btree.h

这是一个利用B+ Trees数据结构存储数据的源码,全部代码用C语言写的.

/***********************************************************************\
|									|
|	B+tree data structures & external interface			|
|									|
|									|
|	Jan Jannink	created 5/27/94		revised 6/16/95		|
|									|
\***********************************************************************/

#ifndef BPLUSTREE
#define BPLUSTREE 1

/*~~~~~~~~~~~~~~~~	sample B+tree parametrization	~~~~~~~~~~~~~~~*/
				/* causes printing of node information */
#define DEBUG 1
#undef DEBUG
				/* pointer vs. array representation of nodes */
#define POINTER 1
				/* 24 bytes is minimal size for 2-3 trees */
#define NODE_SIZE 72
				/*  16 bytes to store a data point */
#define DATA_SIZE 16
				/* maximum number of available nodes */
#define ARRAY_SIZE 24576


/*~~~~~~~	flag bits (5 of 16 used, 11 for magic value)	~~~~~~~*/
				/* bits set at node creation/split/merge */
#define isLEAF	0x1
#define isROOT	0x2
				/* bits set at key insertion/deletion */
#define isFULL	0x4
#define FEWEST	0x8
#define FLAGS	0xF
				/* identifies data as being a B+tree node */
#define MAGIC	0xDEC0
#define MASK	0xFFF0


/*~~~~~~~~~~~~~~~~~~~~~~~~	constants	~~~~~~~~~~~~~~~~~~~~~~~*/
			/* ARRAY is a place holder value for:  fanout */
#define ARRAY	1
			/* corresponds to a NULL node pointer value */
#define NONODE	(nodearrayhead - 1)
			/* special node slot values used in key search */
#define ERROR	-1
#define UPPER	-2
#define LOWER	-3


/*/*~~~~~~~~~~~~~~~~~~~~~~~~	node pointer and key type	~~~~~~~*/
#ifdef POINTER
   typedef struct node	*Nptr;	/* streamlined pointer representation */
#else
   typedef int		Nptr;	/* more intuitive array representation */
#endif

typedef int		keyT;	/* adapt key type to requirements */
typedef char		*dataT;	/* adapt data type to requirements */


/*~~~~~~~~~~~~~~~~~~~~~~~~	node status	~~~~~~~~~~~~~~~~~~~~~~~*/
typedef struct state {
  short	flags;
  short	pairs;
} State;			/* sizeof(State) must be <= sizeof(keyT) */


/*~~~~~~~~~~~~~~	single node entry with key value	~~~~~~~*/
typedef struct entrY {
  keyT	key;			/* can be a hashed value */
  Nptr	downNode;
} Entry;			/* WARNING: entry was a RESERVED word in C */


/*~~~~~~~~~~~~~~~~~~~~	special header entry for internal node	~~~~~~~*/
typedef struct inner {
  State info;
  Nptr	firstNode;		/* node of smallest values */
} Inner;


/*~~~~~~~~~~~~~~~~~~~~	special header entry for leaf node	~~~~~~~*/
typedef struct leaf {
  State info;
  Nptr	nextNode;		/* next leaf in sequential scan */
} Leaf;


/*~~~~~~~~~~~~~~~~~~~~	unstructured data node	~~~~~~~~~~~~~~~~~~~~~~~*/
typedef struct data {
  char	value[NODE_SIZE];
} Data;


/*~~~~~~~~~~~~	data node header to handle duplicates	~~~~~~~~~~~~~~~*/
typedef struct dupdata {
  int	copy;			/* tallies the duplicate keys */
  Nptr	next;			/* next node with same key value */
  char  value[DATA_SIZE];
} DupData;


/*/*~~~~~~~~~~~~~~~~~~~~~~~~	structured tree node	~~~~~~~~~~~~~~~*\
|
|	The structures Entry, Inner and Leaf are all identical in size.
|	Each node is of size:  fanout * sizeof(Entry).  Through the
|	union X, it is possible to access the first space in any node
|	as: X.e[0], X.i, X.l, depending on the algorithms' needs.  The
|	value of the status flag isLEAF should always determine how the
|	first node space is used.  The node structure is defined below.
|
|	Internal node:			Leaf node:
|
|	+---------------+		+---------------+
|	|Inner: X.i	|		|Leaf: X.l	|
|	|  info		|		|  info		|
|	|  firstNode	|		|  nextNode	|
|	|---------------|		|---------------|
|	|Entry: X.e[1]	|		|Entry: X.e[1]	|
|	|  key		|		|  key		|
|	|  downNode	|		|  downNode	|
|	|---------------|		|---------------|
|	|	.	|		|	.	|
|	|	.	|		|	.	|
|	|	.	|		|	.	|
|	|---------------|		|---------------|
|	|Entry: X.e[n]	|		|Entry: X.e[n]	|
|	|  key		|		|  key		|
|	|  downNode	|		|  downNode	|
|	+---------------+		+---------------+
|
\*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
typedef struct node {
  union {
    Entry	e[ARRAY];	/* allows access to entry array */
    Inner	i;
    Leaf	l;
    Data	d;
    DupData	dd;
  } X;
} Node;


/*/*~~~~~~~~~~~~~~~~~~~~~~~~	key comparison function type	~~~~~~~*/
typedef int (*KeyCmp)(keyT, keyT);


/*~~~~~~~~~~~~~~~~~~~~~~~~	tree definitions	~~~~~~~~~~~~~~~*/
typedef struct tree {
			/* `private' variables */
  unsigned int	poolsize;	/* # of nodes allocated for tree */
  Node		*tree;		/* pointer to array of nodes (NOT Nptr !) */
  Nptr		root;		/* pointer to root node */
  Nptr		leaf;		/* pointer to first leaf node in B+tree */
  unsigned int	fanout;		/* # of pointers to other nodes */
  unsigned int	minfanout;	/* usually minfanout == ceil(fanout/2) */
  unsigned int	height;		/* nodes traversed from root to leaves */
  Nptr		pool;		/* list of empty nodes */
  keyT		theKey;		/*  the key value used in tree operations */
  dataT		theData;	/*  data used for insertions/deletions */
  union {			/* nodes to change in insert and delete */
    Nptr	split;
    Nptr	merge;
  } branch;
  KeyCmp	keycmp;		/* pointer to function comparing two keys */
} Tree;


/*~~~~~~~~~~~~~~~~~~~~~~~~	B+tree methods		~~~~~~~~~~~~~~~*/
Tree	*initBtree(unsigned int poolsz, unsigned int fan, KeyCmp keyCmp);
/* Tree	*remakeBtree(Tree * B, int fillfactor); */
void	freeBtree(Tree *B);

#ifdef DEBUG
void	showNode(Tree *B, Nptr node);
void	showBtree(Tree *B);
#endif

void	listBtreeValues(Tree *B, Nptr start, int count);
void	listAllBtreeValues(Tree *B);

int	compareKeys(keyT key1, keyT key2);

Nptr	search(Tree *B, keyT key);
void	insert(Tree *B, keyT key);
void	delete(Tree *B, keyT key);

#endif