Add a wait-for command which blocks a client on a named channel until it is

wokrn up again (with wait-for -S). From Thiago Padilha.

cmd-wait-for.c

@@ -0,0 +1,124 @@
+/* $Id$ */
+
+/*
+ * Copyright (c) 2013 Nicholas Marriott <nicm@users.sourceforge.net>
+ * Copyright (c) 2013 Thiago de Arruda <tpadilha84@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "tmux.h"
+
+/*
+ * Block or wake a client on a named wait channel.
+ */
+
+enum cmd_retval cmd_wait_for_exec(struct cmd *, struct cmd_q *);
+
+const struct cmd_entry cmd_wait_for_entry = {
+	"wait-for", "wait",
+	"S", 1, 1,
+	"[-S] channel",
+	0,
+	NULL,
+	NULL,
+	cmd_wait_for_exec
+};
+
+struct wait_channel {
+	const char	       *name;
+	TAILQ_HEAD(, cmd_q)	waiters;
+
+	RB_ENTRY(wait_channel)	entry;
+};
+RB_HEAD(wait_channels, wait_channel);
+struct wait_channels wait_channels = RB_INITIALIZER(wait_channels);
+
+int	wait_channel_cmp(struct wait_channel *, struct wait_channel *);
+RB_PROTOTYPE(wait_channels, wait_channel, entry, wait_channel_cmp);
+RB_GENERATE(wait_channels, wait_channel, entry, wait_channel_cmp);
+
+int
+wait_channel_cmp(struct wait_channel *wc1, struct wait_channel *wc2)
+{
+	return (strcmp(wc1->name, wc2->name));
+}
+
+enum cmd_retval	cmd_wait_for_signal(struct cmd_q *, const char *,
+		    struct wait_channel *);
+enum cmd_retval	cmd_wait_for_wait(struct cmd_q *, const char *,
+		    struct wait_channel *);
+
+enum cmd_retval
+cmd_wait_for_exec(struct cmd *self, struct cmd_q *cmdq)
+{
+	struct args     	*args = self->args;
+	const char		*name = args->argv[0];
+	struct wait_channel	*wc, wc0;
+
+	wc0.name = name;
+	wc = RB_FIND(wait_channels, &wait_channels, &wc0);
+
+	if (args_has(args, 'S'))
+		return (cmd_wait_for_signal(cmdq, name, wc));
+	return (cmd_wait_for_wait(cmdq, name, wc));
+}
+
+enum cmd_retval
+cmd_wait_for_signal(struct cmd_q *cmdq, const char *name,
+    struct wait_channel *wc)
+{
+	struct cmd_q	*wq, *wq1;
+
+	if (wc == NULL || TAILQ_EMPTY(&wc->waiters)) {
+		cmdq_error(cmdq, "no waiting clients on %s", name);
+		return (CMD_RETURN_ERROR);
+	}
+
+	TAILQ_FOREACH_SAFE(wq, &wc->waiters, waitentry, wq1) {
+		TAILQ_REMOVE(&wc->waiters, wq, waitentry);
+		if (!cmdq_free(wq))
+			cmdq_continue(wq);
+	}
+	RB_REMOVE(wait_channels, &wait_channels, wc);
+	free((void*) wc->name);
+	free(wc);
+
+	return (CMD_RETURN_NORMAL);
+}
+
+enum cmd_retval
+cmd_wait_for_wait(struct cmd_q *cmdq, const char *name,
+    struct wait_channel *wc)
+{
+	if (cmdq->client == NULL || cmdq->client->session != NULL) {
+		cmdq_error(cmdq, "not able to wait");
+		return (CMD_RETURN_ERROR);
+	}
+
+	if (wc == NULL) {
+		wc = xmalloc(sizeof *wc);
+		wc->name = xstrdup(name);
+		TAILQ_INIT(&wc->waiters);
+		RB_INSERT(wait_channels, &wait_channels, wc);
+	}
+	TAILQ_INSERT_TAIL(&wc->waiters, cmdq, waitentry);
+	cmdq->references++;
+
+	return (CMD_RETURN_WAIT);
+}