工作总结（一）：Linux C

这三个月以来一直忙着赶进度，没有停下来记录一些东西，很多很好的东西往往只能零零散散地记在草稿本上，这样偶尔想起来自己都找不到，所以现在抽空总结下来。

这些天做了三件事，其一是在Linux下开发了对接service的IPTV client lib on PC，之所以是on PC，因为我写的这段程序只是为了以后移植到一个运行RTOS的机顶盒上面；其二是基于PayPal做的支付系统，其三是一个监控服务器和用户状态的简单后台管理页面，这两个都是用cakephp + bootstrap做的，并没有涉及到数据库，与数据库交互是使用了已经写好的API。这篇记录C的内容。

一、打印指针值：

int a = 0;
int *p = &a;
printf("%p", p);

二、

PHPStorm： PHP IDE

PyCharm： PYTHON IDE

Brackets ：强大免费的开源跨平台Web前端开发工具IDE

coolshell.com : 酷壳网

三、

问题：VMWare Workstation虚拟机出现故障，非正常关机时，无法再次打开。

解决：删除虚拟磁盘目录下的*.lck文件（可能需要重启）。

四、字符串的正确使用：

#include <stdio.h>

#include <stdlib.h>

#include <string.h>



int main(int argc, char *argv[])

{

    char str1[27] = "abcdefghijklmnopqrstuvwxyz";//编译器将在末尾自动添加“”，但是需要保证，字符数组中有空余的位置

    char *str2 = NULL;

    str2 = (char *)malloc(26 + 1);

    memset(str2, 0, 26 + 1);

    memcpy(str2, str1, 26);



    printf("str1 length is %ld, size is %ld
", strlen(str1), sizeof(str1));

    printf("str2 length is %ld, size is %ld
", strlen(str2), sizeof(str2));

    int i = 0;

    for(i = 0; i < 30; i++)

        printf("%02x ", str1[i]);

    printf("
");

    for(i = 0; i < 30; i++)

        printf(" %c ", str1[i]);



    printf("
");

    if(NULL != str2) free(str2);

    return 0;

}

输出：

hubery@hubery-VirtualBox:~/CP/HW$ ./shellInput 
str1 length is 26, size is 27
str2 length is 26, size is 8
61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 78 79 7a 00 00 00 00 
 a  b  c  d  e  f  g  h  i  j  k  l  m  n  o  p  q  r  s  t  u  v  w  x  y  z

尽量不要使用strlen、strcpy、strcat这些需要通过结束符“”来判断字符串长度的函数，因为一旦字符串没有正常的结束符，你将得到意想不到的结果。

五、在子函数中malloc变量（声明时字符串大小不可知）：

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

int malloc_inner(char **p)
{
*p = (char *)malloc(10);
return 0;
}

int main()
{
char *str = null;
malloc_inner(&str);
free(str);
return 0;
}

六、命令行参数：

//shellInput.c
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    printf("argc = %d, argv[0] = %s, argv[1] = %s
", argc, argv[0], argv[1]);
    return 0;
}

//output
#./shellInput hello
argc = 2, argv[0] = ./shellInput, argv[1] = hello

七、使用CGDB调试一个程序：

objdump,cgdb,dmesg -c.

编译参数： -g -rdynamic

调试： cgdb ./a.out

加断点： b func_name

步进： n

步入： s

打印： p

GDB/CGDB 调试时打印完整内容：set print element 0

查看dumped的位置： bt/where

使down一个程序： kill -s SIGSEGV pid

八、C读写文件：

snprintf(filename, sizeof(filename), "%s.sig", arv[2]);
//write
if((f = fopen(filename, "wb+")) == NULL)
{
ret = 1;
printf("...");
//...
}
if(fwrite(buf, 1, olen ,f) != olen)
{
printf("...");
//...
}
fclose(f);

//read
f = fopen(filename,"rb");
i = fread(buf, 1, sizeof(buf), f);
fclose(f);

九、结构体

typedef struct {
    slist_node node;
    VdsChannel channel;
    CHAR *type;
    CHAR *video_id;
    CHAR *url;//需要url时，先查询链表，若没有再作请求
}VdsChanInfo;

struct timerr
{
    time_t time_begin;
    unsigned int time_long;
    unsigned int time_refresh;
    char user_id[50];
    char token[32];
};
struct timerr timer ;//用法1

//结构体数组
struct
{
    UINT32 isValid;//1 for true, 0 for false
    UINT32 decode_type;//0 for all, 1 for sha1+rsa, 2 for aes+rsa
    CHAR *request_encrypt_key;
    CHAR *response_encrypt_key;

}keyPairs[KEY_PAIR_SUM];

//构造枚举类型
typedef enum {
    VDS_READY,
    VDS_AUTH_OK,
    VDS_GET_KEY_OK,
    VDS_GET_CHAN_INIT_OK,
    VDS_GET_CHAN_URL_OK
}VdsStatus;

typedef struct {

    BOOL running;
    BOOL exit;
    VdsStatus status;

    VdsIptvParam param;
    pthread_t thread_id;
    pthread_mutex_t lock;
    pthread_mutex_t debug_lock;
    UINT32 chan_num;
    slist channel_list;

}VdsIptvMgr;

VdsIptvMgr * get_mgr(void);//用法2

十、链表使用

  1 //singly_linked_list.h
  2 #ifndef __SINGLY_LINKED_LIST_H__
  3 #define __SINGLY_LINKED_LIST_H__
  4 #include "porting.h"
  5 
  6 #ifdef  __cplusplus
  7 extern "C" {
  8 #endif
  9 
 10 typedef struct _slist_node {
 11     struct _slist_node *next;
 12 } slist_node;
 13 
 14 typedef struct {
 15     UINT32            count;
 16     slist_node       *head;
 17     slist_node       *tail;
 18 } slist;
 19 
 20 static __inline__ void slist_add_head(slist *list, slist_node *node) {
 21     if (list->count == 0) {
 22         list->head = node;
 23         list->tail = node;
 24     }
 25     else {
 26         node->next = list->head;
 27         list->head = node;
 28     }
 29     list->count++;
 30 }
 31 
 32 static __inline__ void slist_add_tail(slist *list, slist_node *node)
 33 {
 34     if (list->count == 0) {
 35         list->head = node;
 36         list->tail = node;
 37     }
 38     else {
 39         list->tail->next = node;
 40         list->tail = node;
 41     }
 42     list->count++;
 43 }
 44 
 45 static __inline__ slist_node * slist_del_head(slist *list)
 46 {
 47     slist_node *node = NULL;
 48     if (list->count > 0) {
 49         node = list->head;
 50         list->head = node->next;
 51         node->next = NULL;
 52         if (--list->count == 0) {
 53             list->tail = NULL;
 54         }
 55     }
 56     return node;
 57 }
 58 
 59 static __inline__ slist_node * slist_del_tail(slist *list) {
 60     slist_node *node = NULL;
 61     if (list->count > 1) {
 62         slist_node *ptr = list->head;
 63         while (ptr) {
 64             if (ptr->next == list->tail) {
 65                 node = list->tail;
 66                 ptr->next = NULL;
 67                 list->tail = ptr;
 68                 list->count--;
 69                 break;
 70             }
 71             ptr = ptr->next;
 72         }
 73     }
 74     else if (list->count == 1) {
 75         node = list->tail;
 76         list->head = list->tail = NULL;
 77         list->count--;
 78     }
 79 
 80     return node;
 81 }
 82 
 83 static __inline__ slist_node * slist_del_node(slist *list,  slist_node *node)
 84 {
 85     slist_node *curr = NULL;
 86     slist_node *temp = NULL;
 87 
 88     if(list->head == node)
 89         return slist_del_head(list);
 90 
 91     if(list->tail == node)
 92         return slist_del_tail(list);
 93 
 94     //if(list->count <= 2)
 95     //{
 96         //ASSERT(0);
 97     //}
 98 
 99     curr = list->head;
100     if(curr == NULL)
101         return NULL;
102 
103     while(curr->next != NULL)
104     {
105         if(curr->next == node)
106         {
107             temp = curr->next;
108             curr->next = temp->next;
109             list->count--;
110 
111 
112             temp->next = NULL;
113 
114 /*
115             if(list->count >= 1)
116             {
117                 if(list->head == NULL || list->tail == NULL)
118                 {
119                     SDBBP();
120                 }
121 
122                 if(list->count == 1 && list->head != list->tail)
123                 {
124                     SDBBP();
125                 }
126 
127                 if(list->count == 2 && list->head->next != list->tail)
128                 {
129                     SDBBP();
130                 }
131 
132                 if(list->tail->next != NULL)
133                 {
134                     SDBBP();
135                 }
136             }
137 */
138 
139             return temp;
140         }
141         else
142             curr = curr->next;
143     }
144 
145 /*
146     if(list->count > 0)
147     {
148         if(list->tail->next != NULL)
149         {
150             SDBBP();
151         }
152     }
153 */
154     return NULL;
155 }
156 
157 static __inline__ void  slist_free(slist *list)
158 {
159     slist_node *node = NULL;
160     if(NULL == list)
161         return;
162     while(list->count > 0)
163     {
164         node = slist_del_head(list);
165         FREE(node);
166     }
167 }
168 
169 #define SLIST_COUNT(slist)    ((slist)->count)
170 
171 /**
172  * SLIST_ENTRY - get the struct for this entry
173  * @ptr:    the struct slist_node pointer.
174  * @type:    the type of the struct @ptr embedded in.
175  * @member:    the name of the slist_node within the struct.
176  */
177 #define SLIST_ENTRY(ptr, type, member) 
178     ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
179 
180 
181 #ifdef __cplusplus
182 }
183 #endif      /* __cplusplus */
184 
185 #endif

singly_linked_list.h

下面展示如何使用以上链表操作。

//
typedef struct {
    UINT32 idx;
    CHAR *name;
    CHAR *img_h;
    CHAR *img_s;
}VdsChannel;

typedef struct {
    slist_node node;
    VdsChannel channel;
    CHAR *type;
    CHAR *video_id;
    CHAR *url;//需要url时，先查询链表，若没有再作请求
}VdsChanInfo;


//declare
vds_list = (slist *)malloc(sizeof(slist));
vds_list->count = 0;
vds_list->head = NULL;
vds_list->tail = NULL;

//add
VdsChanInfo *channels = (VdsChanInfo *)malloc(sizeof(VdsChanInfo));
channels->type = ( CHAR * )malloc( strlen( value ) + 1 );
channels->video_id = ( CHAR * )malloc( strlen( value ) + 1 );
channels->channel.name = ( CHAR * )malloc( strlen( value ) + 1 );
channels->channel.img_h = ( CHAR * )malloc( strlen( value ) + 1 );
channels->channel.img_s = ( CHAR * )malloc( strlen( value ) + 1 );
strcpy( channels->type , value );
strcpy( channels->video_id, value );
strcpy( channels->channel.name, value );
strcpy( channels->channel.img_h, value );
strcpy( channels->channel.img_s, value );
channels->channel.idx = i;
channels->url = NULL;
channels->node.next = NULL;
slist_add_tail(list, &(channels->node));

//search
slist_node *node;
VdsChanInfo *vds;
VdsChannel *channel_info = (VdsChannel *)malloc(sizeof(VdsChannel));;
for(node = vds_list->head; node != NULL; node = node->next)
{
    vds = SLIST_ENTRY(node, VdsChanInfo, node);
    if(idx == vds->channel.idx)
    {
        channel_info->idx = vds->channel.idx;
        channel_info->img_h = vds->channel.img_h;
        channel_info->img_s = vds->channel.img_s;
        channel_info->name = vds->channel.name;
        VDS_DBG(VDS_D_SYS, " . Got channel info.");
        return channel_info;
    }
}

//free and destory
void vds_free(slist *list)
{
    slist_node *node;
    VdsChanInfo *vds;
    for(node = list->head; node != NULL; node = node->next)
    {
        vds = SLIST_ENTRY(node, VdsChanInfo, node);
        if(NULL != vds->type)
        {
            free(vds->type);
            vds->type = NULL;
        }
        if(NULL != vds->video_id)
        {
            free(vds->video_id);
            vds->video_id = NULL;
        }
        if(NULL != vds->url)
        {
            free(vds->url);
            vds->url = NULL;
        }
        if(NULL != vds->channel.name)
        {
            free(vds->channel.name);
            vds->channel.name = NULL;
        }
        if(NULL != vds->channel.img_h)
        {
            free(vds->channel.img_h);
            vds->channel.img_h = NULL;
        }
        if(NULL != vds->channel.img_s)
        {
            free(vds->channel.img_s);
            vds->channel.img_s = NULL;
        }
    }

//    slist_free(vds_list);
}
vds_free(vds_list);
slist_free(vds_list);