aio: Add support for lock -wait

Sometimes it is useful to wait for a lock to become available.

Signed-off-by: Steve Bennett <steveb@workware.net.au>

3 files changed, 36 insertions, 13 deletions

diff --git a/jim-aio.c b/jim-aio.c
index ba8216f..a5fa24e 100644
--- a/jim-aio.c
+++ b/jim-aio.c
@@ -1440,13 +1440,21 @@ static int aio_cmd_lock(Jim_Interp *interp, int argc, Jim_Obj *const *argv)
 {
     AioFile *af = Jim_CmdPrivData(interp);
     struct flock fl;
+    int lockmode = F_SETLK;
+
+    if (argc == 1) {
+        if (!Jim_CompareStringImmediate(interp, argv[0], "-wait")) {
+            return -1;
+        }
+        lockmode = F_SETLKW;
+    }
 
     fl.l_start = 0;
     fl.l_len = 0;
     fl.l_type = F_WRLCK;
     fl.l_whence = SEEK_SET;
 
-    switch (fcntl(af->fd, F_SETLK, &fl))
+    switch (fcntl(af->fd, lockmode, &fl))
     {
         case 0:
             Jim_SetResultInt(interp, 1);
@@ -1732,12 +1740,12 @@ static const jim_subcmd_type aio_command_table[] = {
     },
 #endif
 #if defined(HAVE_STRUCT_FLOCK)
-    {   "lock",
+    {   "lock ?-wait?",
         NULL,
         aio_cmd_lock,
         0,
-        0,
-        /* Description: Attempt to get a lock. */
+        1,
+        /* Description: Attempt to get a lock, possibly waiting */
     },
     {   "unlock",
         NULL,
diff --git a/jim_tcl.txt b/jim_tcl.txt
index 77c4b35..247ad7e 100644
--- a/jim_tcl.txt
+++ b/jim_tcl.txt
@@ -56,6 +56,7 @@ Changes since 0.78
 ~~~~~~~~~~~~~~~~~~
 1. Add `file mtimeus` for high resolution file timestamps
 2. `aio` now supports datagram Unix-Domain sockets
+3. Add support for `aio lock -wait`
 
 Changes between 0.77 and 0.78
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -4581,9 +4582,9 @@ aio
 +$handle *buffering none|line|full*+::
     Sets the buffering mode of the stream.
 
-+$handle *close* ?r(ead)|w(rite)|-nodelete?+::
++$handle *close ?r(ead)|w(rite)|-nodelete?*+::
     Closes the stream.
-    The +'read'+ and +'write'+ arguments perform a "half-close" on a socket. See the +shutdown(2)+ man page.
+    The +'read'+ and +'write'+ arguments perform a "half-close" on a socket. See the 'shutdown(2)' man page.
     The +'-nodelete'+ option is applicable only for Unix domain sockets. It closes the socket
     but does not delete the bound path (e.g. after `os.fork`).
 
@@ -4609,9 +4610,10 @@ aio
 +$handle *isatty*+::
     Returns 1 if the stream is a tty device.
 
-+$handle *lock*+::
++$handle *lock ?-wait?*+::
     Apply a POSIX lock to the open file associated with the handle using
-    fcntl(2).
+    'fcntl(F_SETLK)', or 'fcntl(F_SETLKW)' to wait for the lock to be available if +'-wait'+
+    is specified.
     The handle must be open for write access.
     Returns 1 if the lock was successfully obtained, 0 otherwise.
     An error occurs if the handle is not suitable for locking (e.g.
@@ -4641,7 +4643,7 @@ aio
     Seeks in the stream (default 'current')
 
 +$handle *sendto* 'str ?address'+::
-    Sends the string, +'str'+, to the given address (host:port or path) via the socket using sendto(2).
+    Sends the string, +'str'+, to the given address (host:port or path) via the socket using 'sendto(2)'.
     This is intended for udp/dgram sockets and may give an error or behave in unintended
     ways for other handle types.
     Returns the number of bytes written.
@@ -4657,8 +4659,8 @@ aio
     integer socket options: +sndbuf, rcvbuf+
 
 +$handle *sync*+::
-    Flush the stream, then fsync(2) to commit any changes to storage.
-    Only available on platforms that support fsync(2).
+    Flush the stream, then 'fsync(2)' to commit any changes to storage.
+    Only available on platforms that support 'fsync(2)'.
 
 +$handle *tell*+::
     Returns the current seek position
@@ -4668,7 +4670,7 @@ aio
     If arguments are given, they must either be a dictionary, or +setting value \...+
     Abbrevations are supported for both settings and values, so the following is acceptable:
     +$f tty parity e input c out raw+.
-    Only available on platforms that support termios(3). Supported settings are:
+    Only available on platforms that support 'termios(3)'. Supported settings are:
 
     +*baud* 'rate'+;;
         Baud rate. e.g. 115200
@@ -4698,7 +4700,7 @@ aio
     +*vtime* 'time'+;;
         Timeout for noncanonical read (units of 0.1 seconds)
 
-+$handle *ssl* *?-server cert priv?*+::
++$handle *ssl* ?*-server* 'cert priv'?+::
     Upgrades the stream to a SSL/TLS session and returns the handle.
 
 +$handle *unlock*+::
diff --git a/tests/lock.test b/tests/lock.test
index 3672d6a..e7b0b2d 100644
--- a/tests/lock.test
+++ b/tests/lock.test
@@ -42,6 +42,19 @@ test lock-1.5 {grab lock from sub-process} {
 	set stat
 } 0
 
+test lock-1.6 {wait for lock} {
+	# Run a child process that grabs the lock for 0.5 seconds
+	set pid [exec [info nameofexecutable] -e {set fh [open locktest.file r+]; $fh lock; sleep 0.5} >/dev/null &]
+	# And wait to acquire the lock in the parent. Should take ~500ms
+	set start [clock millis]
+	sleep 0.1
+	$fh lock -wait
+	set delta [expr {[clock millis] - $start}]
+	if {$delta < 100} {
+		error "Lock acquired after ${delta}ms"
+	}
+} {}
+
 $fh close
 file delete locktest.file