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/**************************************************//**
@file buf/buf0checksum.cc
Buffer pool checksum functions, also linked from /extra/innochecksum.cc

Created Aug 11, 2011 Vasil Dimov
*******************************************************/

#include "univ.i"
#include "fil0fil.h"
#include "ut0crc32.h"
#include "ut0rnd.h"

#ifndef UNIV_INNOCHECKSUM

#include "srv0srv.h"
#endif /* !UNIV_INNOCHECKSUM */
#include "buf0types.h"

/** the macro MYSQL_SYSVAR_ENUM() requires "long unsigned int" and if we
use srv_checksum_algorithm_t here then we get a compiler error:
ha_innodb.cc:12251: error: cannot convert 'srv_checksum_algorithm_t*' to
  'long unsigned int*' in initialization */
ulong	srv_checksum_algorithm = SRV_CHECKSUM_ALGORITHM_INNODB;

/** set if we have found pages matching legacy big endian checksum */
bool	legacy_big_endian_checksum = false;
/** Calculates the CRC32 checksum of a page. The value is stored to the page
when it is written to a file and also checked for a match when reading from
the file. When reading we allow both normal CRC32 and CRC-legacy-big-endian
variants. Note that we must be careful to calculate the same value on 32-bit
and 64-bit architectures.
@param[in]	page			buffer page (UNIV_PAGE_SIZE bytes)
@param[in]	use_legacy_big_endian	if true then use big endian
byteorder when converting byte strings to integers
@return checksum */
uint32_t
buf_calc_page_crc32(
	const byte*	page,
	bool		use_legacy_big_endian /* = false */)
{
	/* Since the field FIL_PAGE_FILE_FLUSH_LSN, and in versions <= 4.1.x
	FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID, are written outside the buffer pool
	to the first pages of data files, we have to skip them in the page
	checksum calculation.
	We must also skip the field FIL_PAGE_SPACE_OR_CHKSUM where the
	checksum is stored, and also the last 8 bytes of page because
	there we store the old formula checksum. */

	ut_crc32_func_t	crc32_func = use_legacy_big_endian
		? ut_crc32_legacy_big_endian
		: ut_crc32;

	const uint32_t	c1 = crc32_func(
		page + FIL_PAGE_OFFSET,
		FIL_PAGE_FILE_FLUSH_LSN - FIL_PAGE_OFFSET);

	const uint32_t	c2 = crc32_func(
		page + FIL_PAGE_DATA,
		UNIV_PAGE_SIZE - FIL_PAGE_DATA - FIL_PAGE_END_LSN_OLD_CHKSUM);

	return(c1 ^ c2);
}

/********************************************************************//**
Calculates a page checksum which is stored to the page when it is written
to a file. Note that we must be careful to calculate the same value on
32-bit and 64-bit architectures.
@return checksum */
ulint
buf_calc_page_new_checksum(
/*=======================*/
	const byte*	page)	/*!< in: buffer page */
{
	ulint checksum;

	/* Since the field FIL_PAGE_FILE_FLUSH_LSN, and in versions <= 4.1.x
	FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID, are written outside the buffer pool
	to the first pages of data files, we have to skip them in the page
	checksum calculation.
	We must also skip the field FIL_PAGE_SPACE_OR_CHKSUM where the
	checksum is stored, and also the last 8 bytes of page because
	there we store the old formula checksum. */

	checksum = ut_fold_binary(page + FIL_PAGE_OFFSET,
				  FIL_PAGE_FILE_FLUSH_LSN - FIL_PAGE_OFFSET)
		+ ut_fold_binary(page + FIL_PAGE_DATA,
				 UNIV_PAGE_SIZE - FIL_PAGE_DATA
				 - FIL_PAGE_END_LSN_OLD_CHKSUM);
	checksum = checksum & 0xFFFFFFFFUL;

	return(checksum);
}

/********************************************************************//**
In versions < 4.0.14 and < 4.1.1 there was a bug that the checksum only
looked at the first few bytes of the page. This calculates that old
checksum.
NOTE: we must first store the new formula checksum to
FIL_PAGE_SPACE_OR_CHKSUM before calculating and storing this old checksum
because this takes that field as an input!
@return checksum */
ulint
buf_calc_page_old_checksum(
/*=======================*/
	const byte*	page)	/*!< in: buffer page */
{
	ulint checksum;

	checksum = ut_fold_binary(page, FIL_PAGE_FILE_FLUSH_LSN);

	checksum = checksum & 0xFFFFFFFFUL;

	return(checksum);
}

/********************************************************************//**
Return a printable string describing the checksum algorithm.
@return algorithm name */
const char*
buf_checksum_algorithm_name(
/*========================*/
	srv_checksum_algorithm_t	algo)	/*!< in: algorithm */
{
	switch (algo) {
	case SRV_CHECKSUM_ALGORITHM_CRC32:
		return("crc32");
	case SRV_CHECKSUM_ALGORITHM_STRICT_CRC32:
		return("strict_crc32");
	case SRV_CHECKSUM_ALGORITHM_INNODB:
		return("innodb");
	case SRV_CHECKSUM_ALGORITHM_STRICT_INNODB:
		return("strict_innodb");
	case SRV_CHECKSUM_ALGORITHM_NONE:
		return("none");
	case SRV_CHECKSUM_ALGORITHM_STRICT_NONE:
		return("strict_none");
	}

	ut_error;
	return(NULL);
}