rec_log

介绍：MySQL是比较出名的数据库软件

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <string.h>
#endif

#include "db_int.h"
#include "db_page.h"
#include "log.h"
#include "log.h"

/*
 * __log_register1_recover --
 *	Recovery function for register1.
 *
 * PUBLIC: int __log_register1_recover
 * PUBLIC:   __P((DB_ENV *, DBT *, DB_LSN *, db_recops, void *));
 */
int
__log_register1_recover(dbenv, dbtp, lsnp, op, info)
	DB_ENV *dbenv;
	DBT *dbtp;
	DB_LSN *lsnp;
	db_recops op;
	void *info;
{
	__log_register1_args *argp;
	DB *file_dbp;
	DBC *dbc;
	DB_MPOOLFILE *mpf;
	PAGE *pagep;
	int cmp_n, cmp_p, modified, ret;

	REC_PRINT(__log_register1_print);
	REC_INTRO(__log_register1_read);

	if ((ret = memp_fget(mpf, &argp->pgno, 0, &pagep)) != 0)
		if (DB_REDO(op)) {
			if ((ret = memp_fget(mpf,
			    &argp->pgno, DB_MPOOL_CREATE, &pagep)) != 0)
				goto out;
		} else {
			*lsnp = argp->prev_lsn;
			ret = 0;
			goto out;
		}

	modified = 0;
	cmp_n = log_compare(lsnp, &LSN(pagep));

	/*
	 * Use this when there is something like "pagelsn" in the argp
	 * structure.  Sometimes, you might need to compare meta-data
	 * lsn's instead.
	 *
	 * cmp_p = log_compare(&LSN(pagep), argp->pagelsn);
	 */
	if (cmp_p == 0 && DB_REDO(op)) {
		/* Need to redo update described. */
		modified = 1;
	} else if (cmp_n == 0 && !DB_REDO(op)) {
		/* Need to undo update described. */
		modified = 1;
	}
	if (ret = memp_fput(mpf, pagep, modified ? DB_MPOOL_DIRTY : 0))
		goto out;

	*lsnp = argp->prev_lsn;
	ret = 0;

out:	REC_CLOSE;
}

/*
 * __log_register_recover --
 *	Recovery function for register.
 *
 * PUBLIC: int __log_register_recover
 * PUBLIC:   __P((DB_ENV *, DBT *, DB_LSN *, db_recops, void *));
 */
int
__log_register_recover(dbenv, dbtp, lsnp, op, info)
	DB_ENV *dbenv;
	DBT *dbtp;
	DB_LSN *lsnp;
	db_recops op;
	void *info;
{
	__log_register_args *argp;
	DB *file_dbp;
	DBC *dbc;
	DB_MPOOLFILE *mpf;
	PAGE *pagep;
	int cmp_n, cmp_p, modified, ret;

	REC_PRINT(__log_register_print);
	REC_INTRO(__log_register_read);

	if ((ret = memp_fget(mpf, &argp->pgno, 0, &pagep)) != 0)
		if (DB_REDO(op)) {
			if ((ret = memp_fget(mpf,
			    &argp->pgno, DB_MPOOL_CREATE, &pagep)) != 0)
				goto out;
		} else {
			*lsnp = argp->prev_lsn;
			ret = 0;
			goto out;
		}

	modified = 0;
	cmp_n = log_compare(lsnp, &LSN(pagep));

	/*
	 * Use this when there is something like "pagelsn" in the argp
	 * structure.  Sometimes, you might need to compare meta-data
	 * lsn's instead.
	 *
	 * cmp_p = log_compare(&LSN(pagep), argp->pagelsn);
	 */
	if (cmp_p == 0 && DB_REDO(op)) {
		/* Need to redo update described. */
		modified = 1;
	} else if (cmp_n == 0 && !DB_REDO(op)) {
		/* Need to undo update described. */
		modified = 1;
	}
	if (ret = memp_fput(mpf, pagep, modified ? DB_MPOOL_DIRTY : 0))
		goto out;

	*lsnp = argp->prev_lsn;
	ret = 0;

out:	REC_CLOSE;
}