From 608f4f254ccf95a01b5480e2dbe7a1b6e54c8609 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@sbcglobal.net>
Date: Fri, 8 Apr 2016 16:39:03 -0400
Subject: sitting here

---
 wg.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 wg.c

(limited to 'wg.c')

diff --git a/wg.c b/wg.c
new file mode 100644
index 0000000..4f60765
--- /dev/null
+++ b/wg.c
@@ -0,0 +1,45 @@
+#include <errno.h>
+#include <error.h>
+#include <stdlib.h> /* for EXIT_FAILURE */
+#include <unistd.h>
+
+#include "wg.h"
+
+/* Thread management tools modeled on https://golang.org/pkg/sync/#WaitGroup */
+
+/* pthread_cond_t is overly complicated. Just use a self-pipe. */
+
+void wg_init(struct wg *wg) {
+	wg->count = 0;
+	pthread_mutex_init(&wg->lock, NULL);
+	int fds[2];
+	if (pipe(fds) != 0)
+		error(EXIT_FAILURE, errno, "pipe");
+	wg->fd_wait = fds[0];
+	wg->fd_signal = fds[1];
+}
+
+void wg_add(struct wg *wg, unsigned int n) {
+	pthread_mutex_lock(&wg->lock);
+	wg->count += n;
+	pthread_mutex_unlock(&wg->lock);
+}
+
+void wg_sub(struct wg *wg, unsigned int n) {
+	pthread_mutex_lock(&wg->lock);
+	wg->count -= n;
+	if (wg->count == 0)
+		if (write(wg->fd_signal, " ", 1) < 1)
+			error(EXIT_FAILURE, errno, "write");
+	pthread_mutex_unlock(&wg->lock);
+}
+
+void wg_wait(struct wg *wg) {
+	char b;
+ retry:
+	if (read(wg->fd_wait, &b, 1) == -1) {
+		if (errno == EINTR)
+			goto retry;
+		error(EXIT_FAILURE, errno, "wg_wait");
+	}
+}
-- 
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