From c85cf18af7eafaf7492b9116be618ba7c3c5ea3c Mon Sep 17 00:00:00 2001
From: Jaremy Creechley <creechley@gmail.com>
Date: Thu, 28 Sep 2023 19:17:43 -0700
Subject: [PATCH] add files lock

---
 datastore/threads/fsbackend.nim | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/datastore/threads/fsbackend.nim b/datastore/threads/fsbackend.nim
index 1de58ef..57358e6 100644
--- a/datastore/threads/fsbackend.nim
+++ b/datastore/threads/fsbackend.nim
@@ -16,12 +16,36 @@ push: {.upraises: [].}
 
 import std/sharedtables
 
-var keyTable: SharedTable[KeyId, int]
+type
+  KeyLock = tuple[locked: bool]
+
+var keyTable: SharedTable[KeyId, KeyLock]
+keyTable.init()
+
+template lockKeyImpl(key: KeyId, blk: untyped) =
+  var hasLock = false
+  try:
+    while not hasLock:
+      keyTable.withKey(key) do (k: KeyId, klock: var KeyLock, exists: var bool):
+        if not exists or not klock.locked:
+          klock.locked = true
+        exists = true
+        hasLock = klock.locked
+      os.sleep(1)
+
+    `blk`
+  finally:
+    if hasLock:
+      keyTable.withKey(key) do (k: KeyId, klock: var KeyLock, exists: var bool):
+        assert exists and klock.locked
+        klock.locked = false
+        exists = false
 
 template withReadLock(key: KeyId, blk: untyped) =
-  `blk`
+  lockKeyImpl(key, blk)
+
 template withWriteLock(key: KeyId, blk: untyped) =
-  `blk`
+  lockKeyImpl(key, blk)
 
 type
   FSBackend*[K, V] = object