86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* kwlookup.c
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* Key word lookup for PostgreSQL
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*
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*
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* Portions Copyright (c) 1996-2024, 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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*
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* IDENTIFICATION
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* src/common/kwlookup.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#include "common/kwlookup.h"
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/*
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* ScanKeywordLookup - see if a given word is a keyword
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*
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* The list of keywords to be matched against is passed as a ScanKeywordList.
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*
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* Returns the keyword number (0..N-1) of the keyword, or -1 if no match.
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* Callers typically use the keyword number to index into information
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* arrays, but that is no concern of this code.
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*
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* The match is done case-insensitively. Note that we deliberately use a
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* dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
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* even if we are in a locale where tolower() would produce more or different
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* translations. This is to conform to the SQL99 spec, which says that
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* keywords are to be matched in this way even though non-keyword identifiers
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* receive a different case-normalization mapping.
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*/
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int
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ScanKeywordLookup(const char *str,
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const ScanKeywordList *keywords)
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{
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size_t len;
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int h;
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const char *kw;
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/*
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* Reject immediately if too long to be any keyword. This saves useless
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* hashing and downcasing work on long strings.
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*/
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len = strlen(str);
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if (len > keywords->max_kw_len)
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return -1;
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/*
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* Compute the hash function. We assume it was generated to produce
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* case-insensitive results. Since it's a perfect hash, we need only
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* match to the specific keyword it identifies.
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*/
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h = keywords->hash(str, len);
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/* An out-of-range result implies no match */
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if (h < 0 || h >= keywords->num_keywords)
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return -1;
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/*
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* Compare character-by-character to see if we have a match, applying an
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* ASCII-only downcasing to the input characters. We must not use
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* tolower() since it may produce the wrong translation in some locales
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* (eg, Turkish).
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*/
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kw = GetScanKeyword(h, keywords);
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while (*str != '\0')
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{
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char ch = *str++;
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if (ch >= 'A' && ch <= 'Z')
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ch += 'a' - 'A';
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if (ch != *kw++)
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return -1;
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}
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if (*kw != '\0')
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return -1;
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/* Success! */
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return h;
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}
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