript/script.go	 setStack			 100.00% (3/3)
+github.com/conformal/btcscript/stack.go		 fromBool			 100.00% (3/3)
 github.com/conformal/btcscript/script.go	 scriptUInt32			 100.00% (3/3)
 github.com/conformal/btcscript/address.go	 ScriptType.String		 100.00% (3/3)
-github.com/conformal/btcscript/script.go	 setStack			 100.00% (3/3)
+github.com/conformal/btcscript/stack.go		 Stack.Depth			 100.00% (2/2)
-github.com/conformal/btcscript/script.go	 scriptUInt16			 100.00% (3/3)
-github.com/conformal/btcscript/opcode.go	 opcodeFalse			 100.00% (2/2)
-github.com/conformal/btcscript/opcode.go	 opcodePushData			 100.00% (2/2)
-github.com/conformal/btcscript/opcode.go	 opcode1Negate			 100.00% (2/2)
-github.com/conformal/btcscript/opcode.go	 opcodeN			 100.00% (2/2)
 github.com/conformal/btcscript/opcode.go	 opcodeDepth			 100.00% (2/2)
 github.com/conformal/btcscript/opcode.go	 calcHash			 100.00% (2/2)
-github.com/conformal/btcscript/opcode.go	 opcodeCodeSeparator		 100.00% (2/2)
+github.com/conformal/btcscript/opcode.go	 opcode1Negate			 100.00% (2/2)
-github.com/conformal/btcscript/stack.go		 Stack.Depth			 100.00% (2/2)
 github.com/conformal/btcscript/stack.go		 Stack.NipN			 100.00% (2/2)
-github.com/conformal/btcscript/script.go	 Script.GetAltStack		 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcodePushData			 100.00% (2/2)
-github.com/conformal/btcscript/stack.go		 Stack.PushBool			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcodeN			 100.00% (2/2)
+github.com/conformal/btcscript/opcode.go	 opcodeFalse			 100.00% (2/2)
+github.com/conformal/btcscript/opcode.go	 opcodeCodeSeparator		 100.00% (2/2)
+github.com/conformal/btcscript/opcode.go	 opcodeDisabled			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 init				 100.00% (1/1)
+github.com/conformal/btcscript/script.go	 Script.SetStack		 100.00% (1/1)
+github.com/conformal/btcscript/log.go		 newLogClosure			 100.00% (1/1)
+github.com/conformal/btcscript/script.go	 Script.SetAltStack		 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcode2Rot			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcode2Over			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcode3Dup			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcode2Dup			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcode2Drop			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeReturn			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcodeNop			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 calcHash160			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcode2Swap			 100.00% (1/1)
+github.com/conformal/btcscript/stack.go		 Stack.PushByteArray		 100.00% (1/1)
+github.com/conformal/btcscript/stack.go		 Stack.PushInt			 100.00% (1/1)
+github.com/conformal/btcscript/stack.go		 Stack.PopByteArray		 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeInvalid			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeReserved			 100.00% (1/1)
+github.com/conformal/btcscript/script.go	 Script.GetStack		 100.00% (1/1)
+github.com/conformal/btcscript/script.go	 Script.GetAltStack		 100.00% (1/1)
+github.com/conformal/btcscript/stack.go		 Stack.PushBool			 100.00% (1/1)
 github.com/conformal/btcscript/script.go	 Script.subScript		 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcodeDisabled			 100.00% (1/1)
+github.com/conformal/btcscript/log.go		 UseLogger			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcode2Swap			 100.00% (1/1)
+github.com/conformal/btcscript/log.go		 DisableLog			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 init				 100.00% (1/1)
 github.com/conformal/btcscript/script.go	 isPubkey			 100.00% (1/1)
 github.com/conformal/btcscript/script.go	 isPubkeyHash			 100.00% (1/1)
 github.com/conformal/btcscript/script.go	 isScriptHash			 100.00% (1/1)
-github.com/conformal/btcscript/log.go		 newLogClosure			 100.00% (1/1)
-github.com/conformal/btcscript/script.go	 Script.disasm			 100.00% (1/1)
-github.com/conformal/btcscript/log.go		 UseLogger			 100.00% (1/1)
-github.com/conformal/btcscript/log.go		 DisableLog			 100.00% (1/1)
 github.com/conformal/btcscript/log.go		 init				 100.00% (1/1)
-github.com/conformal/btcscript/script.go	 Script.GetStack		 100.00% (1/1)
+github.com/conformal/btcscript/script.go	 Script.disasm			 100.00% (1/1)
-github.com/conformal/btcscript/script.go	 Script.SetStack		 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 calcHash160			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeTuck			 100.00% (1/1)
-github.com/conformal/btcscript/stack.go		 Stack.PushByteArray		 100.00% (1/1)
-github.com/conformal/btcscript/stack.go		 Stack.PushInt			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeSwap			 100.00% (1/1)
-github.com/conformal/btcscript/stack.go		 Stack.PopByteArray		 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeRot			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeOver			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeNip			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeDup			 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeDrop			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcode2Rot			 100.00% (1/1)
+github.com/conformal/btcscript/opcode.go	 opcodeNop			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcode2Over			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcode3Dup			 100.00% (1/1)
-github.com/conformal/btcscript/opcode.go	 opcode2Dup			 100.00% (1/1)
-github.com/conformal/btcscript/script.go	 Script.SetAltStack		 100.00% (1/1)
 github.com/conformal/btcscript/opcode.go	 opcodeCheckMultiSig		 96.43% (54/56)
 github.com/conformal/btcscript/script.go	 NewScript			 95.24% (20/21)
 github.com/conformal/btcscript/address.go	 ScriptToAddress		 94.92% (56/59)
 github.com/conformal/btcscript/script.go	 parseScript			 93.75% (30/32)
+github.com/conformal/btcscript/script.go	 Script.Step			 89.19% (33/37)
 github.com/conformal/btcscript/stack.go		 fromInt			 87.50% (14/16)
-github.com/conformal/btcscript/script.go	 Script.Step			 86.11% (31/36)
 github.com/conformal/btcscript/script.go	 typeOfScript			 83.33% (5/6)
 github.com/conformal/btcscript/opcode.go	 opcodeCheckSig			 80.77% (21/26)
 github.com/conformal/btcscript/opcode.go	 parsedOpcode.exec		 80.00% (4/5)
 github.com/conformal/btcscript/script.go	 Script.DisasmScript		 80.00% (4/5)
-github.com/conformal/btcscript/script.go	 Script.DisasmPC		 75.00% (3/4)
-github.com/conformal/btcscript/script.go	 Script.curPC			 75.00% (3/4)
-github.com/conformal/btcscript/script.go	 isPushOnly			 75.00% (3/4)
 github.com/conformal/btcscript/opcode.go	 opcodeCheckSigVerify		 75.00% (3/4)
+github.com/conformal/btcscript/script.go	 Script.curPC			 75.00% (3/4)
+github.com/conformal/btcscript/script.go	 Script.DisasmPC		 75.00% (3/4)
+github.com/conformal/btcscript/script.go	 isPushOnly			 75.00% (3/4)
 github.com/conformal/btcscript/script.go	 Script.calcScriptHash		 71.43% (25/35)
+github.com/conformal/btcscript/script.go	 Script.CheckErrorCondition	 71.43% (10/14)
 github.com/conformal/btcscript/script.go	 isMultiSig			 61.54% (8/13)
 github.com/conformal/btcscript/opcode.go	 opcodeSha1			 60.00% (3/5)
 github.com/conformal/btcscript/script.go	 Script.validPC			 60.00% (3/5)
-github.com/conformal/btcscript/script.go	 Script.Execute			 55.17% (16/29)
+github.com/conformal/btcscript/script.go	 Script.Execute			 44.44% (8/18)
 github.com/conformal/btcscript/log.go		 SetLogWriter			 0.00% (0/7)
 github.com/conformal/btcscript/log.go		 logClosure.String		 0.00% (0/1)
-github.com/conformal/btcscript			 -------------------------	 92.51% (828/895)
+github.com/conformal/btcscript			 --------------------------	 92.55% (832/899)