Add simplified locking code.

[mLib] / lock.h

diff --git a/lock.h b/lock.h
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+/* -*-c-*-
+ *
+ * $Id: lock.h,v 1.1 1999/05/15 10:33:53 mdw Exp $
+ *
+ * Simplified POSIX locking interface
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of the mLib utilities library.
+ *
+ * mLib is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * mLib is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with mLib; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: lock.h,v $
+ * Revision 1.1  1999/05/15 10:33:53  mdw
+ * Add simplified locking code.
+ *
+ */
+
+#ifndef LOCK_H
+#define LOCK_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Magic constants ---------------------------------------------------*/
+
+enum {
+  LOCK_UNLOCK,                         /* Release a lock I obtained */
+  LOCK_EXCL,                           /* Obtain an exclusive lock */
+  LOCK_NONEXCL                         /* Obtain a nonexclusive lock */
+};
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @lock_file@ --- *
+ *
+ * Arguments:  @int fd@ = file descriptor to lock
+ *             @unsigned how@ = type of lock required
+ *
+ * Returns:    0 if OK, -1 if it failed.
+ *
+ * Use:                Acquires a lock on the given file.  The value @how@
+ *             specifies the type of lock to acquire: @LOCK_EXCL@ gets
+ *             an exclusive (write) lock; @LOCK_NONEXCL@ gets a non-
+ *             exclusive (read) lock and @LOCK_UNLOCK@ releases any locks.
+ *             Acquiring a lock gets timed out after a while with an
+ *             error.
+ */
+
+extern int lock_file(int /*fd*/, unsigned /*how*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif