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package tengo
import (
"fmt"
"github.com/d5/tengo/v2/parser"
)
// MakeInstruction returns a bytecode for an opcode and the operands.
func MakeInstruction(opcode parser.Opcode, operands ...int) []byte {
numOperands := parser.OpcodeOperands[opcode]
totalLen := 1
for _, w := range numOperands {
totalLen += w
}
instruction := make([]byte, totalLen)
instruction[0] = 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 := parser.OpcodeOperands[b[i]]
operands, read := parser.ReadOperands(numOperands, b[i+1:])
switch len(numOperands) {
case 0:
out = append(out, fmt.Sprintf("%04d %-7s",
posOffset+i, parser.OpcodeNames[b[i]]))
case 1:
out = append(out, fmt.Sprintf("%04d %-7s %-5d",
posOffset+i, parser.OpcodeNames[b[i]], operands[0]))
case 2:
out = append(out, fmt.Sprintf("%04d %-7s %-5d %-5d",
posOffset+i, parser.OpcodeNames[b[i]],
operands[0], operands[1]))
}
i += 1 + read
}
return out
}
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