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//===========================================================================
//
// rand.cxx
//
// ISO and POSIX 1003.1 standard random number generation functions
//
//===========================================================================
// ####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 or (at your option) any later
// version.
//
// eCos is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with eCos; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
//
// As a special exception, if other files instantiate templates or use
// macros or inline functions from this file, or you compile this file
// and link it with other works to produce a work based on this file,
// this file does not by itself cause the resulting work to be covered by
// the GNU General Public License. However the source code for this file
// must still be made available in accordance with section (3) of the GNU
// General Public License v2.
//
// This exception does not invalidate any other reasons why a work based
// on this file might be covered by the GNU General Public License.
// -------------------------------------------
// ####ECOSGPLCOPYRIGHTEND####
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s): jlarmour
// Contributors:
// Date: 2000-04-30
// Purpose: Provides ISO C rand() and srand() functions, along with
// POSIX 1003.1 rand_r() function
// Description: This implements rand() and srand() of section 7.10.2.1 of
// the ISO C standard. Also rand_r() defined in section 8.3.8
// of the POSIX 1003.1 standard
// Usage:
//
//####DESCRIPTIONEND####
//
//===========================================================================
// CONFIGURATION
#include <pkgconf/libc_stdlib.h> // Configuration header
// INCLUDES
#include <cyg/infra/cyg_type.h> // Common type definitions and support
#include <cyg/infra/cyg_trac.h> // Tracing support
#include <cyg/infra/cyg_ass.h> // Assertion support
#include <stdlib.h> // Header for all stdlib functions
// (like this one)
#ifdef CYGSEM_LIBC_PER_THREAD_RAND
# include <pkgconf/kernel.h> // kernel configuration
# include <cyg/kernel/thread.hxx> // per-thread data
# include <cyg/kernel/thread.inl> // per-thread data
# include <cyg/kernel/mutex.hxx> // mutexes
#endif
// TRACE
#if defined(CYGDBG_USE_TRACING) && defined(CYGNUM_LIBC_RAND_TRACE_LEVEL)
static int rand_trace = CYGNUM_LIBC_RAND_TRACE_LEVEL;
# define TL1 (0 < rand_trace)
#else
# define TL1 (0)
#endif
// STATICS
#ifdef CYGSEM_LIBC_PER_THREAD_RAND
static Cyg_Thread::cyg_data_index
rand_data_index=CYGNUM_KERNEL_THREADS_DATA_MAX;
static Cyg_Mutex rand_data_mutex CYGBLD_ATTRIB_INIT_PRI(CYG_INIT_LIBC);
#else
static unsigned int cyg_libc_rand_seed = CYGNUM_LIBC_RAND_SEED;
#endif
// FUNCTIONS
int
rand( void )
{
unsigned int *seed_p;
int retval;
CYG_REPORT_FUNCNAMETYPE( "rand", "returning %d" );
// get seed for this thread (if relevant )
#ifdef CYGSEM_LIBC_PER_THREAD_RAND
Cyg_Thread *self = Cyg_Thread::self();
// Get a per-thread data slot if we haven't got one already
// Do a simple test before locking and retrying test, as this is a
// rare situation
if (CYGNUM_KERNEL_THREADS_DATA_MAX==rand_data_index) {
rand_data_mutex.lock();
if (CYGNUM_KERNEL_THREADS_DATA_MAX==rand_data_index) {
// FIXME: Should use real CDL to pre-allocate a slot at compile
// time to ensure there are enough slots
rand_data_index = self->new_data_index();
CYG_ASSERT(rand_data_index >= 0, "failed to allocate data index" );
// Initialize seed
self->set_data(rand_data_index, CYGNUM_LIBC_RAND_SEED);
}
rand_data_mutex.unlock();
} // if
// we have a valid index now
seed_p = (unsigned int *)self->get_data_ptr(rand_data_index);
#else
seed_p = &cyg_libc_rand_seed;
#endif
CYG_TRACE2( TL1, "Retrieved seed address %08x containing %d",
seed_p, *seed_p );
CYG_CHECK_DATA_PTR( seed_p, "Help! Returned address of seed is invalid!" );
retval = rand_r( seed_p );
CYG_REPORT_RETVAL( retval );
return retval;
} // rand()
int
rand_r( unsigned int *seed )
{
int retval;
CYG_REPORT_FUNCNAMETYPE( "rand_r", "returning %d" );
CYG_CHECK_DATA_PTR( seed, "pointer to seed invalid!" );
#if defined(CYGIMP_LIBC_RAND_SIMPLEST)
// This algorithm sucks in the lower bits
*seed = (*seed * 1103515245) + 12345; // permutate seed
retval = (int)( *seed & RAND_MAX );
#elif defined(CYGIMP_LIBC_RAND_SIMPLE1)
// The above algorithm sucks in the lower bits, so we shave them off
// and repeat a couple of times to make it up
unsigned int s=*seed;
unsigned int uret;
s = (s * 1103515245) + 12345; // permutate seed
// Only use top 11 bits
uret = s & 0xffe00000;
s = (s * 1103515245) + 12345; // permutate seed
// Only use top 14 bits
uret += (s & 0xfffc0000) >> 11;
s = (s * 1103515245) + 12345; // permutate seed
// Only use top 7 bits
uret += (s & 0xfe000000) >> (11+14);
retval = (int)(uret & RAND_MAX);
*seed = s;
#elif defined(CYGIMP_LIBC_RAND_KNUTH1)
// This is the code supplied in Knuth Vol 2 section 3.6 p.185 bottom
#define MM 2147483647 // a Mersenne prime
#define AA 48271 // this does well in the spectral test
#define QQ 44488 // (long)(MM/AA)
#define RR 3399 // MM % AA; it is important that RR<QQ
*seed = AA*(*seed % QQ) - RR*(unsigned int)(*seed/QQ);
if (*seed < 0)
*seed += MM;
retval = (int)( *seed & RAND_MAX );
#else
# error No valid implementation for rand()!
#endif
CYG_REPORT_RETVAL( retval );
return retval;
} // rand_r()
void
srand( unsigned int seed )
{
CYG_REPORT_FUNCNAME( "srand" );
CYG_REPORT_FUNCARG1DV( (int)seed );
// get seed for this thread ( if relevant )
#ifdef CYGSEM_LIBC_PER_THREAD_RAND
Cyg_Thread *self = Cyg_Thread::self();
// Get a per-thread data slot if we haven't got one already
// Do a simple test before locking and retrying test, as this is a
// rare situation
if (CYGNUM_KERNEL_THREADS_DATA_MAX==rand_data_index) {
rand_data_mutex.lock();
if (CYGNUM_KERNEL_THREADS_DATA_MAX==rand_data_index) {
// FIXME: Should use real CDL to pre-allocate a slot at compile
// time to ensure there are enough slots
rand_data_index = self->new_data_index();
CYG_ASSERT(rand_data_index >= 0, "failed to allocate data index" );
}
rand_data_mutex.unlock();
} // if
// we have a valid index now
self->set_data(rand_data_index, (CYG_ADDRWORD) seed);
#else
cyg_libc_rand_seed = seed;
#endif
CYG_REPORT_RETURN();
} // srand()
// EOF rand.cxx
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