From 9bcbc8f919fc1c779d3b9c649dcbe3606fdbed32 Mon Sep 17 00:00:00 2001
From: Mike Buland <mbuland@penny-arcade.com>
Date: Fri, 25 May 2018 14:17:20 -0700
Subject: Added locking support to Bu::File.

---
 src/stable/file.cpp | 16 ++++++++++++++++
 src/stable/file.h   | 19 +++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/src/stable/file.cpp b/src/stable/file.cpp
index 35933f1..a15f394 100644
--- a/src/stable/file.cpp
+++ b/src/stable/file.cpp
@@ -9,6 +9,7 @@
 #include <errno.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/file.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <time.h>
@@ -200,6 +201,21 @@ void Bu::File::setBlocking( bool bBlocking )
 #endif
 }
 
+bool Bu::File::canLock() const
+{
+    return true;
+}
+
+void Bu::File::lock( bool bExclusive )
+{
+    ::flock( fd, bExclusive?LOCK_EX:LOCK_SH );
+}
+
+void Bu::File::unlock()
+{
+    ::flock( fd, LOCK_UN );
+}
+
 Bu::File Bu::File::tempFile( Bu::String &sName )
 {
     int iXes;
diff --git a/src/stable/file.h b/src/stable/file.h
index e3497d3..6e05dc7 100644
--- a/src/stable/file.h
+++ b/src/stable/file.h
@@ -56,6 +56,25 @@ namespace Bu
         virtual bool isBlocking();
         virtual void setBlocking( bool bBlocking=true );
 
+        /**
+         * Tells you if advisory locks are supported.
+         */
+        bool canLock() const;
+
+        /**
+         * Acquires an advisory lock on the file.  On posix/linux this is done
+         * via flock.
+         *@param bExclusive Set to true to acquire an exclusive lock (i.e. a
+         * write lock).  If this is false then a shared lock (i.e. read lock) is
+         * acquired.  A file cannot have both an exclusive and shared lock.
+         */
+        void lock( bool bExclusive=true );
+
+        /**
+         * Release the held advisory lock.
+         */
+        void unlock();
+
         enum {
             // Flags
             Read        = 0x01, ///< Open file for reading
-- 
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