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%
% (c) The GRASP/AQUA Project, Glasgow University, 1994
%
\subsection[inputReady.lc]{hReady Runtime Support}
\begin{code}
#include "rtsdefs.h"
#include "stgio.h"
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
StgInt
inputReady(fp)
StgAddr fp;
{
int flags;
int c;
if (feof((FILE *) fp))
return 0;
/* Get the original file status flags */
while ((flags = fcntl(fileno((FILE *) fp), F_GETFL)) < 0) {
/* highly unlikely */
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
/* If it's not already non-blocking, make it so */
if (!(flags & O_NONBLOCK)) {
while (fcntl(fileno((FILE *) fp), F_SETFL, flags | O_NONBLOCK) < 0) {
/* still highly unlikely */
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
}
/* Now try to get a character */
while ((c = getc((FILE *) fp)) == EOF && errno == EINTR)
clearerr((FILE *) fp);
/* If we made it non-blocking for this, switch it back */
if (!(flags & O_NONBLOCK)) {
while (fcntl(fileno((FILE *) fp), F_SETFL, flags) < 0) {
/* still highly unlikely */
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
}
if (c == EOF) {
if (errno == EAGAIN || feof((FILE *) fp)) {
clearerr((FILE *) fp);
return 0;
} else {
cvtErrno();
stdErrno();
return -1;
}
} else if (ungetc(c, (FILE *) fp) == EOF) {
cvtErrno();
stdErrno();
return -1;
} else
return 1;
}
\end{code}
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