/*
* Scan a string of hexadecimal digits (the format nan(3) expects) and
* make a bit array (using the local endianness). We stop when we
* encounter an invalid character, NUL, etc. If we overflow, we do
* the same as gcc's __builtin_nan(), namely, discard the high order bits.
*
* The format this routine accepts needs to be compatible with what is used
* in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
* __builtin_nan(). In fact, we're only 100% compatible for strings we
* consider valid, so we might be violating the C standard. But it's
* impossible to use nan(3) portably anyway, so this seems good enough.
*/
void
_scan_nan(uint32_t *words, int num_words, const char *s)
{
int si; /* index into s */
int bitpos; /* index into words (in bits) */
bzero(words, num_words * sizeof(uint32_t));
/* Allow a leading '0x'. (It's expected, but redundant.) */
if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
s += 2;
/* Scan forwards in the string, looking for the end of the sequence. */
for (si = 0; isxdigit(s[si]); si++)
;
/* Scan backwards, filling in the bits in words[] as we go. */
#if _BYTE_ORDER == _LITTLE_ENDIAN
for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
#else
for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
#endif
if (--si < 0)
break;
words[bitpos / 32] |= _digittoint(s[si]) << (bitpos % 32);
}
}
double
nan(const char *s)
{
union {
double d;
uint32_t bits[2];
} u;
_scan_nan(u.bits, 2, s);
#if _BYTE_ORDER == _LITTLE_ENDIAN
u.bits[1] |= 0x7ff80000;
#else
u.bits[0] |= 0x7ff80000;
#endif
return (u.d);
}
float
nanf(const char *s)
{
union {
float f;
uint32_t bits[1];
} u;
_scan_nan(u.bits, 1, s);
u.bits[0] |= 0x7fc00000;
return (u.f);
}
#if LDBL_MANT_DIG == DBL_MANT_DIG
__strong_alias(nanl, nan);
long double
nanl(const char *s)
{
union {
union IEEEl2bits ieee;
uint32_t bits[3];
} u;
_scan_nan(u.bits, 3, s);
u.ieee.bits.exp = 0x7fff;
u.ieee.bits.manh |= 0xc0000000; /* make it a quiet NaN */
return (u.ieee.e);
}
long double
nanl(const char *s)
{
union {
long double e;
struct ieee_ext ieee;
uint32_t bits[3];
} u;
_scan_nan(u.bits, 3, s);
u.ieee.ext_exp = 0x7fff;
u.ieee.ext_frach |= 0xc0000000; /* make it a quiet NaN */
return (u.e);
}