c语⾔printf函数原型,printf函数原型typedef char *va_list;
#define _AUPBND (sizeof (acpi_native_int) - 1)
#define _ADNBND (sizeof (acpi_native_int) - 1)
c语言编程入门指南pdf#define _bnd(X, bnd) (((sizeof (X)) + (bnd)) & (~(bnd)))
#define va_arg(ap, T) (*(T *)(((ap) += (_bnd (T, _AUPBND))) - (_bnd (T,_ADNBND))))
#define va_end(ap) (void) 0
#define va_start(ap, A) (void) ((ap) = (((char *) &(A)) + (_bnd (A,_AUPBND))))
//start.c
];
int printf(char *fmt, ...)
{
va_list args;
int n;
va_start(args, fmt);
n = vsprintf(sprint_buf, fmt, args);
va_end(args);
write(stdout, sprint_buf, n);
return n;
}
int vsprintf(char *buf, const char *fmt, va_list args)
{
int len;
unsigned long num;
int i, base;
char *str;
char *s;
int flags; // Flags to number()
int field_width; // Width of output field
int precision; // Min. # of digits for integers; max number of chars for from string
int qualifier; // 'h', 'l', or 'L' for integer fields
for (str = buf; *fmt; fmt++)
{
if (*fmt != '%')
{
*str++ = *fmt;
continue;
}
// Process flags
flags = ;
repeat:
fmt++; // This also skips first '%' switch (*fmt)
{
case '-': flags |= LEFT; goto repeat; case '+': flags |= PLUS; goto repeat; case ' ': flags |= SPACE; goto repeat; case '#': flags |= SPECIAL; goto repeat; ': flags |= ZEROPAD; goto repeat;
}
// Get field width
field_width = -;
if (is_digit(*fmt))
field_width = skip_atoi(&fmt);
else if (*fmt == '*')
{
fmt++;
field_width = va_arg(args, int);
)
{
field_width = -field_width;
flags |= LEFT;
}
}
// Get the precision
precision = -;
if (*fmt == '.')
{
if (is_digit(*fmt))
precision = skip_atoi(&fmt);
else if (*fmt == '*')
{
++fmt;
precision = va_arg(args, int);
}
) precision = ;
}
// Get the conversion qualifier
qualifier = -;
if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L')
{
qualifier = *fmt;
fmt++;
}
// Default base
;
switch (*fmt)
{
case 'c':
) *str++ = ' ';
*str++ = (unsigned char) va_arg(args, int);
) *str++ = ' ';
continue;
case 's':
s = va_arg(args, char *);
if (!s) s = "";
len = strnlen(s, precision);
if (!(flags & LEFT)) while (len < field_width--) *str++ = ' '; ; i < len; ++i) *str++ = *s++;
while (len < field_width--) *str++ = ' ';
continue;
{
field_width = * sizeof(void *);
flags |= ZEROPAD;
}
str = number(str, (unsigned , field_width, precision, flags);
continue;
case 'n':
if (qualifier == 'l')
{
long *ip = va_arg(args, long *);
*ip = (str - buf);
}
else
{
int *ip = va_arg(args, int *);
*ip = (str - buf);
}
continue;
case 'A':
flags |= LARGE;
case 'a':
if (qualifier == 'l')
str = eaddr(str, va_arg(args, unsigned char *), field_width, precision, flags); else
str = iaddr(str, va_arg(args, unsigned char *), field_width, precision, flags); continue;
// Integer number formats - set up the flags and "break"
case 'o':
;
break;
case 'X':
flags |= LARGE;
break;
case 'd':
case 'i':
flags |= SIGN;
case 'u':
break;
case 'E':
case 'G':
case 'e':
case 'f':
case 'g':
str = flt(str, va_arg(args, double), field_width, precision, *fmt, flags | SIGN); continue;
default:
if (*fmt != '%') *str++ = '%';
if (*fmt)
*str++ = *fmt;
else
--fmt;
continue;
}
if (qualifier == 'l')
num = va_arg(args, unsigned long);
else if (qualifier == 'h')
{
if (flags & SIGN)
num = va_arg(args, short);
else
num = va_arg(args, unsigned short);
}
else if (flags & SIGN)
num = va_arg(args, int);

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