/*****************************************************************************

Copyright (c) 2006, 2014, Oracle and/or its affiliates. All Rights Reserved.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.

This program is also distributed with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation.  The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have included with MySQL.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License, version 2.0, for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file row/row0ext.cc
Caching of externally stored column prefixes

Created September 2006 Marko Makela
*******************************************************/

#include "row0ext.h"

#ifdef UNIV_NONINL
#include "row0ext.ic"
#endif

#include "btr0cur.h"

/** Fills the column prefix cache of an externally stored column.
@param[in,out]	ext		column prefix cache
@param[in]	i		index of ext->ext[]
@param[in]	page_size	page size
@param[in]	dfield		data field */
static
void
row_ext_cache_fill(
	row_ext_t*		ext,
	ulint			i,
	const page_size_t&	page_size,
	const dfield_t*		dfield)
{
	const byte*	field	= static_cast<const byte*>(
					dfield_get_data(dfield));
	ulint		f_len	= dfield_get_len(dfield);
	byte*		buf	= ext->buf + i * ext->max_len;

	ut_ad(ext->max_len > 0);
	ut_ad(i < ext->n_ext);
	ut_ad(dfield_is_ext(dfield));
	ut_a(f_len >= BTR_EXTERN_FIELD_REF_SIZE);

	if (UNIV_UNLIKELY(!memcmp(field_ref_zero,
				  field + f_len - BTR_EXTERN_FIELD_REF_SIZE,
				  BTR_EXTERN_FIELD_REF_SIZE))) {
		/* The BLOB pointer is not set: we cannot fetch it */
		ext->len[i] = 0;
	} else {
		if (ext->max_len == REC_VERSION_56_MAX_INDEX_COL_LEN
		    && f_len > BTR_EXTERN_FIELD_REF_SIZE) {
			/* In this case, the field is in B format or beyond,
			(refer to the definition of row_ext_t.max_len)
			and the field is already fill with prefix, otherwise
			f_len would be BTR_EXTERN_FIELD_REF_SIZE.
			So there is no need to re-read the prefix externally,
			but just copy the local prefix to buf. Please note
			if the ext->len[i] is zero, it means an error
			as above. */
			memcpy(buf, field, f_len - BTR_EXTERN_FIELD_REF_SIZE);
			ext->len[i] = f_len - BTR_EXTERN_FIELD_REF_SIZE;
		} else {
			/* Fetch at most ext->max_len of the column.
			The column should be non-empty.  However,
			trx_rollback_or_clean_all_recovered() may try to
			access a half-deleted BLOB if the server previously
			crashed during the execution of
			btr_free_externally_stored_field(). */
			ext->len[i] = btr_copy_externally_stored_field_prefix(
				buf, ext->max_len, page_size, field, f_len);
		}
	}
}

/********************************************************************//**
Creates a cache of column prefixes of externally stored columns.
@return own: column prefix cache */
row_ext_t*
row_ext_create(
/*===========*/
	ulint		n_ext,	/*!< in: number of externally stored columns */
	const ulint*	ext,	/*!< in: col_no's of externally stored columns
				in the InnoDB table object, as reported by
				dict_col_get_no(); NOT relative to the records
				in the clustered index */
	ulint		flags,	/*!< in: table->flags */
	const dtuple_t*	tuple,	/*!< in: data tuple containing the field
				references of the externally stored
				columns; must be indexed by col_no;
				the clustered index record must be
				covered by a lock or a page latch
				to prevent deletion (rollback or purge). */
	mem_heap_t*	heap)	/*!< in: heap where created */
{
	ulint		i;
	const page_size_t&	page_size = dict_tf_get_page_size(flags);

	row_ext_t*	ret;

	ut_ad(n_ext > 0);

	ret = static_cast<row_ext_t*>(
		mem_heap_alloc(heap,
			       (sizeof *ret) + (n_ext - 1) * sizeof ret->len));

	ret->n_ext = n_ext;
	ret->ext = ext;
	ret->max_len = DICT_MAX_FIELD_LEN_BY_FORMAT_FLAG(flags);
	ret->page_size.copy_from(page_size);

	ret->buf = static_cast<byte*>(
		mem_heap_alloc(heap, n_ext * ret->max_len));

#ifdef UNIV_DEBUG
	memset(ret->buf, 0xaa, n_ext * ret->max_len);
	UNIV_MEM_ALLOC(ret->buf, n_ext * ret->max_len);
#endif

	/* Fetch the BLOB prefixes */
	for (i = 0; i < n_ext; i++) {
		const dfield_t*	dfield;

		dfield = dtuple_get_nth_field(tuple, ext[i]);
		row_ext_cache_fill(ret, i, page_size, dfield);
	}

	return(ret);
}
