Mercurial > hg
changeset 24016:fb93721cc229
util: add getbefloat64
As far as I can tell, this is wrong. double's format isn't strictly
specified in the C standard, but the wikipedia article implies that
platforms implementing optional Annex F "IEC 60559 floating-point
arithmetic" will work correctly.
My local C experts believe doing *((double *) &t) is a strict aliasing
violation, and that using a union is also one. Doing memcpy appears to
be the least-undefined behavior possible.
| author | Augie Fackler <augie@google.com> |
|---|---|
| date | Tue, 03 Feb 2015 13:17:21 -0500 |
| parents | e2bf959a5a0d |
| children | 72c9b5ae7278 |
| files | mercurial/util.h |
| diffstat | 1 files changed, 13 insertions(+), 0 deletions(-) [+] |
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--- a/mercurial/util.h Tue Jan 20 14:09:57 2015 -0500 +++ b/mercurial/util.h Tue Feb 03 13:17:21 2015 -0500 @@ -196,4 +196,17 @@ c[3] = (x) & 0xff; } +static inline double getbefloat64(const char *c) +{ + const unsigned char *d = (const unsigned char *)c; + double ret; + int i; + uint64_t t = 0; + for (i = 0; i < 8; i++) { + t = (t<<8) + d[i]; + } + memcpy(&ret, &t, sizeof(t)); + return ret; +} + #endif /* _HG_UTIL_H_ */