dwarf_getabbrev.c revision 441f72d43a9b550baa779fc82f70816da5f74f0e 
1/* Get abbreviation at given offset.
2   Copyright (C) 2003, 2004 Red Hat, Inc.
3   Written by Ulrich Drepper <drepper@redhat.com>, 2003.
4
5   This program is Open Source software; you can redistribute it and/or
6   modify it under the terms of the Open Software License version 1.0 as
7   published by the Open Source Initiative.
8
9   You should have received a copy of the Open Software License along
10   with this program; if not, you may obtain a copy of the Open Software
11   License version 1.0 from http://www.opensource.org/licenses/osl.php or
12   by writing the Open Source Initiative c/o Lawrence Rosen, Esq.,
13   3001 King Ranch Road, Ukiah, CA 95482.   */
14
15#ifdef HAVE_CONFIG_H
16# include <config.h>
17#endif
18
19#include <assert.h>
20#include <dwarf.h>
21#include "libdwP.h"
22
23
24Dwarf_Abbrev *
25internal_function_def
26__libdw_getabbrev (dbg, cu, offset, lengthp, result)
27     Dwarf *dbg;
28     struct Dwarf_CU *cu;
29     Dwarf_Off offset;
30     size_t *lengthp;
31     Dwarf_Abbrev *result;
32{
33  /* Don't fail if there is not .debug_abbrev section.  */
34  if (dbg->sectiondata[IDX_debug_abbrev] == NULL)
35    return NULL;
36
37  unsigned char *abbrevp
38    = (unsigned char *) dbg->sectiondata[IDX_debug_abbrev]->d_buf + offset;
39  if (*abbrevp == '\0')
40    /* We are past the last entry.  */
41    return NULL;
42
43  /* 7.5.3 Abbreviations Tables
44
45     [...] Each declaration begins with an unsigned LEB128 number
46     representing the abbreviation code itself.  [...]  The
47     abbreviation code is followed by another unsigned LEB128
48     number that encodes the entry's tag.  [...]
49
50     [...] Following the tag encoding is a 1-byte value that
51     determines whether a debugging information entry using this
52     abbreviation has child entries or not. [...]
53
54     [...] Finally, the child encoding is followed by a series of
55     attribute specifications. Each attribute specification
56     consists of two parts. The first part is an unsigned LEB128
57     number representing the attribute's name. The second part is
58     an unsigned LEB128 number representing the attribute's form.  */
59  unsigned char *start_abbrevp = abbrevp;
60  unsigned int code;
61  get_uleb128 (code, abbrevp);
62
63  /* Check whether this code is already in the hash table.  */
64  bool foundit = false;
65  Dwarf_Abbrev *abb = NULL;
66  if (cu == NULL
67      || (abb = Dwarf_Abbrev_Hash_find (&cu->abbrev_hash, code, NULL)) == NULL)
68    {
69      if (result == NULL)
70	abb = libdw_typed_alloc (dbg, Dwarf_Abbrev);
71      else
72	abb = result;
73    }
74  else
75    {
76      foundit = true;
77
78      assert (abb->offset == offset);
79
80      /* If the caller doesn't need the length we are done.  */
81      if (lengthp == NULL)
82	goto out;
83    }
84
85  /* If there is already a value in the hash table we are going to
86     overwrite its content.  This must not be a problem, since the
87     content better be the same.  */
88  abb->code = code;
89  get_uleb128 (abb->tag, abbrevp);
90  abb->has_children = *abbrevp++ == DW_CHILDREN_yes;
91  abb->attrp = abbrevp;
92  abb->offset = offset;
93
94  /* Skip over all the attributes and count them while doing so.  */
95  abb->attrcnt = 0;
96  unsigned int attrname;
97  unsigned int attrform;
98  do
99    {
100      get_uleb128 (attrname, abbrevp);
101      get_uleb128 (attrform, abbrevp);
102    }
103  while (attrname != 0 && attrform != 0 && ++abb->attrcnt);
104
105  /* Return the length to the caller if she asked for it.  */
106  if (lengthp != NULL)
107    *lengthp = abbrevp - start_abbrevp;
108
109  /* Add the entry to the hash table.  */
110  if (cu != NULL && ! foundit)
111    (void) Dwarf_Abbrev_Hash_insert (&cu->abbrev_hash, abb->code, abb);
112
113 out:
114  return abb;
115}
116
117
118Dwarf_Abbrev *
119dwarf_getabbrev (die, offset, lengthp)
120     Dwarf_Die *die;
121     Dwarf_Off offset;
122     size_t *lengthp;
123{
124  return __libdw_getabbrev (die->cu->dbg, die->cu,
125			    die->cu->orig_abbrev_offset + offset, lengthp,
126			    NULL);
127}
128