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keywords.c
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1 /*-------------------------------------------------------------------------
2  *
3  * keywords.c
4  * lexical token lookup for key words in PostgreSQL
5  *
6  *
7  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  *
11  * IDENTIFICATION
12  * src/common/keywords.c
13  *
14  *-------------------------------------------------------------------------
15  */
16 #ifndef FRONTEND
17 #include "postgres.h"
18 #else
19 #include "postgres_fe.h"
20 #endif
21 
22 #ifndef FRONTEND
23 
24 #include "parser/gramparse.h"
25 
26 #define PG_KEYWORD(a,b,c) {a,b,c},
27 
28 #else
29 
30 #include "common/keywords.h"
31 
32 /*
33  * We don't need the token number for frontend uses, so leave it out to avoid
34  * requiring backend headers that won't compile cleanly here.
35  */
36 #define PG_KEYWORD(a,b,c) {a,0,c},
37 
38 #endif /* FRONTEND */
39 
40 
42 #include "parser/kwlist.h"
43 };
44 
45 const int NumScanKeywords = lengthof(ScanKeywords);
46 
47 
48 /*
49  * ScanKeywordLookup - see if a given word is a keyword
50  *
51  * The table to be searched is passed explicitly, so that this can be used
52  * to search keyword lists other than the standard list appearing above.
53  *
54  * Returns a pointer to the ScanKeyword table entry, or NULL if no match.
55  *
56  * The match is done case-insensitively. Note that we deliberately use a
57  * dumbed-down case conversion that will only translate 'A'-'Z' into 'a'-'z',
58  * even if we are in a locale where tolower() would produce more or different
59  * translations. This is to conform to the SQL99 spec, which says that
60  * keywords are to be matched in this way even though non-keyword identifiers
61  * receive a different case-normalization mapping.
62  */
63 const ScanKeyword *
64 ScanKeywordLookup(const char *text,
65  const ScanKeyword *keywords,
66  int num_keywords)
67 {
68  int len,
69  i;
70  char word[NAMEDATALEN];
71  const ScanKeyword *low;
72  const ScanKeyword *high;
73 
74  len = strlen(text);
75  /* We assume all keywords are shorter than NAMEDATALEN. */
76  if (len >= NAMEDATALEN)
77  return NULL;
78 
79  /*
80  * Apply an ASCII-only downcasing. We must not use tolower() since it may
81  * produce the wrong translation in some locales (eg, Turkish).
82  */
83  for (i = 0; i < len; i++)
84  {
85  char ch = text[i];
86 
87  if (ch >= 'A' && ch <= 'Z')
88  ch += 'a' - 'A';
89  word[i] = ch;
90  }
91  word[len] = '\0';
92 
93  /*
94  * Now do a binary search using plain strcmp() comparison.
95  */
96  low = keywords;
97  high = keywords + (num_keywords - 1);
98  while (low <= high)
99  {
100  const ScanKeyword *middle;
101  int difference;
102 
103  middle = low + (high - low) / 2;
104  difference = strcmp(middle->name, word);
105  if (difference == 0)
106  return middle;
107  else if (difference < 0)
108  low = middle + 1;
109  else
110  high = middle - 1;
111  }
112 
113  return NULL;
114 }
const ScanKeyword * ScanKeywordLookup(const char *text, const ScanKeyword *keywords, int num_keywords)
Definition: keywords.c:64
const int NumScanKeywords
Definition: keywords.c:45
#define lengthof(array)
Definition: c.h:562
#define NAMEDATALEN
const ScanKeyword ScanKeywords[]
Definition: keywords.c:41
const char * name
Definition: keywords.h:26
Datum difference(PG_FUNCTION_ARGS)
#define NULL
Definition: c.h:229
static void word(struct vars *, int, struct state *, struct state *)
Definition: regcomp.c:1243
int i
Definition: c.h:439