| /*------------------------------------------------------------------------- | |
| * | |
| * block.h | |
| * POSTGRES disk block definitions. | |
| * | |
| * | |
| * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group | |
| * Portions Copyright (c) 1994, Regents of the University of California | |
| * | |
| * src/include/storage/block.h | |
| * | |
| *------------------------------------------------------------------------- | |
| */ | |
| /* | |
| * BlockNumber: | |
| * | |
| * each data file (heap or index) is divided into postgres disk blocks | |
| * (which may be thought of as the unit of i/o -- a postgres buffer | |
| * contains exactly one disk block). the blocks are numbered | |
| * sequentially, 0 to 0xFFFFFFFE. | |
| * | |
| * InvalidBlockNumber is the same thing as P_NEW in bufmgr.h. | |
| * | |
| * the access methods, the buffer manager and the storage manager are | |
| * more or less the only pieces of code that should be accessing disk | |
| * blocks directly. | |
| */ | |
| typedef uint32 BlockNumber; | |
| /* | |
| * BlockId: | |
| * | |
| * this is a storage type for BlockNumber. in other words, this type | |
| * is used for on-disk structures (e.g., in HeapTupleData) whereas | |
| * BlockNumber is the type on which calculations are performed (e.g., | |
| * in access method code). | |
| * | |
| * there doesn't appear to be any reason to have separate types except | |
| * for the fact that BlockIds can be SHORTALIGN'd (and therefore any | |
| * structures that contains them, such as ItemPointerData, can also be | |
| * SHORTALIGN'd). this is an important consideration for reducing the | |
| * space requirements of the line pointer (ItemIdData) array on each | |
| * page and the header of each heap or index tuple, so it doesn't seem | |
| * wise to change this without good reason. | |
| */ | |
| typedef struct BlockIdData | |
| { | |
| uint16 bi_hi; | |
| uint16 bi_lo; | |
| } BlockIdData; | |
| typedef BlockIdData *BlockId; /* block identifier */ | |
| /* ---------------- | |
| * support functions | |
| * ---------------- | |
| */ | |
| /* | |
| * BlockNumberIsValid | |
| * True iff blockNumber is valid. | |
| */ | |
| static inline bool | |
| BlockNumberIsValid(BlockNumber blockNumber) | |
| { | |
| return blockNumber != InvalidBlockNumber; | |
| } | |
| /* | |
| * BlockIdSet | |
| * Sets a block identifier to the specified value. | |
| */ | |
| static inline void | |
| BlockIdSet(BlockIdData *blockId, BlockNumber blockNumber) | |
| { | |
| blockId->bi_hi = blockNumber >> 16; | |
| blockId->bi_lo = blockNumber & 0xffff; | |
| } | |
| /* | |
| * BlockIdEquals | |
| * Check for block number equality. | |
| */ | |
| static inline bool | |
| BlockIdEquals(const BlockIdData *blockId1, const BlockIdData *blockId2) | |
| { | |
| return (blockId1->bi_hi == blockId2->bi_hi && | |
| blockId1->bi_lo == blockId2->bi_lo); | |
| } | |
| /* | |
| * BlockIdGetBlockNumber | |
| * Retrieve the block number from a block identifier. | |
| */ | |
| static inline BlockNumber | |
| BlockIdGetBlockNumber(const BlockIdData *blockId) | |
| { | |
| return (((BlockNumber) blockId->bi_hi) << 16) | ((BlockNumber) blockId->bi_lo); | |
| } | |