2 * (c) The GRASP/AQUA Project, Glasgow University, 1994-2004
4 * $Id: lockFile.c,v 1.5 2005/01/28 13:36:32 simonmar Exp $
6 * stdin/stout/stderr Runtime Support
9 #ifndef mingw32_HOST_OS
21 static Lock readLock[FD_SETSIZE];
22 static Lock writeLock[FD_SETSIZE];
24 static int readLocks = 0;
25 static int writeLocks = 0;
28 lockFile(int fd, int for_writing, int exclusive)
33 if (fd > FD_SETSIZE) {
34 barf("lockFile: fd out of range");
37 while (fstat(fd, &sb) < 0) {
43 /* opening a file for writing, check to see whether
44 we don't have any read locks on it already.. */
45 for (i = 0; i < readLocks; i++) {
46 if (readLock[i].inode == sb.st_ino && readLock[i].device == sb.st_dev)
49 /* If we're determined that there is only a single
50 writer to the file, check to see whether the file
51 hasn't already been opened for writing..
54 for (i = 0; i < writeLocks; i++) {
55 if (writeLock[i].inode == sb.st_ino && writeLock[i].device == sb.st_dev) {
60 /* OK, everything is cool lock-wise, record it and leave. */
62 writeLock[i].device = sb.st_dev;
63 writeLock[i].inode = sb.st_ino;
67 /* For reading, it's simpler - just check to see
68 that there's no-one writing to the underlying file. */
69 for (i = 0; i < writeLocks; i++) {
70 if (writeLock[i].inode == sb.st_ino && writeLock[i].device == sb.st_dev)
73 /* Fit in new entry, reusing an existing table entry, if possible. */
74 for (i = 0; i < readLocks; i++) {
75 if (readLock[i].inode == sb.st_ino && readLock[i].device == sb.st_dev) {
80 readLock[i].device = sb.st_dev;
81 readLock[i].inode = sb.st_ino;
93 for (i = 0; i < readLocks; i++)
94 if (readLock[i].fd == fd) {
95 while (++i < readLocks)
96 readLock[i - 1] = readLock[i];
101 for (i = 0; i < writeLocks; i++)
102 if (writeLock[i].fd == fd) {
103 while (++i < writeLocks)
104 writeLock[i - 1] = writeLock[i];
108 /* Signal that we did not find an entry */