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//==========================================================================

//

//      lib/select.c

//

//      'select()' system call

//

//==========================================================================

//####BSDCOPYRIGHTBEGIN####

//

// -------------------------------------------

//

// Portions of this software may have been derived from OpenBSD or other sources,

// and are covered by the appropriate copyright disclaimers included herein.

//

// -------------------------------------------

//

//####BSDCOPYRIGHTEND####

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):    gthomas

// Contributors: gthomas

// Date:         2000-01-10

// Purpose:      

// Description:  eCos implementation of 'select()' system call

//              

//

//####DESCRIPTIONEND####

//

//==========================================================================

#include <sys/param.h>

#include <cyg/io/file.h>

#include <cyg/kernel/kapi.h>

#include <sys/select.h>

#include <sys/bsdselect.h>

static cyg_flag_t select_flag;

static cyg_bool   select_flag_init = false;

#define SELECT_WAKE  0x01

#define SELECT_ABORT 0x02

//

// Private function which does all the work for 'select()'

//

static int

_cyg_select(int nfd, fd_set *in, fd_set *out, fd_set *ex,

            struct timeval *tv, cyg_bool_t abortable)

{

    int fd, mode, num, ticks;

    struct file *fp;

    fd_set in_res, out_res, ex_res;  // Result sets

    fd_set *selection[3], *result[3];

    cyg_tick_count_t now, then;

    int mode_type[] = {FREAD, FWRITE, 0};

    cyg_flag_value_t flag, wait_flag;

    // Note: since this is called by application programs, it needs no protection

    if (!select_flag_init) {

        select_flag_init = true;

        cyg_flag_init(&select_flag);

    }

    wait_flag = SELECT_WAKE;

    if (abortable) wait_flag |= SELECT_ABORT;

    FD_ZERO(&in_res);

    FD_ZERO(&out_res);

    FD_ZERO(&ex_res);

    // Set up sets

    selection[0] = in;   result[0] = &in_res;

    selection[1] = out;  result[1] = &out_res;

    selection[2] = ex;   result[2] = &ex_res;

    // Compute end time

    if (tv) {

        now = cyg_current_time();

        ticks = (tv->tv_sec * 100) + (tv->tv_usec / 10000);

        then = now + ticks;

    } else {

        then = 0;  // Compiler warnings :-(

        ticks = 0;

    }

    // Scan sets for possible I/O until something found, timeout or error.

    while (true) {

        num = 0;  // Total file descriptors "ready"

        cyg_scheduler_lock(); // Scan the list atomically wrt electing to sleep

        for (mode = 0;  mode < 3;  mode++) {

            if (selection[mode]) {

                for (fd = 0;  fd < nfd;  fd++) {

                    if (FD_ISSET(fd, selection[mode])) {

                        if (getfp(fd, &fp)) {

                            cyg_scheduler_unlock(); // return.

                            errno = EBADF;

                            return -1;

                        }

                        if ((*fp->f_ops->fo_select)(fp, mode_type[mode])) {

                            FD_SET(fd, result[mode]);

                            num++;

                        }

                    }

                }

            }

        }

        if (num) {

            cyg_scheduler_unlock(); // Happy, about to return.

            // Found something, update user's sets

            if (in) {

                memcpy(in, &in_res, sizeof(in_res));

            }

            if (out) {

                memcpy(out, &out_res, sizeof(out_res));

            }

            if (ex) {

                memcpy(ex, &ex_res, sizeof(ex_res));

            }

            return num;

        }

        // Nothing found, see if we want to wait

        if (tv) {

            if (ticks == 0) {

                // Special case of "poll"

                cyg_scheduler_unlock(); // About to return.

                return 0;

            }

            flag = cyg_flag_timed_wait(&select_flag, wait_flag,

                                       CYG_FLAG_WAITMODE_OR,

                                       then);

        } else {

            // Wait forever (until something happens)

            flag = cyg_flag_wait(&select_flag, wait_flag,

                                 CYG_FLAG_WAITMODE_OR);

        }

        cyg_scheduler_unlock(); // waited atomically

        if (flag & SELECT_ABORT) {

            errno = EINTR;

            return -1;

        }

        if (!flag) {

            return 0; // meaning no activity, ergo timeout occurred

        }

    }

    errno = ENOSYS;

    return -1;

}

//

// This function is called by the lower layers to record the

// fact that a particular 'select' event is being requested.

//

void

selrecord(void *selector, struct selinfo *info)

{

    // Unused by this implementation

}

//

// This function is called to indicate that a 'select' event

// may have occurred.

//

void

selwakeup(struct selinfo *info)

{

    // Need these ops to be atomic to make sure the clear occurs -

    // otherwise a higher prio thread could hog the CPU when its fds are

    // not ready, but the flag is (already) set, or set for someone else.

    cyg_scheduler_lock();

    cyg_flag_setbits(&select_flag, SELECT_WAKE);

    cyg_flag_maskbits(&select_flag,    0      ); // clear all

    cyg_scheduler_unlock();

}

//

// The public function used by 'normal' programs.  This interface does not allow

// the 'select()' to be externally interrupted.

//

int

select(int nfd, fd_set *in, fd_set *out, fd_set *ex,

       struct timeval *tv)

{

    return _cyg_select(nfd, in, out, ex, tv, false);

}

//

// The public function used by programs which wish to allow interruption,

// using the 'cyg_select_abort()' function below.

//

int

cyg_select_with_abort(int nfd, fd_set *in, fd_set *out, fd_set *ex,

                      struct timeval *tv)

{

    return _cyg_select(nfd, in, out, ex, tv, true);

}

//

// This function can be called by the user to forceably abort any

// current selects.

//

void

cyg_select_abort(void)

{

    // See comments in selwakeup()...

    cyg_scheduler_lock();

    cyg_flag_setbits(&select_flag, SELECT_ABORT);

    cyg_flag_maskbits(&select_flag,    0       );

    cyg_scheduler_unlock();

}