From e79a7d4e07632ae3a428f4363effffbbb52c7a1d Mon Sep 17 00:00:00 2001
From: H.G. Muller <h.g.muller@hccnet.nl>
Date: Mon, 2 May 2011 13:38:14 +0200
Subject: [PATCH] Implement flock in WinBoard

This system function seems unknown in a MinGW compile, so it is
implemented with the aid of file byte-range locking, using a lock on the
first 1024 bytes of the file as a semaphore.
---
 backend.c           |    3 +++
 winboard/winboard.c |   17 +++++++++++++++++
 2 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/backend.c b/backend.c
index d68df79..f6e75c4 100644
--- a/backend.c
+++ b/backend.c
@@ -57,6 +57,9 @@
 
 #define DoSleep( n ) if( (n) != 0 ) Sleep( (n) );
 
+int flock(int f, int code);
+#define LOCK_EX 2
+
 #else
 
 #define DoSleep( n ) if( (n) >= 0) sleep(n)
diff --git a/winboard/winboard.c b/winboard/winboard.c
index 3938cf2..4d823eb 100644
--- a/winboard/winboard.c
+++ b/winboard/winboard.c
@@ -73,6 +73,7 @@
 #include <richedit.h>
 #include <mmsystem.h>
 #include <ctype.h>
+#include <io.h>
 
 #if __GNUC__
 #include <errno.h>
@@ -9783,3 +9784,19 @@ SettingsPopUp(ChessProgramState *cps)
 {     // [HGM] wrapper needed because handles must not be passed through back-end
       EngineOptionsPopup(savedHwnd, cps);
 }
+
+int flock(int fid, int code)
+{
+    HANDLE hFile = (HANDLE) _get_osfhandle(fid);
+    OVERLAPPED ov;
+    ov.hEvent = NULL;
+    ov.Offset = 0;
+    ov.OffsetHigh = 0;
+    switch(code) {
+      case 1: LockFileEx(hFile, LOCKFILE_EXCLUSIVE_LOCK, 0, 1024, 0, &ov); break;   // LOCK_SH
+      case 2: LockFileEx(hFile, LOCKFILE_EXCLUSIVE_LOCK, 0, 1024, 0, &ov); break;   // LOCK_EX
+      case 3: UnlockFileEx(hFile, 0, 1024, 0, &ov); break; // LOCK_UN
+      default: return -1;
+    }
+    return 0;
+}
-- 
1.7.0.4