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