/*-
 * Copyright (c) 2008-2013 WiredTiger, Inc.
 *	All rights reserved.
 *
 * See the file LICENSE for redistribution information.
 */

#define	WT_BTREE_MAJOR_VERSION	1	/* Version */
#define	WT_BTREE_MINOR_VERSION	0

/*
 * The maximum btree leaf and internal page size is 512MB. (The maximum of
 * 512MB is enforced by the software, it could be set as high as 4GB.)
 */
#define	WT_BTREE_PAGE_SIZE_MAX		(512 * WT_MEGABYTE)

/*
 * Variable-length value items and row-store key/value item lengths are stored
 * in 32-bit unsigned integers, meaning the largest theoretical key/value item
 * is 4GB.  However, in the WT_UPDATE structure we use the UINT32_MAX size as a
 * "deleted" flag.  Limit the size of a single object to 4GB - 512B: it's a few
 * additional bytes if we ever want to store a small structure length plus the
 * object size in 32 bits, or if we ever need more denoted values.  Storing 4GB
 * objects in a Btree borders on clinical insanity, anyway.
 *
 * Record numbers are stored in 64-bit unsigned integers, meaning the largest
 * record number is "really, really big".
 */
#define	WT_BTREE_MAX_OBJECT_SIZE	(UINT32_MAX - 512)

/*
 * A location in a file is a variable-length cookie, but it has a maximum size
 * so it's easy to create temporary space in which to store them.  (Locations
 * can't be much larger than this anyway, they must fit onto the minimum size
 * page because a reference to an overflow page is itself a location.)
 */
#define	WT_BTREE_MAX_ADDR_COOKIE	255	/* Maximum address cookie */

/*
 * XXX
 * The server threads use their own WT_SESSION_IMPL handles because they may
 * want to block (for example, the eviction server calls reconciliation, and
 * some of the reconciliation diagnostic code reads pages), and the user's
 * session handle is already blocking on a server thread.  The problem is the
 * server thread needs to reference the correct btree handle, and that's
 * hanging off the application's thread of control.  For now, I'm just making
 * it obvious where that's getting done.
 */
#define	WT_SET_BTREE_IN_SESSION(s, b)	((s)->btree = (b))
#define	WT_CLEAR_BTREE_IN_SESSION(s)	((s)->btree = NULL)

/*
 * WT_BTREE --
 *	A btree handle.
 */
struct __wt_btree {
	WT_RWLOCK *rwlock;		/* Lock for shared/exclusive ops */
	uint32_t   refcnt;		/* Sessions using this tree. */
	TAILQ_ENTRY(__wt_btree) q;	/* Linked list of handles */

	const char *name;		/* Object name as a URI */
	const char *checkpoint;		/* Checkpoint name (or NULL) */
	const char **cfg;		/* Configuration information */

	WT_DSRC_STATS stats;		/* Data-source statistics */
	int maximum_depth;		/* Maximum tree depth */

	/*
	 * XXX Everything above here should move into the session-level
	 * handle structure.
	 */

	WT_CKPT	  *ckpt;		/* Checkpoint information */

	enum {	BTREE_COL_FIX=1,	/* Fixed-length column store */
		BTREE_COL_VAR=2,	/* Variable-length column store */
		BTREE_ROW=3		/* Row-store */
	} type;				/* Type */

	const char *key_format;		/* Key format */
	const char *value_format;	/* Value format */
	uint8_t bitcnt;			/* Fixed-length field size in bits */

					/* Row-store comparison function */
	WT_COLLATOR *collator;		/* Comparison function */

	uint32_t key_gap;		/* Row-store prefix key gap */

	uint32_t allocsize;		/* Allocation size */
	uint32_t maxintlpage;		/* Internal page max size */
	uint32_t maxintlitem;		/* Internal page max item size */
	uint32_t maxleafpage;		/* Leaf page max size */
	uint32_t maxleafitem;		/* Leaf page max item size */
	uint64_t maxmempage;		/* In memory page max size */

	void *huffman_key;		/* Key huffman encoding */
	void *huffman_value;		/* Value huffman encoding */

	enum {	CKSUM_ON=1,		/* On */
		CKSUM_OFF=2,		/* Off */
		CKSUM_UNCOMPRESSED=3	/* Uncompressed blocks only */
	} checksum;			/* Checksum configuration */

	u_int dictionary;		/* Reconcile: dictionary slots */
	int   internal_key_truncate;	/* Reconcile: internal key truncate */
	int   prefix_compression;	/* Reconcile: key prefix compression */
	u_int split_pct;		/* Reconcile: split page percent */
	WT_COMPRESSOR *compressor;	/* Reconcile: page compressor */
	WT_RWLOCK *val_ovfl_lock;	/* Reconcile: overflow value lock */

	uint64_t last_recno;		/* Column-store last record number */

	WT_PAGE *root_page;		/* Root page */
	int modified;			/* If the tree ever modified */
	int bulk_load_ok;		/* Bulk-load is a possibility */

	WT_BM	*bm;			/* Block manager reference */
	u_int	 block_header;		/* WT_PAGE_HEADER_BYTE_SIZE */

	uint64_t write_gen;		/* Write generation */

	WT_PAGE *evict_page;		/* Eviction thread's location */
	uint64_t evict_priority;	/* Relative priority of cached pages. */
	volatile uint32_t lru_count;	/* Count of threads in LRU eviction */

	volatile int checkpointing;	/* Checkpoint in progress */

#define	WT_BTREE_BULK		0x0001	/* Bulk-load handle */
#define	WT_BTREE_DISCARD	0x0002	/* Discard on release */
#define	WT_BTREE_DISCARD_CLOSE	0x0004	/* Discard on last close */
#define	WT_BTREE_EXCLUSIVE	0x0008	/* Need exclusive access to handle */
#define	WT_BTREE_LOCK_ONLY	0x0010	/* Handle is only needed for locking */
#define	WT_BTREE_NO_EVICTION	0x0020	/* Disable eviction */
#define	WT_BTREE_NO_HAZARD	0x0040	/* Disable hazard pointers */
#define	WT_BTREE_OPEN		0x0080	/* Handle is open */
#define	WT_BTREE_SALVAGE	0x0100	/* Handle is for salvage */
#define	WT_BTREE_UPGRADE	0x0200	/* Handle is for upgrade */
#define	WT_BTREE_VERIFY		0x0400	/* Handle is for verify */
	uint32_t flags;
};

/* Flags that make a btree handle special (not for normal use). */
#define	WT_BTREE_SPECIAL_FLAGS	 					\
	(WT_BTREE_BULK | WT_BTREE_SALVAGE | WT_BTREE_UPGRADE | WT_BTREE_VERIFY)

/*
 * WT_SALVAGE_COOKIE --
 *	Encapsulation of salvage information for reconciliation.
 */
struct __wt_salvage_cookie {
	uint64_t missing;			/* Initial items to create */
	uint64_t skip;				/* Initial items to skip */
	uint64_t take;				/* Items to take */

	int	 done;				/* Ignore the rest */
};