c自定义日志方法va_list

 

/*
 * Portions created by SGI are Copyright (C) 2000 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met: 
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Silicon Graphics, Inc. nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include 
#include 
#include 
#include 
#include 
#include 
#include "st.h"

/*
 * Simple error reporting functions.
 * Suggested in W. Richard Stevens' "Advanced Programming in UNIX
 * Environment".
 */

#define MAXLINE 4096  /* max line length */

static void err_doit(int, int, const char *, va_list);


/*
 * Nonfatal error related to a system call.
 * Print a message and return.
 */
void err_sys_report(int fd, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  err_doit(fd, 1, fmt, ap);
  va_end(ap);
}


/*
 * Fatal error related to a system call.
 * Print a message and terminate.
 */
void err_sys_quit(int fd, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  err_doit(fd, 1, fmt, ap);
  va_end(ap);
  exit(1);
}


/*
 * Fatal error related to a system call.
 * Print a message, dump core, and terminate.
 */
void err_sys_dump(int fd, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  err_doit(fd, 1, fmt, ap);
  va_end(ap);
  abort();  /* dump core and terminate */
  exit(1);  /* shouldn't get here */
}


/*
 * Nonfatal error unrelated to a system call.
 * Print a message and return.
 */
void err_report(int fd, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  err_doit(fd, 0, fmt, ap);
  va_end(ap);
}


/*
 * Fatal error unrelated to a system call.
 * Print a message and terminate.
 */
void err_quit(int fd, const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  err_doit(fd, 0, fmt, ap);
  va_end(ap);
  exit(1);
}


/*
 * Return a pointer to a string containing current time.
 */
char *err_tstamp(void)
{
  static char *months[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                            "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
  static char str[32];
  static time_t lastt = 0;
  struct tm *tmp;
  time_t currt = st_time();

  if (currt == lastt)
    return str;

  tmp = localtime(&currt);
  sprintf(str, "[%02d/%s/%d:%02d:%02d:%02d] ", tmp->tm_mday,
          months[tmp->tm_mon], 1900 + tmp->tm_year, tmp->tm_hour,
          tmp->tm_min, tmp->tm_sec);
  lastt = currt;

  return str;
}


/*
 * Print a message and return to caller.
 * Caller specifies "errnoflag".
 */
static void err_doit(int fd, int errnoflag, const char *fmt, va_list ap)
{
  int errno_save;
  char buf[MAXLINE];

  errno_save = errno;         /* value caller might want printed   */
  strcpy(buf, err_tstamp());  /* prepend a message with time stamp */
  vsprintf(buf + strlen(buf), fmt, ap);
  if (errnoflag)
    sprintf(buf + strlen(buf), ": %s\n", strerror(errno_save));
  else
    strcat(buf, "\n");
  write(fd, buf, strlen(buf));
  errno = errno_save;
}

  

 

#include
#include
#include
#include

void simple_va_fun(char * fmt, ...) {
#define TEMP_BUF_LEN 200
    char buf[TEMP_BUF_LEN];
    unsigned int index,i,len,prelen;
    int itemp;
    char *stemp;
    va_list ap;

    memset(buf,0, TEMP_BUF_LEN);
    len = strlen(fmt);
    va_start(ap,fmt);
    for (index = 0, i=0;i        // 如果不是控制字符
        if (fmt[i] != '%') {
            buf[index++] = fmt[i]; // 直接输出
            continue;
        }
        i++;
        if ('\0'==fmt[i]) {
            assert(0); // 这是一个错误
            break;
        }
        switch(fmt[i]) {
        case '%': // 连续两个'%'输出一个'%'
            buf[index++] = '%';
            break;
        case 'd': // 按照int输出
            itemp = va_arg(ap, int);
            prelen = strlen(buf);
            sprintf(buf + index, "%d", itemp);
            index += strlen(buf)- prelen;
            break;
        case 's':
            stemp = va_arg(ap, char*);
            strcpy(buf + index, stemp);
            index += strlen(stemp);
            break;
        }
    }
    buf[index] = '\0';
    va_end(ap);

    printf("Result:%s\n",buf);
}

int main() {

    simple_va_fun("index=%d,context=%s\n",123,"Hello");

    printf("Over");
    getchar();
    return 0;
}

 

 

自定义调试信息的输出

  调试信息的输出方法有很多种,  例如直接用printf,  或者出错时使用perror, fprintf等将信息直接打印到终端上, 在Qt上面一般使用qDebug,而守护进程则一般是使用syslog将调试信息输出到日志文件中等等...
  使用标准的方法打印调试信息有时候不是很方便,  例如Qt编程, 在调试已有的代码时, 我想在打印调试信息的地方, 把代码位置也打印出来以方便定位错误, 或者需要在调试信息前面加一个前辍, 好方便在调试信息太多的时候可以用grep过滤一下, 仅显示本模块的调试信息, 这时就需要一个一个地修改已有的qDebug, 使其成为以下形式:
  qDebug( "[模块名称] 调试信息  File:%s, Line:%d", __FILE__, __LINE__ );
  这样的修改比较烦人, 而且一不小心会遗漏某个没改的...
  为了能方便地管理调试信息的输出,一个比较简单的方法就是自已定义一个打印调试信息的宏, 然后替换原来的,废话就不多说了,直接给出一个现成的,下面是一个例子, 我用WiFi表示当前代码的模块名称,我要求在模块中的所有调试信息前面均带有[WiFi]前辍,这样我就能方便地只需使用命令行 | grep "\[WiFi\]"来过滤掉来自其它模块的调试信息了:
#define qWiFiDebug(format, ...) qDebug("[WiFi] "format" File:%s, Line:%d, Function:%s", ##__VA_ARGS__, __FILE__, __LINE__ , __FUNCTION__);
  上面的宏是使用qDebug输出调试信息,在非Qt的程序中也可以改为printf,守护进程则可以改为syslog等等...  其中,决窍其实就是这几个宏 ##__VA_ARGS__, __FILE__, __LINE__ 和__FUNCTION__,下面介绍一下这几个宏:
  1)  __VA_ARGS__ 是一个可变参数的宏,很少人知道这个宏,这个可变参数的宏是新的C99规范中新增的,目前似乎只有gcc支持(VC6.0的编译器不支持)。宏前面加上##的作用在于,当可变参数的个数为0时,这里的##起到把前面多余的","去掉的作用,否则会编译出错, 你可以试试。
  2) __FILE__ 宏在预编译时会替换成当前的源文件名
  3) __LINE__宏在预编译时会替换成当前的行号
  4) __FUNCTION__宏在预编译时会替换成当前的函数名称
  有了以上这几个宏,特别是有了__VA_ARGS__ ,调试信息的输出就变得灵活多了。
  有时,我们想把调试信息输出到屏幕上,而有时则又想把它输出到一个文件中,可参考下面的例子:
//debug.c
#include
#include
//开启下面的宏表示程序运行在调试版本, 否则为发行版本, 这里假设只有调试版本才输出调试信息
#define _DEBUG
#ifdef _DEBUG
    //开启下面的宏就把调试信息输出到文件,注释即输出到终端
    #define DEBUG_TO_FILE
    #ifdef DEBUG_TO_FILE
        //调试信息输出到以下文件
        #define DEBUG_FILE "/tmp/debugmsg"
        //调试信息的缓冲长度
        #define DEBUG_BUFFER_MAX 4096
        //将调试信息输出到文件中
        #define printDebugMsg(moduleName, format, ...) {\
            char buffer[DEBUG_BUFFER_MAX+1]={0};\
            snprintf( buffer, DEBUG_BUFFER_MAX \
                    , "[%s] "format" File:%s, Line:%d\n", moduleName, ##__VA_ARGS__, __FILE__, __LINE__ );\
            FILE* fd = fopen(DEBUG_FILE, "a");\
            if ( fd != NULL ) {\
                fwrite( buffer, strlen(buffer), 1, fd );\
                fflush( fd );\
                fclose( fd );\
            }\
        }
    #else
        //将调试信息输出到终端
        #define printDebugMsg(moduleName, format, ...) \
                  printf( "[%s] "format" File:%s, Line:%d\n", moduleName, ##__VA_ARGS__, __FILE__, __LINE__ );
    #endif //end for #ifdef DEBUG_TO_FILE
#else
    //发行版本,什么也不做
    #define printDebugMsg(moduleName, format, ...)
#endif  //end for #ifdef _DEBUG
int main(int argc, char** argv)
{
    int data = 999;
    printDebugMsg( "TestProgram", "data = %d", data );
    return 0;
}
 
 
  上面也说了,只有支持C99规范的gcc编译器才有__VA_ARGS__这个宏,如果不是gcc编译器,或者所用的gcc编译器版本不支持__VA_ARGS__宏怎么办? 可参考下面的代码片段,我们换一种做法,可先将可变参数转换成字符串后,再进行输出即可:
void printDebugMsg( const char* format, ...)
{
    char buffer[DEBUG_BUFFER_MAX_LENGTH + 1]={0};
    va_list arg;
    va_start (arg, format);
    vsnprintf(buffer, DEBUG_BUFFER_MAX_LENGTH, format, arg);
    va_end (arg);
    printf( "%s", buffer );
}

转载于:https://www.cnblogs.com/tiancun/p/7793282.html

你可能感兴趣的:(c自定义日志方法va_list)