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#include <unistd.h>
#include <sys/time.h>
#include <errno.h>
#include "io_internal.h"
void io_wantwrite_really(int64 d, io_entry* e);
int64 io_canwrite() {
io_entry* e;
#if defined(HAVE_SIGIO)
/* We promise that the user can call io_canread() and read, and
* the user uses io_tryread or calls io_eagain_read to signal if
* there is no more data to read. That means if the user does not
* call io_eagain_read, we need to know which fd it was so we can
* keep it in the alternative queue. */
if (alt_curwrite!=-1) {
e=iarray_get(&io_fds,alt_curwrite);
e->next_write=alt_firstwrite;
alt_firstwrite=alt_curwrite;
alt_curwrite=-1;
}
#endif
if (first_writeable==-1)
#if defined(HAVE_SIGIO)
{
if (alt_firstwrite>=0 && (e=iarray_get(&io_fds,alt_firstwrite)) && e->canwrite) {
debug_printf(("io_canwrite: normal write queue is empty, swapping in alt write queue (starting with %ld)\n",alt_firstwrite));
first_writeable=alt_firstwrite;
alt_firstwrite=-1;
} else
return -1;
}
#else
return -1;
#endif
for (;;) {
int64 r;
e=iarray_get(&io_fds,first_writeable);
if (!e) break;
r=first_writeable;
first_writeable=e->next_write;
e->next_write=-1;
if (e->closed) {
/* The fd was previously closed, but there were still open events on it.
* To prevent race conditions, we did not actually close the fd
* but only marked it as closed, so we can skip this event here */
continue;
}
debug_printf(("io_canwrite: dequeue %lld from normal write queue (next is %ld)\n",r,first_writeable));
if (e->wantwrite &&
#ifdef __MINGW32__
(e->canwrite || e->sendfilequeued==1)
#else
e->canwrite
#endif
) {
#if defined(HAVE_SIGIO)
#if 0
/* this code violates an invariant that the other code has, namely
* that e->next_read is -1 once the fd is dequeued. */
e->next_write=alt_firstwrite;
alt_firstwrite=r;
debug_printf(("io_canwrite: enqueue %ld in alt write queue (next is %ld)\n",alt_firstwrite,e->next_write));
#else
alt_curwrite=r;
#endif
if (io_waitmode!=_SIGIO)
#endif
e->canwrite=0;
if (!e->kernelwantwrite)
io_wantwrite_really(r,e);
return r;
}
}
return -1;
}