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Simplify custom types for punning, use better names #128

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Dec 30, 2024
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Simplify custom types for punning, use better names #128

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26 changes: 12 additions & 14 deletions src/integer64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -50,14 +50,12 @@
/** **/
/*****************************************************************************/

typedef struct Unsigned32x2TStruct {
unsigned int low;
unsigned int high;
} Unsigned32x2T;

typedef union {
Unsigned32x2T u32;
long long ll;
struct {
unsigned int low;
unsigned int high;
} U32x2Repr;
long long LongLongRepr;
} PunnedU32x2AndLongLong;

/*****************************************************************************/
Expand Down Expand Up @@ -1010,20 +1008,20 @@ SEXP runif_integer64(SEXP n_, SEXP min_, SEXP max_){
SEXP ret_;
PROTECT(ret_ = allocVector(REALSXP, n));
long long * ret = (long long *) REAL(ret_);
PunnedU32x2AndLongLong ii;
PunnedU32x2AndLongLong rand_draw;
GetRNGstate();
for (i=0; i<n; i++){
ii.u32.low = (unsigned int) floor(unif_rand()*4294967296);
ii.u32.high = (unsigned int) floor(unif_rand()*4294967296);
while(ii.ll == NA_INTEGER64) {
rand_draw.U32x2Repr.low = (unsigned int) floor(unif_rand()*4294967296);
rand_draw.U32x2Repr.high = (unsigned int) floor(unif_rand()*4294967296);
while(rand_draw.LongLongRepr == NA_INTEGER64) {
// # nocov start. Requires exceedingly rare (2^(-64) probability) occurrence.
// In principle can be found with the 'perfect' random seed, not worth burning compute to find out what that seed is.
// xx optimisation opportunity: if we know endianess, we only need to replace one of the two
ii.u32.low = (unsigned int) floor(unif_rand()*4294967296);
ii.u32.high = (unsigned int) floor(unif_rand()*4294967296);
rand_draw.U32x2Repr.low = (unsigned int) floor(unif_rand()*4294967296);
rand_draw.U32x2Repr.high = (unsigned int) floor(unif_rand()*4294967296);
// # nocov end
}
ret[i] = min + (ii.ll % d);
ret[i] = min + (rand_draw.LongLongRepr % d);
}
PutRNGstate();
UNPROTECT(1);
Expand Down
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