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dix: add utility functions for double to/fro FP1616/FP3232 conversion

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Co-authored-by: Jeremy Huddleston <jeremyhu@apple.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jeremy Huddleston <jeremyhu@apple.com>
Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
This commit is contained in:
Jeremy Huddleston 2011-10-05 15:02:52 -07:00
commit f9c6903d4a
3 changed files with 197 additions and 0 deletions
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63
dix/inpututils.c
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@ -759,3 +759,66 @@ input_option_set_value(InputOption *opt, const char *value)
if (value)
opt->value = strdup(value);
}
/* FP1616/FP3232 conversion functions.
* Fixed point types are encoded as signed integral and unsigned frac. So any
* negative number -n.m is encoded as floor(n) + (1 - 0.m).
*/
double
fp1616_to_double(FP1616 in)
{
double ret;
ret = (double)(in >> 16);
ret += (double)(in & 0xffff) * (1.0 / (1UL << 16)); /* Optimized: ldexp((double)(in & 0xffff), -16); */
return ret;
}
double
fp3232_to_double(FP3232 in)
{
double ret;
ret = (double)in.integral;
ret += (double)in.frac * (1.0 / (1ULL << 32)); /* Optimized: ldexp((double)in.frac, -32); */
return ret;
}
FP1616
double_to_fp1616(double in)
{
FP1616 ret;
int32_t integral;
double tmp;
uint32_t frac_d;
tmp = floor(in);
integral = (int32_t)tmp;
tmp = (in - integral) * (1UL << 16); /* Optimized: ldexp(in - integral, 16) */
frac_d = (uint16_t)tmp;
ret = integral << 16;
ret |= frac_d & 0xffff;
return ret;
}
FP3232
double_to_fp3232(double in)
{
FP3232 ret;
int32_t integral;
double tmp;
uint32_t frac_d;
tmp = floor(in);
integral = (int32_t)tmp;
tmp = (in - integral) * (1ULL << 32); /* Optimized: ldexp(in - integral, 32) */
frac_d = (uint32_t)tmp;
ret.integral = integral;
ret.frac = frac_d;
return ret;
}