1 files changed, 115 insertions, 0 deletions
diff --git a/ghc/lib/std/cbits/lockFile.c b/ghc/lib/std/cbits/lockFile.c
new file mode 100644
index 0000000000..14a0a38854
--- /dev/null
+++ b/ghc/lib/std/cbits/lockFile.c
@@ -0,0 +1,115 @@
+/* 
+ * (c) The GRASP/AQUA Project, Glasgow University, 1994-1998
+ *
+ * $Id: lockFile.c,v 1.1 2001/05/18 16:54:06 simonmar Exp $
+ *
+ * stdin/stout/stderr Runtime Support
+ */
+
+#include "HsStd.h"
+
+#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(int fd, int for_writing, int exclusive)
+{
+    int i;
+    struct stat sb;
+
+    if (for_writing) {
+      /* opening a file for writing, check to see whether
+         we don't have any read locks on it already.. */
+      for (i = 0; i < readLocks; i++) {
+	 if (readLock[i].inode == sb.st_ino && readLock[i].device == sb.st_dev) {
+#ifndef __MINGW32__
+	    return -1;
+#else
+	    break;    
+#endif
+	 }	    
+      }
+      /* If we're determined that there is only a single
+         writer to the file, check to see whether the file
+	 hasn't already been opened for writing..
+      */
+      if (exclusive) {
+	for (i = 0; i < writeLocks; i++) {
+	  if (writeLock[i].inode == sb.st_ino && writeLock[i].device == sb.st_dev) {
+#ifndef __MINGW32__
+	     return -1;
+#else
+	     break;
+#endif
+	  }
+        }
+      }
+      /* OK, everything is cool lock-wise, record it and leave. */
+      i = writeLocks++;
+      writeLock[i].device = sb.st_dev;
+      writeLock[i].inode = sb.st_ino;
+      writeLock[i].fd = fd;
+      return 0;
+    } else { 
+      /* For reading, it's simpler - just check to see
+         that there's no-one writing to the underlying file. */
+      for (i = 0; i < writeLocks; i++) {
+	if (writeLock[i].inode == sb.st_ino && writeLock[i].device == sb.st_dev) {
+#ifndef __MINGW32__
+	     return -1;
+#else
+	     break;
+#endif
+        }
+      }
+      /* Fit in new entry, reusing an existing table entry, if possible. */
+      for (i = 0; i < readLocks; i++) {
+	 if (readLock[i].inode == sb.st_ino && readLock[i].device == sb.st_dev) {
+	   return 0;
+	 }
+      }
+      i = readLocks++;
+      readLock[i].device = sb.st_dev;
+      readLock[i].inode = sb.st_ino;
+      readLock[i].fd = fd;
+      return 0;
+    }
+
+}
+
+int
+unlockFile(int fd)
+{
+    int i;
+
+    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;
+}