1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
package compiler
import (
"fmt"
)
// MakeInstruction returns a bytecode for an opcode and the operands.
func MakeInstruction(opcode Opcode, operands ...int) []byte {
numOperands := OpcodeOperands[opcode]
totalLen := 1
for _, w := range numOperands {
totalLen += w
}
instruction := make([]byte, totalLen, totalLen)
instruction[0] = byte(opcode)
offset := 1
for i, o := range operands {
width := numOperands[i]
switch width {
case 1:
instruction[offset] = byte(o)
case 2:
n := uint16(o)
instruction[offset] = byte(n >> 8)
instruction[offset+1] = byte(n)
}
offset += width
}
return instruction
}
// FormatInstructions returns string representation of
// bytecode instructions.
func FormatInstructions(b []byte, posOffset int) []string {
var out []string
i := 0
for i < len(b) {
numOperands := OpcodeOperands[Opcode(b[i])]
operands, read := ReadOperands(numOperands, b[i+1:])
switch len(numOperands) {
case 0:
out = append(out, fmt.Sprintf("%04d %-7s", posOffset+i, OpcodeNames[Opcode(b[i])]))
case 1:
out = append(out, fmt.Sprintf("%04d %-7s %-5d", posOffset+i, OpcodeNames[Opcode(b[i])], operands[0]))
case 2:
out = append(out, fmt.Sprintf("%04d %-7s %-5d %-5d", posOffset+i, OpcodeNames[Opcode(b[i])], operands[0], operands[1]))
}
i += 1 + read
}
return out
}
|
