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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 Red Hat, 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., // 59 Temple Place, Suite 330, Boston, MA 02111-1307 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. // // This exception does not invalidate any other reasons why a work based on // this file might be covered by the GNU General Public License. // // Alternative licenses for eCos may be arranged by contacting Red Hat, Inc. // at http://sources.redhat.com/ecos/ecos-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_ucount32 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) { // the kernel just throws an assert if this doesn't work // 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(); // 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) { // the kernel just throws an assert if this doesn't work // 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(); } 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