Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * kwlookup.c
4 : : * Key word lookup for PostgreSQL
5 : : *
6 : : *
7 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
8 : : * Portions Copyright (c) 1994, Regents of the University of California
9 : : *
10 : : *
11 : : * IDENTIFICATION
12 : : * src/common/kwlookup.c
13 : : *
14 : : *-------------------------------------------------------------------------
15 : : */
16 : : #include "c.h"
17 : :
18 : : #include "common/kwlookup.h"
19 : :
20 : :
21 : : /*
22 : : * ScanKeywordLookup - see if a given word is a keyword
23 : : *
24 : : * The list of keywords to be matched against is passed as a ScanKeywordList.
25 : : *
26 : : * Returns the keyword number (0..N-1) of the keyword, or -1 if no match.
27 : : * Callers typically use the keyword number to index into information
28 : : * arrays, but that is no concern of this code.
29 : : *
30 : : * The match is done case-insensitively. Note that we deliberately use a
31 : : * dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
32 : : * even if we are in a locale where tolower() would produce more or different
33 : : * translations. This is to conform to the SQL99 spec, which says that
34 : : * keywords are to be matched in this way even though non-keyword identifiers
35 : : * receive a different case-normalization mapping.
36 : : */
37 : : int
2622 tgl@sss.pgh.pa.us 38 :CBC 7661508 : ScanKeywordLookup(const char *str,
39 : : const ScanKeywordList *keywords)
40 : : {
41 : : size_t len;
42 : : int h;
43 : : const char *kw;
44 : :
45 : : /*
46 : : * Reject immediately if too long to be any keyword. This saves useless
47 : : * hashing and downcasing work on long strings.
48 : : */
49 : 7661508 : len = strlen(str);
2625 50 [ + + ]: 7661508 : if (len > keywords->max_kw_len)
2622 51 : 282245 : return -1;
52 : :
53 : : /*
54 : : * Compute the hash function. We assume it was generated to produce
55 : : * case-insensitive results. Since it's a perfect hash, we need only
56 : : * match to the specific keyword it identifies.
57 : : */
58 : 7379263 : h = keywords->hash(str, len);
59 : :
60 : : /* An out-of-range result implies no match */
61 [ + + + + ]: 7379263 : if (h < 0 || h >= keywords->num_keywords)
62 : 3571109 : return -1;
63 : :
64 : : /*
65 : : * Compare character-by-character to see if we have a match, applying an
66 : : * ASCII-only downcasing to the input characters. We must not use
67 : : * tolower() since it may produce the wrong translation in some locales
68 : : * (eg, Turkish).
69 : : */
70 : 3808154 : kw = GetScanKeyword(h, keywords);
71 [ + + ]: 17221633 : while (*str != '\0')
72 : : {
73 : 14251125 : char ch = *str++;
74 : :
75 [ + + + + ]: 14251125 : if (ch >= 'A' && ch <= 'Z')
76 : 9359069 : ch += 'a' - 'A';
77 [ + + ]: 14251125 : if (ch != *kw++)
78 : 837646 : return -1;
79 : : }
80 [ + + ]: 2970508 : if (*kw != '\0')
81 : 547 : return -1;
82 : :
83 : : /* Success! */
84 : 2969961 : return h;
85 : : }
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