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#include <stdio.h>
#include <string.h>
int myvsprintf(char *buf, const char *fmt, char *args)
{
char* p;
char tmp[256];
char* p_next_arg = args;
for (p=buf;*fmt;fmt++) {
if (*fmt != '%') {
*p++ = *fmt;
continue;
}
fmt++;
switch (*fmt) {
case 'x':
//itoa(tmp, *((int*)p_next_arg));
sprintf(tmp, "%d", *((int*)p_next_arg));
printf("%d", *((int*)p_next_arg));
strcpy(p, tmp);
p_next_arg += 4;
p += strlen(tmp);
break;
case 's':
break;
default:
break;
}
}
return (p - buf);
}
int myprintf(const char *fmt, ...)
{
int i, j;
char buf[256];
char* arg;
arg = ((char*)(&fmt) + 4); /*4是参数fmt所占堆栈中的大小*/
i = myvsprintf(buf, fmt, arg);
for(j = 0; j < i; j++)
{
putchar(buf[i]);
}
return i;
}
int main()
{
myprintf("%x", 1);
return 0;
}
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
//-----------------------------------------------------------------------------
typedef char * va_list;
#define _ADDRESSOF(v) ( &reinterpret_cast<const char &>(v) )
#define _INTSIZEOF(n) ( (sizeof(n) + sizeof(int) - 1) & ~(sizeof(int) - 1) )
#define _crt_va_start(ap,v) ( ap = (va_list)_ADDRESSOF(v) + _INTSIZEOF(v) )
#define _crt_va_arg(ap,t) ( *(t *)((ap += _INTSIZEOF(t)) - _INTSIZEOF(t)) )
#define _crt_va_end(ap) ( ap = (va_list)0 )
#define va_start _crt_va_start
#define va_arg _crt_va_arg
#define va_end _crt_va_end
//-----------------------------------------------------------------------------
/*
* A simple printf function. Only support the following format:
* Code Format
* %c character
* %d signed integers
* %i signed integers
* %s a string of characters
* %o octal
* %x unsigned hexadecimal
*/
int my_printf( const char* format, ...)
{
va_list arg;
int done = 0;
va_start (arg, format);
//done = vfprintf (stdout, format, arg);
while( *format != '\0')
{
if( *format == '%')
{
if( *(format+1) == 'c' )
{
char c = (char)va_arg(arg, int);
putc(c, stdout);
} else if( *(format+1) == 'd' || *(format+1) == 'i')
{
char store[20];
int i = va_arg(arg, int);
char* str = store;
itoa(i, store, 10);
while( *str != '\0') putc(*str++, stdout);
} else if( *(format+1) == 'o')
{
char store[20];
int i = va_arg(arg, int);
char* str = store;
itoa(i, store, 8);
while( *str != '\0') putc(*str++, stdout);
} else if( *(format+1) == 'x')
{
char store[20];
int i = va_arg(arg, int);
char* str = store;
itoa(i, store, 16);
while( *str != '\0') putc(*str++, stdout);
} else if( *(format+1) == 's' )
{
char* str = va_arg(arg, char*);
while( *str != '\0') putc(*str++, stdout);
}
// Skip this two characters.
format += 2;
} else {
putc(*format++, stdout);
}
}
va_end (arg);
return done;
}