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%
% (c) The GRASP/AQUA Project, Glasgow University, 1994
%
\subsection[getLock.lc]{stdin/stout/stderr 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
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifndef FD_SETSIZE
#define FD_SETSIZE 256
#endif
typedef struct {
dev_t device;
ino_t inode;
int fd;
} Lock;
static Lock readLock[FD_SETSIZE];
static Lock writeLock[FD_SETSIZE];
static int readLocks = 0;
static int writeLocks = 0;
int
lockFile(fd, exclusive)
int fd;
int exclusive;
{
int i;
struct stat sb;
while (fstat(fd, &sb) < 0) {
if (errno != EINTR) {
return -1;
}
}
/* Only lock regular files */
if (!S_ISREG(sb.st_mode))
return 0;
for (i = 0; i < writeLocks; i++)
if (writeLock[i].inode == sb.st_ino && writeLock[i].device == sb.st_dev) {
errno = EAGAIN;
return -1;
}
if (!exclusive) {
i = readLocks++;
readLock[i].device = sb.st_dev;
readLock[i].inode = sb.st_ino;
readLock[i].fd = fd;
return 0;
}
for (i = 0; i < readLocks; i++)
if (readLock[i].inode == sb.st_ino && readLock[i].device == sb.st_dev) {
errno = EAGAIN;
return -1;
}
i = writeLocks++;
writeLock[i].device = sb.st_dev;
writeLock[i].inode = sb.st_ino;
writeLock[i].fd = fd;
return 0;
}
int
unlockFile(fd)
int fd;
{
int i, rc;
for (i = 0; i < readLocks; i++)
if (readLock[i].fd == fd) {
while (++i < readLocks)
readLock[i - 1] = readLock[i];
readLocks--;
return 0;
}
for (i = 0; i < writeLocks; i++)
if (writeLock[i].fd == fd) {
while (++i < writeLocks)
writeLock[i - 1] = writeLock[i];
writeLocks--;
return 0;
}
/* Signal that we did not find an entry */
return 1;
}
StgInt
getLock(fp, exclusive)
StgForeignObj fp;
StgInt exclusive;
{
if (lockFile(fileno((FILE *) fp), exclusive) < 0) {
if (errno == EBADF)
return 0;
else {
cvtErrno();
switch (ghc_errno) {
default:
stdErrno();
break;
case GHC_EACCES:
case GHC_EAGAIN:
ghc_errtype = ERR_RESOURCEBUSY;
ghc_errstr = "file is locked";
break;
}
(void) fclose((FILE *) fp);
return -1;
}
}
return 1;
}
\end{code}
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