stringpool.c revision 90075 
1/* String pool for GCC.
2   Copyright (C) 2000, 2001 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 2, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING.  If not, write to the Free
18Software Foundation, 59 Temple Place - Suite 330, Boston, MA
1902111-1307, USA.  */
20
21/* String text, identifier text and identifier node allocator.  Strings
22   allocated by ggc_alloc_string are stored in an obstack which is
23   never shrunk.  Identifiers are uniquely stored in a hash table.
24
25   We have our own private hash table implementation.  libiberty's
26   hashtab.c is not used because it requires 100% average space
27   overhead per string, which is unacceptable.  Also, this algorithm
28   is faster.  */
29
30#include "config.h"
31#include "system.h"
32#include "ggc.h"
33#include "tree.h"
34#include "hashtable.h"
35
36/* The "" allocated string.  */
37const char empty_string[] = "";
38
39/* Character strings, each containing a single decimal digit.
40   Written this way to save space.  */
41const char digit_vector[] = {
42  '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
43  '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
44};
45
46struct ht *ident_hash;
47static struct obstack string_stack;
48
49static hashnode alloc_node PARAMS ((hash_table *));
50static int mark_ident PARAMS ((struct cpp_reader *, hashnode, const PTR));
51static void mark_ident_hash PARAMS ((void *));
52
53/* Initialize the string pool.  */
54void
55init_stringpool ()
56{
57  /* Create with 16K (2^14) entries.  */
58  ident_hash = ht_create (14);
59  ident_hash->alloc_node = alloc_node;
60  gcc_obstack_init (&string_stack);
61  ggc_add_root (&ident_hash, 1, sizeof ident_hash, mark_ident_hash);
62}
63
64/* Allocate a hash node.  */
65static hashnode
66alloc_node (table)
67     hash_table *table ATTRIBUTE_UNUSED;
68{
69  return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
70}
71
72/* Allocate and return a string constant of length LENGTH, containing
73   CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
74   nul-terminated string, and the length is calculated using strlen.
75   If the same string constant has been allocated before, that copy is
76   returned this time too.  */
77
78const char *
79ggc_alloc_string (contents, length)
80     const char *contents;
81     int length;
82{
83  if (length == -1)
84    length = strlen (contents);
85
86  if (length == 0)
87    return empty_string;
88  if (length == 1 && ISDIGIT (contents[0]))
89    return digit_string (contents[0] - '0');
90
91  obstack_grow0 (&string_stack, contents, length);
92  return obstack_finish (&string_stack);
93}
94
95/* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
96   If an identifier with that name has previously been referred to,
97   the same node is returned this time.  */
98
99tree
100get_identifier (text)
101     const char *text;
102{
103  hashnode ht_node = ht_lookup (ident_hash,
104				(const unsigned char *) text,
105				strlen (text), HT_ALLOC);
106
107  /* ht_node can't be NULL here.  */
108  return HT_IDENT_TO_GCC_IDENT (ht_node);
109}
110
111/* Identical to get_identifier, except that the length is assumed
112   known.  */
113
114tree
115get_identifier_with_length (text, length)
116     const char *text;
117     unsigned int length;
118{
119  hashnode ht_node = ht_lookup (ident_hash,
120				(const unsigned char *) text,
121				length, HT_ALLOC);
122
123  /* ht_node can't be NULL here.  */
124  return HT_IDENT_TO_GCC_IDENT (ht_node);
125}
126
127/* If an identifier with the name TEXT (a null-terminated string) has
128   previously been referred to, return that node; otherwise return
129   NULL_TREE.  */
130
131tree
132maybe_get_identifier (text)
133     const char *text;
134{
135  hashnode ht_node;
136
137  ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
138		       strlen (text), HT_NO_INSERT);
139  if (ht_node)
140    return HT_IDENT_TO_GCC_IDENT (ht_node);
141
142  return NULL_TREE;
143}
144
145/* Report some basic statistics about the string pool.  */
146
147void
148stringpool_statistics ()
149{
150  ht_dump_statistics (ident_hash);
151}
152
153/* Mark an identifier for GC.  */
154
155static int
156mark_ident (pfile, h, v)
157     struct cpp_reader *pfile ATTRIBUTE_UNUSED;
158     hashnode h;
159     const PTR v ATTRIBUTE_UNUSED;
160{
161  ggc_mark_nonnull_tree (HT_IDENT_TO_GCC_IDENT (h));
162  return 1;
163}
164
165/* Mark all identifiers for GC.  */
166
167static void
168mark_ident_hash (arg)
169     PTR arg ATTRIBUTE_UNUSED;
170{
171  ht_forall (ident_hash, mark_ident, NULL);
172}
173