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c7b8998ebb
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4d wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
108 lines
3.4 KiB
C
108 lines
3.4 KiB
C
/*
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* pg_crc.h
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*
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* PostgreSQL CRC support
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*
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* See Ross Williams' excellent introduction
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* A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
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* http://www.ross.net/crc/ or several other net sites.
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*
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* We have three slightly different variants of a 32-bit CRC calculation:
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* CRC-32C (Castagnoli polynomial), CRC-32 (Ethernet polynomial), and a legacy
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* CRC-32 version that uses the lookup table in a funny way. They all consist
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* of four macros:
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*
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* INIT_<variant>(crc)
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* Initialize a CRC accumulator
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*
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* COMP_<variant>(crc, data, len)
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* Accumulate some (more) bytes into a CRC
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*
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* FIN_<variant>(crc)
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* Finish a CRC calculation
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*
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* EQ_<variant>(c1, c2)
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* Check for equality of two CRCs.
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*
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* The CRC-32C variant is in port/pg_crc32c.h.
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*
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* Portions Copyright (c) 1996-2017, 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/utils/pg_crc.h
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*/
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#ifndef PG_CRC_H
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#define PG_CRC_H
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typedef uint32 pg_crc32;
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/*
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* CRC-32, the same used e.g. in Ethernet.
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*
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* This is currently only used in ltree and hstore contrib modules. It uses
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* the same lookup table as the legacy algorithm below. New code should
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* use the Castagnoli version instead.
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*/
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#define INIT_TRADITIONAL_CRC32(crc) ((crc) = 0xFFFFFFFF)
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#define FIN_TRADITIONAL_CRC32(crc) ((crc) ^= 0xFFFFFFFF)
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#define COMP_TRADITIONAL_CRC32(crc, data, len) \
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COMP_CRC32_NORMAL_TABLE(crc, data, len, pg_crc32_table)
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#define EQ_TRADITIONAL_CRC32(c1, c2) ((c1) == (c2))
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/* Sarwate's algorithm, for use with a "normal" lookup table */
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#define COMP_CRC32_NORMAL_TABLE(crc, data, len, table) \
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do { \
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const unsigned char *__data = (const unsigned char *) (data); \
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uint32 __len = (len); \
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\
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while (__len-- > 0) \
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{ \
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int __tab_index = ((int) (crc) ^ *__data++) & 0xFF; \
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(crc) = table[__tab_index] ^ ((crc) >> 8); \
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} \
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} while (0)
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/*
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* The CRC algorithm used for WAL et al in pre-9.5 versions.
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*
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* This closely resembles the normal CRC-32 algorithm, but is subtly
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* different. Using Williams' terms, we use the "normal" table, but with
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* "reflected" code. That's bogus, but it was like that for years before
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* anyone noticed. It does not correspond to any polynomial in a normal CRC
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* algorithm, so it's not clear what the error-detection properties of this
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* algorithm actually are.
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*
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* We still need to carry this around because it is used in a few on-disk
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* structures that need to be pg_upgradeable. It should not be used in new
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* code.
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*/
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#define INIT_LEGACY_CRC32(crc) ((crc) = 0xFFFFFFFF)
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#define FIN_LEGACY_CRC32(crc) ((crc) ^= 0xFFFFFFFF)
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#define COMP_LEGACY_CRC32(crc, data, len) \
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COMP_CRC32_REFLECTED_TABLE(crc, data, len, pg_crc32_table)
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#define EQ_LEGACY_CRC32(c1, c2) ((c1) == (c2))
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/*
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* Sarwate's algorithm, for use with a "reflected" lookup table (but in the
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* legacy algorithm, we actually use it on a "normal" table, see above)
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*/
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#define COMP_CRC32_REFLECTED_TABLE(crc, data, len, table) \
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do { \
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const unsigned char *__data = (const unsigned char *) (data); \
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uint32 __len = (len); \
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\
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while (__len-- > 0) \
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{ \
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int __tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \
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(crc) = table[__tab_index] ^ ((crc) << 8); \
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} \
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} while (0)
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/*
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* Constant table for the CRC-32 polynomials. The same table is used by both
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* the normal and traditional variants.
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*/
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extern PGDLLIMPORT const uint32 pg_crc32_table[256];
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#endif /* PG_CRC_H */
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