From 27ffe0583b71adcfb7814a3af1358271c1800877 Mon Sep 17 00:00:00 2001
From: hyche <cvghy116@gmail.com>
Date: Thu, 24 Aug 2017 02:22:02 +0700
Subject: [PATCH] BTRFS: Implement some space relevant helpers.

Signed-off-by: Augustin Cavalier <waddlesplash@gmail.com>
---
 .../kernel/file_systems/btrfs/BTree.cpp       | 58 +++++++++++++++++++
 src/add-ons/kernel/file_systems/btrfs/BTree.h |  9 ++-
 2 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/src/add-ons/kernel/file_systems/btrfs/BTree.cpp b/src/add-ons/kernel/file_systems/btrfs/BTree.cpp
index bf93bf358f..9e43ad808d 100644
--- a/src/add-ons/kernel/file_systems/btrfs/BTree.cpp
+++ b/src/add-ons/kernel/file_systems/btrfs/BTree.cpp
@@ -140,6 +140,64 @@ BTree::Node::SearchSlot(const btrfs_key& key, int* slot, btree_traversing type)
 }
 
 
+/*
+ * calculate used space except the header.
+ * type is only for leaf node
+ * type 1: only item space
+ * type 2: only item data space
+ * type 3: both type 1 and 2
+ */
+int
+BTree::Node::_CalculateSpace(uint32 from, uint32 to, uint8 type) const
+{
+	if (to < from || to >= ItemCount())
+		return 0;
+
+	if (Level() != 0)
+		return sizeof(btrfs_index) * (to - from + 1);
+
+	uint32 result = 0;
+	if ((type & 1) == 1) {
+		result += sizeof(btrfs_entry) * (to - from + 1);
+	}
+	if ((type & 2) == 2) {
+		result += Item(from)->Offset() + Item(from)->Size()
+			- Item(to)->Offset();
+	}
+
+	return result;
+}
+
+
+int
+BTree::Node::SpaceUsed() const
+{
+	if (Level() == 0)
+		return _CalculateSpace(0, ItemCount() - 1, 3);
+	return _CalculateSpace(0, ItemCount() - 1, 0);
+}
+
+
+int
+BTree::Node::SpaceLeft() const
+{
+	return fVolume->BlockSize() - SpaceUsed() - sizeof(btrfs_header);
+}
+
+
+status_t
+BTree::Node::_SpaceCheck(int length) const
+{
+	// this is a little bit weird here because we can't find
+	// any suitable error code
+	if (length < 0 && std::abs(length) >= SpaceUsed())
+		return B_DIRECTORY_NOT_EMPTY;	// not enough data to delete
+	if (length > 0 && length >= SpaceLeft())
+		return B_DEVICE_FULL;			// no spare space
+	return B_OK;
+}
+
+
 //	#pragma mark - BTree::Path implementation
 
 
diff --git a/src/add-ons/kernel/file_systems/btrfs/BTree.h b/src/add-ons/kernel/file_systems/btrfs/BTree.h
index d44a40102f..f1c0e5b83f 100644
--- a/src/add-ons/kernel/file_systems/btrfs/BTree.h
+++ b/src/add-ons/kernel/file_systems/btrfs/BTree.h
@@ -128,18 +128,23 @@ public:
 
 		void	SetTo(off_t block);
 		void	SetToWritable(off_t block, int32 transactionId, bool empty);
+		int		SpaceUsed() const;
+		int		SpaceLeft() const;
 
 		off_t	BlockNum() const { return fBlockNumber;}
 		bool	IsWritable() const { return fWritable; }
 
 		status_t	SearchSlot(const btrfs_key& key, int* slot,
 						btree_traversing type) const;
-		private:
+	private:
 		Node(const Node&);
 		Node& operator=(const Node&);
 			//no implementation
 
-		btrfs_stream* 		fNode;
+		status_t	_SpaceCheck(int length) const;
+		int		_CalculateSpace(uint32 from, uint32 to, uint8 type = 1) const;
+
+		btrfs_stream*		fNode;
 		Volume*				fVolume;
 		off_t				fBlockNumber;
 		bool				fWritable;