library/bitmap/bitmap.go

package bitmap

import (
	"encoding/base64"
	"sync"
)

/*
@Author: by LH
@date:  2019-06-12
@function:位图算法go语言版本类型抽象
*/
const byteBitLength = 8 //一个字节的位数，也是一个uint8类型的位数

type BitMap struct {
	value []uint8
	//bit   uint64
	mu    sync.RWMutex
	count uint64
}

func NewBitMapFromBase64String(s string) (*BitMap, error) { //不要太长比较好
	decodeBytes, e := base64.StdEncoding.DecodeString(s)
	if e != nil {
		return nil, e
	}

	return &BitMap{
		value: decodeBytes,
		count: count(decodeBytes),
		mu:    sync.RWMutex{},
	}, nil
}

//统计1数量
func count(m []byte) (r uint64) {
	for _, v := range m {
		for i := 0; i < byteBitLength; i++ {
			if ByteIndexIsOne(v, i) {
				r++
			}
		}
	}
	return
}

//从string加载
func NewBitMapFromString(s string) *BitMap {

	return &BitMap{
		value: []byte(s),
		mu:    sync.RWMutex{},
		count: count([]byte(s)),
	}
}

func (b *BitMap) Reset() {
	b.mu.Lock()
	defer b.mu.Unlock()
	b.value = make([]uint8, 0)
	b.count = 0
}

func (b *BitMap) Count() uint64 {
	return b.count
}

//获取当前位数长度
func (b *BitMap) Length() int {
	b.mu.RLock()
	defer b.mu.RUnlock()
	return len(b.value) * byteBitLength
}

//func (b *BitMap) BitLength() uint64 {
//	return b.bit
//}

//判断指定位置是否为1
func (b *BitMap) IsBit(index int) (r bool) {
	b.mu.RLock()
	defer b.mu.RUnlock()
	if index < 0 || index >= len(b.value)*byteBitLength { //边界情况
		return
	}
	x := index / byteBitLength
	y := index % byteBitLength
	if ByteIndexIsOne(b.value[x], y) {
		r = true
	}
	return
}

//value数组增加num个长度
func (b *BitMap) addLength(n int) {
	for i := 0; i < n; i++ {
		b.value = append(b.value, 0)
	}
}

//设置指定位置为1
func (b *BitMap) SetBit(index int) {
	if index < 0 {
		return
	}

	b.mu.Lock()
	defer b.mu.Unlock()
	if index >= len(b.value)*byteBitLength { //需要加长度
		b.addLength(index/byteBitLength + 1 - len(b.value))
	}

	arrIndex := index / byteBitLength
	bitIndex := index % byteBitLength

	if !ByteIndexIsOne(b.value[arrIndex], bitIndex) { //不为1时设置为1
		b.value[arrIndex] ^= 128 >> bitIndex
		b.count++
	}

}

//设置指定位置为0
func (b *BitMap) CancelBit(index int) {
	if index < 0 || index >= len(b.value)*byteBitLength {
		return
	}

	arrIndex := index / byteBitLength
	bitIndex := index % byteBitLength

	if ByteIndexIsOne(b.value[arrIndex], bitIndex) { //为1时设置为0
		b.mu.Lock()
		defer b.mu.Unlock()
		b.value[arrIndex] ^= 128 >> bitIndex
		b.count--
	}
}

//base64转化为string
func (b *BitMap) Base64String() string {
	b.mu.RLock()
	defer b.mu.RUnlock()
	return base64.StdEncoding.EncodeToString(b.value)
}

//转 string
func (b *BitMap) String() string {
	b.mu.RLock()
	defer b.mu.RUnlock()
	return string(b.value)
}

//判断一个byte的指定位置是否为1,顺序为从高位到低位下标分别为0->7
func ByteIndexIsOne(a byte, index int) bool {
	if index < 0 || index >= byteBitLength {
		return false
	}

	//t := a
	//t ^= 128 >> index //判断t是否和a相等
	a <<= index
	a >>= 7
	if a == 0 {
		return false
	}
	return true
}

func ByteReverse(b byte) byte {
	for i := 0; i < 4; i++ {
		if (b&(128>>i))>>(7-i) != (b&(1<<i))>>i {
			b ^= 128 >> i
			b ^= 1 << i
		}
	}
	return b
}

//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>以下函数为测试，封装好类型的在上面<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
//从第0位开始判断
func GetBit(s []uint8, index int) (r bool) {
	if index < 0 || index >= len(s)*byteBitLength { //边界情况
		return
	}
	a := index / byteBitLength
	b := index % byteBitLength
	if ByteIndexIsOne(s[a], b) {
		r = true
	}
	return
}