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-rw-r--r--libguile/random.c42
1 files changed, 27 insertions, 15 deletions
diff --git a/libguile/random.c b/libguile/random.c
index 83870f6ad..c0a3e046b 100644
--- a/libguile/random.c
+++ b/libguile/random.c
@@ -241,21 +241,42 @@ scm_c_exp1 (scm_t_rstate *state)
unsigned char scm_masktab[256];
-scm_t_uint32
-scm_c_random (scm_t_rstate *state, scm_t_uint32 m)
+static inline scm_t_uint32
+scm_i_mask32 (scm_t_uint32 m)
{
- scm_t_uint32 r, mask;
- mask = (m < 0x100
+ return (m < 0x100
? scm_masktab[m]
: (m < 0x10000
? scm_masktab[m >> 8] << 8 | 0xff
: (m < 0x1000000
? scm_masktab[m >> 16] << 16 | 0xffff
: scm_masktab[m >> 24] << 24 | 0xffffff)));
+}
+
+scm_t_uint32
+scm_c_random (scm_t_rstate *state, scm_t_uint32 m)
+{
+ scm_t_uint32 r, mask = scm_i_mask32 (m);
while ((r = state->rng->random_bits (state) & mask) >= m);
return r;
}
+scm_t_uint64
+scm_c_random64 (scm_t_rstate *state, scm_t_uint64 m)
+{
+ scm_t_uint64 r;
+ scm_t_uint32 mask;
+
+ if (m <= SCM_T_UINT32_MAX)
+ return scm_c_random (state, (scm_t_uint32) m);
+
+ mask = scm_i_mask32 (m >> 32);
+ while ((r = ((scm_t_uint64) (state->rng->random_bits (state) & mask) << 32)
+ | state->rng->random_bits (state)) >= m)
+ ;
+ return r;
+}
+
/*
SCM scm_c_random_bignum (scm_t_rstate *state, SCM m)
@@ -377,17 +398,8 @@ SCM_DEFINE (scm_random, "random", 1, 1, 0,
return scm_from_uint32 (scm_c_random (SCM_RSTATE (state),
(scm_t_uint32) m));
#elif SCM_SIZEOF_UNSIGNED_LONG <= 8
- if (m <= SCM_T_UINT32_MAX)
- return scm_from_uint32 (scm_c_random (SCM_RSTATE (state),
- (scm_t_uint32) m));
- else
- {
- scm_t_uint64 upper, lower;
-
- upper = scm_c_random (SCM_RSTATE (state), (scm_t_uint32) (m >> 32));
- lower = scm_c_random (SCM_RSTATE (state), SCM_T_UINT32_MAX);
- return scm_from_uint64 ((upper << 32) | lower);
- }
+ return scm_from_uint64 (scm_c_random64 (SCM_RSTATE (state),
+ (scm_t_uint64) m));
#else
#error "Cannot deal with this platform's unsigned long size"
#endif