flock() by fcntl()

1 files changed, 44 insertions, 0 deletions

diff --git a/src/flopen.c b/src/flopen.c
index f5f7338..e93ac7f 100644
--- a/src/flopen.c
+++ b/src/flopen.c
@@ -36,6 +36,50 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 #include <libutil.h>
 
+#ifndef LOCK_EX
+#include <fcntl.h>
+#include <memory.h>
+#define LOCK_SH 1
+#define LOCK_EX 2
+#define LOCK_NB 4
+#define LOCK_UN 8
+
+/* Assume there is not flock() at all */
+static int flock (int fd, int op)
+{
+    struct flock fl;
+    int c, r;
+
+    if (op & LOCK_NB) {
+        c = F_SETLK;
+    } else {
+        c = F_SETLKW;
+        op &= ~LOCK_NB;
+    }
+
+    memset(&fl, 0, sizeof(fl));
+    fl.l_whence = SEEK_SET;
+
+    switch (op) {
+    case LOCK_SH:
+        fl.l_type = F_RDLCK; break;
+    case LOCK_EX:
+        fl.l_type = F_WRLCK; break;
+    case LOCK_UN:
+        fl.l_type = F_UNLCK; break;
+    default:
+        errno = EINVAL;
+        return (-1);
+    }
+
+    r = fcntl(fd, c, &fl);
+    if ((r == -1) && (errno == EACCES)) {
+        errno = EAGAIN;
+    }
+    return (r);
+}
+#endif
+
 int
 flopen(const char *path, int flags, ...)
 {