diff options
Diffstat (limited to 'shell')
| -rw-r--r-- | shell/Kbuild | 3 | ||||
| -rw-r--r-- | shell/ash.c | 46 | ||||
| -rw-r--r-- | shell/random.c | 37 | ||||
| -rw-r--r-- | shell/random.h | 19 |
4 files changed, 77 insertions, 28 deletions
diff --git a/shell/Kbuild b/shell/Kbuild index 4d4741e..03960a8 100644 --- a/shell/Kbuild +++ b/shell/Kbuild @@ -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 diff --git a/shell/ash.c b/shell/ash.c index f2d372f..6ce6215 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -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); diff --git a/shell/random.c b/shell/random.c new file mode 100644 index 0000000..a4dce84 --- /dev/null +++ b/shell/random.c @@ -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; +} diff --git a/shell/random.h b/shell/random.h new file mode 100644 index 0000000..2d29a60 --- /dev/null +++ b/shell/random.h @@ -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; |