log.c

这是国外的resip协议栈

 */
int
__log_vtruncate(dbenv, lsn, ckplsn, trunclsn)
	DB_ENV *dbenv;
	DB_LSN *lsn, *ckplsn, *trunclsn;
{
	DBT log_dbt;
	DB_LOG *dblp;
	DB_LOGC *logc;
	DB_LSN end_lsn;
	DB_MUTEX *flush_mutexp;
	LOG *lp;
	u_int32_t bytes, c_len;
	int ret, t_ret;

	/* Need to find out the length of this soon-to-be-last record. */
	if ((ret = __log_cursor(dbenv, &logc)) != 0)
		return (ret);
	memset(&log_dbt, 0, sizeof(log_dbt));
	ret = __log_c_get(logc, lsn, &log_dbt, DB_SET);
	c_len = logc->c_len;
	if ((t_ret = __log_c_close(logc)) != 0 && ret == 0)
		ret = t_ret;
	if (ret != 0)
		return (ret);

	/* Now do the truncate. */
	dblp = (DB_LOG *)dbenv->lg_handle;
	lp = (LOG *)dblp->reginfo.primary;

	R_LOCK(dbenv, &dblp->reginfo);

	/*
	 * Flush the log so we can simply initialize the in-memory buffer
	 * after the truncate.
	 */
	if ((ret = __log_flush_int(dblp, NULL, 0)) != 0)
		goto err;

	end_lsn = lp->lsn;
	lp->lsn = *lsn;
	lp->len = c_len;
	lp->lsn.offset += lp->len;

	if (lp->db_log_inmemory &&
	    (ret = __log_inmem_lsnoff(dblp, &lp->lsn, &lp->b_off)) != 0)
		goto err;

	/*
	 * I am going to assume that the number of bytes written since
	 * the last checkpoint doesn't exceed a 32-bit number.
	 */
	DB_ASSERT(lp->lsn.file >= ckplsn->file);
	bytes = 0;
	if (ckplsn->file != lp->lsn.file) {
		bytes = lp->log_size - ckplsn->offset;
		if (lp->lsn.file > ckplsn->file + 1)
			bytes += lp->log_size *
			    ((lp->lsn.file - ckplsn->file) - 1);
		bytes += lp->lsn.offset;
	} else
		bytes = lp->lsn.offset - ckplsn->offset;

	lp->stat.st_wc_mbytes += bytes / MEGABYTE;
	lp->stat.st_wc_bytes += bytes % MEGABYTE;

	/*
	 * If the saved lsn is greater than our new end of log, reset it
	 * to our current end of log.
	 */
	flush_mutexp = R_ADDR(&dblp->reginfo, lp->flush_mutex_off);
	MUTEX_LOCK(dbenv, flush_mutexp);
	if (log_compare(&lp->s_lsn, lsn) > 0)
		lp->s_lsn = lp->lsn;
	MUTEX_UNLOCK(dbenv, flush_mutexp);

	/* Initialize the in-region buffer to a pristine state. */
	ZERO_LSN(lp->f_lsn);
	lp->w_off = lp->lsn.offset;

	if (trunclsn != NULL)
		*trunclsn = lp->lsn;

	/* Truncate the log to the new point. */
	if ((ret = __log_zero(dbenv, &lp->lsn, &end_lsn)) != 0)
		goto err;

err:	R_UNLOCK(dbenv, &dblp->reginfo);
	return (ret);
}

/*
 * __log_is_outdated --
 *	Used by the replication system to identify if a client's logs
 * are too old.  The log represented by dbenv is compared to the file
 * number passed in fnum.  If the log file fnum does not exist and is
 * lower-numbered than the current logs, the we return *outdatedp non
 * zero, else we return it 0.
 *
 * PUBLIC: int __log_is_outdated __P((DB_ENV *, u_int32_t, int *));
 */
int
__log_is_outdated(dbenv, fnum, outdatedp)
	DB_ENV *dbenv;
	u_int32_t fnum;
	int *outdatedp;
{
	DB_LOG *dblp;
	LOG *lp;
	char *name;
	int ret;
	u_int32_t cfile;
	struct __db_filestart *filestart;

	dblp = dbenv->lg_handle;

	if (F_ISSET(dbenv, DB_ENV_LOG_INMEMORY)) {
		R_LOCK(dbenv, &dblp->reginfo);
		lp = (LOG *)dblp->reginfo.primary;
		filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
		*outdatedp = (fnum < filestart->file);
		R_UNLOCK(dbenv, &dblp->reginfo);
		return (0);
	}

	*outdatedp = 0;
	if ((ret = __log_name(dblp, fnum, &name, NULL, 0)) != 0)
		return (ret);

	/* If the file exists, we're just fine. */
	if (__os_exists(name, NULL) == 0)
		goto out;

	/*
	 * It didn't exist, decide if the file number is too big or
	 * too little.  If it's too little, then we need to indicate
	 * that the LSN is outdated.
	 */
	R_LOCK(dbenv, &dblp->reginfo);
	lp = (LOG *)dblp->reginfo.primary;
	cfile = lp->lsn.file;
	R_UNLOCK(dbenv, &dblp->reginfo);

	if (cfile > fnum)
		*outdatedp = 1;
out:	__os_free(dbenv, name);
	return (ret);
}

/*
 * __log_zero --
 *	Zero out the tail of a log after a truncate.
 */
static int
__log_zero(dbenv, from_lsn, to_lsn)
	DB_ENV *dbenv;
	DB_LSN *from_lsn, *to_lsn;
{
	DB_FH *fhp;
	DB_LOG *dblp;
	LOG *lp;
	struct __db_filestart *filestart, *nextstart;
	size_t nbytes, len, nw;
	u_int32_t fn, mbytes, bytes;
	u_int8_t buf[4096];
	int ret;
	char *fname;

	dblp = dbenv->lg_handle;
	DB_ASSERT(log_compare(from_lsn, to_lsn) <= 0);
	if (log_compare(from_lsn, to_lsn) > 0) {
		__db_err(dbenv,
		    "Warning: truncating to point beyond end of log");
		return (0);
	}

	lp = (LOG *)dblp->reginfo.primary;
	if (lp->db_log_inmemory) {
		/*
		 * Remove the first file if it is invalidated by this write.
		 * Log records can't be bigger than a file, so we only need to
		 * check the first file.
		 */
		for (filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
		    filestart != NULL && from_lsn->file < filestart->file;
		    filestart = nextstart) {
			nextstart = SH_TAILQ_NEXT(filestart,
			    links, __db_filestart);
			SH_TAILQ_REMOVE(&lp->logfiles, filestart,
			    links, __db_filestart);
			SH_TAILQ_INSERT_HEAD(&lp->free_logfiles, filestart,
			    links, __db_filestart);
		}

		return (0);
	}

	/* Close any open file handles so unlinks don't fail. */
	if (dblp->lfhp != NULL) {
		(void)__os_closehandle(dbenv, dblp->lfhp);
		dblp->lfhp = NULL;
	}

	/* Throw away any extra log files that we have around. */
	for (fn = from_lsn->file + 1;; fn++) {
		if (__log_name(dblp, fn, &fname, &fhp, DB_OSO_RDONLY) != 0) {
			__os_free(dbenv, fname);
			break;
		}
		(void)__os_closehandle(dbenv, fhp);
		ret = __os_unlink(dbenv, fname);
		__os_free(dbenv, fname);
		if (ret != 0)
			return (ret);
	}

	/* We removed some log files; have to 0 to end of file. */
	if ((ret =
	    __log_name(dblp, from_lsn->file, &fname, &dblp->lfhp, 0)) != 0)
		return (ret);
	__os_free(dbenv, fname);
	if ((ret = __os_ioinfo(dbenv,
	    NULL, dblp->lfhp, &mbytes, &bytes, NULL)) != 0)
		goto err;
	DB_ASSERT((mbytes * MEGABYTE + bytes) >= from_lsn->offset);
	len = (mbytes * MEGABYTE + bytes) - from_lsn->offset;

	memset(buf, 0, sizeof(buf));

	/* Initialize the write position. */
	if ((ret = __os_seek(dbenv,
	    dblp->lfhp, 0, 0, from_lsn->offset, 0, DB_OS_SEEK_SET)) != 0)
		goto err;

	while (len > 0) {
		nbytes = len > sizeof(buf) ? sizeof(buf) : len;
		if ((ret =
		    __os_write(dbenv, dblp->lfhp, buf, nbytes, &nw)) != 0)
			goto err;
		len -= nbytes;
	}

err:	(void)__os_closehandle(dbenv, dblp->lfhp);
	dblp->lfhp = NULL;

	return (ret);
}

/*
 * __log_inmem_lsnoff --
 *	Find the offset in the buffer of a given LSN.
 *
 * PUBLIC: int __log_inmem_lsnoff __P((DB_LOG *, DB_LSN *, size_t *));
 */
int
__log_inmem_lsnoff(dblp, lsn, offsetp)
	DB_LOG *dblp;
	DB_LSN *lsn;
	size_t *offsetp;
{
	LOG *lp;
	struct __db_filestart *filestart;

	lp = (LOG *)dblp->reginfo.primary;

	SH_TAILQ_FOREACH(filestart, &lp->logfiles, links, __db_filestart)
		if (filestart->file == lsn->file) {
			*offsetp =
			    (filestart->b_off + lsn->offset) % lp->buffer_size;
			return (0);
		}

	return (DB_NOTFOUND);
}

/*
 * __log_inmem_newfile --
 *	Records the offset of the beginning of a new file in the in-memory
 *	buffer.
 *
 * PUBLIC: int __log_inmem_newfile __P((DB_LOG *, u_int32_t));
 */
int
__log_inmem_newfile(dblp, file)
	DB_LOG *dblp;
	u_int32_t file;
{
	HDR hdr;
	LOG *lp;
	struct __db_filestart *filestart;
	int ret;
#ifdef DIAGNOSTIC
	struct __db_filestart *first, *last;
#endif

	lp = (LOG *)dblp->reginfo.primary;

	/*
	 * We write an empty header at the end of every in-memory log file.
	 * This is used during cursor traversal to indicate when to switch the
	 * LSN to the next file.
	 */
	if (file > 1) {
		memset(&hdr, 0, sizeof(HDR));
		__log_inmem_copyin(dblp, lp->b_off, &hdr, sizeof(HDR));
		lp->b_off = (lp->b_off + sizeof(HDR)) % lp->buffer_size;
	}

	filestart = SH_TAILQ_FIRST(&lp->free_logfiles, __db_filestart);
	if (filestart == NULL) {
		if ((ret = __db_shalloc(&dblp->reginfo,
		    sizeof(struct __db_filestart), 0, &filestart)) != 0)
			return (ret);
		memset(filestart, 0, sizeof(*filestart));
	} else
		SH_TAILQ_REMOVE(&lp->free_logfiles, filestart,
		    links, __db_filestart);

	filestart->file = file;
	filestart->b_off = lp->b_off;

#ifdef DIAGNOSTIC
	first = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
	last = SH_TAILQ_LAST(&(lp)->logfiles, links, __db_filestart);

	/* Check that we don't wrap. */
	DB_ASSERT(!first || first == last ||
	    RINGBUF_LEN(lp, first->b_off, lp->b_off) ==
	    RINGBUF_LEN(lp, first->b_off, last->b_off) +
	    RINGBUF_LEN(lp, last->b_off, lp->b_off));
#endif

	SH_TAILQ_INSERT_TAIL(&lp->logfiles, filestart, links);
	return (0);
}

/*
 * __log_inmem_chkspace --
 *	Ensure that the requested amount of space is available in the buffer,
 *	and invalidate the region.
 *      Note: assumes that the region lock is held on entry.
 *
 * PUBLIC: int __log_inmem_chkspace __P((DB_LOG *, size_t));
 */
int
__log_inmem_chkspace(dblp, len)
	DB_LOG *dblp;
	size_t len;
{
	LOG *lp;
	DB_LSN active_lsn, old_active_lsn;
	struct __db_filestart *filestart;

	lp = dblp->reginfo.primary;

	DB_ASSERT(lp->db_log_inmemory);

	/*
	 * Allow room for an extra header so that we don't need to check for
	 * space when switching files.
	 */
	len += sizeof(HDR);

	/*
	 * If transactions are enabled and we're about to fill available space,
	 * update the active LSN and recheck.  If transactions aren't enabled,
	 * don't even bother checking: in that case we can always overwrite old
	 * log records, because we're never going to abort.
	 */
	while (TXN_ON(dblp->dbenv) &&
	    RINGBUF_LEN(lp, lp->b_off, lp->a_off) <= len) {
		old_active_lsn = lp->active_lsn;
		active_lsn = lp->lsn;

		/*
		 * Drop the log region lock so we don't hold it while
		 * taking the transaction region lock.
		 */
		R_UNLOCK(dblp->dbenv, &dblp->reginfo);
		__txn_getactive(dblp->dbenv, &active_lsn);
		R_LOCK(dblp->dbenv, &dblp->reginfo);
		active_lsn.offset = 0;

		/* If we didn't make any progress, give up. */
		if (log_compare(&active_lsn, &old_active_lsn) == 0) {
			__db_err(dblp->dbenv,
      "In-memory log buffer is full (an active transaction spans the buffer)");
			return (DB_LOG_BUFFER_FULL);
		}

		/* Make sure we're moving the region LSN forwards. */
		if (log_compare(&active_lsn, &lp->active_lsn) > 0) {
			lp->active_lsn = active_lsn;
			(void)__log_inmem_lsnoff(dblp, &active_lsn,
			    &lp->a_off);
		}
	}

	/*
	 * Remove the first file if it is invalidated by this write.
	 * Log records can't be bigger than a file, so we only need to
	 * check the first file.
	 */
	filestart = SH_TAILQ_FIRST(&lp->logfiles, __db_filestart);
	if (filestart != NULL &&
	    RINGBUF_LEN(lp, lp->b_off, filestart->b_off) <= len) {
		SH_TAILQ_REMOVE(&lp->logfiles, filestart,
		    links, __db_filestart);
		SH_TAILQ_INSERT_HEAD(&lp->free_logfiles, filestart,
		    links, __db_filestart);
		lp->f_lsn.file = filestart->file + 1;
	}

	return (0);
}

/*
 * __log_inmem_copyout --
 *	Copies the given number of bytes from the buffer -- no checking.
 *      Note: assumes that the region lock is held on entry.
 *
 * PUBLIC: void __log_inmem_copyout __P((DB_LOG *, size_t, void *, size_t));
 */
void
__log_inmem_copyout(dblp, offset, buf, size)
	DB_LOG *dblp;
	size_t offset;
	void *buf;
	size_t size;
{
	LOG *lp;
	size_t nbytes;

	lp = (LOG *)dblp->reginfo.primary;
	nbytes = (offset + size < lp->buffer_size) ?
	    size : lp->buffer_size - offset;
	memcpy(buf, dblp->bufp + offset, nbytes);
	if (nbytes < size)
		memcpy((u_int8_t *)buf + nbytes, dblp->bufp, size - nbytes);
}

/*
 * __log_inmem_copyin --
 *	Copies the given number of bytes into the buffer -- no checking.
 *      Note: assumes that the region lock is held on entry.
 *
 * PUBLIC: void __log_inmem_copyin __P((DB_LOG *, size_t, void *, size_t));
 */
void
__log_inmem_copyin(dblp, offset, buf, size)
	DB_LOG *dblp;
	size_t offset;
	void *buf;
	size_t size;
{
	LOG *lp;
	size_t nbytes;

	lp = (LOG *)dblp->reginfo.primary;
	nbytes = (offset + size < lp->buffer_size) ?
	    size : lp->buffer_size - offset;
	memcpy(dblp->bufp + offset, buf, nbytes);
	if (nbytes < size)
		memcpy(dblp->bufp, (u_int8_t *)buf + nbytes, size - nbytes);
}