1 files changed, 126 insertions, 0 deletions
diff --git a/src/cmd/fossil/9excl.c b/src/cmd/fossil/9excl.c
new file mode 100644
index 00000000..6fce280a
--- /dev/null
+++ b/src/cmd/fossil/9excl.c
@@ -0,0 +1,126 @@
+#include "stdinc.h"
+
+#include "9.h"
+
+static struct {
+	VtLock*	lock;
+
+	Excl*	head;
+	Excl*	tail;
+} ebox;
+
+struct Excl {
+	Fsys*	fsys;
+	uvlong	path;
+	ulong	time;
+
+	Excl*	next;
+	Excl*	prev;
+};
+
+enum {
+	LifeTime	= (5*60),
+};
+
+int
+exclAlloc(Fid* fid)
+{
+	ulong t;
+	Excl *excl;
+
+	assert(fid->excl == nil);
+
+	t = time(0L);
+	vtLock(ebox.lock);
+	for(excl = ebox.head; excl != nil; excl = excl->next){
+		if(excl->fsys != fid->fsys || excl->path != fid->qid.path)
+			continue;
+		/*
+		 * Found it.
+		 * Now, check if it's timed out.
+		 * If not, return error, it's locked.
+		 * If it has timed out, zap the old
+		 * one and continue on to allocate a
+		 * a new one.
+		 */
+		if(excl->time >= t){
+			vtUnlock(ebox.lock);
+			vtSetError("exclusive lock");
+			return 0;
+		}
+		excl->fsys = nil;
+	}
+
+	/*
+	 * Not found or timed-out.
+	 * Alloc a new one and initialise.
+	 */
+	excl = vtMemAllocZ(sizeof(Excl));
+	excl->fsys = fid->fsys;
+	excl->path = fid->qid.path;
+	excl->time = t+LifeTime;
+	if(ebox.tail != nil){
+		excl->prev = ebox.tail;
+		ebox.tail->next = excl;
+	}
+	else{
+		ebox.head = excl;
+		excl->prev = nil;
+	}
+	ebox.tail = excl;
+	excl->next = nil;
+	vtUnlock(ebox.lock);
+
+	fid->excl = excl;
+	return 1;
+}
+
+int
+exclUpdate(Fid* fid)
+{
+	ulong t;
+	Excl *excl;
+
+	excl = fid->excl;
+
+	t = time(0L);
+	vtLock(ebox.lock);
+	if(excl->time < t || excl->fsys != fid->fsys){
+		vtUnlock(ebox.lock);
+		vtSetError("exclusive lock broken");
+		return 0;
+	}
+	excl->time = t+LifeTime;
+	vtUnlock(ebox.lock);
+
+	return 1;
+}
+
+void
+exclFree(Fid* fid)
+{
+	Excl *excl;
+
+	if((excl = fid->excl) == nil)
+		return;
+	fid->excl = nil;
+
+	vtLock(ebox.lock);
+	if(excl->prev != nil)
+		excl->prev->next = excl->next;
+	else
+		ebox.head = excl->next;
+	if(excl->next != nil)
+		excl->next->prev = excl->prev;
+	else
+		ebox.tail = excl->prev;
+	vtUnlock(ebox.lock);
+
+	vtMemFree(excl);
+}
+
+void
+exclInit(void)
+{
+	ebox.lock = vtLockAlloc();
+}