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/* hash.c -- hash table routines for BFD

   Copyright 1993, 1994, 1995, 1997, 1999, 2001, 2002, 2003, 2004, 2005,

   2006, 2007, 2009 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.

*/

/* 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 unsigned long

higher_prime_number (unsigned long n)

{

  /* These are primes that are near, but slightly smaller than, a

     power of two.  */

  static const unsigned long primes[] = {

    (unsigned long) 127,

    (unsigned long) 2039,

    (unsigned long) 32749,

    (unsigned long) 65521,

    (unsigned long) 131071,

    (unsigned long) 262139,

    (unsigned long) 524287,

    (unsigned long) 1048573,

    (unsigned long) 2097143,

    (unsigned long) 4194301,

    (unsigned long) 8388593,

    (unsigned long) 16777213,

    (unsigned long) 33554393,

    (unsigned long) 67108859,

    (unsigned long) 134217689,

    (unsigned long) 268435399,

    (unsigned long) 536870909,

    (unsigned long) 1073741789,

    (unsigned long) 2147483647,

                                        /* 4294967291L */

    ((unsigned long) 2147483647) + ((unsigned long) 2147483644),

  };

  const unsigned long *low = &primes[0];

  const unsigned long *high = &primes[sizeof (primes) / sizeof (primes[0])];

  while (low != high)

    {

      const unsigned long *mid = low + (high - low) / 2;

      if (n >= *mid)

        low = mid + 1;

      else

        high = mid;

    }

  if (n >= *low)

    return 0;

  return *low;

}

static size_t bfd_default_hash_table_size = DEFAULT_SIZE;

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

bfd_boolean

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 int alloc;

  alloc = size * sizeof (struct bfd_hash_entry *);

  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_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;

}

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

bfd_boolean

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);

}

/* Free a hash table.  */

void

bfd_hash_table_free (struct bfd_hash_table *table)

{

  objalloc_free ((struct objalloc *) table->memory);

  table->memory = NULL;

}

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

struct bfd_hash_entry *

bfd_hash_lookup (struct bfd_hash_table *table,

                 const char *string,

                 bfd_boolean create,

                 bfd_boolean copy)

{

  const unsigned char *s;

  unsigned long hash;

  unsigned int c;

  struct bfd_hash_entry *hashp;

  unsigned int len;

  unsigned int index;

  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;

  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);

}

/* 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 ((PTR) 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;

}

/* 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 ();

}

/* 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;

}

/* 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;

}

/* Traverse a hash table.  */

void

bfd_hash_traverse (struct bfd_hash_table *table,

                   bfd_boolean (*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;

}

void

bfd_hash_set_default_size (bfd_size_type hash_size)

{

  /* Extend this prime list if you want more granularity of hash table size.  */

  static const bfd_size_type hash_size_primes[] =

    {

      251, 509, 1021, 2039, 4051, 8599, 16699, 32749

    };

  size_t index;

  /* Work out best prime number near the hash_size.  */

  for (index = 0; index < ARRAY_SIZE (hash_size_primes) - 1; ++index)

    if (hash_size <= hash_size_primes[index])

      break;

  bfd_default_hash_table_size = hash_size_primes[index];

}

/* 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 byte length, as in the

     XCOFF .debug section.  */

  bfd_boolean xcoff;

};

/* 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)))

/* Create a new strtab.  */

struct bfd_strtab_hash *

_bfd_stringtab_init (void)

{

  struct bfd_strtab_hash *table;

  bfd_size_type 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->xcoff = FALSE;

  return table;

}

/* 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 (void)

{

  struct bfd_strtab_hash *ret;

  ret = _bfd_stringtab_init ();

  if (ret != NULL)

    ret->xcoff = TRUE;

  return ret;

}