C指针灵活应用集锦

解析CGI字符串: 

NET=0&SSID=linux&KEY=&WIP1=192&WIP2=168&WIP3=144&WIP4=010&MASK1=255&MASK2=255&MASK3=255&MASK4=000&GW1=192&GW2=168&GW3=001&GW4=001&DNS1=202&DNS2=114&DNS3=134&DNS4=133&WMAC0=00&WMAC1=DF&WMAC2=24&WMAC3=6C&WMAC4=74&WMAC5=96&OK=%B1%A3%B4%E6

static int extract_uri_parameters(struct http_request *hs, char *params)
{
  char *pair = NULL;
  char *equals = NULL;
  int loop;

  /* If we have no parameters at all, return immediately. */
  if(!params || (params[0] == '\0')) {
      return(0);
  }

  if (hs->postfile) {
      loop = 1;
      hs->param_vals[0] = params;
    }
    else {
     /* Get a pointer to our first parameter */
      pair = params;
     for(loop = 0; (loop < MAX_CGI_PARAMETERS) && pair; loop++) {

     /* Save the name of the parameter */
        hs->params[loop] = pair;

     /* Remember the start of this name=value pair */
        equals = pair;

        pair = strchr(pair, '&');
     if(pair) {
     *pair = '\0';
          pair++;
     }

        equals = strchr(equals, '=');
     if(equals) {
     *equals = '\0';
          hs->param_vals[loop] = equals + 1;
     } else {
          hs->param_vals[loop] = NULL;
     }
            //DEBUGP("CGI para %d: %s = %s\n", loop, hs->params[loop], hs->param_vals[loop]);
     }
    }

  return(loop);
}

t%20%3C%3Fxml%20version%3D%221.0%22%20encoding%3D%22UTF-8%22%3F%3E%0D%0At%20%3Croot%3E%0D%0At%20%3Cproject%20width%3D%22802%22%20height%3D%22629%22%20background%3D%221%22%2F%3E%0D%0At%20%3Citems%3E%0D%0At%20%3Citem%20itype%3D%22image%22%20device%3D%22undefined%22%20describe%3D%22undefined%22%3E%0D%0At%20%3Cimage%20x%3D%22189%22%20y%3D%22102%22%20width%3D%22100%22%20height%3D%22202%22%20href%3D%22icebox%22%2F%3E%0D%0At%20%3C%2Fitem%3E%0D%0At%20%3Citem%20itype%3D%22text%22%20device%3D%22undefined%22%20describe%3D%22undefined%22%3E%0D%0At%20%3Ctext%20%0D%0At%20textx%3D%22132%22%20texty%3D%22240%22%20text-anchor%3D%22left%22%20fontfamily%3D%22Arial%22%20%0D%0At%20fontsize%3D%2216%22%20fill%3D%22%23ffffff%22%20text%3D%22XXXXXX%22%20%2F%3E%0D%0At%20%3C%2Fitem%3E%0D%0At%20%3C%2Fitems%3E%0D%0At%20%3C%2Froot%3E%0D%0A.,  

decode: len = 482, t

t

t

t

t

t

t

t

t

t textx="132" texty="240" text-anchor="left" fontfamily="Arial" 

t fontsize="16" fill="#ffffff" text="XXXXXX" />

t

t

t

.

u16 URLDecode(char *str, u16 len)
{
  char *dest = str;
  char *data = str;
  u16 value;
  u16 c;

  while (len--) {
    if (*data == '+') {
        *dest = ' ';
    }
    else
    if (*data == '%' && len >= 2 && isxdigit((int) *(data + 1)) && isxdigit((int) *(data + 2))) {
        c = ((unsigned char *)(data+1))[0];
        if (isupper(c))
            c = tolower(c);
        value = (c >= '0' && c <= '9' ? c - '0' : c - 'a' + 10) * 16;
        c = ((unsigned char *)(data+1))[1];
        if (isupper(c))
            c = tolower(c);
        value += c >= '0' && c <= '9' ? c - '0' : c - 'a' + 10;

        *dest = (char)value ;
        data += 2;
        len -= 2;
    }
    else {
        *dest = *data;
    }
    data++;
    dest++;
  }
  *dest = '\0';

  return (dest - str);
}

3. 

struct llhead {
    struct llhead    *prev;
    struct llhead    *next;
};

#define    LL_INIT(N)    ((N)->next = (N)->prev = (N))

#define LL_HEAD(H)    struct llhead H = { &H, &H }

#define LL_ENTRY(P,T,N) ((T *)((char *)(P) - offsetof(T, N)))

#define    LL_ADD(H, N)                            \\
    do {                                \\
        ((H)->next)->prev = (N);                \\
        (N)->next = ((H)->next);                \\
        (N)->prev = (H);                    \\
        (H)->next = (N);                    \\
    } while (0)

#define    LL_TAIL(H, N)                            \\
    do {                                \\
        ((H)->prev)->next = (N);                \\
        (N)->prev = ((H)->prev);                \\
        (N)->next = (H);                    \\
        (H)->prev = (N);                    \\
    } while (0)

#define    LL_DEL(N)                            \\
    do {                                \\
        ((N)->next)->prev = ((N)->prev);            \\
        ((N)->prev)->next = ((N)->next);            \\
        LL_INIT(N);                        \\
    } while (0)

#define    LL_EMPTY(N)    ((N)->next == (N))

#define    LL_FOREACH(H,N)    for (N = (H)->next; N != (H); N = (N)->next)

#define LL_FOREACH_SAFE(H,N,T)                        \\
    for (N = (H)->next, T = (N)->next; N != (H);            \\
            N = (T), T = (N)->next)

应用例程: 
struct shttpd_ctx {
SSL_CTX *ssl_ctx; /* SSL context */
struct llhead registered_uris;/* User urls */
struct llhead error_handlers; /* Embedded error handlers */
struct llhead acl; /* Access control list */
struct llhead ssi_funcs; /* SSI callback functions */
struct llhead listeners; /* Listening sockets */
struct llhead workers; /* Worker workers */
FILE *access_log; /* Access log stream */
FILE *error_log; /* Error log stream */
char *options[NUM_OPTIONS]; /* Configurable options */
#if defined(__rtems__)
rtems_id         mutex;
#endif /* _WIN32 */
};

struct shttpd_ctx *ctx;

LL_INIT(&ctx->registered_uris);
LL_INIT(&ctx->error_handlers);



4.
5. 

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