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path: root/ber/int.go
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package ber

func intLen(i int64) int {
	n := 1
	for i > 255 {
		n++
		i >>= 8
	}
	for i < -256 {
		n++
		i >>= 8
	}
	return n
}

func unmarshalInt(b []byte) (i int64) {
	nn := len(b)
	neg := b[0]&0x80 != 0
	if b[0] == 0xFF {
		b = b[1:]
		nn -= 1
	}
	for n, v := range b {
		if neg {
			v = ^v
		}
		i += int64(v) << uint((nn-n-1)*8)
	}
	if neg {
		i = -i - 1
	}
	return
}

func marshalInt(i int64) (b []byte) {
	for n := intLen(i); n > 0; n-- {
		b = append(b, byte(i>>uint((n-1)*8)))
	}
	if i > 0 && b[0]&0x80 != 0 {
		b = append([]byte{0x00}, b...)
	}
	if i < 0 && b[0]&0x80 == 0 {
		b = append([]byte{0xFF}, b...)
	}
	return
}

func UnmarshalInt(b []byte) int {
	return int(unmarshalInt(b))
}