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authorRoland McGrath <roland@gnu.org>1996-03-17 02:00:05 +0000
committerRoland McGrath <roland@gnu.org>1996-03-17 02:00:05 +0000
commit5aab07eb5615fa5baec4161579f03c72280b88e2 (patch)
tree7a5e18d6175d80cf2ad54ff05efd9f37d558a702 /stdlib
parent6025c399e9fd73efeb5b93db78ec021d3fce2b1c (diff)
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Sat Mar 16 20:58:43 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu>cvs/libc-960317
* stdlib/erand48_r.c: Use FP division by powers of two to distribute short bits into double.
Diffstat (limited to 'stdlib')
-rw-r--r--stdlib/erand48_r.c32
1 files changed, 8 insertions, 24 deletions
diff --git a/stdlib/erand48_r.c b/stdlib/erand48_r.c
index ab41474..17caae5 100644
--- a/stdlib/erand48_r.c
+++ b/stdlib/erand48_r.c
@@ -18,45 +18,29 @@ not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <stdlib.h>
-#include "gmp.h"
-#include "gmp-mparam.h"
-#include <float.h>
+#include <limits.h>
-/* Function to construct a floating point number from an MP integer
- containing the fraction bits, a base 2 exponent, and a sign flag. */
-extern double __mpn_construct_double (mp_srcptr mpn, int exponent, int neg);
-
int
erand48_r (xsubi, buffer, result)
unsigned short int xsubi[3];
struct drand48_data *buffer;
double *result;
{
- mp_limb mpn[(3 * sizeof (unsigned short int) + sizeof (mp_limb) - 1)
- / sizeof (mp_limb)];
-
/* Compute next state. */
if (__drand48_iterate (xsubi, buffer) < 0)
return -1;
- /* Build a 48-bit mpn containing the 48 random bits. */
+ /* Construct a positive double with the 48 random bits distributed over
+ its fractional part so the resulting FP number is [0.0,1.0). */
-#if BITS_PER_MP_LIMB == 64
- mpn[0] = (xsubi[0] << 32) | (xsubi[1] << 16) | xsubi[2];
-#elif BITS_PER_MP_LIMB == 32
- mpn[0] = (xsubi[1] << 16) | xsubi[2];
- mpn[1] = xsubi[0];
+#if USHRT_MAX == 65535
+ *result = ((double) xsubi[2] / (1ULL << 48) +
+ (double) xsubi[1] / (1ULL << 32) +
+ (double) xsubi[0] / (1ULL << 16));
#else
- #error "BITS_PER_MP_LIMB value not handled"
+# error Unsupported size of short int
#endif
- /* Shift them up so they are most significant bits of the fraction. */
- __mpn_lshift (mpn, mpn, sizeof mpn / sizeof mpn[0], DBL_MANT_DIG - 48);
-
- /* Construct a positive double using those bits for the fractional part,
- and a zero exponent so the resulting FP number is [0.0,1.0). */
- *result = __mpn_construct_double (mpn, 0, 0);
-
return 0;
}