From f79d99c80dc5f18a0a59b9caaff3d73b7ca9570a Mon Sep 17 00:00:00 2001
From: Tyler Dauwalder <tylerdauwalder@nowhere.fake>
Date: Tue, 2 Dec 2003 10:50:23 +0000
Subject: [PATCH] - DiskStructures.{h,cpp} -> UdfStructures.{h,cpp} - Added
 Udf::get_block_shift()

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@5529 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 src/add-ons/kernel/file_systems/udf/Utils.cpp | 25 +++++++++++++++++++
 src/add-ons/kernel/file_systems/udf/Utils.h   |  4 ++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/add-ons/kernel/file_systems/udf/Utils.cpp b/src/add-ons/kernel/file_systems/udf/Utils.cpp
index e4df9cfee9..ec67fd0ee1 100644
--- a/src/add-ons/kernel/file_systems/udf/Utils.cpp
+++ b/src/add-ons/kernel/file_systems/udf/Utils.cpp
@@ -103,4 +103,29 @@ make_time(timestamp &timestamp)
 	return result;
 }
 
+/*! \brief Calculates the block shift amount for the given
+ 	block size, which must be a positive power of 2.
+*/
+status_t
+Udf::get_block_shift(uint32 blockSize, uint32 &blockShift)
+{
+	if (blockSize == 0)
+		return B_BAD_VALUE;		
+	uint32 bitCount = 0;
+	uint32 result = 0;
+	for (int i = 0; i < 32; i++) {
+		// Zero out all bits except bit i
+		uint32 block = blockSize & (uint32(1) << i);
+		if (block) {
+			if (++bitCount > 1) {
+				return B_BAD_VALUE;
+			} else {
+				result = i;
+			}			
+		}
+	}
+	blockShift = result;
+	return B_OK;
+}	
+
 } // namespace Udf
diff --git a/src/add-ons/kernel/file_systems/udf/Utils.h b/src/add-ons/kernel/file_systems/udf/Utils.h
index ad4cb52e29..f3ca36be0e 100644
--- a/src/add-ons/kernel/file_systems/udf/Utils.h
+++ b/src/add-ons/kernel/file_systems/udf/Utils.h
@@ -20,7 +20,7 @@ extern "C" {
 	#include <fsproto.h>
 }
 
-#include "DiskStructures.h"
+#include "UdfStructures.h"
 
 namespace Udf {
 
@@ -30,6 +30,8 @@ vnode_id to_vnode_id(long_address address);
 
 time_t make_time(timestamp &timestamp);
 
+status_t get_block_shift(uint32 blockSize, uint32 &blockShift);
+
 } // namespace Udf
 
 #endif	// _UDF_UTILS_H