根据给定的范围生成掩码块（c语言实现、任意字节）

废话少说，上代码（可在linux上编译运行，字符数组里的数按照大端存放，main里采用6字节），最下边的__rang_reduce函数作为参考，它计算一个短整型范围的掩码块。

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int numlistcmp(unsigned char *num1,unsigned char *num2,int bytes)
{
    int i,ret;
    for(i=0;i<bytes;i++)
        if(0 != (ret=num1[i]-num2[i]))
            return ret;

    return 0;
}
int numlistiszero(unsigned char *num,int bytes)
{
    int i;

    for(i=0;i<bytes;i++)
        if(num[i]!=0)
            return 0;

    return 1;
}
void maskbitsf(unsigned char *mask,int bits)
{
    int i,bytes;

    bytes=(bits+7)/8;
    mask[0]=0xff>>(bytes*8-bits);

    for(i=1;i<bytes;i++)
        mask[i]=0xff;
}
void numlistshr(unsigned char *num,int bytes,int shbits)
{//移位运算符为算术右移,最高位为1时不易处理，故用unsigned char
    int i,shbyte,shbit;

    shbyte = shbits/8;
    shbit = shbits%8;

    for(i=bytes-1;i>0;i--)
    {
        num[i] >>= shbit;
        num[i] |= num[i-1] << 8-shbit;
    }
    num[i] >>= shbit;

    if(shbyte>0)
        for(i=bytes-1-shbyte;i>0;i--)
            num[i+shbyte]=num[i];

    for(i=0;i<shbyte;i++)
        num[i]=0;
}
void numlistshl(unsigned char *num,int bits,int shbits)
{
    int i,bytes,shbyte,shbit;

    bytes=(bits+7)/8;
    shbyte = shbits/8;
    shbit = shbits%8;

    for(i=0;i<bytes-1;i++)
    {
        num[i] <<= shbit;
        num[i] |= num[i+1] >> 8-shbit;
    }
    num[i] <<= shbit;

    if(shbyte>0)
        for(i=shbyte;i<bytes;i++)
            num[i-shbyte] = num[i];

    for(i=bytes-shbyte;i<bytes;i++)
        num[i] = 0;

    num[0] &= 0xff>>(bytes*8-bits);
}
void numlistadd1(unsigned char *num,int bits)
{
    int i,bytes;

    bytes=(bits+7)/8;
        for(i=bytes-1;i>-1&&(num[i]+=1)==0;i--)
            ;
    if(i==0)
        num[0] &= 0xff>>(bytes*8-bits);
}
void numlistnor(unsigned char * num,int bits)
{
    int i,bytes;

    bytes = (bits+7)/8;

    for(i=0;i<bytes;i++)
        num[i] = ~num[i];

    num[0] &= 0xff>>(bytes*8-bits);
}
void numlistand(unsigned char * num1,unsigned char *num2,int bytes)
{
    int i;

    for(i=0;i<bytes;i++)
        num1[i] = num1[i]&num2[i];
}
void numlistor(unsigned char * num1,unsigned char *num2,int bytes)
{
    int i;

    for(i=0;i<bytes;i++)
        num1[i] = num1[i]|num2[i];
}
int _range_reduce(char *mi, char *max, char* (*list)[2],int mbits)
{
    int nentry=0;
    int bytes=(mbits+sizeof(char)-1)/sizeof(char);
    char *temp=NULL,*mask=NULL,*temp1=NULL,*min=NULL;

    if(NULL==(temp=malloc(bytes))
        goto export;
    if(NULL==(temp1=malloc(bytes))
        goto export;
    if(NULL==(mask=malloc(bytes))
        goto export;
    if(NULL=(min=malloc(bytes))
        goto export;

    memcpy(min,mi,bytes);
    //printf("max:%02x:%02x:%02x:%02x:%02x:%02x\n",max[0]&0xff,max[1]&0xff,max[2]&0xff,max[3]&0xff,max[4]&0xff,max[5]&0xff);

    while (numlistcmp(min,max,bytes)<=0)
    {/* count low order 0 bits in min */
        //printf("1\n");
        if (numlistiszero(min,bytes) != 0)
        {
            maskbitsf(mask,mbits);
        }
        else
        {
            for (memcpy(temp,min,bytes), memset(mask,0,bytes); (temp[bytes-1] & 1) == 0; numlistshr(temp,bytes,1))
            {
                //printf("2\n");
                numlistshl(mask,mbits,1);
                mask[bytes-1] |= 1;
            }
            //printf("temp:%02x:%02x:%02x:%02x:%02x:%02x\n",temp[0]&0xff,temp[1]&0xff,temp[2]&0xff,temp[3]&0xff,temp[4]&0xff,temp[5]&0xff);
        }
        //printf("temp:%02x:%02x:%02x:%02x:%02x:%02x\n",temp[0]&0xff,temp[1]&0xff,temp[2]&0xff,temp[3]&0xff,temp[4]&0xff,temp[5]&0xff);
        //printf("mask:%02x:%02x:%02x:%02x:%02x:%02x\n",mask[0]&0xff,mask[1]&0xff,mask[2]&0xff,mask[3]&0xff,mask[4]&0xff,mask[5]&0xff);
        memcpy(temp1,mask,bytes);
        numlistnor(temp1,mbits);
        numlistand(temp1,min,bytes);
        numlistor(temp1,mask,bytes);
        memcpy(temp,temp1,bytes);

        if (numlistcmp(temp,max,bytes)<=0)
        {
            ;
        }
        else
        {
            //printf("temp:%02x:%02x:%02x:%02x:%02x:%02x\n",temp[0]&0xff,temp[1]&0xff,temp[2]&0xff,temp[3]&0xff,temp[4]&0xff,temp[5]&0xff);
            while (numlistcmp(temp,max,bytes)>0)
            {
                //printf("3\n");
                //printf("temp:%02x:%02x:%02x:%02x:%02x:%02x\n",temp[0]&0xff,temp[1]&0xff,temp[2]&0xff,temp[3]&0xff,temp[4]&0xff,temp[5]&0xff);
                //printf("mask:%02x:%02x:%02x:%02x:%02x:%02x\n",mask[0]&0xff,mask[1]&0xff,mask[2]&0xff,mask[3]&0xff,mask[4]&0xff,mask[5]&0xff);
                numlistshr(mask,bytes,1);
                //printf("mask:%02x:%02x:%02x:%02x:%02x:%02x\n",mask[0]&0xff,mask[1]&0xff,mask[2]&0xff,mask[3]&0xff,mask[4]&0xff,mask[5]&0xff);
                memcpy(temp1,mask,bytes);
                numlistnor(temp1,mbits);
                numlistand(temp1,min,bytes);
                numlistor(temp1,mask,bytes);
                memcpy(temp,temp1,bytes);
            }
        }

        if (list)
        {
            memcpy(list[nentry][0],min,bytes);
            memcpy(temp1,mask,bytes);
            numlistnor(temp1,mbits);
            memcpy(list[nentry][1],temp1,bytes);
        }

        nentry += 1;
        if(numlistcmp(temp,max,bytes)==0)
        {
            break;
        }

        memcpy(temp1,temp,bytes);
        numlistadd1(temp1,mbits);
        memcpy(min,temp1,bytes);
        //printf("temp:%02x:%02x:%02x:%02x:%02x:%02x\n",temp[0]&0xff,temp[1]&0xff,temp[2]&0xff,temp[3]&0xff,temp[4]&0xff,temp[5]&0xff);
        //printf("min:%02x:%02x:%02x:%02x:%02x:%02x\n",min[0]&0xff,min[1]&0xff,min[2]&0xff,min[3]&0xff,min[4]&0xff,min[5]&0xff);
    }
export:
    if(temp)
        free(temp);
    if(temp1)
        free(temp1);
    if(mask)
        free(mask);
    if(min)
        free(min);

    return nentry;
}
int main(int argc,char *argv[])
{
    char macmin[6]={0x00,0x11,0x22,0x33,0x44,0x55};
    char macmax[6]={0x00,0x11,0x22,0x33,0x66,0x55};
    char *(*list)[2]=NULL;
    int temp,i,totol;
    int mbits=0;

    for(i=0;i<6;i++)
    {
        scanf("%x",&temp);
        macmin[i]=temp;
    }
    for(i=0;i<6;i++)
    {
        scanf("%x",&temp);
        macmax[i]=temp;
    }
    scanf("%d",&mbits);
    totol = _range_reduce(macmin, macmax,list,mbits);
    printf("%d\n",totol);
    list =(char *(*)[2])calloc(totol,sizeof(char *[2]));
    for(i=0;i<totol;i++)
    {
        list[i][0]=(char *)calloc(6,1);
        list[i][1]=(char *)calloc(6,1);
    }
    printf("%d\n",i);
    _range_reduce(macmin, macmax,list,mbits);
    for(i=0;i<totol;i++)
    {
        printf("%02x:%02x:%02x:%02x:%02x:%02x\t",list[i][0][0]&0xff,list[i][0][1]&0xff,list[i][0][2]&0xff,list[i][0][3]&0xff,list[i][0][4]&0xff,list[i][0][5]&0xff);
        printf("%02x:%02x:%02x:%02x:%02x:%02x\n",list[i][1][0]&0xff,list[i][1][1]&0xff,list[i][1][2]&0xff,list[i][1][3]&0xff,list[i][1][4]&0xff,list[i][1][5]&0xff);
    }
    for(i=0;i<totol;i++)
    {
        free(list[i][0]);
        free(list[i][1]);
    }
    free(list);
}
int __range_reduce(unsigned short min, unsigned short max, unsigned short (*list)[2])
{
    int nentry;
    unsigned short      temp, mask;
    nentry = 0;

    while (min <= max)
    {/* count low order 0 bits in min */
        if (min == 0)
            mask = 0xffff;
        else
            for (temp = min, mask = 0; (temp & 1) == 0; temp >>= 1)
                mask = (mask << 1) | 1;

        temp = (min & ~mask) | mask;

        if (temp <= max)
            ;
        else
            while (temp > max)
            {
                mask >>= 1;
                temp = (min & ~mask) | mask;
            }

        if (list)
        {
            list[nentry][0] = min;
            list[nentry][1] = ~mask & 0xffff;
        }
        nentry += 1;
        if (temp >= max)
            break;
        min = temp + 1;
    }
    return nentry;
}