[perl #115928] a consistent (public) rand() implementation

Based on Yves's random branch work.

This version makes the new random number visible to external modules,
for example, List::Util's XS shuffle() implementation.

I've also added a 64-bit implementation when HAS_QUAD is true, this
should be significantly faster, even on 32-bit CPUs.  This is intended to
produce exactly the same sequence as the original implementation.

The original version of this commit retained the "freebsd" name from
Yves's original work for the function and data structure names.  I've
removed "freebsd" from most function names so the name isn't an issue
if we choose to replace the implementation,

1 files changed, 100 insertions, 0 deletions

diff --git a/util.c b/util.c
index 55f6d9ee88..28cc7064ed 100644
--- a/util.c
+++ b/util.c
@@ -37,6 +37,9 @@
 #endif
 #endif
 
+#include <math.h>
+#include <stdlib.h>
+
 #ifdef __Lynx__
 /* Missing protos on LynxOS */
 int putenv(char *);
@@ -6213,6 +6216,103 @@ Perl_get_re_arg(pTHX_ SV *sv) {
 }
 
 /*
+ * This code is derived from drand48() implementation from FreeBSD,
+ * found in lib/libc/gen/_rand48.c.
+ *
+ * The U64 implementation is original, based on the POSIX
+ * specification for drand48().
+ */
+
+/*
+* Copyright (c) 1993 Martin Birgmeier
+* All rights reserved.
+*
+* You may redistribute unmodified or modified versions of this source
+* code provided that the above copyright notice and this and the
+* following conditions are retained.
+*
+* This software is provided ``as is'', and comes with no warranties
+* of any kind. I shall in no event be liable for anything that happens
+* to anyone/anything when using this software.
+*/
+
+#define FREEBSD_DRAND48_SEED_0   (0x330e)
+
+#ifdef PERL_DRAND48_QUAD
+
+#define DRAND48_MULT 0x5deece66d
+#define DRAND48_ADD  0xb
+#define DRAND48_MASK 0xffffffffffff
+
+#else
+
+#define FREEBSD_DRAND48_SEED_1   (0xabcd)
+#define FREEBSD_DRAND48_SEED_2   (0x1234)
+#define FREEBSD_DRAND48_MULT_0   (0xe66d)
+#define FREEBSD_DRAND48_MULT_1   (0xdeec)
+#define FREEBSD_DRAND48_MULT_2   (0x0005)
+#define FREEBSD_DRAND48_ADD      (0x000b)
+
+const unsigned short _rand48_mult[3] = {
+                FREEBSD_DRAND48_MULT_0,
+                FREEBSD_DRAND48_MULT_1,
+                FREEBSD_DRAND48_MULT_2
+};
+const unsigned short _rand48_add = FREEBSD_DRAND48_ADD;
+
+#endif
+
+void
+Perl_drand48_init_r(perl_drand48_t *random_state, U32 seed)
+{
+    PERL_ARGS_ASSERT_DRAND48_INIT_R;
+
+#ifdef PERL_DRAND48_QUAD
+    *random_state = FREEBSD_DRAND48_SEED_0 + ((U64TYPE)seed << 16);
+#else
+    random_state->seed[0] = FREEBSD_DRAND48_SEED_0;
+    random_state->seed[1] = (U16) seed;
+    random_state->seed[2] = (U16) (seed >> 16);
+#endif
+}
+
+double
+Perl_drand48_r(perl_drand48_t *random_state)
+{
+    PERL_ARGS_ASSERT_DRAND48_R;
+
+#ifdef PERL_DRAND48_QUAD
+    *random_state = (*random_state * DRAND48_MULT + DRAND48_ADD)
+        & DRAND48_MASK;
+
+    return ldexp(*random_state, -48);
+#else
+    U32 accu;
+    U16 temp[2];
+
+    accu = (U32) _rand48_mult[0] * (U32) random_state->seed[0]
+         + (U32) _rand48_add;
+    temp[0] = (U16) accu;        /* lower 16 bits */
+    accu >>= sizeof(U16) * 8;
+    accu += (U32) _rand48_mult[0] * (U32) random_state->seed[1]
+          + (U32) _rand48_mult[1] * (U32) random_state->seed[0];
+    temp[1] = (U16) accu;        /* middle 16 bits */
+    accu >>= sizeof(U16) * 8;
+    accu += _rand48_mult[0] * random_state->seed[2]
+          + _rand48_mult[1] * random_state->seed[1]
+          + _rand48_mult[2] * random_state->seed[0];
+    random_state->seed[0] = temp[0];
+    random_state->seed[1] = temp[1];
+    random_state->seed[2] = (U16) accu;
+
+    return ldexp((double) random_state->seed[0], -48) +
+           ldexp((double) random_state->seed[1], -32) +
+           ldexp((double) random_state->seed[2], -16);
+#endif
+}
+ 
+
+/*
  * Local variables:
  * c-indentation-style: bsd
  * c-basic-offset: 4