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//==========================================================================
//
//      sem.cxx
//
//      POSIX semaphore implementation
//
//==========================================================================
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// -------------------------------------------                              
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//
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// for more details.                                                        
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//
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//==========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):           nickg
// Contributors:        nickg
// Date:                2000-03-27
// Purpose:             POSIX semaphore implementation
// Description:         This file contains the implementation of the POSIX semaphore
//                      functions.
//              
//              
//
//####DESCRIPTIONEND####
//
//==========================================================================
 
#include <pkgconf/hal.h>
#include <pkgconf/kernel.h>
#include <pkgconf/posix.h>
 
#include <cyg/kernel/ktypes.h>          // base kernel types
#include <cyg/infra/cyg_trac.h>         // tracing macros
#include <cyg/infra/cyg_ass.h>          // assertion macros
 
#include <semaphore.h>                  // our header
 
#include "pprivate.h"                   // POSIX private header
 
#include <cyg/kernel/thread.hxx>        // Kernel threads
 
#include <cyg/kernel/thread.inl>        // Cyg_ThreadQueue::empty()
 
#include <cyg/kernel/sema.hxx>          // Kernel semaphores
 
// -------------------------------------------------------------------------
// Internal definitions
 
// Handle entry to a pthread package function. 
#define SEMA_ENTRY() CYG_REPORT_FUNCTYPE( "returning %d" );
 
// Do a semaphore package defined return. This requires the error code
// to be placed in errno, and if it is non-zero, -1 returned as the
// result of the function. This also gives us a place to put any
// generic tidyup handling needed for things like signal delivery and
// cancellation.
#define SEMA_RETURN(err)                        \
CYG_MACRO_START                                 \
    int __retval = 0;                           \
    if( err != 0 ) __retval = -1, errno = err;  \
    CYG_REPORT_RETVAL( __retval );              \
    return __retval;                            \
CYG_MACRO_END
 
//-----------------------------------------------------------------------------
// new operator to allow us to invoke the Cyg_Thread constructor on the
// user's semaphore object.
 
inline void *operator new(size_t size,  void *ptr) { return (void *)ptr; };
 
// -------------------------------------------------------------------------
// Initialize semaphore to value.
// pshared is not supported under eCos.
 
externC int sem_init  (sem_t *sem, int pshared, unsigned int value)
{
    SEMA_ENTRY();
 
    if( value > SEM_VALUE_MAX )
        SEMA_RETURN(EINVAL);
 
    Cyg_Counting_Semaphore *sema;
 
    sema = new((void *)sem) Cyg_Counting_Semaphore(value);
 
    sema=sema;
 
    SEMA_RETURN(0);
}
 
// -------------------------------------------------------------------------
// Destroy the semaphore.
 
externC int sem_destroy  (sem_t *sem)
{
    SEMA_ENTRY();
 
    Cyg_Counting_Semaphore *sema = (Cyg_Counting_Semaphore *)sem;
 
    // Check that the semaphore has no waiters
    if( sema->waiting() )
        SEMA_RETURN(EBUSY);
 
    // Call the destructor
    sema->~Cyg_Counting_Semaphore();
 
    SEMA_RETURN(0);
}
 
// -------------------------------------------------------------------------
// Decrement value if >0 or wait for a post.
 
externC int sem_wait  (sem_t *sem)
{
    int retval = 0;
 
    SEMA_ENTRY();
 
#ifdef CYGPKG_POSIX_PTHREAD
    // check for cancellation first.
    pthread_testcancel();
#endif
 
    Cyg_Counting_Semaphore *sema = (Cyg_Counting_Semaphore *)sem;
 
    if( !sema->wait() ) retval = EINTR;
 
#ifdef CYGPKG_POSIX_PTHREAD
    // check if we were woken because we were being cancelled
    pthread_testcancel();
#endif
 
    SEMA_RETURN(retval);
}
 
// -------------------------------------------------------------------------
// Decrement value if >0, return -1 if not.
 
externC int sem_trywait  (sem_t *sem)
{
    int retval = 0;
 
    SEMA_ENTRY();
 
    Cyg_Counting_Semaphore *sema = (Cyg_Counting_Semaphore *)sem;
 
    if( !sema->trywait() ) retval = EAGAIN;
 
    SEMA_RETURN(retval);
}
 
// -------------------------------------------------------------------------
// Increment value and wake a waiter if one is present.
 
externC int sem_post  (sem_t *sem)
{
    SEMA_ENTRY();
 
    Cyg_Counting_Semaphore *sema = (Cyg_Counting_Semaphore *)sem;
 
    sema->post();
 
    SEMA_RETURN(0);
}
 
 
// -------------------------------------------------------------------------
// Get current value
 
externC int sem_getvalue  (sem_t *sem, int *sval)
{
    SEMA_ENTRY();
 
    Cyg_Counting_Semaphore *sema = (Cyg_Counting_Semaphore *)sem;
 
    *sval = sema->peek();
 
    CYG_REPORT_RETVAL( 0 );
    return 0;
}
 
// -------------------------------------------------------------------------
// Open an existing named semaphore, or create it.
 
externC sem_t *sem_open  (const char *name, int oflag, ...)
{
    SEMA_ENTRY();
 
    errno = ENOSYS;
 
    CYG_REPORT_RETVAL( SEM_FAILED );
    return SEM_FAILED;
}
 
// -------------------------------------------------------------------------
// Close descriptor for semaphore.
 
externC int sem_close  (sem_t *sem)
{
    SEMA_ENTRY();
 
    SEMA_RETURN(ENOSYS);
}   
 
// -------------------------------------------------------------------------
// Remove named semaphore
 
externC int sem_unlink  (const char *name)
{
    SEMA_ENTRY();
 
    SEMA_RETURN(ENOSYS);
}    
 
// -------------------------------------------------------------------------
// EOF sem.cxx