package consts

import "fmt"

// 获取字节数组中的位值
// bs - 原始字节数组
// bitIndex - 位索引
func GetBitOfBytes(bs []byte, bitIndex int) bool {
	bi := bitIndex / 8
	i := bitIndex % 8
	if bi >= len(bs) {
		panic(fmt.Errorf("从字节数组获取位值错误,位索引超出字节数组范围: 数组len=%d,位索引=%d", len(bs), bitIndex))
	}
	by := bs[bi]
	v := byte(1 << (7 - i))
	return (by & v) == v
}

// 设置字节数组中的位值
// bs - 原始字节数组
// bitIndex - 位索引
// v - 位值
func SetBitOfBytes(bs []byte, bitIndex int, v bool) []byte {
	bi := bitIndex / 8
	i := bitIndex % 8
	if bi >= len(bs) {
		panic(fmt.Errorf("设置字节数组位值错误,位索引超出字节数组范围: 数组len=%d,位索引=%d", len(bs), bitIndex))
	}
	by := bs[bi]
	if v {
		by |= (1 << (7 - i))
	} else {
		by &= ((1 << (7 - i)) ^ byte(0xff))
	}
	bs[bi] = by
	return bs
}