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Add jrand48()/nrand48() compat functions

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These functions are not available on all platforms.
This commit is contained in:
Romain Vimont 2023-01-21 19:35:04 +01:00
parent e6cd42355b
commit 059ec45f82
3 changed files with 54 additions and 0 deletions
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2
app/meson.build
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@ -170,6 +170,8 @@ check_functions = [
'strdup',
'asprintf',
'vasprintf',
'nrand48',
'jrand48',
]
foreach f : check_functions

44
app/src/compat.c
View file

@ -51,3 +51,47 @@ int vasprintf(char **strp, const char *fmt, va_list ap) {
return len;
}
#endif
#if !defined(HAVE_NRAND48) || !defined(HAVE_JRAND48)
#define SC_RAND48_MASK UINT64_C(0xFFFFFFFFFFFF) // 48 bits
#define SC_RAND48_A UINT64_C(0x5DEECE66D)
#define SC_RAND48_C 0xB
static inline uint64_t rand_iter48(uint64_t x) {
assert((x & ~SC_RAND48_MASK) == 0);
return (x * SC_RAND48_A + SC_RAND48_C) & SC_RAND48_MASK;
}
static uint64_t rand_iter48_xsubi(unsigned short xsubi[3]) {
uint64_t x = ((uint64_t) xsubi[0] << 32)
| ((uint64_t) xsubi[1] << 16)
| xsubi[2];
x = rand_iter48(x);
xsubi[0] = (x >> 32) & 0XFFFF;
xsubi[1] = (x >> 16) & 0XFFFF;
xsubi[2] = x & 0XFFFF;
return x;
}
#ifndef HAVE_NRAND48
long nrand48(unsigned short xsubi[3]) {
// range [0, 2^31)
return rand_iter48_xsubi(xsubi) >> 17;
}
#endif
#ifndef HAVE_JRAND48
long jrand48(unsigned short xsubi[3]) {
// range [-2^31, 2^31)
union {
uint32_t u;
int32_t i;
} v;
v.u = rand_iter48_xsubi(xsubi) >> 16;
return v.i;
}
#endif
#endif

8
app/src/compat.h
View file

@ -59,4 +59,12 @@ int asprintf(char **strp, const char *fmt, ...);
int vasprintf(char **strp, const char *fmt, va_list ap);
#endif
#ifndef HAVE_NRAND48
long nrand48(unsigned short xsubi[3]);
#endif
#ifndef HAVE_JRAND48
long jrand48(unsigned short xsubi[3]);
#endif
#endif