newlib-cygwin/newlib/libc/stdlib/rand.c

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2000-02-18 03:39:52 +08:00
/*
FUNCTION
<<rand>>, <<srand>>---pseudo-random numbers
INDEX
rand
INDEX
srand
INDEX
rand_r
ANSI_SYNOPSIS
#include <stdlib.h>
int rand(void);
void srand(unsigned int <[seed]>);
int rand_r(unsigned int *<[seed]>);
TRAD_SYNOPSIS
#include <stdlib.h>
int rand();
void srand(<[seed]>)
unsigned int <[seed]>;
void rand_r(<[seed]>)
unsigned int *<[seed]>;
DESCRIPTION
<<rand>> returns a different integer each time it is called; each
integer is chosen by an algorithm designed to be unpredictable, so
that you can use <<rand>> when you require a random number.
The algorithm depends on a static variable called the ``random seed'';
starting with a given value of the random seed always produces the
same sequence of numbers in successive calls to <<rand>>.
You can set the random seed using <<srand>>; it does nothing beyond
storing its argument in the static variable used by <<rand>>. You can
exploit this to make the pseudo-random sequence less predictable, if
you wish, by using some other unpredictable value (often the least
significant parts of a time-varying value) as the random seed before
beginning a sequence of calls to <<rand>>; or, if you wish to ensure
(for example, while debugging) that successive runs of your program
use the same ``random'' numbers, you can use <<srand>> to set the same
random seed at the outset.
RETURNS
<<rand>> returns the next pseudo-random integer in sequence; it is a
number between <<0>> and <<RAND_MAX>> (inclusive).
<<srand>> does not return a result.
NOTES
2005-10-28 Bob Wilson <bob.wilson@acm.org> * libc/misc/unctrl.c: Replace FUNCTION description. * libc/signal/signal.c: Remove documentation for raise and _raise_r. * libc/stdio/getdelim.c: Fix spelling errors. * libc/stdio/getw.c: Put RETURNS on a separate line. Fix punctuation. * libc/stdio/putw.c: Likewise. * libc/stdlib/a64l.c: Fix formatting, spelling and punctuation in documentation. * libc/stdlib/assert.c: Do not capitalize FUNCTION description. * libc/stdlib/efgcvt.c: Add spaces to FUNCTION description. * libc/stdlib/envlock.c: Use em-dash in FUNCTION description. * libc/stdlib/mlock.c: Likewise. * libc/stdlib/mstats.c: Likewise. * libc/time/tzlock.c: Likewise. * libc/stdlib/rand.c: Use "multi-threaded" and "thread-safe" in NOTES. * libc/stdlib/rand48.c: Remove extra space in FUNCTION description and hyphenate "pseudo-random". * libc/string/bcmp.c: Remove extra blank lines in documentation. * libc/string/strncat.c: Likewise. * libc/string/memchr.c: Remove extra ">" character in documentation. * libc/string/strcspn.c: Use "characters" instead of "chars". * libc/string/strpbrk.c: Likewise. * libc/string/strerror_r.c: Capitalize "GNU". * libc/string/strnlen.c: Likewise. * libc/string/strtok.c: Fix formatting, spelling and punctuation in documentation. Use "multi-threaded" and "thread-safe" in NOTES. * libc/string/wcscat.c: Split PORTABILITY into two paragraphs. * libc/string/wcschr.c: Likewise. * libc/string/wcscmp.c: Likewise. * libc/string/wcscpy.c: Likewise. * libc/string/wcscspn.c: Likewise. * libc/string/wcslen.c: Likewise. * libc/string/wcsncat.c: Likewise. * libc/string/wcsncmp.c: Likewise. * libc/string/wcsncpy.c: Likewise. * libc/string/wcsnlen.c: Likewise. * libc/string/wcspbrk.c: Likewise. * libc/string/wcsrchr.c: Likewise. * libc/string/wcsspn.c: Likewise. * libc/string/wmemchr.c: Likewise. * libc/string/wmemcmp.c: Likewise. * libc/string/wmemcpy.c: Likewise. * libc/string/wmemset.c: Likewise. * libc/string/wmemmove.c: Likewise. Also fix FUNCTION description. * libc/string/wcswidth.c: Formatting and punctuation in documentation. * libc/string/wcwidth.c: Likewise. * libm/common/s_modf.c: Remove extra period from documentation. * libm/math/s_isnan.c: Fix formatting, grammar and punctuation in documentation. * libm/mathfp/s_isnan.c: Likewise. * libm/math/s_ldexp.c: Fix punctuation. * libm/mathfp/s_ldexp.c: Likewise. * libm/math/w_log.c: Likewise. * libm/mathfp/s_logarithm.c: Likewise. * libm/math/w_j0.c: Add spaces to FUNCTION description. * libm/mathfp/w_jn.c: Likewise.
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<<rand>> and <<srand>> are unsafe for multi-threaded applications.
<<rand_r>> is thread-safe and should be used instead.
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PORTABILITY
<<rand>> is required by ANSI, but the algorithm for pseudo-random
number generation is not specified; therefore, even if you use
the same random seed, you cannot expect the same sequence of results
on two different systems.
<<rand>> requires no supporting OS subroutines.
*/
#ifndef _REENT_ONLY
#include <stdlib.h>
#include <reent.h>
void
_DEFUN (srand, (seed), unsigned int seed)
{
2013-04-29 Sebastian Huber <sebastian.huber@embedded-brains.de> * libc/stdio/local.h (CHECK_INIT): Evaluate argument only once. (CHECK_STD_INIT): Likewise. * libc/stdio/fgetc.c (fgetc): Use local variable for _REENT. * libc/stdio/fgetwc.c (fwgetc): Likewise. * libc/stdio/fgetws.c (fgetws): Likewise. * libc/stdio/fputc.c (fputc): Likewise. * libc/stdio/fputwc.c (fputwc): Likewise. * libc/stdio/fputws.c (fputws): Likewise. * libc/stdio/getc.c (getc): Likewise. * libc/stdio/getchar.c (_getchar_r): Likewise. * libc/stdio/putc.c (putc): Likewise. * libc/stdio/putchar.c (putchar): Likewise. * libc/stdio/scanf.c (scanf): Likewise. * libc/stdio/setvbuf.c (setvbuf): Likewise. * libc/stdio/ungetwc.c (ungetwc): Likewise. * libc/stdio/vfscanf.c (VFSCANF): Likewise. * libc/stdio/vfwscanf.c (VFWSCANF): Likewise. * libc/stdio/viprintf.c (viprintf): Likewise. * libc/stdio/viscanf.c (viscanf): Likewise. * libc/stdio/vprintf.c (vprintf): Likewise. * libc/stdio/vscanf.c (vscanf): Likewise. * libc/stdio/vwprintf.c (vwprintf): Likewise. * libc/stdio/vwscanf.c (vwscanf): Likewise. * libc/stdio/wscanf.c (wscanf): Likewise. * libc/stdlib/ecvtbuf.c (fcvtbuf): Likewise. (fcvtbuf): Likewise. (ecvtbuf): Likewise. (ecvtbuf): Likewise. * libc/stdlib/mblen.c (mblen): Likewise. * libc/stdlib/mbrlen.c (mbrlen): Likewise. * libc/stdlib/mbrtowc.c (mbrtowc): Likewise. * libc/stdlib/mbtowc.c (mbtowc): Likewise. * libc/stdlib/rand.c (srand): Likewise. (rand): Likewise. * libc/stdlib/wcrtomb.c (wcrtomb): Likewise. * libc/stdlib/wctob.c (wctob): Likewise. * libc/stdlib/wctomb.c (wctomb): Likewise. * libc/string/strtok.c (strtok): Likewise. * libc/time/asctime.c (asctime): Likewise. * libc/time/gmtime.c (gmtime): Likewise. * libc/time/lcltime.c (lcltime): Likewise.
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struct _reent *reent = _REENT;
_REENT_CHECK_RAND48(reent);
_REENT_RAND_NEXT(reent) = seed;
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}
int
_DEFUN_VOID (rand)
{
2013-04-29 Sebastian Huber <sebastian.huber@embedded-brains.de> * libc/stdio/local.h (CHECK_INIT): Evaluate argument only once. (CHECK_STD_INIT): Likewise. * libc/stdio/fgetc.c (fgetc): Use local variable for _REENT. * libc/stdio/fgetwc.c (fwgetc): Likewise. * libc/stdio/fgetws.c (fgetws): Likewise. * libc/stdio/fputc.c (fputc): Likewise. * libc/stdio/fputwc.c (fputwc): Likewise. * libc/stdio/fputws.c (fputws): Likewise. * libc/stdio/getc.c (getc): Likewise. * libc/stdio/getchar.c (_getchar_r): Likewise. * libc/stdio/putc.c (putc): Likewise. * libc/stdio/putchar.c (putchar): Likewise. * libc/stdio/scanf.c (scanf): Likewise. * libc/stdio/setvbuf.c (setvbuf): Likewise. * libc/stdio/ungetwc.c (ungetwc): Likewise. * libc/stdio/vfscanf.c (VFSCANF): Likewise. * libc/stdio/vfwscanf.c (VFWSCANF): Likewise. * libc/stdio/viprintf.c (viprintf): Likewise. * libc/stdio/viscanf.c (viscanf): Likewise. * libc/stdio/vprintf.c (vprintf): Likewise. * libc/stdio/vscanf.c (vscanf): Likewise. * libc/stdio/vwprintf.c (vwprintf): Likewise. * libc/stdio/vwscanf.c (vwscanf): Likewise. * libc/stdio/wscanf.c (wscanf): Likewise. * libc/stdlib/ecvtbuf.c (fcvtbuf): Likewise. (fcvtbuf): Likewise. (ecvtbuf): Likewise. (ecvtbuf): Likewise. * libc/stdlib/mblen.c (mblen): Likewise. * libc/stdlib/mbrlen.c (mbrlen): Likewise. * libc/stdlib/mbrtowc.c (mbrtowc): Likewise. * libc/stdlib/mbtowc.c (mbtowc): Likewise. * libc/stdlib/rand.c (srand): Likewise. (rand): Likewise. * libc/stdlib/wcrtomb.c (wcrtomb): Likewise. * libc/stdlib/wctob.c (wctob): Likewise. * libc/stdlib/wctomb.c (wctomb): Likewise. * libc/string/strtok.c (strtok): Likewise. * libc/time/asctime.c (asctime): Likewise. * libc/time/gmtime.c (gmtime): Likewise. * libc/time/lcltime.c (lcltime): Likewise.
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struct _reent *reent = _REENT;
/* This multiplier was obtained from Knuth, D.E., "The Art of
Computer Programming," Vol 2, Seminumerical Algorithms, Third
Edition, Addison-Wesley, 1998, p. 106 (line 26) & p. 108 */
2013-04-29 Sebastian Huber <sebastian.huber@embedded-brains.de> * libc/stdio/local.h (CHECK_INIT): Evaluate argument only once. (CHECK_STD_INIT): Likewise. * libc/stdio/fgetc.c (fgetc): Use local variable for _REENT. * libc/stdio/fgetwc.c (fwgetc): Likewise. * libc/stdio/fgetws.c (fgetws): Likewise. * libc/stdio/fputc.c (fputc): Likewise. * libc/stdio/fputwc.c (fputwc): Likewise. * libc/stdio/fputws.c (fputws): Likewise. * libc/stdio/getc.c (getc): Likewise. * libc/stdio/getchar.c (_getchar_r): Likewise. * libc/stdio/putc.c (putc): Likewise. * libc/stdio/putchar.c (putchar): Likewise. * libc/stdio/scanf.c (scanf): Likewise. * libc/stdio/setvbuf.c (setvbuf): Likewise. * libc/stdio/ungetwc.c (ungetwc): Likewise. * libc/stdio/vfscanf.c (VFSCANF): Likewise. * libc/stdio/vfwscanf.c (VFWSCANF): Likewise. * libc/stdio/viprintf.c (viprintf): Likewise. * libc/stdio/viscanf.c (viscanf): Likewise. * libc/stdio/vprintf.c (vprintf): Likewise. * libc/stdio/vscanf.c (vscanf): Likewise. * libc/stdio/vwprintf.c (vwprintf): Likewise. * libc/stdio/vwscanf.c (vwscanf): Likewise. * libc/stdio/wscanf.c (wscanf): Likewise. * libc/stdlib/ecvtbuf.c (fcvtbuf): Likewise. (fcvtbuf): Likewise. (ecvtbuf): Likewise. (ecvtbuf): Likewise. * libc/stdlib/mblen.c (mblen): Likewise. * libc/stdlib/mbrlen.c (mbrlen): Likewise. * libc/stdlib/mbrtowc.c (mbrtowc): Likewise. * libc/stdlib/mbtowc.c (mbtowc): Likewise. * libc/stdlib/rand.c (srand): Likewise. (rand): Likewise. * libc/stdlib/wcrtomb.c (wcrtomb): Likewise. * libc/stdlib/wctob.c (wctob): Likewise. * libc/stdlib/wctomb.c (wctomb): Likewise. * libc/string/strtok.c (strtok): Likewise. * libc/time/asctime.c (asctime): Likewise. * libc/time/gmtime.c (gmtime): Likewise. * libc/time/lcltime.c (lcltime): Likewise.
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_REENT_CHECK_RAND48(reent);
_REENT_RAND_NEXT(reent) =
_REENT_RAND_NEXT(reent) * __extension__ 6364136223846793005LL + 1;
return (int)((_REENT_RAND_NEXT(reent) >> 32) & RAND_MAX);
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}
#endif /* _REENT_ONLY */