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[binutils-gdb.git] / bfd / hash.c

/* hash.c -- hash table routines for BFD
   Copyright (C) 1993-2024 Free Software Foundation, Inc.
   Written by Steve Chamberlain <sac@cygnus.com>

   This file is part of BFD, the Binary File Descriptor library.

   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, write to the Free Software
   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
   MA 02110-1301, USA.  */

#include "sysdep.h"
#include "bfd.h"
#include "libbfd.h"
#include "objalloc.h"
#include "libiberty.h"

/*
SECTION
        Hash Tables

@cindex Hash tables
        BFD provides a simple set of hash table functions.  Routines
        are provided to initialize a hash table, to free a hash table,
        to look up a string in a hash table and optionally create an
        entry for it, and to traverse a hash table.  There is
        currently no routine to delete an string from a hash table.

        The basic hash table does not permit any data to be stored
        with a string.  However, a hash table is designed to present a
        base class from which other types of hash tables may be
        derived.  These derived types may store additional information
        with the string.  Hash tables were implemented in this way,
        rather than simply providing a data pointer in a hash table
        entry, because they were designed for use by the linker back
        ends.  The linker may create thousands of hash table entries,
        and the overhead of allocating private data and storing and
        following pointers becomes noticeable.

        The basic hash table code is in <<hash.c>>.

@menu
@* Creating and Freeing a Hash Table::
@* Looking Up or Entering a String::
@* Traversing a Hash Table::
@* Deriving a New Hash Table Type::
@end menu

INODE
Creating and Freeing a Hash Table, Looking Up or Entering a String, Hash Tables, Hash Tables
SUBSECTION
        Creating and freeing a hash table

@findex bfd_hash_table_init
@findex bfd_hash_table_init_n
        To create a hash table, create an instance of a <<struct
        bfd_hash_table>> (defined in <<bfd.h>>) and call
        <<bfd_hash_table_init>> (if you know approximately how many
        entries you will need, the function <<bfd_hash_table_init_n>>,
        which takes a @var{size} argument, may be used).
        <<bfd_hash_table_init>> returns <<FALSE>> if some sort of
        error occurs.

@findex bfd_hash_newfunc
        The function <<bfd_hash_table_init>> take as an argument a
        function to use to create new entries.  For a basic hash
        table, use the function <<bfd_hash_newfunc>>.  @xref{Deriving
        a New Hash Table Type}, for why you would want to use a
        different value for this argument.

@findex bfd_hash_allocate
        <<bfd_hash_table_init>> will create an objalloc which will be
        used to allocate new entries.  You may allocate memory on this
        objalloc using <<bfd_hash_allocate>>.

@findex bfd_hash_table_free
        Use <<bfd_hash_table_free>> to free up all the memory that has
        been allocated for a hash table.  This will not free up the
        <<struct bfd_hash_table>> itself, which you must provide.

@findex bfd_hash_set_default_size
        Use <<bfd_hash_set_default_size>> to set the default size of
        hash table to use.

INODE
Looking Up or Entering a String, Traversing a Hash Table, Creating and Freeing a Hash Table, Hash Tables
SUBSECTION
        Looking up or entering a string

@findex bfd_hash_lookup
        The function <<bfd_hash_lookup>> is used both to look up a
        string in the hash table and to create a new entry.

        If the @var{create} argument is <<FALSE>>, <<bfd_hash_lookup>>
        will look up a string.  If the string is found, it will
        returns a pointer to a <<struct bfd_hash_entry>>.  If the
        string is not found in the table <<bfd_hash_lookup>> will
        return <<NULL>>.  You should not modify any of the fields in
        the returns <<struct bfd_hash_entry>>.

        If the @var{create} argument is <<TRUE>>, the string will be
        entered into the hash table if it is not already there.
        Either way a pointer to a <<struct bfd_hash_entry>> will be
        returned, either to the existing structure or to a newly
        created one.  In this case, a <<NULL>> return means that an
        error occurred.

        If the @var{create} argument is <<TRUE>>, and a new entry is
        created, the @var{copy} argument is used to decide whether to
        copy the string onto the hash table objalloc or not.  If
        @var{copy} is passed as <<FALSE>>, you must be careful not to
        deallocate or modify the string as long as the hash table
        exists.

INODE
Traversing a Hash Table, Deriving a New Hash Table Type, Looking Up or Entering a String, Hash Tables
SUBSECTION
        Traversing a hash table

@findex bfd_hash_traverse
        The function <<bfd_hash_traverse>> may be used to traverse a
        hash table, calling a function on each element.  The traversal
        is done in a random order.

        <<bfd_hash_traverse>> takes as arguments a function and a
        generic <<void *>> pointer.  The function is called with a
        hash table entry (a <<struct bfd_hash_entry *>>) and the
        generic pointer passed to <<bfd_hash_traverse>>.  The function
        must return a <<boolean>> value, which indicates whether to
        continue traversing the hash table.  If the function returns
        <<FALSE>>, <<bfd_hash_traverse>> will stop the traversal and
        return immediately.

INODE
Deriving a New Hash Table Type, , Traversing a Hash Table, Hash Tables
SUBSECTION
        Deriving a new hash table type

        Many uses of hash tables want to store additional information
        which each entry in the hash table.  Some also find it
        convenient to store additional information with the hash table
        itself.  This may be done using a derived hash table.

        Since C is not an object oriented language, creating a derived
        hash table requires sticking together some boilerplate
        routines with a few differences specific to the type of hash
        table you want to create.

        An example of a derived hash table is the linker hash table.
        The structures for this are defined in <<bfdlink.h>>.  The
        functions are in <<linker.c>>.

        You may also derive a hash table from an already derived hash
        table.  For example, the a.out linker backend code uses a hash
        table derived from the linker hash table.

@menu
@* Define the Derived Structures::
@* Write the Derived Creation Routine::
@* Write Other Derived Routines::
@end menu

INODE
Define the Derived Structures, Write the Derived Creation Routine, Deriving a New Hash Table Type, Deriving a New Hash Table Type
SUBSUBSECTION
        Define the derived structures

        You must define a structure for an entry in the hash table,
        and a structure for the hash table itself.

        The first field in the structure for an entry in the hash
        table must be of the type used for an entry in the hash table
        you are deriving from.  If you are deriving from a basic hash
        table this is <<struct bfd_hash_entry>>, which is defined in
        <<bfd.h>>.  The first field in the structure for the hash
        table itself must be of the type of the hash table you are
        deriving from itself.  If you are deriving from a basic hash
        table, this is <<struct bfd_hash_table>>.

        For example, the linker hash table defines <<struct
        bfd_link_hash_entry>> (in <<bfdlink.h>>).  The first field,
        <<root>>, is of type <<struct bfd_hash_entry>>.  Similarly,
        the first field in <<struct bfd_link_hash_table>>, <<table>>,
        is of type <<struct bfd_hash_table>>.

INODE
Write the Derived Creation Routine, Write Other Derived Routines, Define the Derived Structures, Deriving a New Hash Table Type
SUBSUBSECTION
        Write the derived creation routine

        You must write a routine which will create and initialize an
        entry in the hash table.  This routine is passed as the
        function argument to <<bfd_hash_table_init>>.

        In order to permit other hash tables to be derived from the
        hash table you are creating, this routine must be written in a
        standard way.

        The first argument to the creation routine is a pointer to a
        hash table entry.  This may be <<NULL>>, in which case the
        routine should allocate the right amount of space.  Otherwise
        the space has already been allocated by a hash table type
        derived from this one.

        After allocating space, the creation routine must call the
        creation routine of the hash table type it is derived from,
        passing in a pointer to the space it just allocated.  This
        will initialize any fields used by the base hash table.

        Finally the creation routine must initialize any local fields
        for the new hash table type.

        Here is a boilerplate example of a creation routine.
        @var{function_name} is the name of the routine.
        @var{entry_type} is the type of an entry in the hash table you
        are creating.  @var{base_newfunc} is the name of the creation
        routine of the hash table type your hash table is derived
        from.

EXAMPLE

.struct bfd_hash_entry *
.@var{function_name} (struct bfd_hash_entry *entry,
.                     struct bfd_hash_table *table,
.                     const char *string)
.{
.  struct @var{entry_type} *ret = (@var{entry_type} *) entry;
.
. {* Allocate the structure if it has not already been allocated by a
.    derived class.  *}
.  if (ret == NULL)
.    {
.      ret = bfd_hash_allocate (table, sizeof (* ret));
.      if (ret == NULL)
.        return NULL;
.    }
.
. {* Call the allocation method of the base class.  *}
.  ret = ((@var{entry_type} *)
.         @var{base_newfunc} ((struct bfd_hash_entry *) ret, table, string));
.
. {* Initialize the local fields here.  *}
.
.  return (struct bfd_hash_entry *) ret;
.}

DESCRIPTION
        The creation routine for the linker hash table, which is in
        <<linker.c>>, looks just like this example.
        @var{function_name} is <<_bfd_link_hash_newfunc>>.
        @var{entry_type} is <<struct bfd_link_hash_entry>>.
        @var{base_newfunc} is <<bfd_hash_newfunc>>, the creation
        routine for a basic hash table.

        <<_bfd_link_hash_newfunc>> also initializes the local fields
        in a linker hash table entry: <<type>>, <<written>> and
        <<next>>.

INODE
Write Other Derived Routines, , Write the Derived Creation Routine, Deriving a New Hash Table Type
SUBSUBSECTION
        Write other derived routines

        You will want to write other routines for your new hash table,
        as well.

        You will want an initialization routine which calls the
        initialization routine of the hash table you are deriving from
        and initializes any other local fields.  For the linker hash
        table, this is <<_bfd_link_hash_table_init>> in <<linker.c>>.

        You will want a lookup routine which calls the lookup routine
        of the hash table you are deriving from and casts the result.
        The linker hash table uses <<bfd_link_hash_lookup>> in
        <<linker.c>> (this actually takes an additional argument which
        it uses to decide how to return the looked up value).

        You may want a traversal routine.  This should just call the
        traversal routine of the hash table you are deriving from with
        appropriate casts.  The linker hash table uses
        <<bfd_link_hash_traverse>> in <<linker.c>>.

        These routines may simply be defined as macros.  For example,
        the a.out backend linker hash table, which is derived from the
        linker hash table, uses macros for the lookup and traversal
        routines.  These are <<aout_link_hash_lookup>> and
        <<aout_link_hash_traverse>> in aoutx.h.

EXTERNAL
.{* An element in the hash table.  Most uses will actually use a larger
.   structure, and an instance of this will be the first field.  *}
.
.struct bfd_hash_entry
.{
.  {* Next entry for this hash code.  *}
.  struct bfd_hash_entry *next;
.  {* String being hashed.  *}
.  const char *string;
.  {* Hash code.  This is the full hash code, not the index into the
.     table.  *}
.  unsigned long hash;
.};
.
.{* A hash table.  *}
.
.struct bfd_hash_table
.{
.  {* The hash array.  *}
.  struct bfd_hash_entry **table;
.  {* A function used to create new elements in the hash table.  The
.     first entry is itself a pointer to an element.  When this
.     function is first invoked, this pointer will be NULL.  However,
.     having the pointer permits a hierarchy of method functions to be
.     built each of which calls the function in the superclass.  Thus
.     each function should be written to allocate a new block of memory
.     only if the argument is NULL.  *}
.  struct bfd_hash_entry *(*newfunc)
.    (struct bfd_hash_entry *, struct bfd_hash_table *, const char *);
.  {* An objalloc for this hash table.  This is a struct objalloc *,
.     but we use void * to avoid requiring the inclusion of objalloc.h.  *}
.  void *memory;
.  {* The number of slots in the hash table.  *}
.  unsigned int size;
.  {* The number of entries in the hash table.  *}
.  unsigned int count;
.  {* The size of elements.  *}
.  unsigned int entsize;
.  {* If non-zero, don't grow the hash table.  *}
.  unsigned int frozen:1;
.};
.
*/

/* The default number of entries to use when creating a hash table.  */
#define DEFAULT_SIZE 4051

/* The following function returns a nearest prime number which is
   greater than N, and near a power of two.  Copied from libiberty.
   Returns zero for ridiculously large N to signify an error.  */

static uint32_t
higher_prime_number (uint32_t n)
{
  /* These are primes that are near, but slightly smaller than, a
     power of two.  */
  static const uint32_t primes[] =
    {
      UINT32_C (31),
      UINT32_C (61),
      UINT32_C (127),
      UINT32_C (251),
      UINT32_C (509),
      UINT32_C (1021),
      UINT32_C (2039),
      UINT32_C (4093),
      UINT32_C (8191),
      UINT32_C (16381),
      UINT32_C (32749),
      UINT32_C (65521),
      UINT32_C (131071),
      UINT32_C (262139),
      UINT32_C (524287),
      UINT32_C (1048573),
      UINT32_C (2097143),
      UINT32_C (4194301),
      UINT32_C (8388593),
      UINT32_C (16777213),
      UINT32_C (33554393),
      UINT32_C (67108859),
      UINT32_C (134217689),
      UINT32_C (268435399),
      UINT32_C (536870909),
      UINT32_C (1073741789),
      UINT32_C (2147483647),
      UINT32_C (4294967291)
  };

  const uint32_t *low = &primes[0];
  const uint32_t *high = &primes[sizeof (primes) / sizeof (primes[0])];

  while (low != high)
    {
      const uint32_t *mid = low + (high - low) / 2;
      if (n >= *mid)
        low = mid + 1;
      else
        high = mid;
    }

  if (n >= *low)
    return 0;

  return *low;
}

static unsigned int bfd_default_hash_table_size = DEFAULT_SIZE;

/*
FUNCTION
        bfd_hash_table_init_n

SYNOPSIS
        bool bfd_hash_table_init_n
          (struct bfd_hash_table *,
           struct bfd_hash_entry *(* {*newfunc*})
             (struct bfd_hash_entry *, struct bfd_hash_table *, const char *),
           unsigned int {*entsize*}, unsigned int {*size*});

DESCRIPTION
        Create a new hash table, given a number of entries.
*/

bool
bfd_hash_table_init_n (struct bfd_hash_table *table,
                       struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,
                                                          struct bfd_hash_table *,
                                                          const char *),
                       unsigned int entsize,
                       unsigned int size)
{
  unsigned long alloc;

  alloc = size;
  alloc *= sizeof (struct bfd_hash_entry *);
  if (alloc / sizeof (struct bfd_hash_entry *) != size)
    {
      bfd_set_error (bfd_error_no_memory);
      return false;
    }

  table->memory = (void *) objalloc_create ();
  if (table->memory == NULL)
    {
      bfd_set_error (bfd_error_no_memory);
      return false;
    }
  table->table = (struct bfd_hash_entry **)
      objalloc_alloc ((struct objalloc *) table->memory, alloc);
  if (table->table == NULL)
    {
      bfd_hash_table_free (table);
      bfd_set_error (bfd_error_no_memory);
      return false;
    }
  memset ((void *) table->table, 0, alloc);
  table->size = size;
  table->entsize = entsize;
  table->count = 0;
  table->frozen = 0;
  table->newfunc = newfunc;
  return true;
}

/*
FUNCTION
        bfd_hash_table_init

SYNOPSIS
        bool bfd_hash_table_init
          (struct bfd_hash_table *,
           struct bfd_hash_entry *(* {*newfunc*})
             (struct bfd_hash_entry *, struct bfd_hash_table *, const char *),
           unsigned int {*entsize*});

DESCRIPTION
        Create a new hash table with the default number of entries.
*/

bool
bfd_hash_table_init (struct bfd_hash_table *table,
                     struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,
                                                        struct bfd_hash_table *,
                                                        const char *),
                     unsigned int entsize)
{
  return bfd_hash_table_init_n (table, newfunc, entsize,
                                bfd_default_hash_table_size);
}

/*
FUNCTION
        bfd_hash_table_free

SYNOPSIS
        void bfd_hash_table_free (struct bfd_hash_table *);

DESCRIPTION
        Free a hash table.
*/

void
bfd_hash_table_free (struct bfd_hash_table *table)
{
  objalloc_free ((struct objalloc *) table->memory);
  table->memory = NULL;
}

static inline unsigned long
bfd_hash_hash (const char *string, unsigned int *lenp)
{
  const unsigned char *s;
  unsigned long hash;
  unsigned int len;
  unsigned int c;

  BFD_ASSERT (string != NULL);
  hash = 0;
  len = 0;
  s = (const unsigned char *) string;
  while ((c = *s++) != '\0')
    {
      hash += c + (c << 17);
      hash ^= hash >> 2;
    }
  len = (s - (const unsigned char *) string) - 1;
  hash += len + (len << 17);
  hash ^= hash >> 2;
  if (lenp != NULL)
    *lenp = len;
  return hash;
}

/*
FUNCTION
        bfd_hash_lookup

SYNOPSIS
        struct bfd_hash_entry *bfd_hash_lookup
          (struct bfd_hash_table *, const char *,
           bool {*create*}, bool {*copy*});

DESCRIPTION
        Look up a string in a hash table.
*/

struct bfd_hash_entry *
bfd_hash_lookup (struct bfd_hash_table *table,
                 const char *string,
                 bool create,
                 bool copy)
{
  unsigned long hash;
  struct bfd_hash_entry *hashp;
  unsigned int len;
  unsigned int _index;

  hash = bfd_hash_hash (string, &len);
  _index = hash % table->size;
  for (hashp = table->table[_index];
       hashp != NULL;
       hashp = hashp->next)
    {
      if (hashp->hash == hash
          && strcmp (hashp->string, string) == 0)
        return hashp;
    }

  if (! create)
    return NULL;

  if (copy)
    {
      char *new_string;

      new_string = (char *) objalloc_alloc ((struct objalloc *) table->memory,
                                            len + 1);
      if (!new_string)
        {
          bfd_set_error (bfd_error_no_memory);
          return NULL;
        }
      memcpy (new_string, string, len + 1);
      string = new_string;
    }

  return bfd_hash_insert (table, string, hash);
}

/*
FUNCTION
        bfd_hash_insert

SYNOPSIS
        struct bfd_hash_entry *bfd_hash_insert
          (struct bfd_hash_table *,
           const char *,
           unsigned long {*hash*});

DESCRIPTION
        Insert an entry in a hash table.
*/

struct bfd_hash_entry *
bfd_hash_insert (struct bfd_hash_table *table,
                 const char *string,
                 unsigned long hash)
{
  struct bfd_hash_entry *hashp;
  unsigned int _index;

  hashp = (*table->newfunc) (NULL, table, string);
  if (hashp == NULL)
    return NULL;
  hashp->string = string;
  hashp->hash = hash;
  _index = hash % table->size;
  hashp->next = table->table[_index];
  table->table[_index] = hashp;
  table->count++;

  if (!table->frozen && table->count > table->size * 3 / 4)
    {
      unsigned long newsize = higher_prime_number (table->size);
      struct bfd_hash_entry **newtable;
      unsigned int hi;
      unsigned long alloc = newsize * sizeof (struct bfd_hash_entry *);

      /* If we can't find a higher prime, or we can't possibly alloc
         that much memory, don't try to grow the table.  */
      if (newsize == 0 || alloc / sizeof (struct bfd_hash_entry *) != newsize)
        {
          table->frozen = 1;
          return hashp;
        }

      newtable = ((struct bfd_hash_entry **)
                  objalloc_alloc ((struct objalloc *) table->memory, alloc));
      if (newtable == NULL)
        {
          table->frozen = 1;
          return hashp;
        }
      memset (newtable, 0, alloc);

      for (hi = 0; hi < table->size; hi ++)
        while (table->table[hi])
          {
            struct bfd_hash_entry *chain = table->table[hi];
            struct bfd_hash_entry *chain_end = chain;

            while (chain_end->next && chain_end->next->hash == chain->hash)
              chain_end = chain_end->next;

            table->table[hi] = chain_end->next;
            _index = chain->hash % newsize;
            chain_end->next = newtable[_index];
            newtable[_index] = chain;
          }
      table->table = newtable;
      table->size = newsize;
    }

  return hashp;
}

/*
FUNCTION
        bfd_hash_rename

SYNOPSIS
        void bfd_hash_rename (struct bfd_hash_table *,
                              const char *,
                              struct bfd_hash_entry *);

DESCRIPTION
        Rename an entry in a hash table.
*/

void
bfd_hash_rename (struct bfd_hash_table *table,
                 const char *string,
                 struct bfd_hash_entry *ent)
{
  unsigned int _index;
  struct bfd_hash_entry **pph;

  _index = ent->hash % table->size;
  for (pph = &table->table[_index]; *pph != NULL; pph = &(*pph)->next)
    if (*pph == ent)
      break;
  if (*pph == NULL)
    abort ();

  *pph = ent->next;
  ent->string = string;
  ent->hash = bfd_hash_hash (string, NULL);
  _index = ent->hash % table->size;
  ent->next = table->table[_index];
  table->table[_index] = ent;
}

/*
FUNCTION
        bfd_hash_replace

SYNOPSIS
        void bfd_hash_replace (struct bfd_hash_table *,
                               struct bfd_hash_entry * {*old*},
                               struct bfd_hash_entry * {*new*});

DESCRIPTION
        Replace an entry in a hash table.
*/

void
bfd_hash_replace (struct bfd_hash_table *table,
                  struct bfd_hash_entry *old,
                  struct bfd_hash_entry *nw)
{
  unsigned int _index;
  struct bfd_hash_entry **pph;

  _index = old->hash % table->size;
  for (pph = &table->table[_index];
       (*pph) != NULL;
       pph = &(*pph)->next)
    {
      if (*pph == old)
        {
          *pph = nw;
          return;
        }
    }

  abort ();
}

/*
FUNCTION
        bfd_hash_allocate

SYNOPSIS
        void *bfd_hash_allocate (struct bfd_hash_table *,
                                 unsigned int {*size*});

DESCRIPTION
        Allocate space in a hash table.
*/

void *
bfd_hash_allocate (struct bfd_hash_table *table,
                   unsigned int size)
{
  void * ret;

  ret = objalloc_alloc ((struct objalloc *) table->memory, size);
  if (ret == NULL && size != 0)
    bfd_set_error (bfd_error_no_memory);
  return ret;
}

/*
FUNCTION
        bfd_hash_newfunc

SYNOPSIS
        struct bfd_hash_entry *bfd_hash_newfunc
          (struct bfd_hash_entry *,
           struct bfd_hash_table *,
           const char *);

DESCRIPTION
        Base method for creating a new hash table entry.
*/

struct bfd_hash_entry *
bfd_hash_newfunc (struct bfd_hash_entry *entry,
                  struct bfd_hash_table *table,
                  const char *string ATTRIBUTE_UNUSED)
{
  if (entry == NULL)
    entry = (struct bfd_hash_entry *) bfd_hash_allocate (table,
                                                         sizeof (* entry));
  return entry;
}

/*
FUNCTION
        bfd_hash_traverse

SYNOPSIS
        void bfd_hash_traverse
          (struct bfd_hash_table *,
           bool (*) (struct bfd_hash_entry *, void *),
           void *);

DESCRIPTION
        Traverse a hash table.
*/

void
bfd_hash_traverse (struct bfd_hash_table *table,
                   bool (*func) (struct bfd_hash_entry *, void *),
                   void *info)
{
  unsigned int i;

  table->frozen = 1;
  for (i = 0; i < table->size; i++)
    {
      struct bfd_hash_entry *p;

      for (p = table->table[i]; p != NULL; p = p->next)
        if (! (*func) (p, info))
          goto out;
    }
 out:
  table->frozen = 0;
}

/*
FUNCTION
        bfd_hash_set_default_size

SYNOPSIS
        unsigned int bfd_hash_set_default_size (unsigned int);

DESCRIPTION
        Set hash table default size.
*/

unsigned int
bfd_hash_set_default_size (unsigned int hash_size)
{
  /* These silly_size values result in around 1G and 32M of memory
     being allocated for the table of pointers.  Note that the number
     of elements allocated will be almost twice the size of any power
     of two chosen here.  */
  unsigned int silly_size = sizeof (size_t) > 4 ? 0x4000000 : 0x400000;
  if (hash_size > silly_size)
    hash_size = silly_size;
  else if (hash_size != 0)
    hash_size--;
  hash_size = higher_prime_number (hash_size);
  BFD_ASSERT (hash_size != 0);
  bfd_default_hash_table_size = hash_size;
  return bfd_default_hash_table_size;
}
\f
/* A few different object file formats (a.out, COFF, ELF) use a string
   table.  These functions support adding strings to a string table,
   returning the byte offset, and writing out the table.

   Possible improvements:
   + look for strings matching trailing substrings of other strings
   + better data structures?  balanced trees?
   + look at reducing memory use elsewhere -- maybe if we didn't have
     to construct the entire symbol table at once, we could get by
     with smaller amounts of VM?  (What effect does that have on the
     string table reductions?)  */

/* An entry in the strtab hash table.  */

struct strtab_hash_entry
{
  struct bfd_hash_entry root;
  /* Index in string table.  */
  bfd_size_type index;
  /* Next string in strtab.  */
  struct strtab_hash_entry *next;
};

/* The strtab hash table.  */

struct bfd_strtab_hash
{
  struct bfd_hash_table table;
  /* Size of strtab--also next available index.  */
  bfd_size_type size;
  /* First string in strtab.  */
  struct strtab_hash_entry *first;
  /* Last string in strtab.  */
  struct strtab_hash_entry *last;
  /* Whether to precede strings with a two or four byte length,
     as in the XCOFF .debug section.  */
  char length_field_size;
};


/* Routine to create an entry in a strtab.  */

static struct bfd_hash_entry *
strtab_hash_newfunc (struct bfd_hash_entry *entry,
                     struct bfd_hash_table *table,
                     const char *string)
{
  struct strtab_hash_entry *ret = (struct strtab_hash_entry *) entry;

  /* Allocate the structure if it has not already been allocated by a
     subclass.  */
  if (ret == NULL)
    ret = (struct strtab_hash_entry *) bfd_hash_allocate (table,
                                                          sizeof (* ret));
  if (ret == NULL)
    return NULL;

  /* Call the allocation method of the superclass.  */
  ret = (struct strtab_hash_entry *)
         bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string);

  if (ret)
    {
      /* Initialize the local fields.  */
      ret->index = (bfd_size_type) -1;
      ret->next = NULL;
    }

  return (struct bfd_hash_entry *) ret;
}

/* Look up an entry in an strtab.  */

#define strtab_hash_lookup(t, string, create, copy) \
  ((struct strtab_hash_entry *) \
   bfd_hash_lookup (&(t)->table, (string), (create), (copy)))

/*
INTERNAL_FUNCTION
        _bfd_stringtab_init

SYNOPSIS
        struct bfd_strtab_hash *_bfd_stringtab_init (void);

DESCRIPTION
        Create a new strtab.
*/

struct bfd_strtab_hash *
_bfd_stringtab_init (void)
{
  struct bfd_strtab_hash *table;
  size_t amt = sizeof (* table);

  table = (struct bfd_strtab_hash *) bfd_malloc (amt);
  if (table == NULL)
    return NULL;

  if (!bfd_hash_table_init (&table->table, strtab_hash_newfunc,
                            sizeof (struct strtab_hash_entry)))
    {
      free (table);
      return NULL;
    }

  table->size = 0;
  table->first = NULL;
  table->last = NULL;
  table->length_field_size = 0;

  return table;
}

/*
INTERNAL_FUNCTION
        _bfd_xcoff_stringtab_init

SYNOPSIS
        struct bfd_strtab_hash *_bfd_xcoff_stringtab_init
          (bool {*isxcoff64*});

DESCRIPTION
        Create a new strtab in which the strings are output in the format
        used in the XCOFF .debug section: a two byte length precedes each
        string.
*/

struct bfd_strtab_hash *
_bfd_xcoff_stringtab_init (bool isxcoff64)
{
  struct bfd_strtab_hash *ret;

  ret = _bfd_stringtab_init ();
  if (ret != NULL)
    ret->length_field_size = isxcoff64 ? 4 : 2;
  return ret;
}

/*
INTERNAL_FUNCTION
        _bfd_stringtab_free

SYNOPSIS
        void _bfd_stringtab_free (struct bfd_strtab_hash *);

DESCRIPTION
        Free a strtab.
*/

void
_bfd_stringtab_free (struct bfd_strtab_hash *table)
{
  bfd_hash_table_free (&table->table);
  free (table);
}

/*
INTERNAL_FUNCTION
        _bfd_stringtab_add

SYNOPSIS
        bfd_size_type _bfd_stringtab_add
          (struct bfd_strtab_hash *, const char *,
           bool {*hash*}, bool {*copy*});

DESCRIPTION
        Get the index of a string in a strtab, adding it if it is not
        already present.  If HASH is FALSE, we don't really use the hash
        table, and we don't eliminate duplicate strings.  If COPY is true
        then store a copy of STR if creating a new entry.
*/

bfd_size_type
_bfd_stringtab_add (struct bfd_strtab_hash *tab,
                    const char *str,
                    bool hash,
                    bool copy)
{
  struct strtab_hash_entry *entry;

  if (hash)
    {
      entry = strtab_hash_lookup (tab, str, true, copy);
      if (entry == NULL)
        return (bfd_size_type) -1;
    }
  else
    {
      entry = (struct strtab_hash_entry *) bfd_hash_allocate (&tab->table,
                                                              sizeof (* entry));
      if (entry == NULL)
        return (bfd_size_type) -1;
      if (! copy)
        entry->root.string = str;
      else
        {
          size_t len = strlen (str) + 1;
          char *n;

          n = (char *) bfd_hash_allocate (&tab->table, len);
          if (n == NULL)
            return (bfd_size_type) -1;
          memcpy (n, str, len);
          entry->root.string = n;
        }
      entry->index = (bfd_size_type) -1;
      entry->next = NULL;
    }

  if (entry->index == (bfd_size_type) -1)
    {
      entry->index = tab->size;
      tab->size += strlen (str) + 1;
      entry->index += tab->length_field_size;
      tab->size += tab->length_field_size;
      if (tab->first == NULL)
        tab->first = entry;
      else
        tab->last->next = entry;
      tab->last = entry;
    }

  return entry->index;
}

/*
INTERNAL_FUNCTION
        _bfd_stringtab_size

SYNOPSIS
        bfd_size_type _bfd_stringtab_size (struct bfd_strtab_hash *);

DESCRIPTION
        Get the number of bytes in a strtab.
*/

bfd_size_type
_bfd_stringtab_size (struct bfd_strtab_hash *tab)
{
  return tab->size;
}

/*
INTERNAL_FUNCTION
        _bfd_stringtab_emit

SYNOPSIS
        bool _bfd_stringtab_emit (bfd *, struct bfd_strtab_hash *);

DESCRIPTION
        Write out a strtab.  ABFD must already be at the right location in
        the file.
*/

bool
_bfd_stringtab_emit (bfd *abfd, struct bfd_strtab_hash *tab)
{
  struct strtab_hash_entry *entry;

  for (entry = tab->first; entry != NULL; entry = entry->next)
    {
      const char *str;
      size_t len;

      str = entry->root.string;
      len = strlen (str) + 1;

      if (tab->length_field_size == 4)
        {
          bfd_byte buf[4];

          /* The output length includes the null byte.  */
          bfd_put_32 (abfd, len, buf);
          if (bfd_write (buf, 4, abfd) != 4)
            return false;
        }
      else if (tab->length_field_size == 2)
        {
          bfd_byte buf[2];

          /* The output length includes the null byte.  */
          bfd_put_16 (abfd, len, buf);
          if (bfd_write (buf, 2, abfd) != 2)
            return false;
        }

      if (bfd_write (str, len, abfd) != len)
        return false;
    }

  return true;
}