Initial revision

2 files changed, 158 insertions, 0 deletions

diff --git a/libfshelp/lock-acquire.c b/libfshelp/lock-acquire.c
new file mode 100644
index 00000000..0c1bb788
--- /dev/null
+++ b/libfshelp/lock-acquire.c
@@ -0,0 +1,128 @@
+/*
+   Copyright (C) 1993, 1994 Free Software Foundation
+
+This file is part of the GNU Hurd.
+
+The GNU Hurd is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+The GNU Hurd 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with the GNU Hurd; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+/* Written by Michael I. Bushnell.  */
+
+#include "fshelp.h"
+
+error_t
+fshelp_acquire_lock (struct lock_box *box, int *user, struct mutex *mut,
+		     int flags)
+{
+  if (!(flags & (LOCK_UN | LOCK_EX | LOCK_SH)))
+    return 0;
+  
+  if ((flags & LOCK_UN)
+      && (flags & (LOCK_SH | LOCK_EX)))
+    return EINVAL;
+  
+  if (flags & LOCK_EX)
+    flags &= ~LOCK_SH;
+  
+  /* flags now contains exactly one of LOCK_UN, LOCK_SH, or LOCK_EX.  */
+
+  if (flags & LOCK_UN)
+    {
+      if (*user & LOCK_UN)
+	return EBADF;
+      assert (*user == box->type);
+      assert (*user == LOCK_SH || *user == LOCK_EX);
+      if (*user == LOCK_SH)
+	{
+	  if (!--box->shcount)
+	    box->lock_type == LOCK_UN;
+	}
+      else if (*user == LOCK_EX)
+	box->lock_type == LOCK_UN;
+      
+      if (box->lock_type == LOCK_UN && box->waiting)
+	{
+	  box->waiting = 0;
+	  condition_broadcast (&box->wait);
+	}
+      *user = LOCK_UN;
+    }
+  else
+    {
+      /* If we have an exclusive lock, release it. */
+      if (*user == LOCK_EX)
+	{
+	  *user = LOCK_UN;
+	  box->type = LOCK_UN;
+	  if (box->waiting)
+	    {
+	      box->waiting = 0;
+	      condition_broadcast (&box->wait);
+	    }
+	}
+      
+      /* If there is an exclusive lock, wait for it to end. */
+      while (lock->type == LOCK_EX)
+	{
+	  if (flags & LOCK_NB)
+	    return EWOULDBLOCK;
+	  box->waiting = 1;
+	  condition_wait (&box->wait, mut);
+	}
+
+      /* If we have a shared lock, release it. */
+      if (*user == LOCK_SH)
+	{
+	  *user = LOCK_UN;
+	  if (!--box->shcount)
+	    {
+	      box->type = LOCK_UN;
+	      if (box->waiting)
+		{
+		  box->waiting = 0;
+		  condition_broadcast (&box->wait);
+		}
+	    }
+	}
+      
+      assert ((flags & LOCK_SH) || (flags & LOCK_EX));
+      if (flags & LOCK_SH)
+	{
+	  assert (box->type != LOCK_EX);
+	  *user = LOCK_SH;
+	  box->type = LOCK_SH;
+	  box->shcount++;
+	}
+      else if (flags & LOCK_EX)
+	{
+	  /* Wait for any shared locks to finish. */
+	  while (box->type == LOCK_SH)
+	    {
+	      if (flags & LOCK_NB)
+		return EWOULDBLOCK;
+	      else
+		{
+		  box->waiting = 1;
+		  condition_wait (&box->wait, mut);
+		}
+	    }
+	  box->type = LOCK_EX;
+	  *user = LOCK_EX;
+	}
+    }
+  return 0;
+}
+
+	      
+	  
diff --git a/libfshelp/lock-init.c b/libfshelp/lock-init.c
new file mode 100644
index 00000000..f32dfae8
--- /dev/null
+++ b/libfshelp/lock-init.c
@@ -0,0 +1,30 @@
+/*
+   Copyright (C) 1993, 1994 Free Software Foundation
+
+This file is part of the GNU Hurd.
+
+The GNU Hurd is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+The GNU Hurd 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with the GNU Hurd; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+/* Written by Michael I. Bushnell.  */
+
+/* Initialize a lock box. */
+void
+fshelp_lock_init (struct lock_box *box)
+{
+  box->type = LOCK_UN;
+  condition_init (&box->wait);
+  box->waiting = 0;
+  box->shcount = 0;
+}