实现自己的printf函数（转载）

转载自：http://blog.csdn.net/xfeng88/article/details/6695848

在嵌入式开发中，常常会通过串口打印一些信息到PC终端，这就需要实现自己的printf函数，下面介绍打印函数print的实现。

print.h

#ifndef     __PRINT_H_
#define    __PRINT_H_

void    print(char* fmt, ...);
void    printch(char ch);
void    printdec(int dec);
void    printflt(double flt);
void    printbin(int bin);
void    printhex(int hex);
void    printstr(char* str);

#define console_print(ch)    putchar(ch)

#endif    /*#ifndef __PRINT_H_*/

上面print函数为全功能的打印函数，可以实现类似printf的功能，printch实现单个字符的打印、printdec实现十进制格式数字的打印，printflt实现浮点数的打印，printbin实现二进制格式数字的打印，printhex实现十六进制格式数字的打印，printstr实现字符串的打印，console_print函数是串口单字符打印函数的宏定义，这里暂时用PC终端单字符打印函数putchar代替。在实际嵌入式环境下，替换成串口单字符打印函数即可。

print.c

#include <stdio.h>
#include <stdarg.h>
#include "print.h"

int main(void)
{
print("print: %c\n", 'c');
print("print %d\n", 1234567);
print("print: %f\n", 1234567.1234567);
print("print: %s\n", "string test");
print("print: %b\n", 0x12345ff);
print("print: %x\n", 0xabcdef);
print("print: %%\n");
return 0;
}

void    print(char* fmt, ...)
{
double vargflt = 0;
int  vargint = 0;
char* vargpch = NULL;
char vargch = 0;
char* pfmt = NULL;
va_list vp;

va_start(vp, fmt);
pfmt = fmt;

while(*pfmt)
{
if(*pfmt == '%')
{
switch(*(++pfmt))
{

case 'c':
vargch = va_arg(vp, int);
/*    va_arg(ap, type), if type is narrow type (char, short, float) an error is given in strict ANSI
mode, or a warning otherwise.In non-strict ANSI mode, 'type' is allowed to be any expression. */
printch(vargch);
break;
case 'd':
case 'i':
vargint = va_arg(vp, int);
printdec(vargint);
break;
case 'f':
vargflt = va_arg(vp, double);
/*    va_arg(ap, type), if type is narrow type (char, short, float) an error is given in strict ANSI
mode, or a warning otherwise.In non-strict ANSI mode, 'type' is allowed to be any expression. */
printflt(vargflt);
break;
case 's':
vargpch = va_arg(vp, char*);
printstr(vargpch);
break;
case 'b':
case 'B':
vargint = va_arg(vp, int);
printbin(vargint);
break;
case 'x':
case 'X':
vargint = va_arg(vp, int);
printhex(vargint);
break;
case '%':
printch('%');
break;
default:
break;
}
pfmt++;
}
else
{
printch(*pfmt++);
}
}
va_end(vp);
}

void    printch(char ch)
{
console_print(ch);
}

void    printdec(int dec)
{
if(dec==0)
{
return;
}
printdec(dec/10);
printch( (char)(dec%10 + '0'));
}

void    printflt(double flt)
{
int icnt = 0;
int tmpint = 0;

tmpint = (int)flt;
printdec(tmpint);
printch('.');
flt = flt - tmpint;
tmpint = (int)(flt * 1000000);
printdec(tmpint);
}

void    printstr(char* str)
{
while(*str)
{
printch(*str++);
}
}

void    printbin(int bin)
{
if(bin == 0)
{
printstr("0b");
return;
}
printbin(bin/2);
printch( (char)(bin%2 + '0'));
}

void    printhex(int hex)
{
if(hex==0)
{
printstr("0x");
return;
}
printhex(hex/16);
if(hex < 10)
{
printch((char)(hex%16 + '0'));
}
else
{
printch((char)(hex%16 - 10 + 'a' ));
}
}

感觉这个程序写得挺漂亮的