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DarkSide SQL Mini Version 1, The embedded database

, 23 Mar 2006
An embedded database library in C++.
/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2002
 *	Sleepycat Software.  All rights reserved.
 *
 * $Id: log.h,v 11.60 2002/08/06 06:37:08 bostic Exp $
 */

#ifndef _LOG_H_
#define	_LOG_H_

struct __db_log;	typedef struct __db_log DB_LOG;
struct __hdr;		typedef struct __hdr HDR;
struct __log;		typedef struct __log LOG;
struct __log_persist;	typedef struct __log_persist LOGP;

#define	LFPREFIX	"log."		/* Log file name prefix. */
#define	LFNAME		"log.%010d"	/* Log file name template. */
#define	LFNAME_V1	"log.%05d"	/* Log file name template, rev 1. */

#define	LG_MAX_DEFAULT		(10 * MEGABYTE)	/* 10 MB. */
#define	LG_BSIZE_DEFAULT	(32 * 1024)	/* 32 KB. */
#define	LG_BASE_REGION_SIZE	(60 * 1024)	/* 60 KB. */

/*
 * The per-process table that maps log file-id's to DB structures.
 */
typedef	struct __db_entry {
	DB	*dbp;			/* Open dbp for this file id. */
	int	deleted;		/* File was not found during open. */
} DB_ENTRY;

/*
 * DB_LOG
 *	Per-process log structure.
 */
struct __db_log {
/*
 * These fields need to be protected for multi-threaded support.
 *
 * !!!
 * As this structure is allocated in per-process memory, the mutex may need
 * to be stored elsewhere on architectures unable to support mutexes in heap
 * memory, e.g., HP/UX 9.
 */
	DB_MUTEX  *mutexp;		/* Mutex for thread protection. */

	DB_ENTRY *dbentry;		/* Recovery file-id mapping. */
#define	DB_GROW_SIZE	64
	int32_t dbentry_cnt;		/* Entries.  Grows by DB_GROW_SIZE. */

/*
 * These fields are always accessed while the region lock is held, so they do
 * not have to be protected by the thread lock as well, OR, they are only used
 * when threads are not being used, i.e. most cursor operations are disallowed
 * on threaded logs.
 */
	u_int32_t lfname;		/* Log file "name". */
	DB_FH	  lfh;			/* Log file handle. */

	u_int8_t *bufp;			/* Region buffer. */

/* These fields are not protected. */
	DB_ENV	 *dbenv;		/* Reference to error information. */
	REGINFO	  reginfo;		/* Region information. */

#define	DBLOG_RECOVER		0x01	/* We are in recovery. */
#define	DBLOG_FORCE_OPEN	0x02	/* Force the DB open even if it appears
					 * to be deleted.
					 */
	u_int32_t flags;
};

/*
 * HDR --
 *	Log record header.
 */
struct __hdr {
	u_int32_t prev;			/* Previous offset. */
	u_int32_t len;			/* Current length. */
	u_int8_t  chksum[DB_MAC_KEY];	/* Current checksum. */
	u_int8_t  iv[DB_IV_BYTES];	/* IV */
	u_int32_t orig_size;		/* Original size of log record */
	/* !!! - 'size' is not written to log, must be last in hdr */
	size_t	  size;			/* Size of header to use */
};

/*
 * We use HDR internally, and then when we write out, we write out
 * prev, len, and then a 4-byte checksum if normal operation or
 * a crypto-checksum and IV and original size if running in crypto
 * mode.  We must store the original size in case we pad.  Set the
 * size when we set up the header.  We compute a DB_MAC_KEY size
 * checksum regardless, but we can safely just use the first 4 bytes.
 */
#define	HDR_NORMAL_SZ	12
#define	HDR_CRYPTO_SZ	12 + DB_MAC_KEY + DB_IV_BYTES

struct __log_persist {
	u_int32_t magic;		/* DB_LOGMAGIC */
	u_int32_t version;		/* DB_LOGVERSION */

	u_int32_t log_size;		/* Log file size. */
	u_int32_t mode;			/* Log file mode. */
};

/*
 * LOG --
 *	Shared log region.  One of these is allocated in shared memory,
 *	and describes the log.
 */
struct __log {
	/*
	 * Due to alignment constraints on some architectures (e.g. HP-UX),
	 * DB_MUTEXes must be the first element of shalloced structures,
	 * and as a corollary there can be only one per structure.  Thus,
	 * flush_mutex_off points to a mutex in a separately-allocated chunk.
	 */
	DB_MUTEX fq_mutex;		/* Mutex guarding file name list. */

	LOGP	 persist;		/* Persistent information. */

	SH_TAILQ_HEAD(__fq1) fq;	/* List of file names. */
	int32_t	fid_max;		/* Max fid allocated. */
	roff_t	free_fid_stack;		/* Stack of free file ids. */
	int	free_fids;		/* Height of free fid stack. */
	int	free_fids_alloced;	/* Number of free fid slots alloc'ed. */

	/*
	 * The lsn LSN is the file offset that we're about to write and which
	 * we will return to the user.
	 */
	DB_LSN	  lsn;			/* LSN at current file offset. */

	/*
	 * The f_lsn LSN is the LSN (returned to the user) that "owns" the
	 * first byte of the buffer.  If the record associated with the LSN
	 * spans buffers, it may not reflect the physical file location of
	 * the first byte of the buffer.
	 */
	DB_LSN	  f_lsn;		/* LSN of first byte in the buffer. */
	size_t	  b_off;		/* Current offset in the buffer. */
	u_int32_t w_off;		/* Current write offset in the file. */
	u_int32_t len;			/* Length of the last record. */

	/*
	 * The s_lsn LSN is the last LSN that we know is on disk, not just
	 * written, but synced.  This field is protected by the flush mutex
	 * rather than by the region mutex.
	 */
	int	  in_flush;		/* Log flush in progress. */
	roff_t	  flush_mutex_off;	/* Mutex guarding flushing. */
	DB_LSN	  s_lsn;		/* LSN of the last sync. */

	DB_LOG_STAT stat;		/* Log statistics. */

	/*
	 * The waiting_lsn is used by the replication system.  It is the
	 * first LSN that we are holding without putting in the log, because
	 * we received one or more log records out of order.  Associated with
	 * the waiting_lsn is the number of log records that we still have to
	 * receive before we decide that we should request it again.
	 */
	DB_LSN	  waiting_lsn;		/* First log record after a gap. */
	DB_LSN	  verify_lsn;		/* LSN we are waiting to verify. */
	u_int32_t wait_recs;		/* Records to wait before requesting. */
	u_int32_t rcvd_recs;		/* Records received while waiting. */

	/*
	 * The ready_lsn is also used by the replication system.  It is the
	 * next LSN we expect to receive.  It's normally equal to "lsn",
	 * except at the beginning of a log file, at which point it's set
	 * to the LSN of the first record of the new file (after the
	 * header), rather than to 0.
	 */
	DB_LSN	  ready_lsn;

	/*
	 * During initialization, the log system walks forward through the
	 * last log file to find its end.  If it runs into a checkpoint
	 * while it's doing so, it caches it here so that the transaction
	 * system doesn't need to walk through the file again on its
	 * initialization.
	 */
	DB_LSN	cached_ckp_lsn;

	roff_t	  buffer_off;		/* Log buffer offset in the region. */
	u_int32_t buffer_size;		/* Log buffer size. */

	u_int32_t log_size;		/* Log file's size. */
	u_int32_t log_nsize;		/* Next log file's size. */

	u_int32_t ncommit;		/* Number of txns waiting to commit. */

	DB_LSN	  t_lsn;		/* LSN of first commit */
	SH_TAILQ_HEAD(__commit) commits;/* list of txns waiting to commit. */
	SH_TAILQ_HEAD(__free) free_commits;/* free list of commit structs. */

#ifdef HAVE_MUTEX_SYSTEM_RESOURCES
#define	LG_MAINT_SIZE	(sizeof(roff_t) * DB_MAX_HANDLES)

	roff_t	  maint_off;		/* offset of region maintenance info */
#endif
};

/*
 * __db_commit structure --
 *	One of these is allocated for each transaction waiting
 * to commit.
 */
struct __db_commit {
	DB_MUTEX	mutex;		/* Mutex for txn to wait on. */
	DB_LSN		lsn;		/* LSN of commit record. */
	SH_TAILQ_ENTRY	links;		/* Either on free or waiting list. */

#define	DB_COMMIT_FLUSH		0x0001	/* Flush the log when you wake up. */
	u_int32_t	flags;
};

/*
 * FNAME --
 *	File name and id.
 */
struct __fname {
	SH_TAILQ_ENTRY q;		/* File name queue. */

	int32_t id;			/* Logging file id. */
	DBTYPE	  s_type;		/* Saved DB type. */

	roff_t	  name_off;		/* Name offset. */
	db_pgno_t meta_pgno;		/* Page number of the meta page. */
	u_int8_t  ufid[DB_FILE_ID_LEN];	/* Unique file id. */

	u_int32_t create_txnid;		/*
					 * Txn ID of the DB create, stored so
					 * we can log it at register time.
					 */
};

/* File open/close register log record opcodes. */
#define	LOG_CHECKPOINT	1		/* Checkpoint: file name/id dump. */
#define	LOG_CLOSE	2		/* File close. */
#define	LOG_OPEN	3		/* File open. */
#define	LOG_RCLOSE	4		/* File close after recovery. */

#define	CHECK_LSN(redo, cmp, lsn, prev)					\
	DB_ASSERT(!DB_REDO(redo) ||					\
	    (cmp) >= 0 || IS_NOT_LOGGED_LSN(*lsn));			\
	if (DB_REDO(redo) && (cmp) < 0 && !IS_NOT_LOGGED_LSN(*(lsn))) {	\
		__db_err(dbenv,						\
	"Log sequence error: page LSN %lu %lu; previous LSN %lu %lu",	\
		    (u_long)(lsn)->file, (u_long)(lsn)->offset,		\
		    (u_long)(prev)->file, (u_long)(prev)->offset);	\
		goto out;						\
	}

/*
 * Status codes indicating the validity of a log file examined by
 * __log_valid().
 */
typedef enum {
	DB_LV_INCOMPLETE,
	DB_LV_NONEXISTENT,
	DB_LV_NORMAL,
	DB_LV_OLD_READABLE,
	DB_LV_OLD_UNREADABLE
} logfile_validity;

#include "dbinc_auto/dbreg_auto.h"
#include "dbinc_auto/dbreg_ext.h"
#include "dbinc_auto/log_ext.h"
#endif /* !_LOG_H_ */

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This article, along with any associated source code and files, is licensed under The BSD License

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