BTreeNode

Full name Microsoft.VisualBasic.Data.IO.HDF5.struct.BTreeNode Assembly Microsoft.VisualBasic.Data.IO.HDF5 Members 11

B-tree Nodes

Version 1 B-trees in HDF5 files are an implementation of the B-link tree. The sibling nodes at a particular level in the tree are stored in a doubly-linked list. See the “Efficient Locking for Concurrent Operations on B-trees” paper by Phillip Lehman and S. Bing Yao as published in the ACM Transactions on Database Systems, Vol. 6, No. 4, December 1981.

The B-trees implemented by the file format contain one more key than the number Of children. In other words, Each child pointer out Of a B-tree node has a left key And a right key. The pointers out Of internal nodes point To Sub-trees While the pointers out Of leaf nodes point To symbol nodes And raw data chunks. Aside from that difference, internal nodes And leaf nodes are identical.

01 Syntax

Microsoft.VisualBasic.Data.IO.HDF5.struct.BTreeNode

02 Methods

Name	Overloads	Summary
first	1	this finds the first entry we dont want to skip.
hasNext	1

03 Properties

Name	Overloads	Summary
magic	1	The ASCII character string “TREE” is used to indicate the beginning of a B-tree node.
type	1	Each B-tree points to a particular type of data.
level	1	The node level indicates the level at which this node appears in the tree (leaf nodes are at level zero).
numberOfEntries	1	This determines the number of children to which this node points.
leftAddress	1	Address of Left Sibling This is the relative file address of the left sibling of the current node.
rightAddress	1	Address of Right Sibling This is the relative file address of the right sibling of the current node.

04 Fields

Name	Overloads	Summary
signature	1	The ASCII character string “TREE” is used to indicate the beginning of a B-tree node.
childPointer	1	"For raw data chunk nodes, the child pointer is the address of a single raw data chunk"
currentEntry	1	track iteration; LOOK this seems fishy - why not an iterator ??

05 Members

method first #

first(BinaryReader, Superblock)

this finds the first entry we dont want to skip. entry i goes from [offset(i),offset(i+1)) we want to skip any entries we dont need, namely those where want >= offset(i+1) so keep skipping until want < offset(i+1)

Parameters

Name	Type	Description
`[in]`	BinaryReader	-
`sb`	Superblock	-

method hasNext #

hasNext

Remarks

LOOK - wouldnt be a bad idea to terminate if possible instead of running through all subsequent entries

property magic #

magic

The ASCII character string “TREE” is used to indicate the beginning of a B-tree node. This gives file consistency checking utilities a better chance of reconstructing a damaged file.

property type #

type

Each B-tree points to a particular type of data. This field indicates the type of data as well as implying the maximum degree K of the tree and the size of each Key field.

1. This tree points to group nodes.
1. This tree points to raw data chunk nodes.

property level #

level

The node level indicates the level at which this node appears in the tree (leaf nodes are at level zero). Not only does the level indicate whether child pointers point to sub-trees or to data, but it can also be used to help file consistency checking utilities reconstruct damaged trees.

property numberOfEntries #

numberOfEntries

This determines the number of children to which this node points. All nodes of a particular type of tree have the same maximum degree, but most nodes will point to less than that number of children. The valid child pointers and keys appear at the beginning of the node and the unused pointers and keys appear at the end of the node. The unused pointers and keys have undefined values.

property leftAddress #

leftAddress

Address of Left Sibling

This is the relative file address of the left sibling of the current node. If the current node is the left-most node at this level then this field is the undefined address.

property rightAddress #

rightAddress

Address of Right Sibling

This is the relative file address of the right sibling of the current node. If the current node is the right-most node at this level then this field is the undefined address.

field signature #

signature

The ASCII character string “TREE” is used to indicate the beginning of a B-tree node. This gives file consistency checking utilities a better chance of reconstructing a damaged file.

field childPointer #

childPointer

"For raw data chunk nodes, the child pointer is the address of a single raw data chunk"

field currentEntry #

currentEntry

track iteration; LOOK this seems fishy - why not an iterator ??