c语言实现bitmap的基本操作

 1 /**

 2  *文件：bit.h

 3  *目的: 实现bitmap数据结构

 4  *作者：杜小波

 5  *联系方式：[email protected]

 6  **/

 7 

 8 #ifndef _BIT_H_

 9 #define _BIT_H_

10 

11 /**

12  *存储bitmap的结构体

13  *存储的顺序从左至右

14  **/

15 struct _Bits;

16 typedef struct _Bits *bits;

17 

18 /**

19  *获得bitmap

20  *@length bitmap的长度

21  *@return 所有位都初始化为0的bitmap

22  */

23 bits bit_new(unsigned int length);

24 

25 /**

26  *销毁一个bitmap

27  **/

28 void bit_destroy(bits bit);

29 

30 /**

31  *获得y一个bitmap的长度

32  *@bit 需要获得长度的bitmap

33  *@return bit的长度

34  **/

35 unsigned int bit_length(bits bit);

36 

37 /**

38  *设置bitmap中相应位置的值

39  *@bit 待设置的bitmap

40  *@pos  需要设置的位置

41  **/

42 void bit_set(bits bit, unsigned int pos, unsigned char value);

43 

44 /**

45  *设置bitmap中相应位置的值

46  *@bit  待获取的bitmap

47  *@pos  获取的位置

48  **/

49 char bit_get(bits bit, unsigned int pos);

50 

51 #endif /*_BITS_H_*/

#include "bit.h"

#include <stdio.h>

#include <stdlib.h>

#include <string.h>



struct _Bits {

    char *bits;

    unsigned int length;

};



bits bit_new(unsigned int length)

{

    bits new_bits = (bits)malloc(sizeof(struct _Bits));

    if (new_bits == NULL)

        return NULL;



    int char_nums = sizeof(char) * (length >> 3) + 1;

    new_bits->bits = (char *)malloc(char_nums);

    if (new_bits == NULL) {

        free(new_bits);

        return NULL;

    }

    memset(new_bits->bits, 0, char_nums);

    new_bits->length = length;



    return new_bits;

}



void bit_destroy(bits bit)

{

    free(bit->bits);

    free(bit);

}



unsigned int bit_length(bits bit)

{

    return bit->length;

}



void bit_set(bits bit, unsigned int pos, unsigned char value)

{

    unsigned char mask = 0x80 >> (pos & 0x7);

    if (value) {

        bit->bits[pos>>3] |= mask;

    } else {

       bit->bits[pos>>3] &= ~mask;

    }

}



char bit_get(bits bit, unsigned int pos)

{

    unsigned char mask = 0x80 >> (pos & 0x7);



    return (mask & bit->bits[pos>>3]) == mask ? 1 : 0;

}

 1 #include <stdio.h>

 2 #include "bit.h"

 3 #define LEN 15

 4 int main(void)

 5 {

 6     bits bit = bit_new(LEN);

 7 

 8     printf("length: %u\n", bit_length(bit));

 9 

10     unsigned int test_value = 0x735D;

11     unsigned char value;

12     int i;

13     for (i = LEN - 1; i >= 0; i--) {

14         value = test_value & 1;

15         bit_set(bit, i, value);

16         test_value >>= 1;

17     }

18 

19     for (i = 0; i < LEN; i++) {

20         printf("%d", bit_get(bit, i));

21     }

22     printf("\n");

23 

24     bit_destroy(bit);

25 

26     return 0;

27 }

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