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%
% (c) The GRASP/AQUA Project, Glasgow University, 1994
%
\subsection[seekFile.lc]{hSeek and hIsSeekable Runtime Support}
\begin{code}
#include "rtsdefs.h"
#include "stgio.h"
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
StgInt
seekFile(fp, whence, size, d)
StgAddr fp;
StgInt whence;
StgInt size;
StgByteArray d;
{
struct stat sb;
long int offset;
/*
* We need to snatch the offset out of an MP_INT. The bits are there sans sign,
* which we pick up from our size parameter. If abs(size) is greater than 1,
* this integer is just too big.
*/
switch (size) {
case -1:
offset = -*(StgInt *) d;
break;
case 0:
offset = 0;
break;
case 1:
offset = *(StgInt *) d;
break;
default:
ghc_errtype = ERR_INVALIDARGUMENT;
ghc_errstr = "offset out of range";
return -1;
}
/* Try to find out the file type & size for a physical file */
while (fstat(fileno((FILE *) fp), &sb) < 0) {
/* highly unlikely */
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
if (S_ISREG(sb.st_mode)) {
/* Verify that we are not seeking beyond end-of-file */
int posn;
switch (whence) {
case SEEK_SET:
posn = offset;
break;
case SEEK_CUR:
while ((posn = ftell((FILE *) fp)) == -1) {
/* the possibility seems awfully remote */
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
posn += offset;
break;
case SEEK_END:
posn = sb.st_size + offset;
break;
}
if (posn > sb.st_size) {
ghc_errtype = ERR_INVALIDARGUMENT;
ghc_errstr = "seek position beyond end of file";
return -1;
}
} else if (S_ISFIFO(sb.st_mode)) {
ghc_errtype = ERR_UNSUPPORTEDOPERATION;
ghc_errstr = "can't seek on a pipe";
return -1;
} else {
ghc_errtype = ERR_UNSUPPORTEDOPERATION;
ghc_errstr = "can't seek on a device";
return -1;
}
while (fseek((FILE *) fp, offset, whence) != 0) {
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
return 0;
}
StgInt
seekFileP(fp)
StgAddr fp;
{
struct stat sb;
/* Try to find out the file type */
while (fstat(fileno((FILE *) fp), &sb) < 0) {
/* highly unlikely */
if (errno != EINTR) {
cvtErrno();
stdErrno();
return -1;
}
}
/* Regular files are okay */
if (S_ISREG(sb.st_mode)) {
return 1;
}
/* For now, everything else is not */
else {
return 0;
}
}
\end{code}
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