Go语言 实现bitmap

package main
import (
    "fmt"
    "math"
    "math/rand"
    "unsafe"
)
const (
    size = 100
)
func main() {
    test_sort()
}
func test_sort() {
    arr := make([]int, size) // int占4字节，100个就占用占用400字节，3200位
    for i := 0; i < len(arr); i++ {
        arr[i] = rand.Intn(size)
    }
    print_array(arr)
    newarr := bitmap_sort(arr)
    print_result(newarr)
}
func print_array(arr []int) {
    fmt.Printf("array:")
    for i := 0; i < len(arr); i++ {
        fmt.Printf(" %d", arr[i])
    }
    fmt.Printf("\n")
}
//内存少数据最大值小可以采用方式，位排序
func bitmap_sort(arr []int) (newarr []int) {
    var left uint32
    size := int(unsafe.Sizeof(arr[0]) * 4)
    newarr = make([]int, len(arr))
    for i := 0; i < len(arr); i++ {
        index := arr[i] / size
        left = uint32(arr[i] % size)
        leftvalue := newarr[index] & (int(math.Pow(2.0, float64(left))) - 1)
        newarr[index] = (newarr[index] >> left)
        if (newarr[index] & 1) == 0 {
            newarr[index] += 1
        }
        newarr[index] = (newarr[index] << left) + leftvalue
    }
    return newarr
}
func print_result(arr []int) {
    index := 0
    size := int(unsafe.Sizeof(arr[0]) * 4)
    fmt.Printf("new array:")
    for i := 0; i < len(arr); i++ {
        for j := 0; j < size; j++ {
            bit := arr[i] & 1
            if bit != 0 {
                fmt.Printf(" %d", index)
            }
            arr[i] = arr[i] >> 1
            index++
        }
    }
}