From fef56cba58472f7d003887b46e3484a0f621a2b4 Mon Sep 17 00:00:00 2001
From: Sayan Nandan <nandansayan@outlook.com>
Date: Fri, 7 Aug 2020 21:12:22 +0530
Subject: [PATCH] Add record-level file locking

---
 server/native/fsc.c | 71 +++++++++++++++++++++++++++++++++++++++++++++
 server/src/dbnet.rs |  1 +
 2 files changed, 72 insertions(+)
 create mode 100644 server/native/fsc.c

diff --git a/server/native/fsc.c b/server/native/fsc.c
new file mode 100644
index 00000000..91ddc7f7
--- /dev/null
+++ b/server/native/fsc.c
@@ -0,0 +1,71 @@
+/*
+ * Created on Fri Aug 07 2020
+ *
+ * This file is a part of the source code for the Terrabase database
+ * Copyright (c) 2020, Sayan Nandan <ohsayan at outlook dot com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifdef __unix__
+#define isnix
+#elif defined(__WIN32)
+#define iswindows
+#elif defined(macintosh || Macintosh || (__APPLE__ && __MACH__))
+#define ismac
+#endif
+
+#ifdef isnix
+#include <errno.h>
+#include <fcntl.h>
+
+// Lock a file on the record level
+int lock_file(int descriptor) {
+  if (descriptor < 0) {
+    return EBADF; // Bad file descriptor
+  }
+
+  struct flock file;
+  file.l_type = F_WRLCK;    // Acquire a write-level lock
+  file.l_whence = SEEK_SET; // From beginning of file
+  file.l_start = 0;         // Lock begins from 0
+  file.l_len = 0;           // Lock until EOF
+
+  if (fcntl(descriptor, F_SETLKW, &file) == -1) {
+    return errno; // Couldn't get record level lock
+  }
+
+  return 0;
+}
+
+// Unlock a file on the record level
+int unlock_file(int descriptor) {
+  struct flock file;
+
+  if (descriptor < 0) {
+    return EBADF; // Bad file descriptor
+  }
+
+  file.l_type = F_UNLCK;
+  file.l_whence = SEEK_SET;
+  file.l_len = 0;
+
+  if (fcntl(descriptor, F_SETLKW, &file) == -1) {
+    return errno;
+  }
+
+  return 0;
+}
+#endif
diff --git a/server/src/dbnet.rs b/server/src/dbnet.rs
index dafc8f06..4fad3f09 100644
--- a/server/src/dbnet.rs
+++ b/server/src/dbnet.rs
@@ -204,4 +204,5 @@ pub async fn run(listener: TcpListener, sig: impl Future) {
     drop(signal);
     drop(terminate_tx);
     let _ = terminate_rx.recv().await;
+    println!("Goodbye :)");
 }