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 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 2 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, MA 02110-1301, USA.  */
  21
  22 #include "bfd.h"
  23 #include "sysdep.h"
  24 #include "libbfd.h"
  25 #include "objalloc.h"
  26 #include "libiberty.h"
  27
  28 /*
  29 SECTION
  30         Hash Tables
  31
  32 @cindex Hash tables
  33         BFD provides a simple set of hash table functions.  Routines
  34         are provided to initialize a hash table, to free a hash table,
  35         to look up a string in a hash table and optionally create an
  36         entry for it, and to traverse a hash table.  There is
  37         currently no routine to delete an string from a hash table.
  38
  39         The basic hash table does not permit any data to be stored
  40         with a string.  However, a hash table is designed to present a
  41         base class from which other types of hash tables may be
  42         derived.  These derived types may store additional information
  43         with the string.  Hash tables were implemented in this way,
  44         rather than simply providing a data pointer in a hash table
  45         entry, because they were designed for use by the linker back
  46         ends.  The linker may create thousands of hash table entries,
  47         and the overhead of allocating private data and storing and
  48         following pointers becomes noticeable.
  49
  50         The basic hash table code is in <<hash.c>>.
  51
  52 @menu
  53 @* Creating and Freeing a Hash Table::
  54 @* Looking Up or Entering a String::
  55 @* Traversing a Hash Table::
  56 @* Deriving a New Hash Table Type::
  57 @end menu
  58
  59 INODE
  60 Creating and Freeing a Hash Table, Looking Up or Entering a String, Hash Tables, Hash Tables
  61 SUBSECTION
  62         Creating and freeing a hash table
  63
  64 @findex bfd_hash_table_init
  65 @findex bfd_hash_table_init_n
  66         To create a hash table, create an instance of a <<struct
  67         bfd_hash_table>> (defined in <<bfd.h>>) and call
  68         <<bfd_hash_table_init>> (if you know approximately how many
  69         entries you will need, the function <<bfd_hash_table_init_n>>,
  70         which takes a @var{size} argument, may be used).
  71         <<bfd_hash_table_init>> returns <<FALSE>> if some sort of
  72         error occurs.
  73
  74 @findex bfd_hash_newfunc
  75         The function <<bfd_hash_table_init>> take as an argument a
  76         function to use to create new entries.  For a basic hash
  77         table, use the function <<bfd_hash_newfunc>>.  @xref{Deriving
  78         a New Hash Table Type}, for why you would want to use a
  79         different value for this argument.
  80
  81 @findex bfd_hash_allocate
  82         <<bfd_hash_table_init>> will create an objalloc which will be
  83         used to allocate new entries.  You may allocate memory on this
  84         objalloc using <<bfd_hash_allocate>>.
  85
  86 @findex bfd_hash_table_free
  87         Use <<bfd_hash_table_free>> to free up all the memory that has
  88         been allocated for a hash table.  This will not free up the
  89         <<struct bfd_hash_table>> itself, which you must provide.
  90
  91 @findex bfd_hash_set_default_size
  92         Use <<bfd_hash_set_default_size>> to set the default size of
  93         hash table to use.
  94
  95 INODE
  96 Looking Up or Entering a String, Traversing a Hash Table, Creating and Freeing a Hash Table, Hash Tables
  97 SUBSECTION
  98         Looking up or entering a string
  99
 100 @findex bfd_hash_lookup
 101         The function <<bfd_hash_lookup>> is used both to look up a
 102         string in the hash table and to create a new entry.
 103
 104         If the @var{create} argument is <<FALSE>>, <<bfd_hash_lookup>>
 105         will look up a string.  If the string is found, it will
 106         returns a pointer to a <<struct bfd_hash_entry>>.  If the
 107         string is not found in the table <<bfd_hash_lookup>> will
 108         return <<NULL>>.  You should not modify any of the fields in
 109         the returns <<struct bfd_hash_entry>>.
 110
 111         If the @var{create} argument is <<TRUE>>, the string will be
 112         entered into the hash table if it is not already there.
 113         Either way a pointer to a <<struct bfd_hash_entry>> will be
 114         returned, either to the existing structure or to a newly
 115         created one.  In this case, a <<NULL>> return means that an
 116         error occurred.
 117
 118         If the @var{create} argument is <<TRUE>>, and a new entry is
 119         created, the @var{copy} argument is used to decide whether to
 120         copy the string onto the hash table objalloc or not.  If
 121         @var{copy} is passed as <<FALSE>>, you must be careful not to
 122         deallocate or modify the string as long as the hash table
 123         exists.
 124
 125 INODE
 126 Traversing a Hash Table, Deriving a New Hash Table Type, Looking Up or Entering a String, Hash Tables
 127 SUBSECTION
 128         Traversing a hash table
 129
 130 @findex bfd_hash_traverse
 131         The function <<bfd_hash_traverse>> may be used to traverse a
 132         hash table, calling a function on each element.  The traversal
 133         is done in a random order.
 134
 135         <<bfd_hash_traverse>> takes as arguments a function and a
 136         generic <<void *>> pointer.  The function is called with a
 137         hash table entry (a <<struct bfd_hash_entry *>>) and the
 138         generic pointer passed to <<bfd_hash_traverse>>.  The function
 139         must return a <<boolean>> value, which indicates whether to
 140         continue traversing the hash table.  If the function returns
 141         <<FALSE>>, <<bfd_hash_traverse>> will stop the traversal and
 142         return immediately.
 143
 144 INODE
 145 Deriving a New Hash Table Type, , Traversing a Hash Table, Hash Tables
 146 SUBSECTION
 147         Deriving a new hash table type
 148
 149         Many uses of hash tables want to store additional information
 150         which each entry in the hash table.  Some also find it
 151         convenient to store additional information with the hash table
 152         itself.  This may be done using a derived hash table.
 153
 154         Since C is not an object oriented language, creating a derived
 155         hash table requires sticking together some boilerplate
 156         routines with a few differences specific to the type of hash
 157         table you want to create.
 158
 159         An example of a derived hash table is the linker hash table.
 160         The structures for this are defined in <<bfdlink.h>>.  The
 161         functions are in <<linker.c>>.
 162
 163         You may also derive a hash table from an already derived hash
 164         table.  For example, the a.out linker backend code uses a hash
 165         table derived from the linker hash table.
 166
 167 @menu
 168 @* Define the Derived Structures::
 169 @* Write the Derived Creation Routine::
 170 @* Write Other Derived Routines::
 171 @end menu
 172
 173 INODE
 174 Define the Derived Structures, Write the Derived Creation Routine, Deriving a New Hash Table Type, Deriving a New Hash Table Type
 175 SUBSUBSECTION
 176         Define the derived structures
 177
 178         You must define a structure for an entry in the hash table,
 179         and a structure for the hash table itself.
 180
 181         The first field in the structure for an entry in the hash
 182         table must be of the type used for an entry in the hash table
 183         you are deriving from.  If you are deriving from a basic hash
 184         table this is <<struct bfd_hash_entry>>, which is defined in
 185         <<bfd.h>>.  The first field in the structure for the hash
 186         table itself must be of the type of the hash table you are
 187         deriving from itself.  If you are deriving from a basic hash
 188         table, this is <<struct bfd_hash_table>>.
 189
 190         For example, the linker hash table defines <<struct
 191         bfd_link_hash_entry>> (in <<bfdlink.h>>).  The first field,
 192         <<root>>, is of type <<struct bfd_hash_entry>>.  Similarly,
 193         the first field in <<struct bfd_link_hash_table>>, <<table>>,
 194         is of type <<struct bfd_hash_table>>.
 195
 196 INODE
 197 Write the Derived Creation Routine, Write Other Derived Routines, Define the Derived Structures, Deriving a New Hash Table Type
 198 SUBSUBSECTION
 199         Write the derived creation routine
 200
 201         You must write a routine which will create and initialize an
 202         entry in the hash table.  This routine is passed as the
 203         function argument to <<bfd_hash_table_init>>.
 204
 205         In order to permit other hash tables to be derived from the
 206         hash table you are creating, this routine must be written in a
 207         standard way.
 208
 209         The first argument to the creation routine is a pointer to a
 210         hash table entry.  This may be <<NULL>>, in which case the
 211         routine should allocate the right amount of space.  Otherwise
 212         the space has already been allocated by a hash table type
 213         derived from this one.
 214
 215         After allocating space, the creation routine must call the
 216         creation routine of the hash table type it is derived from,
 217         passing in a pointer to the space it just allocated.  This
 218         will initialize any fields used by the base hash table.
 219
 220         Finally the creation routine must initialize any local fields
 221         for the new hash table type.
 222
 223         Here is a boilerplate example of a creation routine.
 224         @var{function_name} is the name of the routine.
 225         @var{entry_type} is the type of an entry in the hash table you
 226         are creating.  @var{base_newfunc} is the name of the creation
 227         routine of the hash table type your hash table is derived
 228         from.
 229
 230 EXAMPLE
 231
 232 .struct bfd_hash_entry *
 233 .@var{function_name} (struct bfd_hash_entry *entry,
 234 .                     struct bfd_hash_table *table,
 235 .                     const char *string)
 236 .{
 237 .  struct @var{entry_type} *ret = (@var{entry_type} *) entry;
 238 .
 239 . {* Allocate the structure if it has not already been allocated by a
 240 .    derived class.  *}
 241 .  if (ret == NULL)
 242 .    {
 243 .      ret = bfd_hash_allocate (table, sizeof (* ret));
 244 .      if (ret == NULL)
 245 .        return NULL;
 246 .    }
 247 .
 248 . {* Call the allocation method of the base class.  *}
 249 .  ret = ((@var{entry_type} *)
 250 .        @var{base_newfunc} ((struct bfd_hash_entry *) ret, table, string));
 251 .
 252 . {* Initialize the local fields here.  *}
 253 .
 254 .  return (struct bfd_hash_entry *) ret;
 255 .}
 256
 257 DESCRIPTION
 258         The creation routine for the linker hash table, which is in
 259         <<linker.c>>, looks just like this example.
 260         @var{function_name} is <<_bfd_link_hash_newfunc>>.
 261         @var{entry_type} is <<struct bfd_link_hash_entry>>.
 262         @var{base_newfunc} is <<bfd_hash_newfunc>>, the creation
 263         routine for a basic hash table.
 264
 265         <<_bfd_link_hash_newfunc>> also initializes the local fields
 266         in a linker hash table entry: <<type>>, <<written>> and
 267         <<next>>.
 268
 269 INODE
 270 Write Other Derived Routines, , Write the Derived Creation Routine, Deriving a New Hash Table Type
 271 SUBSUBSECTION
 272         Write other derived routines
 273
 274         You will want to write other routines for your new hash table,
 275         as well.
 276
 277         You will want an initialization routine which calls the
 278         initialization routine of the hash table you are deriving from
 279         and initializes any other local fields.  For the linker hash
 280         table, this is <<_bfd_link_hash_table_init>> in <<linker.c>>.
 281
 282         You will want a lookup routine which calls the lookup routine
 283         of the hash table you are deriving from and casts the result.
 284         The linker hash table uses <<bfd_link_hash_lookup>> in
 285         <<linker.c>> (this actually takes an additional argument which
 286         it uses to decide how to return the looked up value).
 287
 288         You may want a traversal routine.  This should just call the
 289         traversal routine of the hash table you are deriving from with
 290         appropriate casts.  The linker hash table uses
 291         <<bfd_link_hash_traverse>> in <<linker.c>>.
 292
 293         These routines may simply be defined as macros.  For example,
 294         the a.out backend linker hash table, which is derived from the
 295         linker hash table, uses macros for the lookup and traversal
 296         routines.  These are <<aout_link_hash_lookup>> and
 297         <<aout_link_hash_traverse>> in aoutx.h.
 298 */
 299
 300 /* The default number of entries to use when creating a hash table.  */
 301 #define DEFAULT_SIZE (4093)
 302
 303 /* The following function returns a nearest prime number which is
 304    greater than N, and near a power of two.  Copied from libiberty.  */
 305
 306 static unsigned long
 307 higher_prime_number (unsigned long n)
 308 {
 309   /* These are primes that are near, but slightly smaller than, a
 310      power of two.  */
 311   static const unsigned long primes[] = {
 312     (unsigned long) 7,
 313     (unsigned long) 13,
 314     (unsigned long) 31,
 315     (unsigned long) 61,
 316     (unsigned long) 127,
 317     (unsigned long) 251,
 318     (unsigned long) 509,
 319     (unsigned long) 1021,
 320     (unsigned long) 2039,
 321     (unsigned long) 4093,
 322     (unsigned long) 8191,
 323     (unsigned long) 16381,
 324     (unsigned long) 32749,
 325     (unsigned long) 65521,
 326     (unsigned long) 131071,
 327     (unsigned long) 262139,
 328     (unsigned long) 524287,
 329     (unsigned long) 1048573,
 330     (unsigned long) 2097143,
 331     (unsigned long) 4194301,
 332     (unsigned long) 8388593,
 333     (unsigned long) 16777213,
 334     (unsigned long) 33554393,
 335     (unsigned long) 67108859,
 336     (unsigned long) 134217689,
 337     (unsigned long) 268435399,
 338     (unsigned long) 536870909,
 339     (unsigned long) 1073741789,
 340     (unsigned long) 2147483647,
 341                                         /* 4294967291L */
 342     ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
 343   };
 344
 345   const unsigned long *low = &primes[0];
 346   const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
 347
 348   while (low != high)
 349     {
 350       const unsigned long *mid = low + (high - low) / 2;
 351       if (n >= *mid)
 352         low = mid + 1;
 353       else
 354         high = mid;
 355     }
 356
 357   /* If we've run out of primes, abort.  */
 358   if (n > *low)
 359     {
 360       fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
 361       abort ();
 362     }
 363
 364   return *low;
 365 }
 366
 367 static size_t bfd_default_hash_table_size = DEFAULT_SIZE;
 368
 369 /* Create a new hash table, given a number of entries.  */
 370
 371 bfd_boolean
 372 bfd_hash_table_init_n (struct bfd_hash_table *table,
 373                        struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,
 374                                                           struct bfd_hash_table *,
 375                                                           const char *),
 376                        unsigned int entsize,
 377                        unsigned int size)
 378 {
 379   unsigned int alloc;
 380
 381   alloc = size * sizeof (struct bfd_hash_entry *);
 382
 383   table->memory = (void *) objalloc_create ();
 384   if (table->memory == NULL)
 385     {
 386       bfd_set_error (bfd_error_no_memory);
 387       return FALSE;
 388     }
 389   table->table = objalloc_alloc ((struct objalloc *) table->memory, alloc);
 390   if (table->table == NULL)
 391     {
 392       bfd_set_error (bfd_error_no_memory);
 393       return FALSE;
 394     }
 395   memset ((void *) table->table, 0, alloc);
 396   table->size = size;
 397   table->entsize = entsize;
 398   table->count = 0;
 399   table->newfunc = newfunc;
 400   return TRUE;
 401 }
 402
 403 /* Create a new hash table with the default number of entries.  */
 404
 405 bfd_boolean
 406 bfd_hash_table_init (struct bfd_hash_table *table,
 407                      struct bfd_hash_entry *(*newfunc) (struct bfd_hash_entry *,
 408                                                         struct bfd_hash_table *,
 409                                                         const char *),
 410                      unsigned int entsize)
 411 {
 412   return bfd_hash_table_init_n (table, newfunc, entsize,
 413                                 bfd_default_hash_table_size);
 414 }
 415
 416 /* Free a hash table.  */
 417
 418 void
 419 bfd_hash_table_free (struct bfd_hash_table *table)
 420 {
 421   objalloc_free (table->memory);
 422   table->memory = NULL;
 423 }
 424
 425 /* Look up a string in a hash table.  */
 426
 427 struct bfd_hash_entry *
 428 bfd_hash_lookup (struct bfd_hash_table *table,
 429                  const char *string,
 430                  bfd_boolean create,
 431                  bfd_boolean copy)
 432 {
 433   const unsigned char *s;
 434   unsigned long hash;
 435   unsigned int c;
 436   struct bfd_hash_entry *hashp;
 437   unsigned int len;
 438   unsigned int index;
 439
 440   hash = 0;
 441   len = 0;
 442   s = (const unsigned char *) string;
 443   while ((c = *s++) != '\0')
 444     {
 445       hash += c + (c << 17);
 446       hash ^= hash >> 2;
 447     }
 448   len = (s - (const unsigned char *) string) - 1;
 449   hash += len + (len << 17);
 450   hash ^= hash >> 2;
 451
 452   index = hash % table->size;
 453   for (hashp = table->table[index];
 454        hashp != NULL;
 455        hashp = hashp->next)
 456     {
 457       if (hashp->hash == hash
 458           && strcmp (hashp->string, string) == 0)
 459         return hashp;
 460     }
 461
 462   if (! create)
 463     return NULL;
 464
 465   hashp = (*table->newfunc) (NULL, table, string);
 466   if (hashp == NULL)
 467     return NULL;
 468   if (copy)
 469     {
 470       char *new;
 471   table->count ++;
 472
 473       new = objalloc_alloc ((struct objalloc *) table->memory, len + 1);
 474       if (!new)
 475         {
 476           bfd_set_error (bfd_error_no_memory);
 477           return NULL;
 478         }
 479       memcpy (new, string, len + 1);
 480       string = new;
 481     }
 482   hashp->string = string;
 483   hashp->hash = hash;
 484   hashp->next = table->table[index];
 485   table->table[index] = hashp;
 486
 487   if (table->count > table->size * 3 / 4)
 488     {
 489       int newsize = higher_prime_number (table->size);
 490       struct bfd_hash_entry **newtable;
 491       unsigned int hi;
 492       unsigned int alloc;
 493
 494       alloc = newsize * sizeof (struct bfd_hash_entry *);
 495
 496       newtable = ((struct bfd_hash_entry **)
 497                   objalloc_alloc ((struct objalloc *) table->memory, alloc));
 498       memset ((PTR) newtable, 0, alloc);
 499
 500       for (hi = 0; hi < table->size; hi ++)
 501         while (table->table[hi])
 502           {
 503             struct bfd_hash_entry *chain = table->table[hi];
 504             struct bfd_hash_entry *chain_end = chain;
 505             int index;
 506
 507             while (chain_end->next && chain_end->next->hash == chain->hash)
 508               chain_end = chain_end->next;
 509
 510             table->table[hi] = chain_end->next;
 511             index = chain->hash % newsize;
 512             chain_end->next = newtable[index];
 513             newtable[index] = chain;
 514           }
 515       table->table = newtable;
 516       table->size = newsize;
 517     }
 518
 519   return hashp;
 520 }
 521
 522 /* Replace an entry in a hash table.  */
 523
 524 void
 525 bfd_hash_replace (struct bfd_hash_table *table,
 526                   struct bfd_hash_entry *old,
 527                   struct bfd_hash_entry *nw)
 528 {
 529   unsigned int index;
 530   struct bfd_hash_entry **pph;
 531
 532   index = old->hash % table->size;
 533   for (pph = &table->table[index];
 534        (*pph) != NULL;
 535        pph = &(*pph)->next)
 536     {
 537       if (*pph == old)
 538         {
 539           *pph = nw;
 540           return;
 541         }
 542     }
 543
 544   abort ();
 545 }
 546
 547 /* Allocate space in a hash table.  */
 548
 549 void *
 550 bfd_hash_allocate (struct bfd_hash_table *table,
 551                    unsigned int size)
 552 {
 553   void * ret;
 554
 555   ret = objalloc_alloc ((struct objalloc *) table->memory, size);
 556   if (ret == NULL && size != 0)
 557     bfd_set_error (bfd_error_no_memory);
 558   return ret;
 559 }
 560
 561 /* Base method for creating a new hash table entry.  */
 562
 563 struct bfd_hash_entry *
 564 bfd_hash_newfunc (struct bfd_hash_entry *entry,
 565                   struct bfd_hash_table *table,
 566                   const char *string ATTRIBUTE_UNUSED)
 567 {
 568   if (entry == NULL)
 569     entry = bfd_hash_allocate (table, sizeof (* entry));
 570   return entry;
 571 }
 572
 573 /* Traverse a hash table.  */
 574
 575 void
 576 bfd_hash_traverse (struct bfd_hash_table *table,
 577                    bfd_boolean (*func) (struct bfd_hash_entry *, void *),
 578                    void * info)
 579 {
 580   unsigned int i;
 581
 582   for (i = 0; i < table->size; i++)
 583     {
 584       struct bfd_hash_entry *p;
 585
 586       for (p = table->table[i]; p != NULL; p = p->next)
 587         if (! (*func) (p, info))
 588           return;
 589     }
 590 }
 591 \f
 592 void
 593 bfd_hash_set_default_size (bfd_size_type hash_size)
 594 {
 595   /* Extend this prime list if you want more granularity of hash table size.  */
 596   static const bfd_size_type hash_size_primes[] =
 597     {
 598       251, 509, 1021, 2039, 4051, 8599, 16699, 32749
 599     };
 600   size_t index;
 601
 602   /* Work out best prime number near the hash_size.  */
 603   for (index = 0; index < ARRAY_SIZE (hash_size_primes) - 1; ++index)
 604     if (hash_size <= hash_size_primes[index])
 605       break;
 606
 607   bfd_default_hash_table_size = hash_size_primes[index];
 608 }
 609 \f
 610 /* A few different object file formats (a.out, COFF, ELF) use a string
 611    table.  These functions support adding strings to a string table,
 612    returning the byte offset, and writing out the table.
 613
 614    Possible improvements:
 615    + look for strings matching trailing substrings of other strings
 616    + better data structures?  balanced trees?
 617    + look at reducing memory use elsewhere -- maybe if we didn't have
 618      to construct the entire symbol table at once, we could get by
 619      with smaller amounts of VM?  (What effect does that have on the
 620      string table reductions?)  */
 621
 622 /* An entry in the strtab hash table.  */
 623
 624 struct strtab_hash_entry
 625 {
 626   struct bfd_hash_entry root;
 627   /* Index in string table.  */
 628   bfd_size_type index;
 629   /* Next string in strtab.  */
 630   struct strtab_hash_entry *next;
 631 };
 632
 633 /* The strtab hash table.  */
 634
 635 struct bfd_strtab_hash
 636 {
 637   struct bfd_hash_table table;
 638   /* Size of strtab--also next available index.  */
 639   bfd_size_type size;
 640   /* First string in strtab.  */
 641   struct strtab_hash_entry *first;
 642   /* Last string in strtab.  */
 643   struct strtab_hash_entry *last;
 644   /* Whether to precede strings with a two byte length, as in the
 645      XCOFF .debug section.  */
 646   bfd_boolean xcoff;
 647 };
 648
 649 /* Routine to create an entry in a strtab.  */
 650
 651 static struct bfd_hash_entry *
 652 strtab_hash_newfunc (struct bfd_hash_entry *entry,
 653                      struct bfd_hash_table *table,
 654                      const char *string)
 655 {
 656   struct strtab_hash_entry *ret = (struct strtab_hash_entry *) entry;
 657
 658   /* Allocate the structure if it has not already been allocated by a
 659      subclass.  */
 660   if (ret == NULL)
 661     ret = bfd_hash_allocate (table, sizeof (* ret));
 662   if (ret == NULL)
 663     return NULL;
 664
 665   /* Call the allocation method of the superclass.  */
 666   ret = (struct strtab_hash_entry *)
 667          bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string);
 668
 669   if (ret)
 670     {
 671       /* Initialize the local fields.  */
 672       ret->index = (bfd_size_type) -1;
 673       ret->next = NULL;
 674     }
 675
 676   return (struct bfd_hash_entry *) ret;
 677 }
 678
 679 /* Look up an entry in an strtab.  */
 680
 681 #define strtab_hash_lookup(t, string, create, copy) \
 682   ((struct strtab_hash_entry *) \
 683    bfd_hash_lookup (&(t)->table, (string), (create), (copy)))
 684
 685 /* Create a new strtab.  */
 686
 687 struct bfd_strtab_hash *
 688 _bfd_stringtab_init (void)
 689 {
 690   struct bfd_strtab_hash *table;
 691   bfd_size_type amt = sizeof (* table);
 692
 693   table = bfd_malloc (amt);
 694   if (table == NULL)
 695     return NULL;
 696
 697   if (!bfd_hash_table_init (&table->table, strtab_hash_newfunc,
 698                             sizeof (struct strtab_hash_entry)))
 699     {
 700       free (table);
 701       return NULL;
 702     }
 703
 704   table->size = 0;
 705   table->first = NULL;
 706   table->last = NULL;
 707   table->xcoff = FALSE;
 708
 709   return table;
 710 }
 711
 712 /* Create a new strtab in which the strings are output in the format
 713    used in the XCOFF .debug section: a two byte length precedes each
 714    string.  */
 715
 716 struct bfd_strtab_hash *
 717 _bfd_xcoff_stringtab_init (void)
 718 {
 719   struct bfd_strtab_hash *ret;
 720
 721   ret = _bfd_stringtab_init ();
 722   if (ret != NULL)
 723     ret->xcoff = TRUE;
 724   return ret;
 725 }
 726
 727 /* Free a strtab.  */
 728
 729 void
 730 _bfd_stringtab_free (struct bfd_strtab_hash *table)
 731 {
 732   bfd_hash_table_free (&table->table);
 733   free (table);
 734 }
 735
 736 /* Get the index of a string in a strtab, adding it if it is not
 737    already present.  If HASH is FALSE, we don't really use the hash
 738    table, and we don't eliminate duplicate strings.  */
 739
 740 bfd_size_type
 741 _bfd_stringtab_add (struct bfd_strtab_hash *tab,
 742                     const char *str,
 743                     bfd_boolean hash,
 744                     bfd_boolean copy)
 745 {
 746   struct strtab_hash_entry *entry;
 747
 748   if (hash)
 749     {
 750       entry = strtab_hash_lookup (tab, str, TRUE, copy);
 751       if (entry == NULL)
 752         return (bfd_size_type) -1;
 753     }
 754   else
 755     {
 756       entry = bfd_hash_allocate (&tab->table, sizeof (* entry));
 757       if (entry == NULL)
 758         return (bfd_size_type) -1;
 759       if (! copy)
 760         entry->root.string = str;
 761       else
 762         {
 763           char *n;
 764
 765           n = bfd_hash_allocate (&tab->table, strlen (str) + 1);
 766           if (n == NULL)
 767             return (bfd_size_type) -1;
 768           entry->root.string = n;
 769         }
 770       entry->index = (bfd_size_type) -1;
 771       entry->next = NULL;
 772     }
 773
 774   if (entry->index == (bfd_size_type) -1)
 775     {
 776       entry->index = tab->size;
 777       tab->size += strlen (str) + 1;
 778       if (tab->xcoff)
 779         {
 780           entry->index += 2;
 781           tab->size += 2;
 782         }
 783       if (tab->first == NULL)
 784         tab->first = entry;
 785       else
 786         tab->last->next = entry;
 787       tab->last = entry;
 788     }
 789
 790   return entry->index;
 791 }
 792
 793 /* Get the number of bytes in a strtab.  */
 794
 795 bfd_size_type
 796 _bfd_stringtab_size (struct bfd_strtab_hash *tab)
 797 {
 798   return tab->size;
 799 }
 800
 801 /* Write out a strtab.  ABFD must already be at the right location in
 802    the file.  */
 803
 804 bfd_boolean
 805 _bfd_stringtab_emit (bfd *abfd, struct bfd_strtab_hash *tab)
 806 {
 807   bfd_boolean xcoff;
 808   struct strtab_hash_entry *entry;
 809
 810   xcoff = tab->xcoff;
 811
 812   for (entry = tab->first; entry != NULL; entry = entry->next)
 813     {
 814       const char *str;
 815       size_t len;
 816
 817       str = entry->root.string;
 818       len = strlen (str) + 1;
 819
 820       if (xcoff)
 821         {
 822           bfd_byte buf[2];
 823
 824           /* The output length includes the null byte.  */
 825           bfd_put_16 (abfd, (bfd_vma) len, buf);
 826           if (bfd_bwrite ((void *) buf, (bfd_size_type) 2, abfd) != 2)
 827             return FALSE;
 828         }
 829
 830       if (bfd_bwrite ((void *) str, (bfd_size_type) len, abfd) != len)
 831         return FALSE;
 832     }
 833
 834   return TRUE;
 835 }