1 files changed, 152 insertions, 0 deletions
diff --git a/src/util/myflock.c b/src/util/myflock.c
new file mode 100644
index 0000000..bd903ee
--- /dev/null
+++ b/src/util/myflock.c
@@ -0,0 +1,152 @@
+/*++
+/* NAME
+/*	myflock 3
+/* SUMMARY
+/*	lock open file
+/* SYNOPSIS
+/*	#include <myflock.h>
+/*
+/*	int	myflock(fd, lock_style, operation)
+/*	int	fd;
+/*	int	lock_style;
+/*	int	operation;
+/* DESCRIPTION
+/*	myflock() locks or unlocks an entire open file.
+/*
+/*	In the case of a blocking request, a call that fails due to
+/*	foreseeable transient problems is retried once per second.
+/*
+/*	Arguments:
+/* .IP fd
+/*	The open file to be locked/unlocked.
+/* .IP lock_style
+/*	One of the following values:
+/* .RS
+/* .IP	MYFLOCK_STYLE_FLOCK
+/*	Use BSD-style flock() locking.
+/* .IP	MYFLOCK_STYLE_FCNTL
+/*	Use POSIX-style fcntl() locking.
+/* .RE
+/* .IP operation
+/*	One of the following values:
+/* .RS
+/* .IP	MYFLOCK_OP_NONE
+/*	Release any locks the process has on the specified open file.
+/* .IP	MYFLOCK_OP_SHARED
+/*	Attempt to acquire a shared lock on the specified open file.
+/*	This is appropriate for read-only access.
+/* .IP	MYFLOCK_OP_EXCLUSIVE
+/*	Attempt to acquire an exclusive lock on the specified open
+/*	file. This is appropriate for write access.
+/* .PP
+/*	In addition, setting the MYFLOCK_OP_NOWAIT bit causes the
+/*	call to return immediately when the requested lock cannot
+/*	be acquired.
+/* .RE
+/* DIAGNOSTICS
+/*	myflock() returns 0 in case of success, -1 in case of failure.
+/*	A problem description is returned via the global \fIerrno\fR
+/*	variable. In the case of a non-blocking lock request the value
+/*	EAGAIN means that a lock is claimed by someone else.
+/*
+/*	Panic: attempts to use an unsupported file locking method or
+/*	to implement an unsupported operation.
+/* LICENSE
+/* .ad
+/* .fi
+/*	The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/*	Wietse Venema
+/*	IBM T.J. Watson Research
+/*	P.O. Box 704
+/*	Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include "sys_defs.h"
+#include <errno.h>
+#include <unistd.h>
+
+#ifdef HAS_FCNTL_LOCK
+#include <fcntl.h>
+#include <string.h>
+#endif
+
+#ifdef HAS_FLOCK_LOCK
+#include <sys/file.h>
+#endif
+
+/* Utility library. */
+
+#include "msg.h"
+#include "myflock.h"
+
+/* myflock - lock/unlock entire open file */
+
+int     myflock(int fd, int lock_style, int operation)
+{
+    int     status;
+
+    /*
+     * Sanity check.
+     */
+    if ((operation & (MYFLOCK_OP_BITS)) != operation)
+	msg_panic("myflock: improper operation type: 0x%x", operation);
+
+    switch (lock_style) {
+
+	/*
+	 * flock() does exactly what we need. Too bad it is not standard.
+	 */
+#ifdef HAS_FLOCK_LOCK
+    case MYFLOCK_STYLE_FLOCK:
+	{
+	    static int lock_ops[] = {
+		LOCK_UN, LOCK_SH, LOCK_EX, -1,
+		-1, LOCK_SH | LOCK_NB, LOCK_EX | LOCK_NB, -1
+	    };
+
+	    while ((status = flock(fd, lock_ops[operation])) < 0
+		   && errno == EINTR)
+		sleep(1);
+	    break;
+	}
+#endif
+
+	/*
+	 * fcntl() is standard and does more than we need, but we can handle
+	 * it.
+	 */
+#ifdef HAS_FCNTL_LOCK
+    case MYFLOCK_STYLE_FCNTL:
+	{
+	    struct flock lock;
+	    int     request;
+	    static int lock_ops[] = {
+		F_UNLCK, F_RDLCK, F_WRLCK
+	    };
+
+	    memset((void *) &lock, 0, sizeof(lock));
+	    lock.l_type = lock_ops[operation & ~MYFLOCK_OP_NOWAIT];
+	    request = (operation & MYFLOCK_OP_NOWAIT) ? F_SETLK : F_SETLKW;
+	    while ((status = fcntl(fd, request, &lock)) < 0
+		   && errno == EINTR)
+		sleep(1);
+	    break;
+	}
+#endif
+    default:
+	msg_panic("myflock: unsupported lock style: 0x%x", lock_style);
+    }
+
+    /*
+     * Return a consistent result. Some systems return EACCES when a lock is
+     * taken by someone else, and that would complicate error processing.
+     */
+    if (status < 0 && (operation & MYFLOCK_OP_NOWAIT) != 0)
+	if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EACCES)
+	    errno = EAGAIN;
+
+    return (status);
+}