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+/*****************************************************************************
+
+Copyright (c) 2005, 2009, Innobase Oy. 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 as published by the Free Software
+Foundation; version 2 of the License.
+
+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 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., 59 Temple
+Place, Suite 330, Boston, MA 02111-1307 USA
+
+*****************************************************************************/
+
+/**************************************************//**
+@file include/page0zip.ic
+Compressed page interface
+
+Created June 2005 by Marko Makela
+*******************************************************/
+
+#ifdef UNIV_MATERIALIZE
+# undef UNIV_INLINE
+# define UNIV_INLINE
+#endif
+
+#include "page0zip.h"
+#include "page0page.h"
+
+/* The format of compressed pages is as follows.
+
+The header and trailer of the uncompressed pages, excluding the page
+directory in the trailer, are copied as is to the header and trailer
+of the compressed page.
+
+At the end of the compressed page, there is a dense page directory
+pointing to every user record contained on the page, including deleted
+records on the free list.  The dense directory is indexed in the
+collation order, i.e., in the order in which the record list is
+linked on the uncompressed page.  The infimum and supremum records are
+excluded.  The two most significant bits of the entries are allocated
+for the delete-mark and an n_owned flag indicating the last record in
+a chain of records pointed to from the sparse page directory on the
+uncompressed page.
+
+The data between PAGE_ZIP_START and the last page directory entry will
+be written in compressed format, starting at offset PAGE_DATA.
+Infimum and supremum records are not stored.  We exclude the
+REC_N_NEW_EXTRA_BYTES in every record header.  These can be recovered
+from the dense page directory stored at the end of the compressed
+page.
+
+The fields node_ptr (in non-leaf B-tree nodes; level>0), trx_id and
+roll_ptr (in leaf B-tree nodes; level=0), and BLOB pointers of
+externally stored columns are stored separately, in ascending order of
+heap_no and column index, starting backwards from the dense page
+directory.
+
+The compressed data stream may be followed by a modification log
+covering the compressed portion of the page, as follows.
+
+MODIFICATION LOG ENTRY FORMAT
+- write record:
+  - (heap_no - 1) << 1 (1..2 bytes)
+  - extra bytes backwards
+  - data bytes
+- clear record:
+  - (heap_no - 1) << 1 | 1 (1..2 bytes)
+
+The integer values are stored in a variable-length format:
+- 0xxxxxxx: 0..127
+- 1xxxxxxx xxxxxxxx: 0..32767
+
+The end of the modification log is marked by a 0 byte.
+
+In summary, the compressed page looks like this:
+
+(1) Uncompressed page header (PAGE_DATA bytes)
+(2) Compressed index information
+(3) Compressed page data
+(4) Page modification log (page_zip->m_start..page_zip->m_end)
+(5) Empty zero-filled space
+(6) BLOB pointers (on leaf pages)
+  - BTR_EXTERN_FIELD_REF_SIZE for each externally stored column
+  - in descending collation order
+(7) Uncompressed columns of user records, n_dense * uncompressed_size bytes,
+  - indexed by heap_no
+  - DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN for leaf pages of clustered indexes
+  - REC_NODE_PTR_SIZE for non-leaf pages
+  - 0 otherwise
+(8) dense page directory, stored backwards
+  - n_dense = n_heap - 2
+  - existing records in ascending collation order
+  - deleted records (free list) in link order
+*/
+
+/** Start offset of the area that will be compressed */
+#define PAGE_ZIP_START		PAGE_NEW_SUPREMUM_END
+/** Size of an compressed page directory entry */
+#define PAGE_ZIP_DIR_SLOT_SIZE	2
+/** Mask of record offsets */
+#define PAGE_ZIP_DIR_SLOT_MASK	0x3fff
+/** 'owned' flag */
+#define PAGE_ZIP_DIR_SLOT_OWNED	0x4000
+/** 'deleted' flag */
+#define PAGE_ZIP_DIR_SLOT_DEL	0x8000
+
+/**********************************************************************//**
+Determine the size of a compressed page in bytes.
+@return	size in bytes */
+UNIV_INLINE
+ulint
+page_zip_get_size(
+/*==============*/
+	const page_zip_des_t*	page_zip)	/*!< in: compressed page */
+{
+	ulint	size;
+
+	if (UNIV_UNLIKELY(!page_zip->ssize)) {
+		return(0);
+	}
+
+	size = (PAGE_ZIP_MIN_SIZE >> 1) << page_zip->ssize;
+
+	ut_ad(size >= PAGE_ZIP_MIN_SIZE);
+	ut_ad(size <= UNIV_PAGE_SIZE);
+
+	return(size);
+}
+/**********************************************************************//**
+Set the size of a compressed page in bytes. */
+UNIV_INLINE
+void
+page_zip_set_size(
+/*==============*/
+	page_zip_des_t*	page_zip,	/*!< in/out: compressed page */
+	ulint		size)		/*!< in: size in bytes */
+{
+	if (size) {
+		int	ssize;
+
+		ut_ad(ut_is_2pow(size));
+
+		for (ssize = 1; size > (ulint) (512 << ssize); ssize++) {
+		}
+
+		page_zip->ssize = ssize;
+	} else {
+		page_zip->ssize = 0;
+	}
+
+	ut_ad(page_zip_get_size(page_zip) == size);
+}
+
+#ifndef UNIV_HOTBACKUP
+/**********************************************************************//**
+Determine if a record is so big that it needs to be stored externally.
+@return	FALSE if the entire record can be stored locally on the page */
+UNIV_INLINE
+ibool
+page_zip_rec_needs_ext(
+/*===================*/
+	ulint	rec_size,	/*!< in: length of the record in bytes */
+	ulint	comp,		/*!< in: nonzero=compact format */
+	ulint	n_fields,	/*!< in: number of fields in the record;
+				ignored if zip_size == 0 */
+	ulint	zip_size)	/*!< in: compressed page size in bytes, or 0 */
+{
+	ut_ad(rec_size > comp ? REC_N_NEW_EXTRA_BYTES : REC_N_OLD_EXTRA_BYTES);
+	ut_ad(ut_is_2pow(zip_size));
+	ut_ad(comp || !zip_size);
+
+#if UNIV_PAGE_SIZE > REC_MAX_DATA_SIZE
+	if (UNIV_UNLIKELY(rec_size >= REC_MAX_DATA_SIZE)) {
+		return(TRUE);
+	}
+#endif
+
+	if (UNIV_UNLIKELY(zip_size)) {
+		ut_ad(comp);
+		/* On a compressed page, there is a two-byte entry in
+		the dense page directory for every record.  But there
+		is no record header.  There should be enough room for
+		one record on an empty leaf page.  Subtract 1 byte for
+		the encoded heap number.  Check also the available space
+		on the uncompressed page. */
+		return(rec_size - (REC_N_NEW_EXTRA_BYTES - 2)
+		       >= (page_zip_empty_size(n_fields, zip_size) - 1)
+		       || rec_size >= page_get_free_space_of_empty(TRUE) / 2);
+	}
+
+	return(rec_size >= page_get_free_space_of_empty(comp) / 2);
+}
+#endif /* !UNIV_HOTBACKUP */
+
+#ifdef UNIV_DEBUG
+/**********************************************************************//**
+Validate a compressed page descriptor.
+@return	TRUE if ok */
+UNIV_INLINE
+ibool
+page_zip_simple_validate(
+/*=====================*/
+	const page_zip_des_t*	page_zip)/*!< in: compressed page descriptor */
+{
+	ut_ad(page_zip);
+	ut_ad(page_zip->data);
+	ut_ad(page_zip->ssize < PAGE_ZIP_NUM_SSIZE);
+	ut_ad(page_zip_get_size(page_zip)
+	      > PAGE_DATA + PAGE_ZIP_DIR_SLOT_SIZE);
+	ut_ad(page_zip->m_start <= page_zip->m_end);
+	ut_ad(page_zip->m_end < page_zip_get_size(page_zip));
+	ut_ad(page_zip->n_blobs
+	      < page_zip_get_size(page_zip) / BTR_EXTERN_FIELD_REF_SIZE);
+	return(TRUE);
+}
+#endif /* UNIV_DEBUG */
+
+/**********************************************************************//**
+Determine if the length of the page trailer.
+@return length of the page trailer, in bytes, not including the
+terminating zero byte of the modification log */
+UNIV_INLINE
+ibool
+page_zip_get_trailer_len(
+/*=====================*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	ibool			is_clust,/*!< in: TRUE if clustered index */
+	ulint*			entry_size)/*!< out: size of the uncompressed
+					portion of a user record */
+{
+	ulint	uncompressed_size;
+
+	ut_ad(page_zip_simple_validate(page_zip));
+	UNIV_MEM_ASSERT_RW(page_zip->data, page_zip_get_size(page_zip));
+
+	if (UNIV_UNLIKELY(!page_is_leaf(page_zip->data))) {
+		uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE
+			+ REC_NODE_PTR_SIZE;
+		ut_ad(!page_zip->n_blobs);
+	} else if (UNIV_UNLIKELY(is_clust)) {
+		uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE
+			+ DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN;
+	} else {
+		uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE;
+		ut_ad(!page_zip->n_blobs);
+	}
+
+	if (entry_size) {
+		*entry_size = uncompressed_size;
+	}
+
+	return((page_dir_get_n_heap(page_zip->data) - 2)
+	       * uncompressed_size
+	       + page_zip->n_blobs * BTR_EXTERN_FIELD_REF_SIZE);
+}
+
+/**********************************************************************//**
+Determine how big record can be inserted without recompressing the page.
+@return a positive number indicating the maximum size of a record
+whose insertion is guaranteed to succeed, or zero or negative */
+UNIV_INLINE
+lint
+page_zip_max_ins_size(
+/*==================*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	ibool			is_clust)/*!< in: TRUE if clustered index */
+{
+	ulint	uncompressed_size;
+	ulint	trailer_len;
+
+	trailer_len = page_zip_get_trailer_len(page_zip, is_clust,
+					       &uncompressed_size);
+
+	/* When a record is created, a pointer may be added to
+	the dense directory.
+	Likewise, space for the columns that will not be
+	compressed will be allocated from the page trailer.
+	Also the BLOB pointers will be allocated from there, but
+	we may as well count them in the length of the record. */
+
+	trailer_len += uncompressed_size;
+
+	return((lint) page_zip_get_size(page_zip)
+	       - trailer_len - page_zip->m_end
+	       - (REC_N_NEW_EXTRA_BYTES - 2));
+}
+
+/**********************************************************************//**
+Determine if enough space is available in the modification log.
+@return	TRUE if enough space is available */
+UNIV_INLINE
+ibool
+page_zip_available(
+/*===============*/
+	const page_zip_des_t*	page_zip,/*!< in: compressed page */
+	ibool			is_clust,/*!< in: TRUE if clustered index */
+	ulint			length,	/*!< in: combined size of the record */
+	ulint			create)	/*!< in: nonzero=add the record to
+					the heap */
+{
+	ulint	uncompressed_size;
+	ulint	trailer_len;
+
+	ut_ad(length > REC_N_NEW_EXTRA_BYTES);
+
+	trailer_len = page_zip_get_trailer_len(page_zip, is_clust,
+					       &uncompressed_size);
+
+	/* Subtract the fixed extra bytes and add the maximum
+	space needed for identifying the record (encoded heap_no). */
+	length -= REC_N_NEW_EXTRA_BYTES - 2;
+
+	if (UNIV_UNLIKELY(create)) {
+		/* When a record is created, a pointer may be added to
+		the dense directory.
+		Likewise, space for the columns that will not be
+		compressed will be allocated from the page trailer.
+		Also the BLOB pointers will be allocated from there, but
+		we may as well count them in the length of the record. */
+
+		trailer_len += uncompressed_size;
+	}
+
+	return(UNIV_LIKELY(length
+			   + trailer_len
+			   + page_zip->m_end
+			   < page_zip_get_size(page_zip)));
+}
+
+/**********************************************************************//**
+Initialize a compressed page descriptor. */
+UNIV_INLINE
+void
+page_zip_des_init(
+/*==============*/
+	page_zip_des_t*	page_zip)	/*!< in/out: compressed page
+					descriptor */
+{
+	memset(page_zip, 0, sizeof *page_zip);
+}
+
+/**********************************************************************//**
+Write a log record of writing to the uncompressed header portion of a page. */
+UNIV_INTERN
+void
+page_zip_write_header_log(
+/*======================*/
+	const byte*	data,/*!< in: data on the uncompressed page */
+	ulint		length,	/*!< in: length of the data */
+	mtr_t*		mtr);	/*!< in: mini-transaction */
+
+/**********************************************************************//**
+Write data to the uncompressed header portion of a page.  The data must
+already have been written to the uncompressed page.
+However, the data portion of the uncompressed page may differ from
+the compressed page when a record is being inserted in
+page_cur_insert_rec_zip(). */
+UNIV_INLINE
+void
+page_zip_write_header(
+/*==================*/
+	page_zip_des_t*	page_zip,/*!< in/out: compressed page */
+	const byte*	str,	/*!< in: address on the uncompressed page */
+	ulint		length,	/*!< in: length of the data */
+	mtr_t*		mtr)	/*!< in: mini-transaction, or NULL */
+{
+	ulint	pos;
+
+	ut_ad(PAGE_ZIP_MATCH(str, page_zip));
+	ut_ad(page_zip_simple_validate(page_zip));
+	UNIV_MEM_ASSERT_RW(page_zip->data, page_zip_get_size(page_zip));
+
+	pos = page_offset(str);
+
+	ut_ad(pos < PAGE_DATA);
+
+	memcpy(page_zip->data + pos, str, length);
+
+	/* The following would fail in page_cur_insert_rec_zip(). */
+	/* ut_ad(page_zip_validate(page_zip, str - pos)); */
+
+	if (UNIV_LIKELY_NULL(mtr)) {
+#ifndef UNIV_HOTBACKUP
+		page_zip_write_header_log(str, length, mtr);
+#endif /* !UNIV_HOTBACKUP */
+	}
+}
+
+#ifdef UNIV_MATERIALIZE
+# undef UNIV_INLINE
+# define UNIV_INLINE	UNIV_INLINE_ORIGINAL
+#endif