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) 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 } func iterateInstructions(b []byte, fn func(pos int, opcode Opcode, operands []int) bool) { for i := 0; i < len(b); i++ { numOperands := OpcodeOperands[Opcode(b[i])] operands, read := ReadOperands(numOperands, b[i+1:]) if !fn(i, b[i], operands) { break } i += read } }