path: root/gdb/dictionary.c

/* Routines for name->symbol lookups in GDB.
   
   Copyright (C) 2003-2018 Free Software Foundation, Inc.

   Contributed by David Carlton <carlton@bactrian.org> and by Kealia,
   Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include <ctype.h>
#include "gdb_obstack.h"
#include "symtab.h"
#include "buildsym.h"
#include "dictionary.h"
#include "safe-ctype.h"

/* This file implements dictionaries, which are tables that associate
   symbols to names.  They are represented by an opaque type 'struct
   dictionary'.  That type has various internal implementations, which
   you can choose between depending on what properties you need
   (e.g. fast lookup, order-preserving, expandable).

   Each dictionary starts with a 'virtual function table' that
   contains the functions that actually implement the various
   operations that dictionaries provide.  (Note, however, that, for
   the sake of client code, we also provide some functions that can be
   implemented generically in terms of the functions in the vtable.)

   To add a new dictionary implementation <impl>, what you should do
   is:

   * Add a new element DICT_<IMPL> to dict_type.
   
   * Create a new structure dictionary_<impl>.  If your new
   implementation is a variant of an existing one, make sure that
   their structs have the same initial data members.  Define accessor
   macros for your new data members.

   * Implement all the functions in dict_vector as static functions,
   whose name is the same as the corresponding member of dict_vector
   plus _<impl>.  You don't have to do this for those members where
   you can reuse existing generic functions
   (e.g. add_symbol_nonexpandable, free_obstack) or in the case where
   your new implementation is a variant of an existing implementation
   and where the variant doesn't affect the member function in
   question.

   * Define a static const struct dict_vector dict_<impl>_vector.

   * Define a function dict_create_<impl> to create these
   gizmos.  Add its declaration to dictionary.h.

   To add a new operation <op> on all existing implementations, what
   you should do is:

   * Add a new member <op> to struct dict_vector.

   * If there is useful generic behavior <op>, define a static
   function <op>_something_informative that implements that behavior.
   (E.g. add_symbol_nonexpandable, free_obstack.)

   * For every implementation <impl> that should have its own specific
   behavior for <op>, define a static function <op>_<impl>
   implementing it.

   * Modify all existing dict_vector_<impl>'s to include the appropriate
   member.

   * Define a function dict_<op> that looks up <op> in the dict_vector
   and calls the appropriate function.  Add a declaration for
   dict_<op> to dictionary.h.  */

/* An enum representing the various implementations of dictionaries.
   Used only for debugging.  */

enum dict_type
  {
    /* Symbols are stored in a fixed-size hash table.  */
    DICT_HASHED,
    /* Symbols are stored in an expandable hash table.  */
    DICT_HASHED_EXPANDABLE,
    /* Symbols are stored in a fixed-size array.  */
    DICT_LINEAR,
    /* Symbols are stored in an expandable array.  */
    DICT_LINEAR_EXPANDABLE
  };

/* The virtual function table.  */

struct dict_vector
{
  /* The type of the dictionary.  This is only here to make debugging
     a bit easier; it's not actually used.  */
  enum dict_type type;
  /* The function to free a dictionary.  */
  void (*free) (struct dictionary *dict);
  /* Add a symbol to a dictionary, if possible.  */
  void (*add_symbol) (struct dictionary *dict, struct symbol *sym);
  /* Iterator functions.  */
  struct symbol *(*iterator_first) (const struct dictionary *dict,
				    struct dict_iterator *iterator);
  struct symbol *(*iterator_next) (struct dict_iterator *iterator);
  /* Functions to iterate over symbols with a given name.  */
  struct symbol *(*iter_match_first) (const struct dictionary *dict,
				      const lookup_name_info &name,
				      struct dict_iterator *iterator);
  struct symbol *(*iter_match_next) (const lookup_name_info &name,
				     struct dict_iterator *iterator);
  /* A size function, for maint print symtabs.  */
  int (*size) (const struct dictionary *dict);
};

/* Now comes the structs used to store the data for different
   implementations.  If two implementations have data in common, put
   the common data at the top of their structs, ordered in the same
   way.  */

struct dictionary_hashed
{
  int nbuckets;
  struct symbol **buckets;
};

struct dictionary_hashed_expandable
{
  /* How many buckets we currently have.  */
  int nbuckets;
  struct symbol **buckets;
  /* How many syms we currently have; we need this so we will know
     when to add more buckets.  */
  int nsyms;
};

struct dictionary_linear
{
  int nsyms;
  struct symbol **syms;
};

struct dictionary_linear_expandable
{
  /* How many symbols we currently have.  */
  int nsyms;
  struct symbol **syms;
  /* How many symbols we can store before needing to reallocate.  */
  int capacity;
};

/* And now, the star of our show.  */

struct dictionary
{
  const struct language_defn *language;
  const struct dict_vector *vector;
  union
  {
    struct dictionary_hashed hashed;
    struct dictionary_hashed_expandable hashed_expandable;
    struct dictionary_linear linear;
    struct dictionary_linear_expandable linear_expandable;
  }
  data;
};

/* Accessor macros.  */

#define DICT_VECTOR(d)			(d)->vector
#define DICT_LANGUAGE(d)                (d)->language

/* These can be used for DICT_HASHED_EXPANDABLE, too.  */

#define DICT_HASHED_NBUCKETS(d)		(d)->data.hashed.nbuckets
#define DICT_HASHED_BUCKETS(d)		(d)->data.hashed.buckets
#define DICT_HASHED_BUCKET(d,i)		DICT_HASHED_BUCKETS (d) [i]

#define DICT_HASHED_EXPANDABLE_NSYMS(d)	(d)->data.hashed_expandable.nsyms

/* These can be used for DICT_LINEAR_EXPANDABLEs, too.  */

#define DICT_LINEAR_NSYMS(d)		(d)->data.linear.nsyms
#define DICT_LINEAR_SYMS(d)		(d)->data.linear.syms
#define DICT_LINEAR_SYM(d,i)		DICT_LINEAR_SYMS (d) [i]

#define DICT_LINEAR_EXPANDABLE_CAPACITY(d) \
		(d)->data.linear_expandable.capacity

/* The initial size of a DICT_*_EXPANDABLE dictionary.  */

#define DICT_EXPANDABLE_INITIAL_CAPACITY 10

/* This calculates the number of buckets we'll use in a hashtable,
   given the number of symbols that it will contain.  */

#define DICT_HASHTABLE_SIZE(n)	((n)/5 + 1)

/* Accessor macros for dict_iterators; they're here rather than
   dictionary.h because code elsewhere should treat dict_iterators as
   opaque.  */

/* The dictionary that the iterator is associated to.  */
#define DICT_ITERATOR_DICT(iter)		(iter)->dict
/* For linear dictionaries, the index of the last symbol returned; for
   hashed dictionaries, the bucket of the last symbol returned.  */
#define DICT_ITERATOR_INDEX(iter)		(iter)->index
/* For hashed dictionaries, this points to the last symbol returned;
   otherwise, this is unused.  */
#define DICT_ITERATOR_CURRENT(iter)		(iter)->current

/* Declarations of functions for vectors.  */

/* Functions that might work across a range of dictionary types.  */

static void add_symbol_nonexpandable (struct dictionary *dict,
				      struct symbol *sym);

static void free_obstack (struct dictionary *dict);

/* Functions for DICT_HASHED and DICT_HASHED_EXPANDABLE
   dictionaries.  */

static struct symbol *iterator_first_hashed (const struct dictionary *dict,
					     struct dict_iterator *iterator);

static struct symbol *iterator_next_hashed (struct dict_iterator *iterator);

static struct symbol *iter_match_first_hashed (const struct dictionary *dict,
					       const lookup_name_info &name,
					      struct dict_iterator *iterator);

static struct symbol *iter_match_next_hashed (const lookup_name_info &name,
					      struct dict_iterator *iterator);

/* Functions only for DICT_HASHED.  */

static int size_hashed (const struct dictionary *dict);

/* Functions only for DICT_HASHED_EXPANDABLE.  */

static void free_hashed_expandable (struct dictionary *dict);

static void add_symbol_hashed_expandable (struct dictionary *dict,
					  struct symbol *sym);

static int size_hashed_expandable (const struct dictionary *dict);

/* Functions for DICT_LINEAR and DICT_LINEAR_EXPANDABLE
   dictionaries.  */

static struct symbol *iterator_first_linear (const struct dictionary *dict,
					     struct dict_iterator *iterator);

static struct symbol *iterator_next_linear (struct dict_iterator *iterator);

static struct symbol *iter_match_first_linear (const struct dictionary *dict,
					       const lookup_name_info &name,
					       struct dict_iterator *iterator);

static struct symbol *iter_match_next_linear (const lookup_name_info &name,
					      struct dict_iterator *iterator);

static int size_linear (const struct dictionary *dict);

/* Functions only for DICT_LINEAR_EXPANDABLE.  */

static void free_linear_expandable (struct dictionary *dict);

static void add_symbol_linear_expandable (struct dictionary *dict,
					  struct symbol *sym);

/* Various vectors that we'll actually use.  */

static const struct dict_vector dict_hashed_vector =
  {
    DICT_HASHED,			/* type */
    free_obstack,			/* free */
    add_symbol_nonexpandable,		/* add_symbol */
    iterator_first_hashed,		/* iterator_first */
    iterator_next_hashed,		/* iterator_next */
    iter_match_first_hashed,		/* iter_name_first */
    iter_match_next_hashed,		/* iter_name_next */
    size_hashed,			/* size */
  };

static const struct dict_vector dict_hashed_expandable_vector =
  {
    DICT_HASHED_EXPANDABLE,		/* type */
    free_hashed_expandable,		/* free */
    add_symbol_hashed_expandable,	/* add_symbol */
    iterator_first_hashed,		/* iterator_first */
    iterator_next_hashed,		/* iterator_next */
    iter_match_first_hashed,		/* iter_name_first */
    iter_match_next_hashed,		/* iter_name_next */
    size_hashed_expandable,		/* size */
  };

static const struct dict_vector dict_linear_vector =
  {
    DICT_LINEAR,			/* type */
    free_obstack,			/* free */
    add_symbol_nonexpandable,		/* add_symbol */
    iterator_first_linear,		/* iterator_first */
    iterator_next_linear,		/* iterator_next */
    iter_match_first_linear,		/* iter_name_first */
    iter_match_next_linear,		/* iter_name_next */
    size_linear,			/* size */
  };

static const struct dict_vector dict_linear_expandable_vector =
  {
    DICT_LINEAR_EXPANDABLE,		/* type */
    free_linear_expandable,		/* free */
    add_symbol_linear_expandable,	/* add_symbol */
    iterator_first_linear,		/* iterator_first */
    iterator_next_linear,		/* iterator_next */
    iter_match_first_linear,		/* iter_name_first */
    iter_match_next_linear,		/* iter_name_next */
    size_linear,			/* size */
  };

/* Declarations of helper functions (i.e. ones that don't go into
   vectors).  */

static struct symbol *iterator_hashed_advance (struct dict_iterator *iter);

static void insert_symbol_hashed (struct dictionary *dict,
				  struct symbol *sym);

static void expand_hashtable (struct dictionary *dict);

/* The creation functions.  */

/* See dictionary.h.  */

struct dictionary *
dict_create_hashed (struct obstack *obstack,
		    enum language language,
		    const struct pending *symbol_list)
{
  struct dictionary *retval;
  int nsyms = 0, nbuckets, i;
  struct symbol **buckets;
  const struct pending *list_counter;

  retval = XOBNEW (obstack, struct dictionary);
  DICT_VECTOR (retval) = &dict_hashed_vector;
  DICT_LANGUAGE (retval) = language_def (language);

  /* Calculate the number of symbols, and allocate space for them.  */
  for (list_counter = symbol_list;
       list_counter != NULL;
       list_counter = list_counter->next)
    {
      nsyms += list_counter->nsyms;
    }
  nbuckets = DICT_HASHTABLE_SIZE (nsyms);
  DICT_HASHED_NBUCKETS (retval) = nbuckets;
  buckets = XOBNEWVEC (obstack, struct symbol *, nbuckets);
  memset (buckets, 0, nbuckets * sizeof (struct symbol *));
  DICT_HASHED_BUCKETS (retval) = buckets;

  /* Now fill the buckets.  */
  for (list_counter = symbol_list;
       list_counter != NULL;
       list_counter = list_counter->next)
    {
      for (i = list_counter->nsyms - 1; i >= 0; --i)
	{
	  insert_symbol_hashed (retval, list_counter->symbol[i]);
	}
    }

  return retval;
}

/* See dictionary.h.  */

extern struct dictionary *
dict_create_hashed_expandable (enum language language)
{
  struct dictionary *retval = XNEW (struct dictionary);

  DICT_VECTOR (retval) = &dict_hashed_expandable_vector;
  DICT_LANGUAGE (retval) = language_def (language);
  DICT_HASHED_NBUCKETS (retval) = DICT_EXPANDABLE_INITIAL_CAPACITY;
  DICT_HASHED_BUCKETS (retval) = XCNEWVEC (struct symbol *,
					   DICT_EXPANDABLE_INITIAL_CAPACITY);
  DICT_HASHED_EXPANDABLE_NSYMS (retval) = 0;

  return retval;
}

/* See dictionary.h.  */

struct dictionary *
dict_create_linear (struct obstack *obstack,
		    enum language language,
		    const struct pending *symbol_list)
{
  struct dictionary *retval;
  int nsyms = 0, i, j;
  struct symbol **syms;
  const struct pending *list_counter;

  retval = XOBNEW (obstack, struct dictionary);
  DICT_VECTOR (retval) = &dict_linear_vector;
  DICT_LANGUAGE (retval) = language_def (language);

  /* Calculate the number of symbols, and allocate space for them.  */
  for (list_counter = symbol_list;
       list_counter != NULL;
       list_counter = list_counter->next)
    {
      nsyms += list_counter->nsyms;
    }
  DICT_LINEAR_NSYMS (retval) = nsyms;
  syms = XOBNEWVEC (obstack, struct symbol *, nsyms );
  DICT_LINEAR_SYMS (retval) = syms;

  /* Now fill in the symbols.  Start filling in from the back, so as
     to preserve the original order of the symbols.  */
  for (list_counter = symbol_list, j = nsyms - 1;
       list_counter != NULL;
       list_counter = list_counter->next)
    {
      for (i = list_counter->nsyms - 1;
	   i >= 0;
	   --i, --j)
	{
	  syms[j] = list_counter->symbol[i];
	}
    }

  return retval;
}

/* See dictionary.h.  */

struct dictionary *
dict_create_linear_expandable (enum language language)
{
  struct dictionary *retval = XNEW (struct dictionary);

  DICT_VECTOR (retval) = &dict_linear_expandable_vector;
  DICT_LANGUAGE (retval) = language_def (language);
  DICT_LINEAR_NSYMS (retval) = 0;
  DICT_LINEAR_EXPANDABLE_CAPACITY (retval) = DICT_EXPANDABLE_INITIAL_CAPACITY;
  DICT_LINEAR_SYMS (retval)
    = XNEWVEC (struct symbol *, DICT_LINEAR_EXPANDABLE_CAPACITY (retval));

  return retval;
}

/* The functions providing the dictionary interface.  */

/* Free the memory used by a dictionary that's not on an obstack.  (If
   any.)  */

void
dict_free (struct dictionary *dict)
{
  (DICT_VECTOR (dict))->free (dict);
}

/* Add SYM to DICT.  DICT had better be expandable.  */

void
dict_add_symbol (struct dictionary *dict, struct symbol *sym)
{
  (DICT_VECTOR (dict))->add_symbol (dict, sym);
}

/* Utility to add a list of symbols to a dictionary.
   DICT must be an expandable dictionary.  */

void
dict_add_pending (struct dictionary *dict, const struct pending *symbol_list)
{
  const struct pending *list;
  int i;

  for (list = symbol_list; list != NULL; list = list->next)
    {
      for (i = 0; i < list->nsyms; ++i)
	dict_add_symbol (dict, list->symbol[i]);
    }
}

/* Initialize ITERATOR to point at the first symbol in DICT, and
   return that first symbol, or NULL if DICT is empty.  */

struct symbol *
dict_iterator_first (const struct dictionary *dict,
		     struct dict_iterator *iterator)
{
  return (DICT_VECTOR (dict))->iterator_first (dict, iterator);
}

/* Advance ITERATOR, and return the next symbol, or NULL if there are
   no more symbols.  */

struct symbol *
dict_iterator_next (struct dict_iterator *iterator)
{
  return (DICT_VECTOR (DICT_ITERATOR_DICT (iterator)))
    ->iterator_next (iterator);
}

struct symbol *
dict_iter_match_first (const struct dictionary *dict,
		       const lookup_name_info &name,
		       struct dict_iterator *iterator)
{
  return (DICT_VECTOR (dict))->iter_match_first (dict, name, iterator);
}

struct symbol *
dict_iter_match_next (const lookup_name_info &name,
		      struct dict_iterator *iterator)
{
  return (DICT_VECTOR (DICT_ITERATOR_DICT (iterator)))
    ->iter_match_next (name, iterator);
}

int
dict_size (const struct dictionary *dict)
{
  return (DICT_VECTOR (dict))->size (dict);
}
 
/* Now come functions (well, one function, currently) that are
   implemented generically by means of the vtable.  Typically, they're
   rarely used.  */

/* Test to see if DICT is empty.  */

int
dict_empty (struct dictionary *dict)
{
  struct dict_iterator iter;

  return (dict_iterator_first (dict, &iter) == NULL);
}


/* The functions implementing the dictionary interface.  */

/* Generic functions, where appropriate.  */

static void
free_obstack (struct dictionary *dict)
{
  /* Do nothing!  */
}

static void
add_symbol_nonexpandable (struct dictionary *dict, struct symbol *sym)
{
  internal_error (__FILE__, __LINE__,
		  _("dict_add_symbol: non-expandable dictionary"));
}

/* Functions for DICT_HASHED and DICT_HASHED_EXPANDABLE.  */

static struct symbol *
iterator_first_hashed (const struct dictionary *dict,
		       struct dict_iterator *iterator)
{
  DICT_ITERATOR_DICT (iterator) = dict;
  DICT_ITERATOR_INDEX (iterator) = -1;
  return iterator_hashed_advance (iterator);
}

static struct symbol *
iterator_next_hashed (struct dict_iterator *iterator)
{
  struct symbol *next;

  next = DICT_ITERATOR_CURRENT (iterator)->hash_next;
  
  if (next == NULL)
    return iterator_hashed_advance (iterator);
  else
    {
      DICT_ITERATOR_CURRENT (iterator) = next;
      return next;
    }
}

static struct symbol *
iterator_hashed_advance (struct dict_iterator *iterator)
{
  const struct dictionary *dict = DICT_ITERATOR_DICT (iterator);
  int nbuckets = DICT_HASHED_NBUCKETS (dict);
  int i;

  for (i = DICT_ITERATOR_INDEX (iterator) + 1; i < nbuckets; ++i)
    {
      struct symbol *sym = DICT_HASHED_BUCKET (dict, i);
      
      if (sym != NULL)
	{
	  DICT_ITERATOR_INDEX (iterator) = i;
	  DICT_ITERATOR_CURRENT (iterator) = sym;
	  return sym;
	}
    }

  return NULL;
}

static struct symbol *
iter_match_first_hashed (const struct dictionary *dict,
			 const lookup_name_info &name,
			 struct dict_iterator *iterator)
{
  const language_defn *lang = DICT_LANGUAGE (dict);
  unsigned int hash_index = (name.search_name_hash (lang->la_language)
			     % DICT_HASHED_NBUCKETS (dict));
  symbol_name_matcher_ftype *matches_name
    = language_get_symbol_name_matcher (lang, name);
  struct symbol *sym;

  DICT_ITERATOR_DICT (iterator) = dict;

  /* Loop through the symbols in the given bucket, breaking when SYM
     first matches.  If SYM never matches, it will be set to NULL;
     either way, we have the right return value.  */
  
  for (sym = DICT_HASHED_BUCKET (dict, hash_index);
       sym != NULL;
       sym = sym->hash_next)
    {
      /* Warning: the order of arguments to compare matters!  */
      if (matches_name (SYMBOL_SEARCH_NAME (sym), name, NULL))
	break;
    }

  DICT_ITERATOR_CURRENT (iterator) = sym;
  return sym;
}

static struct symbol *
iter_match_next_hashed (const lookup_name_info &name,
			struct dict_iterator *iterator)
{
  const language_defn *lang = DICT_LANGUAGE (DICT_ITERATOR_DICT (iterator));
  symbol_name_matcher_ftype *matches_name
    = language_get_symbol_name_matcher (lang, name);
  struct symbol *next;

  for (next = DICT_ITERATOR_CURRENT (iterator)->hash_next;
       next != NULL;
       next = next->hash_next)
    {
      if (matches_name (SYMBOL_SEARCH_NAME (next), name, NULL))
	break;
    }

  DICT_ITERATOR_CURRENT (iterator) = next;

  return next;
}

/* Insert SYM into DICT.  */

static void
insert_symbol_hashed (struct dictionary *dict,
		      struct symbol *sym)
{
  unsigned int hash_index;
  unsigned int hash;
  struct symbol **buckets = DICT_HASHED_BUCKETS (dict);

  /* We don't want to insert a symbol into a dictionary of a different
     language.  The two may not use the same hashing algorithm.  */
  gdb_assert (SYMBOL_LANGUAGE (sym) == DICT_LANGUAGE (dict)->la_language);

  hash = search_name_hash (SYMBOL_LANGUAGE (sym), SYMBOL_SEARCH_NAME (sym));
  hash_index = hash % DICT_HASHED_NBUCKETS (dict);
  sym->hash_next = buckets[hash_index];
  buckets[hash_index] = sym;
}

static int
size_hashed (const struct dictionary *dict)
{
  return DICT_HASHED_NBUCKETS (dict);
}

/* Functions only for DICT_HASHED_EXPANDABLE.  */

static void
free_hashed_expandable (struct dictionary *dict)
{
  xfree (DICT_HASHED_BUCKETS (dict));
  xfree (dict);
}

static void
add_symbol_hashed_expandable (struct dictionary *dict,
			      struct symbol *sym)
{
  int nsyms = ++DICT_HASHED_EXPANDABLE_NSYMS (dict);

  if (DICT_HASHTABLE_SIZE (nsyms) > DICT_HASHED_NBUCKETS (dict))
    expand_hashtable (dict);

  insert_symbol_hashed (dict, sym);
  DICT_HASHED_EXPANDABLE_NSYMS (dict) = nsyms;
}

static int
size_hashed_expandable (const struct dictionary *dict)
{
  return DICT_HASHED_EXPANDABLE_NSYMS (dict);
}

static void
expand_hashtable (struct dictionary *dict)
{
  int old_nbuckets = DICT_HASHED_NBUCKETS (dict);
  struct symbol **old_buckets = DICT_HASHED_BUCKETS (dict);
  int new_nbuckets = 2 * old_nbuckets + 1;
  struct symbol **new_buckets = XCNEWVEC (struct symbol *, new_nbuckets);
  int i;

  DICT_HASHED_NBUCKETS (dict) = new_nbuckets;
  DICT_HASHED_BUCKETS (dict) = new_buckets;

  for (i = 0; i < old_nbuckets; ++i)
    {
      struct symbol *sym, *next_sym;

      sym = old_buckets[i];
      if (sym != NULL) 
	{
	  for (next_sym = sym->hash_next;
	       next_sym != NULL;
	       next_sym = sym->hash_next)
	    {
	      insert_symbol_hashed (dict, sym);
	      sym = next_sym;
	    }

	  insert_symbol_hashed (dict, sym);
	}
    }

  xfree (old_buckets);
}

/* See dictionary.h.  */

unsigned int
default_search_name_hash (const char *string0)
{
  /* The Ada-encoded version of a name P1.P2...Pn has either the form
     P1__P2__...Pn<suffix> or _ada_P1__P2__...Pn<suffix> (where the Pi
     are lower-cased identifiers).  The <suffix> (which can be empty)
     encodes additional information about the denoted entity.  This
     routine hashes such names to msymbol_hash_iw(Pn).  It actually
     does this for a superset of both valid Pi and of <suffix>, but 
     in other cases it simply returns msymbol_hash_iw(STRING0).  */

  const char *string;
  unsigned int hash;

  string = string0;
  if (*string == '_')
    {
      if (startswith (string, "_ada_"))
	string += 5;
      else
	return msymbol_hash_iw (string0);
    }

  hash = 0;
  while (*string)
    {
      switch (*string)
	{
	case '$':
	case '.':
	case 'X':
	  if (string0 == string)
	    return msymbol_hash_iw (string0);
	  else
	    return hash;
	case ' ':
	case '(':
	  return msymbol_hash_iw (string0);
	case '_':
	  if (string[1] == '_' && string != string0)
	    {
	      int c = string[2];

	      if ((c < 'a' || c > 'z') && c != 'O')
		return hash;
	      hash = 0;
	      string += 2;
	      continue;
	    }
	  break;
	case 'T':
	  /* Ignore "TKB" suffixes.

	     These are used by Ada for subprograms implementing a task body.
	     For instance for a task T inside package Pck, the name of the
	     subprogram implementing T's body is `pck__tTKB'.  We need to
	     ignore the "TKB" suffix because searches for this task body
	     subprogram are going to be performed using `pck__t' (the encoded
	     version of the natural name `pck.t').  */
	  if (strcmp (string, "TKB") == 0)
	    return hash;
	  break;
	}

      hash = SYMBOL_HASH_NEXT (hash, *string);
      string += 1;
    }
  return hash;
}

/* Functions for DICT_LINEAR and DICT_LINEAR_EXPANDABLE.  */

static struct symbol *
iterator_first_linear (const struct dictionary *dict,
		       struct dict_iterator *iterator)
{
  DICT_ITERATOR_DICT (iterator) = dict;
  DICT_ITERATOR_INDEX (iterator) = 0;
  return DICT_LINEAR_NSYMS (dict) ? DICT_LINEAR_SYM (dict, 0) : NULL;
}

static struct symbol *
iterator_next_linear (struct dict_iterator *iterator)
{
  const struct dictionary *dict = DICT_ITERATOR_DICT (iterator);

  if (++DICT_ITERATOR_INDEX (iterator) >= DICT_LINEAR_NSYMS (dict))
    return NULL;
  else
    return DICT_LINEAR_SYM (dict, DICT_ITERATOR_INDEX (iterator));
}

static struct symbol *
iter_match_first_linear (const struct dictionary *dict,
			 const lookup_name_info &name,
			 struct dict_iterator *iterator)
{
  DICT_ITERATOR_DICT (iterator) = dict;
  DICT_ITERATOR_INDEX (iterator) = -1;

  return iter_match_next_linear (name, iterator);
}

static struct symbol *
iter_match_next_linear (const lookup_name_info &name,
			struct dict_iterator *iterator)
{
  const struct dictionary *dict = DICT_ITERATOR_DICT (iterator);
  const language_defn *lang = DICT_LANGUAGE (dict);
  symbol_name_matcher_ftype *matches_name
    = language_get_symbol_name_matcher (lang, name);

  int i, nsyms = DICT_LINEAR_NSYMS (dict);
  struct symbol *sym, *retval = NULL;

  for (i = DICT_ITERATOR_INDEX (iterator) + 1; i < nsyms; ++i)
    {
      sym = DICT_LINEAR_SYM (dict, i);

      if (matches_name (SYMBOL_SEARCH_NAME (sym), name, NULL))
	{
	  retval = sym;
	  break;
	}
    }

  DICT_ITERATOR_INDEX (iterator) = i;
  
  return retval;
}

static int
size_linear (const struct dictionary *dict)
{
  return DICT_LINEAR_NSYMS (dict);
}

/* Functions only for DICT_LINEAR_EXPANDABLE.  */

static void
free_linear_expandable (struct dictionary *dict)
{
  xfree (DICT_LINEAR_SYMS (dict));
  xfree (dict);
}


static void
add_symbol_linear_expandable (struct dictionary *dict,
			      struct symbol *sym)
{
  int nsyms = ++DICT_LINEAR_NSYMS (dict);

  /* Do we have enough room?  If not, grow it.  */
  if (nsyms > DICT_LINEAR_EXPANDABLE_CAPACITY (dict))
    {
      DICT_LINEAR_EXPANDABLE_CAPACITY (dict) *= 2;
      DICT_LINEAR_SYMS (dict)
	= XRESIZEVEC (struct symbol *, DICT_LINEAR_SYMS (dict),
		      DICT_LINEAR_EXPANDABLE_CAPACITY (dict));
    }

  DICT_LINEAR_SYM (dict, nsyms - 1) = sym;
}