Programs are now loaded with a function and not a member var

Machine would segfault when poking address 0 on an uninitialized
block. this has been fixed.

README.md

@@ -16,6 +16,11 @@ Each documented instruction has a list of what is pushed, and what is popped.
 the items are listed in chronological order, from first pushed/popped to last
 pushed/popped.
 
+You'll notice that words specifying an address are always at the top of the
+stack. This helps increse security and reduce the likelihood of bugs. When
+writing functions to extend creature, it is highly advised that you follow this
+principle when deciding on an order to pop arguments off of the stack in.
+
 ### 0x0 PUSH
 
 Pushes the next word in program memory onto the stack.
@@ -53,8 +58,8 @@ Pops:
 Adds two words. Tip: this can be used as a logical OR.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand + right operand
@@ -64,8 +69,8 @@ Pushes:
 Subtracts two words.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand - right operand
@@ -75,8 +80,8 @@ Pushes:
 Multiplies two words.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand * right operand
@@ -86,8 +91,8 @@ Pushes:
 Divides two words.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand / right operand
@@ -97,8 +102,8 @@ Pushes:
 Checks if two words are equal. Pushes 1 if true, zero if false.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand == right operand
@@ -108,8 +113,8 @@ Pushes:
 Checks if a word is greater than another word. Pushes 1 if true, zero if false.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand > right operand
@@ -119,8 +124,8 @@ Pushes:
 Checks if a word is less than another word. Pushes 1 if true, zero if false.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand < right operand
@@ -130,8 +135,8 @@ Pushes:
 Checks if two words are *not* equal. Pushes 1 if true, zero if false.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand != right operand
@@ -142,8 +147,8 @@ Performs a modulo operation on two words. Tip: this can be used as a logical
 AND.
 
 Pops:
-1. left operand
-2. right operand
+1. right operand
+2. left operand
 
 Pushes:
 1. left operand % right operand

creature.go

@@ -11,10 +11,7 @@ type Word interface {
 // data, and provides methods to run this program data, as well as interact with
 // it.
 type Machine [WORD Word] struct {
-	// Program is not modified by the machine, and can be freely set before
-	// the machine is started.
-	Program []WORD
-
+	program   []WORD
 	stack     []WORD
 	block     []WORD
 	counter   WORD
@@ -87,45 +84,41 @@ func (machine *Machine[WORD]) Reset() {
 func (machine *Machine[WORD]) Execute(offset WORD) (err error) {
 	machine.counter = offset
 
-	for int(machine.counter) < len(machine.Program) {
+	for int(machine.counter) < len(machine.program) {
 		switch machine.instruction() {
 		case PUSH:
-			// push the next word in program memory onto the stack
 			machine.counter++
 			machine.Push(machine.instruction())
 
 		case POP:
-			// pop the top word off of the stack, and discard it
 			machine.Pop()
 
 		case PEEK:
-			// push the word at an address onto the stack
 			machine.Push(machine.Peek(machine.Pop()))
 
 		case POKE:
-			// store a word at an address
 			address := machine.Pop()
 			word := machine.Pop()
 			machine.Poke(address, word)
 
 		case ADD:
-			// adds the last two words on the stack
-			machine.Push(machine.Pop() + machine.Pop())
+			right := machine.Pop()
+			left  := machine.Pop()
+			machine.Push(left + right)
 
 		case SUB:
-			// subtracts the second to last word on the stack from
-			// the last word on the stack
-			machine.Push(machine.Pop() - machine.Pop())
+			right := machine.Pop()
+			left  := machine.Pop()
+			machine.Push(left - right)
 
 		case MUL:
-			// multiplies the last two words on the stack
-			machine.Push(machine.Pop() * machine.Pop())
+			right := machine.Pop()
+			left  := machine.Pop()
+			machine.Push(left * right)
 
 		case DIV:
-			// divides the last word on the stack by the second to
-			// last word on the stack
-			left  := machine.Pop()
 			right := machine.Pop()
+			left  := machine.Pop()
 			if right == 0 {
 				err = ErrorDivideByZero
 				return
@@ -133,62 +126,56 @@ func (machine *Machine[WORD]) Execute(offset WORD) (err error) {
 			machine.Push(left / right)
 
 		case EQ:
-			// checks if the last two words on the stack are equal
+			right := machine.Pop()
+			left  := machine.Pop()
 			equal := 0
-			if machine.Pop() == machine.Pop() {
+			if left == right {
 				equal = 1
 			}
 			machine.Push(WORD(equal))
 
 		case GT:
-			// checks if the last word on the stack is greater than
-			// the second to last word on the stack
+			right := machine.Pop()
+			left  := machine.Pop()
 			greater := 0
-			if machine.Pop() > machine.Pop() {
+			if left > right {
 				greater = 1
 			}
 			machine.Push(WORD(greater))
 
 		case LT:
-			// checks if the last word on the stack is less than the
-			// second to last word on the stack
+			right := machine.Pop()
+			left  := machine.Pop()
 			less := 0
-			if machine.Pop() < machine.Pop() {
+			if left < right {
 				less = 1
 			}
 			machine.Push(WORD(less))
 
 		case NEQ:
-			// checks if the last two words on the stack are not
-			// equal
+			right := machine.Pop()
+			left  := machine.Pop()
 			notEqual := 0
-			if machine.Pop() != machine.Pop() {
+			if left != right {
 				notEqual = 1
 			}
 			machine.Push(WORD(notEqual))
 
 		case MOD:
-			// performs a modulo operation of the second to last
-			// word on the stack to the last word on the stack
-			machine.Push(machine.Pop() % machine.Pop())
+			right := machine.Pop()
+			left  := machine.Pop()
+			machine.Push(left % right)
 
 		case HALT:
-			// stops execution
 			return
 
 		case JMP:
-			// jump to the address specified by the last word on the
-			// stack if the second to last word on the stack is
-			// nonzero
 			jumpTo := machine.Pop()
 			if machine.Pop() != 0 {
 				machine.counter = jumpTo - 1
 			}
 
 		case CAL:
-			// call an implementation-defined subroutine, with the
-			// id specified by the last word on the stack. this may
-			// push and pop various things from the stack
 			id := machine.Pop()
 			if machine.functions == nil {
 				break
@@ -212,7 +199,7 @@ func (machine *Machine[WORD]) Execute(offset WORD) (err error) {
 
 // Instruction returns the current instruction in program memory.
 func (machine *Machine[WORD]) instruction() (instruction WORD) {
-	instruction = machine.Program[machine.counter]
+	instruction = machine.program[machine.counter]
 	return
 }
 
@@ -263,7 +250,7 @@ func (machine *Machine[WORD]) Peek(address WORD) (word WORD) {
 // Poke sets the value at address in the block to word.
 func (machine *Machine[WORD]) Poke(address WORD, word WORD) {
 	if int(address) >= len(machine.block) {
-		reallocatedBlock := make([]WORD, address*3/2)
+		reallocatedBlock := make([]WORD, address*3/2+1)
 		copy(reallocatedBlock, machine.block)
 		machine.block = reallocatedBlock
 	}
@@ -301,6 +288,12 @@ func (machine *Machine[WORD]) Unregister(id WORD) {
 	delete(machine.functions, id)
 }
 
+// LoadProgram loads the contents of program into the machine's program memory.
+func (machine *Machine[WORD]) LoadProgram(program []WORD) {
+	machine.program = make([]WORD, len(program))
+	copy(machine.program, program)
+}
+
 // LoadMemory loads the contents of block into the machine's memory.
 func (machine *Machine[WORD]) LoadMemory(block []WORD) {
 	machine.block = make([]WORD, len(block))

creature_test.go

@@ -9,7 +9,8 @@ func runMachineTest (
 ) (
 	machine *Machine[int],
 ) {
-	machine = &Machine[int] { Program: program }
+	machine = &Machine[int] {}
+	machine.LoadProgram(program)
 	if memory != nil {
 		machine.LoadMemory(memory)
 	}
@@ -41,24 +42,24 @@ func TestPush(test *testing.T) {
 
 func TestArithmetic(test *testing.T) {
 	machine := runMachineTest([]int {
-		PUSH, 2,
 		PUSH, 3,
+		PUSH, 2,
 		ADD,
 		
-		PUSH, 4,
 		PUSH, 10,
+		PUSH, 4,
 		SUB,
 		
-		PUSH, 7,
 		PUSH, 2,
+		PUSH, 7,
 		MUL,
 		
-		PUSH, 3,
 		PUSH, 12,
+		PUSH, 3,
 		DIV,
 		
-		PUSH, 6,
 		PUSH, 8,
+		PUSH, 6,
 		MOD,
 	}, nil, test)
 
@@ -106,16 +107,16 @@ func TestComparison(test *testing.T) {
 		PUSH, 6,
 		EQ,
 		
-		PUSH, 4,
 		PUSH, 324,
+		PUSH, 4,
 		GT,
 		
-		PUSH, 324,
 		PUSH, 4,
+		PUSH, 324,
 		LT,
 		
-		PUSH, 6,
 		PUSH, 54,
+		PUSH, 6,
 		NEQ,
 		
 	}, nil, test)
@@ -230,7 +231,8 @@ func TestJump(test *testing.T) {
 
 func TestRegister(test *testing.T) {
 	output := ""
-	machine := &Machine[int] { Program: []int {
+	machine := &Machine[int] {}
+	machine.LoadProgram([]int {
 		PUSH, int('h'),
 		PUSH, 4,
 		CAL,
@@ -258,7 +260,7 @@ func TestRegister(test *testing.T) {
 		PUSH, int('!'),
 		PUSH, 4,
 		CAL,
-	}}
+	})
 	machine.Register(4, func(machine *Machine[int]) (stop bool) {
 		output += string(rune(machine.Pop()))
 		return

examples/echo.go

@@ -9,7 +9,8 @@ func main () {
 	// this is a simple echo program. it will take in input indefinetly and
 	// repeat it. due to line buffering in the terminal however, it will
 	// only print output once you have pressed enter.
-	machine := cre.Machine[int] { Program: []int {
+	machine := cre.Machine[int] {}
+	machine.LoadProgram([]int {
 		cre.PUSH, 0,
 		cre.CAL,
 
@@ -19,7 +20,7 @@ func main () {
 		cre.PUSH, 1,
 		cre.PUSH, 0,
 		cre.JMP,
-	}}
+	})
 
 	machine.Register (0, read)
 	machine.Register (1, write)

examples/psychiatrist.go

@@ -20,7 +20,8 @@ func main () {
 	responseStart     := 71
 	responseLoopStart := 50
 	
-	machine := cre.Machine[int] { Program: []int {
+	machine := cre.Machine[int] {}
+	machine.LoadProgram([]int {
 		// reset x
 		cre.PUSH, introStart,
 		cre.PUSH, x,
@@ -108,7 +109,7 @@ func main () {
 		cre.PUSH, 1,
 		cre.PUSH, responseLoopStart,
 		cre.JMP,
-	}}
+	})
 
 	stringData := []byte (
 		"\x00" +

go.mod

@@ -1,3 +1,3 @@
 module git.tebibyte.media/sashakoshka/creature
 
-go 1.19
+go 1.18