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

 Copyright (C) 2014 eperi GmbH. 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

/******************************************************************//**
@file include/fsp0pageencryption.ic
Implementation for helper functions for encrypting/decrypting pages
and atomic writes information to file space.

Created 08/28/2014
***********************************************************************/

#include "fsp0fsp.h"
#include "fil0pageencryption.h"

/********************************************************************//**
Determine if the tablespace is page encrypted from dict_table_t::flags.
@return	TRUE if page encrypted, FALSE if not page encrypted */
UNIV_INLINE
ibool
fsp_flags_is_page_encrypted(
/*=========================*/
	ulint	flags)	/*!< in: tablespace flags */
{
	return(FSP_FLAGS_GET_PAGE_ENCRYPTION(flags));
}

/********************************************************************//**
Extract the page encryption key from tablespace flags.
A tablespace has only one physical page encryption key
whether that page is encrypted or not.
@return	page encryption key of the file-per-table tablespace,
or zero if the table is not encrypted.  */
UNIV_INLINE
ulint
fsp_flags_get_page_encryption_key(
/*=================================*/
	ulint	flags)	/*!< in: tablespace flags */
{
	return(FSP_FLAGS_GET_PAGE_ENCRYPTION_KEY(flags));
}


/*******************************************************************//**
Returns the page encryption flag of the space, or false if the space
is not encrypted. The tablespace must be cached in the memory cache.
@return	true if page encrypted, false if not or space not found */
UNIV_INLINE
ibool
fil_space_is_page_encrypted(
/*=========================*/
    ulint   id)	/*!< in: space id */
{
	ulint	flags;

	flags = fil_space_get_flags(id);

	if (flags && flags != ULINT_UNDEFINED) {

		return(fsp_flags_is_page_encrypted(flags));
	}

	return(flags);
}

/*******************************************************************//**
Returns the page encryption key of the space, or 0 if the space
is not encrypted. The tablespace must be cached in the memory cache.
@return	page compression level, ULINT_UNDEFINED if space not found */
UNIV_INLINE
ulint
fil_space_get_page_encryption_key(
/*=================================*/
	ulint	id)	/*!< in: space id */
{
	ulint	flags;

	flags = fil_space_get_flags(id);

	if (flags && flags != ULINT_UNDEFINED) {

		return(fsp_flags_get_page_encryption_key(flags));
	}

	return(flags);
}



/*******************************************************************//**
Find out whether the page is page encrypted
@return	true if page is page encrypted, false if not */
UNIV_INLINE
ibool
fil_page_is_encrypted(
/*===================*/
    const byte *buf)	/*!< in: page */
{    
    return(mach_read_from_2(buf+FIL_PAGE_TYPE) == FIL_PAGE_PAGE_ENCRYPTED); 
}

/*******************************************************************//**
Find out whether the page is page is first compressed and then encrypted
@return	true if page is page compressed+encrypted, false if not */
UNIV_INLINE
ibool
fil_page_is_compressed_encrypted(
/*=============================*/
	const byte *buf)	/*!< in: page */
{
	return(mach_read_from_2(buf+FIL_PAGE_TYPE) == FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED);
}

/*******************************************************************//**
Find out whether the page can be decrypted.
This is the case, if the page is already decrypted and is not the first page of the table space.
If the page is already decrypted it is not of the FIL_PAGE_PAGE_ENCRYPTED type.
if it is the first page of the table space, it is assumed that a page can be decrypted if the
key found in the flags (part of the 1st page) can be read from the key provider.
The case, if the key changed, is currently not caught.
The function for decrypting the page should already be executed before this.
@return	PAGE_ENCRYPTION_KEY_MISSING if key provider is available, but key is not available
		PAGE_ENCRYPTION_ERROR if other error occurred
		0  if decryption should be possible
*/
UNIV_INLINE
ulint
fil_page_encryption_status(
/*===================*/
    const byte *buf)	/*!< in: page */
{
	ulint page_type = mach_read_from_2(buf+FIL_PAGE_TYPE);

	if (page_type == FIL_PAGE_TYPE_FSP_HDR) {
		ulint flags = mach_read_from_4(FSP_HEADER_OFFSET + FSP_SPACE_FLAGS + buf);
		if (fsp_flags_is_page_encrypted(flags)) {
			if (!encryption_key_exists(fsp_flags_get_page_encryption_key(flags))) {
				/* accessing table would surely fail, because no key or no key provider available */
				if (!encryption_key_exists(fsp_flags_get_page_encryption_key(flags))) {
					return PAGE_ENCRYPTION_KEY_MISSING;
				}
				return PAGE_ENCRYPTION_ERROR;
			}
		}
	}

	if(page_type == FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED) {
		ulint key = mach_read_from_4(buf + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION);
		if (!encryption_key_exists(key)) {
			return PAGE_ENCRYPTION_KEY_MISSING;
		}
		return PAGE_ENCRYPTION_ERROR;
	}
	return 0;
}