部分重要代碼：
main.c
#include "s3c2440_soc.h"
#include "uart.h"
#include "my_printf.h"
int main(void)
{
unsigned char c;
uart0_init();
puts("Hello, world!\n\r");
my_printf_test();
while(1)
{
c = getchar();
if (c == '\r')
{
putchar('\n');
}
if (c == '\n')
{
putchar('\r');
}
putchar(c);
}
return 0;
}
my_printf.c
#include "my_printf.h"
//==================================================================================================
typedef char * va_list;
#define _INTSIZEOF(n) ( (sizeof(n) + sizeof(int) - 1) & ~(sizeof(int) - 1) )
#define va_start(ap,v) ( ap = (va_list)&v + _INTSIZEOF(v) )
//#define va_arg(ap,t) ( *(t *)((ap += _INTSIZEOF(t)) - _INTSIZEOF(t)) )
#define va_arg(ap,t) ( *(t *)( ap=ap + _INTSIZEOF(t), ap- _INTSIZEOF(t)) )
#define va_end(ap) ( ap = (va_list)0 )
//==================================================================================================
unsigned char hex_tab[]={'0','1','2','3','4','5','6','7',\
'8','9','a','b','c','d','e','f'};
static int outc(int c)
{
__out_putchar(c);
return 0;
}
static int outs (const char *s)
{
while (*s != '\0')
__out_putchar(*s++);
return 0;
}
static int out_num(long n, int base,char lead,int maxwidth)
{
unsigned long m=0;
char buf[MAX_NUMBER_BYTES], *s = buf + sizeof(buf);
int count=0,i=0;
*--s = '\0';
if (n < 0){
m = -n;
}
else{
m = n;
}
do{
*--s = hex_tab[m%base];
count++;
}while ((m /= base) != 0);
if( maxwidth && count < maxwidth){
for (i=maxwidth - count; i; i--)
*--s = lead;
}
if (n < 0)
*--s = '-';
return outs(s);
}
/*reference : int vprintf(const char *format, va_list ap); */
static int my_vprintf(const char *fmt, va_list ap)
{
char lead=' ';
int maxwidth=0;
for(; *fmt != '\0'; fmt++)
{
if (*fmt != '%') {
outc(*fmt);
continue;
}
//format : %08d, %8d,%d,%u,%x,%f,%c,%s
fmt++;
if(*fmt == '0'){
lead = '0';
fmt++;
}
while(*fmt >= '0' && *fmt <= '9'){
maxwidth *=10;
maxwidth += (*fmt - '0');
fmt++;
}
switch (*fmt) {
case 'd': out_num(va_arg(ap, int), 10,lead,maxwidth); break;
case 'o': out_num(va_arg(ap, unsigned int), 8,lead,maxwidth); break;
case 'u': out_num(va_arg(ap, unsigned int), 10,lead,maxwidth); break;
case 'x': out_num(va_arg(ap, unsigned int), 16,lead,maxwidth); break;
case 'c': outc(va_arg(ap, int )); break;
case 's': outs(va_arg(ap, char *)); break;
default:
outc(*fmt);
break;
}
}
return 0;
}
//reference : int printf(const char *format, ...);
int printf(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
my_vprintf(fmt, ap);
va_end(ap);
return 0;
}
int my_printf_test(void)
{
printf("This is www.100ask.org my_printf test\n\r") ;
printf("test char =%c,%c\n\r", 'A','a') ;
printf("test decimal number =%d\n\r", 123456) ;
printf("test decimal number =%d\n\r", -123456) ;
printf("test hex number =0x%x\n\r", 0x55aa55aa) ;
printf("test string =%s\n\r", "www.100ask.org") ;
printf("num=%08d\n\r", 12345);
printf("num=%8d\n\r", 12345);
printf("num=0x%08x\n\r", 0x12345);
printf("num=0x%8x\n\r", 0x12345);
printf("num=0x%02x\n\r", 0x1);
printf("num=0x%2x\n\r", 0x1);
printf("num=%05d\n\r", 0x1);
printf("num=%5d\n\r", 0x1);
return 0;
}
my_printf.h
#include "my_printf.h"
//==================================================================================================
typedef char * va_list;
#define _INTSIZEOF(n) ( (sizeof(n) + sizeof(int) - 1) & ~(sizeof(int) - 1) )
#define va_start(ap,v) ( ap = (va_list)&v + _INTSIZEOF(v) )
//#define va_arg(ap,t) ( *(t *)((ap += _INTSIZEOF(t)) - _INTSIZEOF(t)) )
#define va_arg(ap,t) ( *(t *)( ap=ap + _INTSIZEOF(t), ap- _INTSIZEOF(t)) )
#define va_end(ap) ( ap = (va_list)0 )
//==================================================================================================
unsigned char hex_tab[]={'0','1','2','3','4','5','6','7',\
'8','9','a','b','c','d','e','f'};
static int outc(int c)
{
__out_putchar(c);
return 0;
}
static int outs (const char *s)
{
while (*s != '\0')
__out_putchar(*s++);
return 0;
}
static int out_num(long n, int base,char lead,int maxwidth)
{
unsigned long m=0;
char buf[MAX_NUMBER_BYTES], *s = buf + sizeof(buf);
int count=0,i=0;
*--s = '\0';
if (n < 0){
m = -n;
}
else{
m = n;
}
do{
*--s = hex_tab[m%base];
count++;
}while ((m /= base) != 0);
if( maxwidth && count < maxwidth){
for (i=maxwidth - count; i; i--)
*--s = lead;
}
if (n < 0)
*--s = '-';
return outs(s);
}
/*reference : int vprintf(const char *format, va_list ap); */
static int my_vprintf(const char *fmt, va_list ap)
{
char lead=' ';
int maxwidth=0;
for(; *fmt != '\0'; fmt++)
{
if (*fmt != '%') {
outc(*fmt);
continue;
}
//format : %08d, %8d,%d,%u,%x,%f,%c,%s
fmt++;
if(*fmt == '0'){
lead = '0';
fmt++;
}
while(*fmt >= '0' && *fmt <= '9'){
maxwidth *=10;
maxwidth += (*fmt - '0');
fmt++;
}
switch (*fmt) {
case 'd': out_num(va_arg(ap, int), 10,lead,maxwidth); break;
case 'o': out_num(va_arg(ap, unsigned int), 8,lead,maxwidth); break;
case 'u': out_num(va_arg(ap, unsigned int), 10,lead,maxwidth); break;
case 'x': out_num(va_arg(ap, unsigned int), 16,lead,maxwidth); break;
case 'c': outc(va_arg(ap, int )); break;
case 's': outs(va_arg(ap, char *)); break;
default:
outc(*fmt);
break;
}
}
return 0;
}
//reference : int printf(const char *format, ...);
int printf(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
my_vprintf(fmt, ap);
va_end(ap);
return 0;
}
int my_printf_test(void)
{
printf("This is www.100ask.org my_printf test\n\r") ;
printf("test char =%c,%c\n\r", 'A','a') ;
printf("test decimal number =%d\n\r", 123456) ;
printf("test decimal number =%d\n\r", -123456) ;
printf("test hex number =0x%x\n\r", 0x55aa55aa) ;
printf("test string =%s\n\r", "www.100ask.org") ;
printf("num=%08d\n\r", 12345);
printf("num=%8d\n\r", 12345);
printf("num=0x%08x\n\r", 0x12345);
printf("num=0x%8x\n\r", 0x12345);
printf("num=0x%02x\n\r", 0x1);
printf("num=0x%2x\n\r", 0x1);
printf("num=%05d\n\r", 0x1);
printf("num=%5d\n\r", 0x1);
return 0;
}
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