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ash: factor out $RANDOM support

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function                                             old     new   delta
next_random                                            -      46     +46
ash_main                                            1361    1356      -5
change_random                                        132      97     -35
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/2 up/down: 46/-40)              Total: 6 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-10-09 20:59:04 +02:00
parent a05b2b856b
commit 3ea2e82dc7
4 changed files with 77 additions and 28 deletions
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3
shell/Kbuild
View File

@ -8,4 +8,7 @@ lib-y:=
lib-$(CONFIG_ASH) += ash.o ash_ptr_hack.o
lib-$(CONFIG_HUSH) += hush.o match.o
lib-$(CONFIG_CTTYHACK) += cttyhack.o
lib-$(CONFIG_SH_MATH_SUPPORT) += math.o
lib-$(CONFIG_ASH_RANDOM_SUPPORT) += random.o
lib-$(CONFIG_HUSH_RANDOM_SUPPORT) += random.o

46
shell/ash.c
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@ -51,16 +51,19 @@
#include <setjmp.h>
#include <fnmatch.h>
#include "math.h"
#if ENABLE_ASH_RANDOM_SUPPORT
# include "random.h"
#endif
#if defined SINGLE_APPLET_MAIN
/* STANDALONE does not make sense, and won't compile */
#undef CONFIG_FEATURE_SH_STANDALONE
#undef ENABLE_FEATURE_SH_STANDALONE
#undef IF_FEATURE_SH_STANDALONE
#undef IF_NOT_FEATURE_SH_STANDALONE(...)
#define ENABLE_FEATURE_SH_STANDALONE 0
#define IF_FEATURE_SH_STANDALONE(...)
#define IF_NOT_FEATURE_SH_STANDALONE(...) __VA_ARGS__
# undef CONFIG_FEATURE_SH_STANDALONE
# undef ENABLE_FEATURE_SH_STANDALONE
# undef IF_FEATURE_SH_STANDALONE
# undef IF_NOT_FEATURE_SH_STANDALONE(...)
# define ENABLE_FEATURE_SH_STANDALONE 0
# define IF_FEATURE_SH_STANDALONE(...)
# define IF_NOT_FEATURE_SH_STANDALONE(...) __VA_ARGS__
#endif
#ifndef PIPE_BUF
@ -197,9 +200,7 @@ struct globals_misc {
/* Rarely referenced stuff */
#if ENABLE_ASH_RANDOM_SUPPORT
/* Random number generators */
int32_t random_galois_LFSR; /* Galois LFSR (fast but weak). signed! */
uint32_t random_LCG; /* LCG (fast but weak) */
random_t random_gen;
#endif
pid_t backgndpid; /* pid of last background process */
smallint job_warning; /* user was warned about stopped jobs (can be 2, 1 or 0). */
@ -224,8 +225,7 @@ extern struct globals_misc *const ash_ptr_to_globals_misc;
#define gotsig (G_misc.gotsig )
#define trap (G_misc.trap )
#define trap_ptr (G_misc.trap_ptr )
#define random_galois_LFSR (G_misc.random_galois_LFSR)
#define random_LCG (G_misc.random_LCG )
#define random_gen (G_misc.random_gen )
#define backgndpid (G_misc.backgndpid )
#define job_warning (G_misc.job_warning)
#define INIT_G_misc() do { \
@ -10075,28 +10075,18 @@ change_random(const char *value)
/* Another example - taps at 32 31 30 10: */
/* MASK = 0x00400007 */
uint32_t t;
if (value == NULL) {
/* "get", generate */
uint32_t t;
/* LCG has period of 2^32 and alternating lowest bit */
random_LCG = 1664525 * random_LCG + 1013904223;
/* Galois LFSR has period of 2^32-1 = 3 * 5 * 17 * 257 * 65537 */
t = (random_galois_LFSR << 1);
if (random_galois_LFSR < 0) /* if we just shifted 1 out of msb... */
t ^= MASK;
random_galois_LFSR = t;
/* Both are weak, combining them gives better randomness
* and ~2^64 period. & 0x7fff is probably bash compat
* for $RANDOM range. Combining with subtraction is
* just for fun. + and ^ would work equally well. */
t = (t - random_LCG) & 0x7fff;
t = next_random(&random_gen);
/* set without recursion */
setvar(vrandom.text, utoa(t), VNOFUNC);
vrandom.flags &= ~VNOFUNC;
} else {
/* set/reset */
random_galois_LFSR = random_LCG = strtoul(value, NULL, 10);
t = strtoul(value, NULL, 10);
INIT_RANDOM_T(&random_gen, (t ? t : 1), t);
}
}
#endif
@ -13271,7 +13261,7 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
#if ENABLE_ASH_RANDOM_SUPPORT
/* Can use monotonic_ns() for better randomness but for now it is
* not used anywhere else in busybox... so avoid bloat */
random_galois_LFSR = random_LCG = rootpid + monotonic_us();
INIT_RANDOM_T(&random_gen, rootpid, monotonic_us());
#endif
init();
setstackmark(&smark);

37
shell/random.c Normal file
View File

@ -0,0 +1,37 @@
/* vi: set sw=4 ts=4: */
/*
* $RANDOM support.
*
* Copyright (C) 2008 Denys Vlasenko
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
#include "libbb.h"
#include "random.h"
uint32_t FAST_FUNC
next_random(random_t *rnd)
{
/* Galois LFSR parameter */
/* Taps at 32 31 29 1: */
enum { MASK = 0x8000000b };
/* Another example - taps at 32 31 30 10: */
/* MASK = 0x00400007 */
uint32_t t;
/* LCG has period of 2^32 and alternating lowest bit */
rnd->LCG = 1664525 * rnd->LCG + 1013904223;
/* Galois LFSR has period of 2^32-1 = 3 * 5 * 17 * 257 * 65537 */
t = (rnd->galois_LFSR << 1);
if (rnd->galois_LFSR < 0) /* if we just shifted 1 out of msb... */
t ^= MASK;
rnd->galois_LFSR = t;
/* Both are weak, combining them gives better randomness
* and ~2^64 period. & 0x7fff is probably bash compat
* for $RANDOM range. Combining with subtraction is
* just for fun. + and ^ would work equally well. */
t = (t - rnd->LCG) & 0x7fff;
return t;
}

19
shell/random.h Normal file
View File

@ -0,0 +1,19 @@
/* vi: set sw=4 ts=4: */
/*
* $RANDOM support.
*
* Copyright (C) 2008 Denys Vlasenko
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
typedef struct random_t {
/* Random number generators */
int32_t galois_LFSR; /* Galois LFSR (fast but weak). signed! */
uint32_t LCG; /* LCG (fast but weak) */
} random_t;
#define INIT_RANDOM_T(rnd, nonzero, v) \
((rnd)->galois_LFSR = (nonzero), (rnd)->LCG = (v))
uint32_t next_random(random_t *rnd) FAST_FUNC;