bfd/hash.c

   1 /* hash.c -- hash table routines for BFD
   2    Copyright 1993, 1994, 1995, 1997, 1999, 2001, 2002, 2003, 2004, 2005,
   3    2006, 2007 Free Software Foundation, Inc.
   4    Written by Steve Chamberlain <sac@cygnus.com>
   5
   6    This file is part of BFD, the Binary File Descriptor library.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21    MA 02110-1301, USA.  */
  22
  23 #include "sysdep.h"
  24 #include "bfd.h"
  25 #include "libbfd.h"
  26 #include "objalloc.h"
  27 #include "libiberty.h"
  28
  29 /*
  30 SECTION
  31         Hash Tables
  32
  33 @cindex Hash tables
  34         BFD provides a simple set of hash table functions.  Routines
  35         are provided to initialize a hash table, to free a hash table,
  36         to look up a string in a hash table and optionally create an
  37         entry for it, and to traverse a hash table.  There is
  38         currently no routine to delete an string from a hash table.
  39
  40         The basic hash table does not permit any data to be stored
  41         with a string.  However, a hash table is designed to present a
  42         base class from which other types of hash tables may be
  43         derived.  These derived types may store additional information
  44         with the string.  Hash tables were implemented in this way,
  45         rather than simply providing a data pointer in a hash table
  46         entry, because they were designed for use by the linker back
  47         ends.  The linker may create thousands of hash table entries,
  48         and the overhead of allocating private data and storing and
  49         following pointers becomes noticeable.
  50
  51         The basic hash table code is in <<hash.c>>.
  52
  53 @menu
  54 @* Creating and Freeing a Hash Table::
  55 @* Looking Up or Entering a String::
  56 @* Traversing a Hash Table::
  57 @* Deriving a New Hash Table Type::
  58 @end menu
  59
  60 INODE
  61 Creating and Freeing a Hash Table, Looking Up or Entering a String, Hash Tables, Hash Tables
  62 SUBSECTION
  63         Creating and freeing a hash table
  64
  65 @findex bfd_hash_table_init
  66 @findex bfd_hash_table_init_n
  67         To create a hash table, create an instance of a <<struct
  68         bfd_hash_table>> (defined in <<bfd.h>>) and call
  69         <<bfd_hash_table_init>> (if you know approximately how many
  70         entries you will need, the function <<bfd_hash_table_init_n>>,
  71         which takes a @var{size} argument, may be used).
  72         <<bfd_hash_table_init>> returns <<FALSE>> if some sort of
  73         error occurs.
  74
  75 @findex bfd_hash_newfunc
  76         The function <<bfd_hash_table_init>> take as an argument a
  77         function to use to create new entries.  For a basic hash
  78         table, use the function <<bfd_hash_newfunc>>.  @xref{Deriving
  79         a New Hash Table Type}, for why you would want to use a
  80         different value for this argument.
  81
  82 @findex bfd_hash_allocate
  83         <<bfd_hash_table_init>> will create an objalloc which will be
  84         used to allocate new entries.  You may allocate memory on this
  85         objalloc using <<bfd_hash_allocate>>.
  86
  87 @findex bfd_hash_table_free
  88         Use <<bfd_hash_table_free>> to free up all the memory that has
  89         been allocated for a hash table.  This will not free up the
  90         <<struct bfd_hash_table>> itself, which you must provide.
  91
  92 @findex bfd_hash_set_default_size
  93         Use <<bfd_hash_set_default_size>> to set the default size of
  94         hash table to use.
  95
  96 INODE
  97 Looking Up or Entering a String, Traversing a Hash Table, Creating and Freeing a Hash Table, Hash Tables
  98 SUBSECTION
  99         Looking up or entering a string
 100
 101 @findex bfd_hash_lookup
 102         The function <<bfd_hash_lookup>> is used both to look up a
 103         string in the hash table and to create a new entry.
 104
 105         If the @var{create} argument is <<FALSE>>, <<bfd_hash_lookup>>
 106         will look up a string.  If the string is found, it will
 107         returns a pointer to a <<struct bfd_hash_entry>>.  If the
 108         string is not found in the table <<bfd_hash_lookup>> will
 109         return <<NULL>>.  You should not modify any of the fields in
 110         the returns <<struct bfd_hash_entry>>.
 111
 112         If the @var{create} argument is <<TRUE>>, the string will be
 113         entered into the hash table if it is not already there.
 114         Either way a pointer to a <<struct bfd_hash_entry>> will be
 115         returned, either to the existing structure or to a newly
 116         created one.  In this case, a <<NULL>> return means that an
 117         error occurred.
 118
 119         If the @var{create} argument is <<TRUE>>, and a new entry is
 120         created, the @var{copy} argument is used to decide whether to
 121         copy the string onto the hash table objalloc or not.  If
 122         @var{copy} is passed as <<FALSE>>, you must be careful not to
 123         deallocate or modify the string as long as the hash table
 124         exists.
 125
 126 INODE
 127 Traversing a Hash Table, Deriving a New Hash Table Type, Looking Up or Entering a String, Hash Tables
 128 SUBSECTION
 129         Traversing a hash table
 130
 131 @findex bfd_hash_traverse
 132         The function <<bfd_hash_traverse>> may be used to traverse a
 133         hash table, calling a function on each element.  The traversal
 134         is done in a random order.
 135
 136         <<bfd_hash_traverse>> takes as arguments a function and a
 137         generic <<void *>> pointer.  The function is called with a
 138         hash table entry (a <<struct bfd_hash_entry *>>) and the
 139         generic pointer passed to <<bfd_hash_traverse>>.  The function
 140         must return a <<boolean>> value, which indicates whether to
 141         continue traversing the hash table.  If the function returns
 142         <<FALSE>>, <<bfd_hash_traverse>> will stop the traversal and
 143         return immediately.
 144
 145 INODE
 146 Deriving a New Hash Table Type, , Traversing a Hash Table, Hash Tables
 147 SUBSECTION
 148         Deriving a new hash table type
 149
 150         Many uses of hash tables want to store additional information
 151         which each entry in the hash table.  Some also find it
 152         convenient to store additional information with the hash table
 153         itself.  This may be done using a derived hash table.
 154
 155         Since C is not an object oriented language, creating a derived
 156         hash table requires sticking together some boilerplate
 157         routines with a few differences specific to the type of hash
 158         table you want to create.
 159
 160         An example of a derived hash table is the linker hash table.
 161         The structures for this are defined in <<bfdlink.h>>.  The
 162         functions are in <<linker.c>>.
 163
 164         You may also derive a hash table from an already derived hash
 165         table.  For example, the a.out linker backend code uses a hash
 166         table derived from the linker hash table.
 167
 168 @menu
 169 @* Define the Derived Structures::
 170 @* Write the Derived Creation Routine::
 171 @* Write Other Derived Routines::
 172 @end menu
 173
 174 INODE
 175 Define the Derived Structures, Write the Derived Creation Routine, Deriving a New Hash Table Type, Deriving a New Hash Table Type
 176 SUBSUBSECTION
 177         Define the derived structures
 178
 179         You must define a structure for an entry in the hash table,
 180         and a structure for the hash table itself.
 181
 182         The first field in the structure for an entry in the hash
 183         table must be of the type used for an entry in the hash table
 184         you are deriving from.  If you are deriving from a basic hash
 185         table this is <<struct bfd_hash_entry>>, which is defined in
 186         <<bfd.h>>.  The first field in the structure for the hash
 187         table itself must be of the type of the hash table you are
 188         deriving from itself.  If you are deriving from a basic hash
 189         table, this is <<struct bfd_hash_table>>.
 190
 191         For example, the linker hash table defines <<struct
 192         bfd_link_hash_entry>> (in <<bfdlink.h>>).  The first field,
 193         <<root>>, is of type <<struct bfd_hash_entry>>.  Similarly,
 194         the first field in <<struct bfd_link_hash_table>>, <<table>>,
 195         is of type <<struct bfd_hash_table>>.
 196
 197 INODE
 198 Write the Derived Creation Routine, Write Other Derived Routines, Define the Derived Structures, Deriving a New Hash Table Type
 199 SUBSUBSECTION
 200         Write the derived creation routine
 201
 202         You must write a routine which will create and initialize an
 203         entry in the hash table.  This routine is passed as the
 204         function argument to <<bfd_hash_table_init>>.
 205
 206         In order to permit other hash tables to be derived from the
 207         hash table you are creating, this routine must be written in a
 208         standard way.
 209
 210         The first argument to the creation routine is a pointer to a
 211         hash table entry.  This may be <<NULL>>, in which case the
 212         routine should allocate the right amount of space.  Otherwise
 213         the space has already been allocated by a hash table type
 214         derived from this one.
 215
 216         After allocating space, the creation routine must call the
 217         creation routine of the hash table type it is derived from,
 218         passing in a pointer to the space it just allocated.  This
 219         will initialize any fields used by the base hash table.
 220
 221         Finally the creation routine must initialize any local fields
 222         for the new hash table type.
 223
 224         Here is a boilerplate example of a creation routine.
 225         @var{function_name} is the name of the routine.
 226         @var{entry_type} is the type of an entry in the hash table you
 227         are creating.  @var{base_newfunc} is the name of the creation
 228         routine of the hash table type your hash table is derived
 229         from.
 230
 231 EXAMPLE
 232
 233 .struct bfd_hash_entry *
 234 .@var{function_name} (struct bfd_hash_entry *entry,
 235 .                     struct bfd_hash_table *table,
 236 .                     const char *string)
 237 .{
 238 .  struct @var{entry_type} *ret = (@var{entry_type} *) entry;
 239 .
 240 . {* Allocate the structure if it has not already been allocated by a
 241 .    derived class.  *}
 242 .  if (ret == NULL)
 243 .    {
 244 .      ret = bfd_hash_allocate (table, sizeof (* ret));
 245 .      if (ret == NULL)
 246 .        return NULL;
 247 .    }
 248 .
 249 . {* Call the allocation method of the base class.  *}
 250 .  ret = ((@var{entry_type} *)
 251 .        @var{base_newfunc} ((struct bfd_hash_entry *) ret, table, string));
 252 .
 253 . {* Initialize the local fields here.  *}
 254 .
 255 .  return (struct bfd_hash_entry *) ret;
 256 .}
 257
 258 DESCRIPTION
 259         The creation routine for the linker hash table, which is in
 260         <<linker.c>>, looks just like this example.
 261         @var{function_name} is <<_bfd_link_hash_newfunc>>.
 262         @var{entry_type} is <<struct bfd_link_hash_entry>>.
 263         @var{base_newfunc} is <<bfd_hash_newfunc>>, the creation
 264         routine for a basic hash table.
 265
 266         <<_bfd_link_hash_newfunc>> also initializes the local fields
 267         in a linker hash table entry: <<type>>, <<written>> and
 268         <<next>>.
 269
 270 INODE
 271 Write Other Derived Routines, , Write the Derived Creation Routine, Deriving a New Hash Table Type
 272 SUBSUBSECTION
 273         Write other derived routines
 274
 275         You will want to write other routines for your new hash table,
 276         as well.
 277
 278         You will want an initialization routine which calls the
 279         initialization routine of the hash table you are deriving from
 280         and initializes any other local fields.  For the linker hash
 281         table, this is <<_bfd_link_hash_table_init>> in <<linker.c>>.
 282
 283         You will want a lookup routine which calls the lookup routine
 284         of the hash table you are deriving from and casts the result.
 285         The linker hash table uses <<bfd_link_hash_lookup>> in
 286         <<linker.c>> (this actually takes an additional argument which
 287         it uses to decide how to return the looked up value).
 288
 289         You may want a traversal routine.  This should just call the
 290         traversal routine of the hash table you are deriving from with
 291         appropriate casts.  The linker hash table uses
 292         <<bfd_link_hash_traverse>> in <<linker.c>>.
 293
 294         These routines may simply be defined as macros.  For example,
 295         the a.out backend linker hash table, which is derived from the
 296         linker hash table, uses macros for the lookup and traversal
 297         routines.  These are <<aout_link_hash_lookup>> and
 298         <<aout_link_hash_traverse>> in aoutx.h.
 299 */
 300
 301 /* The default number of entries to use when creating a hash table.  */
 302 #define DEFAULT_SIZE 4051
 303
 304 /* The following function returns a nearest prime number which is
 305    greater than N, and near a power of two.  Copied from libiberty.
 306    Returns zero for ridiculously large N to signify an error.  */
 307
 308 static unsigned long
 309 higher_prime_number (unsigned long n)
 310 {
 311   /* These are primes that are near, but slightly smaller than, a
 312      power of two.  */
 313   static const unsigned long primes[] = {
 314     (unsigned long) 127,
 315     (unsigned long) 2039,
 316     (unsigned long) 32749,
 317     (unsigned long) 65521,
 318     (unsigned long) 131071,
 319     (unsigned long) 262139,
 320     (unsigned long) 524287,
 321     (unsigned long) 1048573,
 322     (unsigned long) 2097143,
 323     (unsigned long) 4194301,
 324     (unsigned long) 8388593,
 325     (unsigned long) 16777213,
 326     (unsigned long) 33554393,
 327     (unsigned long) 67108859,
 328     (unsigned long) 134217689,
 329     (unsigned long) 268435399,
 330     (unsigned long) 536870909,
 331     (unsigned long) 1073741789,
 332     (unsigned long) 2147483647,
 333                                         /* 4294967291L */
 334     ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
 335   };
 336
 337   const unsigned long *low = &primes[0];
 338   const unsigned long *high = &primes[sizeof (primes) / sizeof (primes[0])];
 339
 340   while (low != high)
 341     {
 342       const unsigned long *mid = low + (high - low) / 2;
 343       if (n >= *mid)
 344         low = mid + 1;
 345       else
 346         high = mid;
 347     }
 348
 349   if (n >= *low)
 350     return 0;
 351
 352   return *low;
 353 }
 354
 355 static size_t bfd_default_hash_table_size = DEFAULT_SIZE;
 356
 357 /* Create a new hash table, given a number of entries.  */
 358
 359 bfd_boolean
 360 bfd_hash_table_init_n (struct bfd_hash_table *table,
 361                        struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,
 362                                                           struct bfd_hash_table *,
 363                                                           const char *),
 364                        unsigned int entsize,
 365                        unsigned int size)
 366 {
 367   unsigned int alloc;
 368
 369   alloc = size * sizeof (struct bfd_hash_entry *);
 370
 371   table->memory = (void *) objalloc_create ();
 372   if (table->memory == NULL)
 373     {
 374       bfd_set_error (bfd_error_no_memory);
 375       return FALSE;
 376     }
 377   table->table = objalloc_alloc ((struct objalloc *) table->memory, alloc);
 378   if (table->table == NULL)
 379     {
 380       bfd_set_error (bfd_error_no_memory);
 381       return FALSE;
 382     }
 383   memset ((void *) table->table, 0, alloc);
 384   table->size = size;
 385   table->entsize = entsize;
 386   table->count = 0;
 387   table->frozen = 0;
 388   table->newfunc = newfunc;
 389   return TRUE;
 390 }
 391
 392 /* Create a new hash table with the default number of entries.  */
 393
 394 bfd_boolean
 395 bfd_hash_table_init (struct bfd_hash_table *table,
 396                      struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,
 397                                                         struct bfd_hash_table *,
 398                                                         const char *),
 399                      unsigned int entsize)
 400 {
 401   return bfd_hash_table_init_n (table, newfunc, entsize,
 402                                 bfd_default_hash_table_size);
 403 }
 404
 405 /* Free a hash table.  */
 406
 407 void
 408 bfd_hash_table_free (struct bfd_hash_table *table)
 409 {
 410   objalloc_free (table->memory);
 411   table->memory = NULL;
 412 }
 413
 414 /* Look up a string in a hash table.  */
 415
 416 struct bfd_hash_entry *
 417 bfd_hash_lookup (struct bfd_hash_table *table,
 418                  const char *string,
 419                  bfd_boolean create,
 420                  bfd_boolean copy)
 421 {
 422   const unsigned char *s;
 423   unsigned long hash;
 424   unsigned int c;
 425   struct bfd_hash_entry *hashp;
 426   unsigned int len;
 427   unsigned int index;
 428
 429   hash = 0;
 430   len = 0;
 431   s = (const unsigned char *) string;
 432   while ((c = *s++) != '\0')
 433     {
 434       hash += c + (c << 17);
 435       hash ^= hash >> 2;
 436     }
 437   len = (s - (const unsigned char *) string) - 1;
 438   hash += len + (len << 17);
 439   hash ^= hash >> 2;
 440
 441   index = hash % table->size;
 442   for (hashp = table->table[index];
 443        hashp != NULL;
 444        hashp = hashp->next)
 445     {
 446       if (hashp->hash == hash
 447           && strcmp (hashp->string, string) == 0)
 448         return hashp;
 449     }
 450
 451   if (! create)
 452     return NULL;
 453
 454   hashp = (*table->newfunc) (NULL, table, string);
 455   if (hashp == NULL)
 456     return NULL;
 457   if (copy)
 458     {
 459       char *new;
 460
 461       new = objalloc_alloc ((struct objalloc *) table->memory, len + 1);
 462       if (!new)
 463         {
 464           bfd_set_error (bfd_error_no_memory);
 465           return NULL;
 466         }
 467       memcpy (new, string, len + 1);
 468       string = new;
 469     }
 470   hashp->string = string;
 471   hashp->hash = hash;
 472   hashp->next = table->table[index];
 473   table->table[index] = hashp;
 474   table->count++;
 475
 476   if (!table->frozen && table->count > table->size * 3 / 4)
 477     {
 478       unsigned long newsize = higher_prime_number (table->size);
 479       struct bfd_hash_entry **newtable;
 480       unsigned int hi;
 481       unsigned long alloc = newsize * sizeof (struct bfd_hash_entry *);
 482
 483       /* If we can't find a higher prime, or we can't possibly alloc
 484          that much memory, don't try to grow the table.  */
 485       if (newsize == 0 || alloc / sizeof (struct bfd_hash_entry *) != newsize)
 486         {
 487           table->frozen = 1;
 488           return hashp;
 489         }
 490
 491       newtable = ((struct bfd_hash_entry **)
 492                   objalloc_alloc ((struct objalloc *) table->memory, alloc));
 493       memset ((PTR) newtable, 0, alloc);
 494
 495       for (hi = 0; hi < table->size; hi ++)
 496         while (table->table[hi])
 497           {
 498             struct bfd_hash_entry *chain = table->table[hi];
 499             struct bfd_hash_entry *chain_end = chain;
 500             int index;
 501
 502             while (chain_end->next && chain_end->next->hash == chain->hash)
 503               chain_end = chain_end->next;
 504
 505             table->table[hi] = chain_end->next;
 506             index = chain->hash % newsize;
 507             chain_end->next = newtable[index];
 508             newtable[index] = chain;
 509           }
 510       table->table = newtable;
 511       table->size = newsize;
 512     }
 513
 514   return hashp;
 515 }
 516
 517 /* Replace an entry in a hash table.  */
 518
 519 void
 520 bfd_hash_replace (struct bfd_hash_table *table,
 521                   struct bfd_hash_entry *old,
 522                   struct bfd_hash_entry *nw)
 523 {
 524   unsigned int index;
 525   struct bfd_hash_entry **pph;
 526
 527   index = old->hash % table->size;
 528   for (pph = &table->table[index];
 529        (*pph) != NULL;
 530        pph = &(*pph)->next)
 531     {
 532       if (*pph == old)
 533         {
 534           *pph = nw;
 535           return;
 536         }
 537     }
 538
 539   abort ();
 540 }
 541
 542 /* Allocate space in a hash table.  */
 543
 544 void *
 545 bfd_hash_allocate (struct bfd_hash_table *table,
 546                    unsigned int size)
 547 {
 548   void * ret;
 549
 550   ret = objalloc_alloc ((struct objalloc *) table->memory, size);
 551   if (ret == NULL && size != 0)
 552     bfd_set_error (bfd_error_no_memory);
 553   return ret;
 554 }
 555
 556 /* Base method for creating a new hash table entry.  */
 557
 558 struct bfd_hash_entry *
 559 bfd_hash_newfunc (struct bfd_hash_entry *entry,
 560                   struct bfd_hash_table *table,
 561                   const char *string ATTRIBUTE_UNUSED)
 562 {
 563   if (entry == NULL)
 564     entry = bfd_hash_allocate (table, sizeof (* entry));
 565   return entry;
 566 }
 567
 568 /* Traverse a hash table.  */
 569
 570 void
 571 bfd_hash_traverse (struct bfd_hash_table *table,
 572                    bfd_boolean (*func) (struct bfd_hash_entry *, void *),
 573                    void * info)
 574 {
 575   unsigned int i;
 576
 577   table->frozen = 1;
 578   for (i = 0; i < table->size; i++)
 579     {
 580       struct bfd_hash_entry *p;
 581
 582       for (p = table->table[i]; p != NULL; p = p->next)
 583         if (! (*func) (p, info))
 584           goto out;
 585     }
 586  out:
 587   table->frozen = 0;
 588 }
 589 \f
 590 void
 591 bfd_hash_set_default_size (bfd_size_type hash_size)
 592 {
 593   /* Extend this prime list if you want more granularity of hash table size.  */
 594   static const bfd_size_type hash_size_primes[] =
 595     {
 596       251, 509, 1021, 2039, 4051, 8599, 16699, 32749
 597     };
 598   size_t index;
 599
 600   /* Work out best prime number near the hash_size.  */
 601   for (index = 0; index < ARRAY_SIZE (hash_size_primes) - 1; ++index)
 602     if (hash_size <= hash_size_primes[index])
 603       break;
 604
 605   bfd_default_hash_table_size = hash_size_primes[index];
 606 }
 607 \f
 608 /* A few different object file formats (a.out, COFF, ELF) use a string
 609    table.  These functions support adding strings to a string table,
 610    returning the byte offset, and writing out the table.
 611
 612    Possible improvements:
 613    + look for strings matching trailing substrings of other strings
 614    + better data structures?  balanced trees?
 615    + look at reducing memory use elsewhere -- maybe if we didn't have
 616      to construct the entire symbol table at once, we could get by
 617      with smaller amounts of VM?  (What effect does that have on the
 618      string table reductions?)  */
 619
 620 /* An entry in the strtab hash table.  */
 621
 622 struct strtab_hash_entry
 623 {
 624   struct bfd_hash_entry root;
 625   /* Index in string table.  */
 626   bfd_size_type index;
 627   /* Next string in strtab.  */
 628   struct strtab_hash_entry *next;
 629 };
 630
 631 /* The strtab hash table.  */
 632
 633 struct bfd_strtab_hash
 634 {
 635   struct bfd_hash_table table;
 636   /* Size of strtab--also next available index.  */
 637   bfd_size_type size;
 638   /* First string in strtab.  */
 639   struct strtab_hash_entry *first;
 640   /* Last string in strtab.  */
 641   struct strtab_hash_entry *last;
 642   /* Whether to precede strings with a two byte length, as in the
 643      XCOFF .debug section.  */
 644   bfd_boolean xcoff;
 645 };
 646
 647 /* Routine to create an entry in a strtab.  */
 648
 649 static struct bfd_hash_entry *
 650 strtab_hash_newfunc (struct bfd_hash_entry *entry,
 651                      struct bfd_hash_table *table,
 652                      const char *string)
 653 {
 654   struct strtab_hash_entry *ret = (struct strtab_hash_entry *) entry;
 655
 656   /* Allocate the structure if it has not already been allocated by a
 657      subclass.  */
 658   if (ret == NULL)
 659     ret = bfd_hash_allocate (table, sizeof (* ret));
 660   if (ret == NULL)
 661     return NULL;
 662
 663   /* Call the allocation method of the superclass.  */
 664   ret = (struct strtab_hash_entry *)
 665          bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string);
 666
 667   if (ret)
 668     {
 669       /* Initialize the local fields.  */
 670       ret->index = (bfd_size_type) -1;
 671       ret->next = NULL;
 672     }
 673
 674   return (struct bfd_hash_entry *) ret;
 675 }
 676
 677 /* Look up an entry in an strtab.  */
 678
 679 #define strtab_hash_lookup(t, string, create, copy) \
 680   ((struct strtab_hash_entry *) \
 681    bfd_hash_lookup (&(t)->table, (string), (create), (copy)))
 682
 683 /* Create a new strtab.  */
 684
 685 struct bfd_strtab_hash *
 686 _bfd_stringtab_init (void)
 687 {
 688   struct bfd_strtab_hash *table;
 689   bfd_size_type amt = sizeof (* table);
 690
 691   table = bfd_malloc (amt);
 692   if (table == NULL)
 693     return NULL;
 694
 695   if (!bfd_hash_table_init (&table->table, strtab_hash_newfunc,
 696                             sizeof (struct strtab_hash_entry)))
 697     {
 698       free (table);
 699       return NULL;
 700     }
 701
 702   table->size = 0;
 703   table->first = NULL;
 704   table->last = NULL;
 705   table->xcoff = FALSE;
 706
 707   return table;
 708 }
 709
 710 /* Create a new strtab in which the strings are output in the format
 711    used in the XCOFF .debug section: a two byte length precedes each
 712    string.  */
 713
 714 struct bfd_strtab_hash *
 715 _bfd_xcoff_stringtab_init (void)
 716 {
 717   struct bfd_strtab_hash *ret;
 718
 719   ret = _bfd_stringtab_init ();
 720   if (ret != NULL)
 721     ret->xcoff = TRUE;
 722   return ret;
 723 }
 724
 725 /* Free a strtab.  */
 726
 727 void
 728 _bfd_stringtab_free (struct bfd_strtab_hash *table)
 729 {
 730   bfd_hash_table_free (&table->table);
 731   free (table);
 732 }
 733
 734 /* Get the index of a string in a strtab, adding it if it is not
 735    already present.  If HASH is FALSE, we don't really use the hash
 736    table, and we don't eliminate duplicate strings.  */
 737
 738 bfd_size_type
 739 _bfd_stringtab_add (struct bfd_strtab_hash *tab,
 740                     const char *str,
 741                     bfd_boolean hash,
 742                     bfd_boolean copy)
 743 {
 744   struct strtab_hash_entry *entry;
 745
 746   if (hash)
 747     {
 748       entry = strtab_hash_lookup (tab, str, TRUE, copy);
 749       if (entry == NULL)
 750         return (bfd_size_type) -1;
 751     }
 752   else
 753     {
 754       entry = bfd_hash_allocate (&tab->table, sizeof (* entry));
 755       if (entry == NULL)
 756         return (bfd_size_type) -1;
 757       if (! copy)
 758         entry->root.string = str;
 759       else
 760         {
 761           char *n;
 762
 763           n = bfd_hash_allocate (&tab->table, strlen (str) + 1);
 764           if (n == NULL)
 765             return (bfd_size_type) -1;
 766           entry->root.string = n;
 767         }
 768       entry->index = (bfd_size_type) -1;
 769       entry->next = NULL;
 770     }
 771
 772   if (entry->index == (bfd_size_type) -1)
 773     {
 774       entry->index = tab->size;
 775       tab->size += strlen (str) + 1;
 776       if (tab->xcoff)
 777         {
 778           entry->index += 2;
 779           tab->size += 2;
 780         }
 781       if (tab->first == NULL)
 782         tab->first = entry;
 783       else
 784         tab->last->next = entry;
 785       tab->last = entry;
 786     }
 787
 788   return entry->index;
 789 }
 790
 791 /* Get the number of bytes in a strtab.  */
 792
 793 bfd_size_type
 794 _bfd_stringtab_size (struct bfd_strtab_hash *tab)
 795 {
 796   return tab->size;
 797 }
 798
 799 /* Write out a strtab.  ABFD must already be at the right location in
 800    the file.  */
 801
 802 bfd_boolean
 803 _bfd_stringtab_emit (bfd *abfd, struct bfd_strtab_hash *tab)
 804 {
 805   bfd_boolean xcoff;
 806   struct strtab_hash_entry *entry;
 807
 808   xcoff = tab->xcoff;
 809
 810   for (entry = tab->first; entry != NULL; entry = entry->next)
 811     {
 812       const char *str;
 813       size_t len;
 814
 815       str = entry->root.string;
 816       len = strlen (str) + 1;
 817
 818       if (xcoff)
 819         {
 820           bfd_byte buf[2];
 821
 822           /* The output length includes the null byte.  */
 823           bfd_put_16 (abfd, (bfd_vma) len, buf);
 824           if (bfd_bwrite ((void *) buf, (bfd_size_type) 2, abfd) != 2)
 825             return FALSE;
 826         }
 827
 828       if (bfd_bwrite ((void *) str, (bfd_size_type) len, abfd) != len)
 829         return FALSE;
 830     }
 831
 832   return TRUE;
 833 }