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8134fe4ad8
There's no visible point in casting the result of a comparison to bool, because it already is that, at least on C99 compilers. I see no point in these assertions that a pointer we're about to dereference isn't null, either. If it is, the resulting SIGSEGV will notify us of the problem just fine. Noted while reviewing Zhihong Yu's patch. This is basically cosmetic, so no need for back-patch. Discussion: https://postgr.es/m/CALNJ-vT9r0DSsAOw9OXVJFxLENoVS_68kJ5x0p44atoYH+H4dg@mail.gmail.com
116 lines
3.0 KiB
C
116 lines
3.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* block.h
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* POSTGRES disk block definitions.
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*
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*
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* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/block.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef BLOCK_H
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#define BLOCK_H
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/*
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* BlockNumber:
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*
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* each data file (heap or index) is divided into postgres disk blocks
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* (which may be thought of as the unit of i/o -- a postgres buffer
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* contains exactly one disk block). the blocks are numbered
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* sequentially, 0 to 0xFFFFFFFE.
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*
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* InvalidBlockNumber is the same thing as P_NEW in bufmgr.h.
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*
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* the access methods, the buffer manager and the storage manager are
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* more or less the only pieces of code that should be accessing disk
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* blocks directly.
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*/
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typedef uint32 BlockNumber;
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#define InvalidBlockNumber ((BlockNumber) 0xFFFFFFFF)
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#define MaxBlockNumber ((BlockNumber) 0xFFFFFFFE)
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/*
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* BlockId:
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*
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* this is a storage type for BlockNumber. in other words, this type
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* is used for on-disk structures (e.g., in HeapTupleData) whereas
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* BlockNumber is the type on which calculations are performed (e.g.,
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* in access method code).
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*
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* there doesn't appear to be any reason to have separate types except
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* for the fact that BlockIds can be SHORTALIGN'd (and therefore any
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* structures that contains them, such as ItemPointerData, can also be
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* SHORTALIGN'd). this is an important consideration for reducing the
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* space requirements of the line pointer (ItemIdData) array on each
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* page and the header of each heap or index tuple, so it doesn't seem
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* wise to change this without good reason.
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*/
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typedef struct BlockIdData
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{
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uint16 bi_hi;
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uint16 bi_lo;
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} BlockIdData;
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typedef BlockIdData *BlockId; /* block identifier */
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/* ----------------
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* support macros
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* ----------------
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*/
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/*
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* BlockNumberIsValid
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* True iff blockNumber is valid.
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*/
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#define BlockNumberIsValid(blockNumber) \
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((BlockNumber) (blockNumber) != InvalidBlockNumber)
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/*
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* BlockIdIsValid
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* True iff the block identifier is valid.
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*/
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#define BlockIdIsValid(blockId) \
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PointerIsValid(blockId)
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/*
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* BlockIdSet
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* Sets a block identifier to the specified value.
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*/
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#define BlockIdSet(blockId, blockNumber) \
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( \
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(blockId)->bi_hi = (blockNumber) >> 16, \
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(blockId)->bi_lo = (blockNumber) & 0xffff \
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)
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/*
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* BlockIdCopy
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* Copy a block identifier.
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*/
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#define BlockIdCopy(toBlockId, fromBlockId) \
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( \
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(toBlockId)->bi_hi = (fromBlockId)->bi_hi, \
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(toBlockId)->bi_lo = (fromBlockId)->bi_lo \
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)
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/*
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* BlockIdEquals
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* Check for block number equality.
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*/
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#define BlockIdEquals(blockId1, blockId2) \
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((blockId1)->bi_hi == (blockId2)->bi_hi && \
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(blockId1)->bi_lo == (blockId2)->bi_lo)
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/*
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* BlockIdGetBlockNumber
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* Retrieve the block number from a block identifier.
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*/
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#define BlockIdGetBlockNumber(blockId) \
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((((BlockNumber) (blockId)->bi_hi) << 16) | ((BlockNumber) (blockId)->bi_lo))
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#endif /* BLOCK_H */
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