go/brainfuck

1 // Copyright 2009 JGL

2 // Use of this source code is governed by a BSD-style

3 // license that can be found in the LICENSE file.

4

5 /*

6 Brainfuck virtual machines.

7

8 Commands:

9 > increment the data pointer (to point to the next cell to the right).

10 < decrement the data pointer (to point to the next cell to the left).

11 + increment (increase by one) the byte at the data pointer.

12 - decrement (decrease by one) the byte at the data pointer.

13 . output the value of the byte at the data pointer.

14 , accept one byte of input, storing its value in the byte at the data pointer.

15 [ if the byte at the data pointer is zero, then instead of moving the instruction

16 pointer forward to the next command, jump it forward to the command after

17 the matching ] command*.

18 ] if the byte at the data pointer is nonzero, then instead of moving the instruction

19 pointer forward to the next command, jump it back to the command after the

20 matching [ command*.

21

22 ToDo: Implement Read/Write methods as an alternative to channels

23

24 See also: http://golang.org/test/turing.go (many thanks to the author of this code!)

25 */

26

27 package brainfuck

28

29 // BrainFuckVM represents the input and output of the virtual machine

30 type BrainFuckVM struct {

31 In chan byte;

32 Out chan byte;

33 }

34

35 func (bf BrainFuckVM) core(prog []byte, size int) {

36 a := make([]byte, size);

37 if len(prog) == 0 || size == 0 {

38 return

39 }

40 p := 0;

41 pc := 0;

42 for {

43 switch prog[pc] {

44 case '>':

45 p++

46 case '<':

47 p--

48 case '+':

49 a[p]++

50 case '-':

51 a[p]--

52 case '.':

53 bf.Out<- a[p]

54 case ',':

55 // test/turing.go cannot do this!

56 a[p] = <-bf.In

57 case '[':

58 if a[p] == 0 {

59 for nest := 1; nest > 0; pc++ {

60 switch prog[pc+1] {

61 case ']':

62 nest--

63 case '[':

64 nest++

65 }

66 }

67 }

68 case ']':

69 if a[p] != 0 {

70 for nest := -1; nest < 0; pc-- {

71 switch prog[pc-1] {

72 case ']':

73 nest--

74 case '[':

75 nest++

76 }

77 }

78 }

79 }

80 pc++;

81 if pc == len(prog) {

82 return

83 }

84 }

85 }

86

87 // BrainFucker launchs a new virtual machine with the specified

88 // program and memory and return a BrainFuckVM struct to

89 // access to its I/O ports

90 func BrainFucker(prog []byte, size int) *BrainFuckVM {

91 bf := new(BrainFuckVM);

92 bf.In = make(chan byte);

93 bf.Out= make(chan byte);

94 go bf.core(prog, size);

95 return bf;

96 }