/*

 * Copyright (c) 2020 Red Hat, Inc.

 *

 * 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; either version 2

 * of the License, or (at your option) any later version.

 * 

 * 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 Street, Fifth Floor, Boston, MA

 * 02110-1301, USA. 

 *

 * $Id: //eng/vdo-releases/aluminum/src/c++/vdo/base/compressedBlock.h#3 $

 */

#ifndef COMPRESSED_BLOCK_H

#define COMPRESSED_BLOCK_H

#include "blockMappingState.h"

#include "header.h"

/**

 * The header of a compressed block.

 **/

typedef union __attribute__((packed)) {

  struct __attribute__((packed)) {

    /** Unsigned 32-bit major and minor versions, in little-endian byte order */

    PackedVersionNumber version;

    /** List of unsigned 16-bit compressed block sizes, in little-endian order */

    byte sizes[MAX_COMPRESSION_SLOTS][2];

  } fields;

  // A raw view of the packed encoding.

  byte raw[4 + 4 + (2 * MAX_COMPRESSION_SLOTS)];

#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__

  // This view is only valid on little-endian machines and is only present for

  // ease of directly examining compressed block headers in GDB.

  struct __attribute__((packed)) {

    VersionNumber version;

    uint16_t      sizes[MAX_COMPRESSION_SLOTS];

  } littleEndian;

#endif

} CompressedBlockHeader;

/**

 * The compressed block overlay.

 **/

typedef struct {

  CompressedBlockHeader header;

  char                  data[];

} __attribute__((packed)) CompressedBlock;

/**

 * Initializes/resets a compressed block header.

 *

 * @param header        the header

 *

 * When done, the version number is set to the current version, and all

 * fragments are empty.

 **/

void resetCompressedBlockHeader(CompressedBlockHeader *header);

/**

 * Get a reference to a compressed fragment from a compression block.

 *

 * @param [in]  mappingState    the mapping state for the look up

 * @param [in]  buffer          buffer that contains compressed data

 * @param [in]  blockSize       size of a data block

 * @param [out] fragmentOffset  the offset of the fragment within a

 *                              compressed block

 * @param [out] fragmentSize    the size of the fragment

 *

 * @return If a valid compressed fragment is found, VDO_SUCCESS;

 *         otherwise, VDO_INVALID_FRAGMENT if the fragment is invalid.

 **/

int getCompressedBlockFragment(BlockMappingState  mappingState,

                               char              *buffer,

                               BlockSize          blockSize,

                               uint16_t          *fragmentOffset,

                               uint16_t          *fragmentSize);

/**

 * Copy a fragment into the compressed block.

 *

 * @param block      the compressed block

 * @param fragment   the number of the fragment

 * @param offset     the byte offset of the fragment in the data area

 * @param data       a pointer to the compressed data

 * @param size       the size of the data

 *

 * @note no bounds checking -- the data better fit without smashing other stuff

 **/

void putCompressedBlockFragment(CompressedBlock *block,

                                unsigned int     fragment,

                                uint16_t         offset,

                                const char      *data,

                                uint16_t         size);

#endif // COMPRESSED_BLOCK_H