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//==========================================================================
//
// lib/select.c
//
// 'select()' system call
//
//==========================================================================
// ####BSDALTCOPYRIGHTBEGIN####
// -------------------------------------------
// Portions of this software may have been derived from OpenBSD
// or other sources, and if so are covered by the appropriate copyright
// and license included herein.
// -------------------------------------------
// ####BSDALTCOPYRIGHTEND####
//==========================================================================
//#####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();
}
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