C语言代码片段#

1. CRC16#

static const unsigned short crc16_table[256] = {
0x0000,0x1021,0x2042,0x3063,0x4084,0x50A5,0x60C6,0x70E7,
0x8108,0x9129,0xA14A,0xB16B,0xC18C,0xD1AD,0xE1CE,0xF1EF,
0x1231,0x0210,0x3273,0x2252,0x52B5,0x4294,0x72F7,0x62D6,
0x9339,0x8318,0xB37B,0xA35A,0xD3BD,0xC39C,0xF3FF,0xE3DE,
0x2462,0x3443,0x0420,0x1401,0x64E6,0x74C7,0x44A4,0x5485,
0xA56A,0xB54B,0x8528,0x9509,0xE5EE,0xF5CF,0xC5AC,0xD58D,
0x3653,0x2672,0x1611,0x0630,0x76D7,0x66F6,0x5695,0x46B4,
0xB75B,0xA77A,0x9719,0x8738,0xF7DF,0xE7FE,0xD79D,0xC7BC,
0x48C4,0x58E5,0x6886,0x78A7,0x0840,0x1861,0x2802,0x3823,
0xC9CC,0xD9ED,0xE98E,0xF9AF,0x8948,0x9969,0xA90A,0xB92B,
0x5AF5,0x4AD4,0x7AB7,0x6A96,0x1A71,0x0A50,0x3A33,0x2A12,
0xDBFD,0xCBDC,0xFBBF,0xEB9E,0x9B79,0x8B58,0xBB3B,0xAB1A,
0x6CA6,0x7C87,0x4CE4,0x5CC5,0x2C22,0x3C03,0x0C60,0x1C41,
0xEDAE,0xFD8F,0xCDEC,0xDDCD,0xAD2A,0xBD0B,0x8D68,0x9D49,
0x7E97,0x6EB6,0x5ED5,0x4EF4,0x3E13,0x2E32,0x1E51,0x0E70,
0xFF9F,0xEFBE,0xDFDD,0xCFFC,0xBF1B,0xAF3A,0x9F59,0x8F78,
0x9188,0x81A9,0xB1CA,0xA1EB,0xD10C,0xC12D,0xF14E,0xE16F,
0x1080,0x00A1,0x30C2,0x20E3,0x5004,0x4025,0x7046,0x6067,
0x83B9,0x9398,0xA3FB,0xB3DA,0xC33D,0xD31C,0xE37F,0xF35E,
0x02B1,0x1290,0x22F3,0x32D2,0x4235,0x5214,0x6277,0x7256,
0xB5EA,0xA5CB,0x95A8,0x8589,0xF56E,0xE54F,0xD52C,0xC50D,
0x34E2,0x24C3,0x14A0,0x0481,0x7466,0x6447,0x5424,0x4405,
0xA7DB,0xB7FA,0x8799,0x97B8,0xE75F,0xF77E,0xC71D,0xD73C,
0x26D3,0x36F2,0x0691,0x16B0,0x6657,0x7676,0x4615,0x5634,
0xD94C,0xC96D,0xF90E,0xE92F,0x99C8,0x89E9,0xB98A,0xA9AB,
0x5844,0x4865,0x7806,0x6827,0x18C0,0x08E1,0x3882,0x28A3,
0xCB7D,0xDB5C,0xEB3F,0xFB1E,0x8BF9,0x9BD8,0xABBB,0xBB9A,
0x4A75,0x5A54,0x6A37,0x7A16,0x0AF1,0x1AD0,0x2AB3,0x3A92,
0xFD2E,0xED0F,0xDD6C,0xCD4D,0xBDAA,0xAD8B,0x9DE8,0x8DC9,
0x7C26,0x6C07,0x5C64,0x4C45,0x3CA2,0x2C83,0x1CE0,0x0CC1,
0xEF1F,0xFF3E,0xCF5D,0xDF7C,0xAF9B,0xBFBA,0x8FD9,0x9FF8,
0x6E17,0x7E36,0x4E55,0x5E74,0x2E93,0x3EB2,0x0ED1,0x1EF0
};

unsigned short crc_16(unsigned char *buf, int len)
{
    unsigned short crc = 0;
    while (len-- > 0)
        crc = (crc<<8) ^ crc16_table[((crc>>8) ^ *buf++)&0xFF];
    return crc;
}

2. swap#

void swap(int *a,int *b)
{
    *a ^= *b ^= *a ^= *b;
}

int main()
{
    int a = 10;
    int b = 20;

    swap(&a,&b);
    return 0;
}

3. 双向链表#

#include <stdio.h>
#include <stdlib.h>


typedef struct _list_t{
    struct _list_t *prev,*next;
}list_t;


typedef struct _data_t{
    int a;
    list_t list;
}data_t;


#define list_entry(ptr,type,member) \
   ((type *) ((unsigned long)(ptr) - (unsigned long)(&(((type *)0)->member))))

void list_init(list_t *head)
{
    head->prev = head;
    head->next = head;
}    


void _list_add(list_t *new,list_t *prev,list_t *next)
{
    prev->next = new;
    next->prev = new;
    new->prev = prev;
    new->next = next;
}

void list_add(list_t *new,list_t *head)
{
    _list_add(new,head,head->next);
}


void _list_delete(list_t *prev,list_t *next)
{
    prev->next = next;
    next->prev = prev;
}

void list_delete(list_t *entry)
{
    _list_delete(entry->prev,entry->next);

    // release the entry
}


void list_loop_backward(list_t *head)
{
    list_t *p = head->next;

    data_t *temp = NULL;

    while(p!=head)
    {
        temp = list_entry(p,data_t,list);
        printf("%d\n",temp->a);
        p = p->next;
    }

}


void list_loop_forward(list_t *head)
{
    list_t *p = head->prev;

    data_t *temp = NULL;

    while(p!=head)
    {
        temp = list_entry(p,data_t,list);
        printf("%d\n",temp->a);
        p = p->prev;
    }
}

void list_loop_recursion(list_t *first,list_t *head)
{
    if(first==head)
    {
        return;
    }

    printf("%d\n", list_entry(first,data_t,list)->a);
    list_loop_recursion(first->next,head);

}



int main()
{
    int i = 0;

    data_t d0,d1,d2,d3,d4,d5;

    data_t *head = &d0;

    d0.a=888;
    d1.a=100;
    d2.a=200;
    d3.a=300;
    d4.a=400;
    d5.a=500;


    list_init(&(head->list));


    list_add(&(d1.list),&(head->list));
    list_add(&(d2.list),&(head->list));
    list_add(&(d3.list),&(head->list));
    list_add(&(d4.list),&(head->list));
    list_add(&(d5.list),&(head->list));

    list_loop_backward(&(head->list));

    printf("--------------------\n");

    list_loop_forward(&(head->list));

    list_delete(&(d3.list));

    printf("--------------------\n");

    list_loop_forward(&(head->list));

    printf("-------------recursion-------\n");

    list_loop_recursion(&(d5.list),&(head->list));

    return 0;
}

4. 二叉树#

#include <stdio.h>

typedef struct _list_t{
    struct _list_t *left,*right;
}list_t;


typedef struct _data_t{
    int a;
    list_t list;
}data_t;


#define list_entry(ptr,type,member) \
  (type *)((char *)(ptr) - ((char *)(&((type *)0)->member)))


void binary_tree_init(list_t *head)
{
    head->left=head->right=NULL;
}


void binary_tree_add(list_t *new,int value,list_t **head)
{
    if((*head)==NULL)
    {
        (*head) = new;        
        return;
    }


    if(value==1)
    {
        binary_tree_add(new,1,&((*head)->left));
    }
    else
    {
        binary_tree_add(new,2,&((*head)->right));
    }

}

void print_binary_tree(list_t *head)
{
    if(head==NULL)
    {
        return;
    }

    printf("%d\n",(list_entry(head,data_t,list))->a);

    print_binary_tree(head->left);

}


int main()
{

    data_t d0,d1,d2,d3,d4,d5;

    d0.a=888;
    d1.a=100;
    d2.a=200;
    d3.a=300;
    d4.a=400;
    d5.a=500;


    data_t *head = &d0;

    binary_tree_init(&(head->list));


    binary_tree_add(&(d1.list),1,(list_t **)(&(head->list)));
    binary_tree_add(&(d2.list),1,(list_t **)(&(head->list)));
    binary_tree_add(&(d3.list),1,(list_t **)(&(head->list)));
    binary_tree_add(&(d4.list),1,(list_t **)(&(head->list)));
    binary_tree_add(&(d5.list),1,(list_t **)(&(head->list)));


    print_binary_tree(&(head->list));

    return 0;
}