| 1 | /* hash.c -- hash table routines for BFD |
| 2 | Copyright (C) 1993, 94 Free Software Foundation, Inc. |
| 3 | Written by Steve Chamberlain <sac@cygnus.com> |
| 4 | |
| 5 | This file is part of BFD, the Binary File Descriptor library. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 2 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program; if not, write to the Free Software |
| 19 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ |
| 20 | |
| 21 | #include "bfd.h" |
| 22 | #include "sysdep.h" |
| 23 | #include "libbfd.h" |
| 24 | #include "obstack.h" |
| 25 | |
| 26 | /* |
| 27 | SECTION |
| 28 | Hash Tables |
| 29 | |
| 30 | @cindex Hash tables |
| 31 | BFD provides a simple set of hash table functions. Routines |
| 32 | are provided to initialize a hash table, to free a hash table, |
| 33 | to look up a string in a hash table and optionally create an |
| 34 | entry for it, and to traverse a hash table. There is |
| 35 | currently no routine to delete an string from a hash table. |
| 36 | |
| 37 | The basic hash table does not permit any data to be stored |
| 38 | with a string. However, a hash table is designed to present a |
| 39 | base class from which other types of hash tables may be |
| 40 | derived. These derived types may store additional information |
| 41 | with the string. Hash tables were implemented in this way, |
| 42 | rather than simply providing a data pointer in a hash table |
| 43 | entry, because they were designed for use by the linker back |
| 44 | ends. The linker may create thousands of hash table entries, |
| 45 | and the overhead of allocating private data and storing and |
| 46 | following pointers becomes noticeable. |
| 47 | |
| 48 | The basic hash table code is in <<hash.c>>. |
| 49 | |
| 50 | @menu |
| 51 | @* Creating and Freeing a Hash Table:: |
| 52 | @* Looking Up or Entering a String:: |
| 53 | @* Traversing a Hash Table:: |
| 54 | @* Deriving a New Hash Table Type:: |
| 55 | @end menu |
| 56 | |
| 57 | INODE |
| 58 | Creating and Freeing a Hash Table, Looking Up or Entering a String, Hash Tables, Hash Tables |
| 59 | SUBSECTION |
| 60 | Creating and freeing a hash table |
| 61 | |
| 62 | @findex bfd_hash_table_init |
| 63 | @findex bfd_hash_table_init_n |
| 64 | To create a hash table, create an instance of a <<struct |
| 65 | bfd_hash_table>> (defined in <<bfd.h>>) and call |
| 66 | <<bfd_hash_table_init>> (if you know approximately how many |
| 67 | entries you will need, the function <<bfd_hash_table_init_n>>, |
| 68 | which takes a @var{size} argument, may be used). |
| 69 | <<bfd_hash_table_init>> returns <<false>> if some sort of |
| 70 | error occurs. |
| 71 | |
| 72 | @findex bfd_hash_newfunc |
| 73 | The function <<bfd_hash_table_init>> take as an argument a |
| 74 | function to use to create new entries. For a basic hash |
| 75 | table, use the function <<bfd_hash_newfunc>>. @xref{Deriving |
| 76 | a New Hash Table Type} for why you would want to use a |
| 77 | different value for this argument. |
| 78 | |
| 79 | @findex bfd_hash_allocate |
| 80 | <<bfd_hash_table_init>> will create an obstack which will be |
| 81 | used to allocate new entries. You may allocate memory on this |
| 82 | obstack using <<bfd_hash_allocate>>. |
| 83 | |
| 84 | @findex bfd_hash_table_free |
| 85 | Use <<bfd_hash_table_free>> to free up all the memory that has |
| 86 | been allocated for a hash table. This will not free up the |
| 87 | <<struct bfd_hash_table>> itself, which you must provide. |
| 88 | |
| 89 | INODE |
| 90 | Looking Up or Entering a String, Traversing a Hash Table, Creating and Freeing a Hash Table, Hash Tables |
| 91 | SUBSECTION |
| 92 | Looking up or entering a string |
| 93 | |
| 94 | @findex bfd_hash_lookup |
| 95 | The function <<bfd_hash_lookup>> is used both to look up a |
| 96 | string in the hash table and to create a new entry. |
| 97 | |
| 98 | If the @var{create} argument is <<false>>, <<bfd_hash_lookup>> |
| 99 | will look up a string. If the string is found, it will |
| 100 | returns a pointer to a <<struct bfd_hash_entry>>. If the |
| 101 | string is not found in the table <<bfd_hash_lookup>> will |
| 102 | return <<NULL>>. You should not modify any of the fields in |
| 103 | the returns <<struct bfd_hash_entry>>. |
| 104 | |
| 105 | If the @var{create} argument is <<true>>, the string will be |
| 106 | entered into the hash table if it is not already there. |
| 107 | Either way a pointer to a <<struct bfd_hash_entry>> will be |
| 108 | returned, either to the existing structure or to a newly |
| 109 | created one. In this case, a <<NULL>> return means that an |
| 110 | error occurred. |
| 111 | |
| 112 | If the @var{create} argument is <<true>>, and a new entry is |
| 113 | created, the @var{copy} argument is used to decide whether to |
| 114 | copy the string onto the hash table obstack or not. If |
| 115 | @var{copy} is passed as <<false>>, you must be careful not to |
| 116 | deallocate or modify the string as long as the hash table |
| 117 | exists. |
| 118 | |
| 119 | INODE |
| 120 | Traversing a Hash Table, Deriving a New Hash Table Type, Looking Up or Entering a String, Hash Tables |
| 121 | SUBSECTION |
| 122 | Traversing a hash table |
| 123 | |
| 124 | @findex bfd_hash_traverse |
| 125 | The function <<bfd_hash_traverse>> may be used to traverse a |
| 126 | hash table, calling a function on each element. The traversal |
| 127 | is done in a random order. |
| 128 | |
| 129 | <<bfd_hash_traverse>> takes as arguments a function and a |
| 130 | generic <<void *>> pointer. The function is called with a |
| 131 | hash table entry (a <<struct bfd_hash_entry *>>) and the |
| 132 | generic pointer passed to <<bfd_hash_traverse>>. The function |
| 133 | must return a <<boolean>> value, which indicates whether to |
| 134 | continue traversing the hash table. If the function returns |
| 135 | <<false>>, <<bfd_hash_traverse>> will stop the traversal and |
| 136 | return immediately. |
| 137 | |
| 138 | INODE |
| 139 | Deriving a New Hash Table Type, , Traversing a Hash Table, Hash Tables |
| 140 | SUBSECTION |
| 141 | Deriving a new hash table type |
| 142 | |
| 143 | Many uses of hash tables want to store additional information |
| 144 | which each entry in the hash table. Some also find it |
| 145 | convenient to store additional information with the hash table |
| 146 | itself. This may be done using a derived hash table. |
| 147 | |
| 148 | Since C is not an object oriented language, creating a derived |
| 149 | hash table requires sticking together some boilerplate |
| 150 | routines with a few differences specific to the type of hash |
| 151 | table you want to create. |
| 152 | |
| 153 | An example of a derived hash table is the linker hash table. |
| 154 | The structures for this are defined in <<bfdlink.h>>. The |
| 155 | functions are in <<linker.c>>. |
| 156 | |
| 157 | You may also derive a hash table from an already derived hash |
| 158 | table. For example, the a.out linker backend code uses a hash |
| 159 | table derived from the linker hash table. |
| 160 | |
| 161 | @menu |
| 162 | @* Define the Derived Structures:: |
| 163 | @* Write the Derived Creation Routine:: |
| 164 | @* Write Other Derived Routines:: |
| 165 | @end menu |
| 166 | |
| 167 | INODE |
| 168 | Define the Derived Structures, Write the Derived Creation Routine, Deriving a New Hash Table Type, Deriving a New Hash Table Type |
| 169 | SUBSUBSECTION |
| 170 | Define the derived structures |
| 171 | |
| 172 | You must define a structure for an entry in the hash table, |
| 173 | and a structure for the hash table itself. |
| 174 | |
| 175 | The first field in the structure for an entry in the hash |
| 176 | table must be of the type used for an entry in the hash table |
| 177 | you are deriving from. If you are deriving from a basic hash |
| 178 | table this is <<struct bfd_hash_entry>>, which is defined in |
| 179 | <<bfd.h>>. The first field in the structure for the hash |
| 180 | table itself must be of the type of the hash table you are |
| 181 | deriving from itself. If you are deriving from a basic hash |
| 182 | table, this is <<struct bfd_hash_table>>. |
| 183 | |
| 184 | For example, the linker hash table defines <<struct |
| 185 | bfd_link_hash_entry>> (in <<bfdlink.h>>). The first field, |
| 186 | <<root>>, is of type <<struct bfd_hash_entry>>. Similarly, |
| 187 | the first field in <<struct bfd_link_hash_table>>, <<table>>, |
| 188 | is of type <<struct bfd_hash_table>>. |
| 189 | |
| 190 | INODE |
| 191 | Write the Derived Creation Routine, Write Other Derived Routines, Define the Derived Structures, Deriving a New Hash Table Type |
| 192 | SUBSUBSECTION |
| 193 | Write the derived creation routine |
| 194 | |
| 195 | You must write a routine which will create and initialize an |
| 196 | entry in the hash table. This routine is passed as the |
| 197 | function argument to <<bfd_hash_table_init>>. |
| 198 | |
| 199 | In order to permit other hash tables to be derived from the |
| 200 | hash table you are creating, this routine must be written in a |
| 201 | standard way. |
| 202 | |
| 203 | The first argument to the creation routine is a pointer to a |
| 204 | hash table entry. This may be <<NULL>>, in which case the |
| 205 | routine should allocate the right amount of space. Otherwise |
| 206 | the space has already been allocated by a hash table type |
| 207 | derived from this one. |
| 208 | |
| 209 | After allocating space, the creation routine must call the |
| 210 | creation routine of the hash table type it is derived from, |
| 211 | passing in a pointer to the space it just allocated. This |
| 212 | will initialize any fields used by the base hash table. |
| 213 | |
| 214 | Finally the creation routine must initialize any local fields |
| 215 | for the new hash table type. |
| 216 | |
| 217 | Here is a boilerplate example of a creation routine. |
| 218 | @var{function_name} is the name of the routine. |
| 219 | @var{entry_type} is the type of an entry in the hash table you |
| 220 | are creating. @var{base_newfunc} is the name of the creation |
| 221 | routine of the hash table type your hash table is derived |
| 222 | from. |
| 223 | |
| 224 | EXAMPLE |
| 225 | |
| 226 | .struct bfd_hash_entry * |
| 227 | .@var{function_name} (entry, table, string) |
| 228 | . struct bfd_hash_entry *entry; |
| 229 | . struct bfd_hash_table *table; |
| 230 | . const char *string; |
| 231 | .{ |
| 232 | . struct @var{entry_type} *ret = (@var{entry_type} *) entry; |
| 233 | . |
| 234 | . {* Allocate the structure if it has not already been allocated by a |
| 235 | . derived class. *} |
| 236 | . if (ret == (@var{entry_type} *) NULL) |
| 237 | . ret = ((@var{entry_type} *) |
| 238 | . bfd_hash_allocate (table, sizeof (@var{entry_type}))); |
| 239 | . |
| 240 | . {* Call the allocation method of the base class. *} |
| 241 | . ret = ((@var{entry_type} *) |
| 242 | . @var{base_newfunc} ((struct bfd_hash_entry *) ret, table, string)); |
| 243 | . |
| 244 | . {* Initialize the local fields here. *} |
| 245 | . |
| 246 | . return (struct bfd_hash_entry *) ret; |
| 247 | .} |
| 248 | |
| 249 | DESCRIPTION |
| 250 | The creation routine for the linker hash table, which is in |
| 251 | <<linker.c>>, looks just like this example. |
| 252 | @var{function_name} is <<_bfd_link_hash_newfunc>>. |
| 253 | @var{entry_type} is <<struct bfd_link_hash_entry>>. |
| 254 | @var{base_newfunc} is <<bfd_hash_newfunc>>, the creation |
| 255 | routine for a basic hash table. |
| 256 | |
| 257 | <<_bfd_link_hash_newfunc>> also initializes the local fields |
| 258 | in a linker hash table entry: <<type>>, <<written>> and |
| 259 | <<next>>. |
| 260 | |
| 261 | INODE |
| 262 | Write Other Derived Routines, , Write the Derived Creation Routine, Deriving a New Hash Table Type |
| 263 | SUBSUBSECTION |
| 264 | Write other derived routines |
| 265 | |
| 266 | You will want to write other routines for your new hash table, |
| 267 | as well. |
| 268 | |
| 269 | You will want an initialization routine which calls the |
| 270 | initialization routine of the hash table you are deriving from |
| 271 | and initializes any other local fields. For the linker hash |
| 272 | table, this is <<_bfd_link_hash_table_init>> in <<linker.c>>. |
| 273 | |
| 274 | You will want a lookup routine which calls the lookup routine |
| 275 | of the hash table you are deriving from and casts the result. |
| 276 | The linker hash table uses <<bfd_link_hash_lookup>> in |
| 277 | <<linker.c>> (this actually takes an additional argument which |
| 278 | it uses to decide how to return the looked up value). |
| 279 | |
| 280 | You may want a traversal routine. This should just call the |
| 281 | traversal routine of the hash table you are deriving from with |
| 282 | appropriate casts. The linker hash table uses |
| 283 | <<bfd_link_hash_traverse>> in <<linker.c>>. |
| 284 | |
| 285 | These routines may simply be defined as macros. For example, |
| 286 | the a.out backend linker hash table, which is derived from the |
| 287 | linker hash table, uses macros for the lookup and traversal |
| 288 | routines. These are <<aout_link_hash_lookup>> and |
| 289 | <<aout_link_hash_traverse>> in aoutx.h. |
| 290 | */ |
| 291 | |
| 292 | /* Obstack allocation and deallocation routines. */ |
| 293 | #define obstack_chunk_alloc malloc |
| 294 | #define obstack_chunk_free free |
| 295 | |
| 296 | /* The default number of entries to use when creating a hash table. */ |
| 297 | #define DEFAULT_SIZE (4051) |
| 298 | |
| 299 | /* Create a new hash table, given a number of entries. */ |
| 300 | |
| 301 | boolean |
| 302 | bfd_hash_table_init_n (table, newfunc, size) |
| 303 | struct bfd_hash_table *table; |
| 304 | struct bfd_hash_entry *(*newfunc) PARAMS ((struct bfd_hash_entry *, |
| 305 | struct bfd_hash_table *, |
| 306 | const char *)); |
| 307 | unsigned int size; |
| 308 | { |
| 309 | unsigned int alloc; |
| 310 | |
| 311 | alloc = size * sizeof (struct bfd_hash_entry *); |
| 312 | if (!obstack_begin (&table->memory, alloc)) |
| 313 | { |
| 314 | bfd_error = no_memory; |
| 315 | return false; |
| 316 | } |
| 317 | table->table = ((struct bfd_hash_entry **) |
| 318 | obstack_alloc (&table->memory, alloc)); |
| 319 | if (!table->table) |
| 320 | { |
| 321 | bfd_error = no_memory; |
| 322 | return false; |
| 323 | } |
| 324 | memset ((PTR) table->table, 0, alloc); |
| 325 | table->size = size; |
| 326 | table->newfunc = newfunc; |
| 327 | return true; |
| 328 | } |
| 329 | |
| 330 | /* Create a new hash table with the default number of entries. */ |
| 331 | |
| 332 | boolean |
| 333 | bfd_hash_table_init (table, newfunc) |
| 334 | struct bfd_hash_table *table; |
| 335 | struct bfd_hash_entry *(*newfunc) PARAMS ((struct bfd_hash_entry *, |
| 336 | struct bfd_hash_table *, |
| 337 | const char *)); |
| 338 | { |
| 339 | return bfd_hash_table_init_n (table, newfunc, DEFAULT_SIZE); |
| 340 | } |
| 341 | |
| 342 | /* Free a hash table. */ |
| 343 | |
| 344 | void |
| 345 | bfd_hash_table_free (table) |
| 346 | struct bfd_hash_table *table; |
| 347 | { |
| 348 | obstack_free (&table->memory, (PTR) NULL); |
| 349 | } |
| 350 | |
| 351 | /* Look up a string in a hash table. */ |
| 352 | |
| 353 | struct bfd_hash_entry * |
| 354 | bfd_hash_lookup (table, string, create, copy) |
| 355 | struct bfd_hash_table *table; |
| 356 | const char *string; |
| 357 | boolean create; |
| 358 | boolean copy; |
| 359 | { |
| 360 | register const unsigned char *s; |
| 361 | register unsigned long hash; |
| 362 | register unsigned int c; |
| 363 | struct bfd_hash_entry *hashp; |
| 364 | unsigned int len; |
| 365 | unsigned int index; |
| 366 | |
| 367 | hash = 0; |
| 368 | len = 0; |
| 369 | s = (const unsigned char *) string; |
| 370 | while ((c = *s++) != '\0') |
| 371 | { |
| 372 | hash += c + (c << 17); |
| 373 | hash ^= hash >> 2; |
| 374 | ++len; |
| 375 | } |
| 376 | hash += len + (len << 17); |
| 377 | hash ^= hash >> 2; |
| 378 | |
| 379 | index = hash % table->size; |
| 380 | for (hashp = table->table[index]; |
| 381 | hashp != (struct bfd_hash_entry *) NULL; |
| 382 | hashp = hashp->next) |
| 383 | { |
| 384 | if (hashp->hash == hash |
| 385 | && strcmp (hashp->string, string) == 0) |
| 386 | return hashp; |
| 387 | } |
| 388 | |
| 389 | if (! create) |
| 390 | return (struct bfd_hash_entry *) NULL; |
| 391 | |
| 392 | hashp = (*table->newfunc) ((struct bfd_hash_entry *) NULL, table, string); |
| 393 | if (hashp == (struct bfd_hash_entry *) NULL) |
| 394 | return (struct bfd_hash_entry *) NULL; |
| 395 | if (copy) |
| 396 | { |
| 397 | char *new; |
| 398 | |
| 399 | new = (char *) obstack_alloc (&table->memory, len + 1); |
| 400 | if (!new) |
| 401 | { |
| 402 | bfd_error = no_memory; |
| 403 | return (struct bfd_hash_entry *) NULL; |
| 404 | } |
| 405 | strcpy (new, string); |
| 406 | string = new; |
| 407 | } |
| 408 | hashp->string = string; |
| 409 | hashp->hash = hash; |
| 410 | hashp->next = table->table[index]; |
| 411 | table->table[index] = hashp; |
| 412 | |
| 413 | return hashp; |
| 414 | } |
| 415 | |
| 416 | /* Base method for creating a new hash table entry. */ |
| 417 | |
| 418 | /*ARGSUSED*/ |
| 419 | struct bfd_hash_entry * |
| 420 | bfd_hash_newfunc (entry, table, string) |
| 421 | struct bfd_hash_entry *entry; |
| 422 | struct bfd_hash_table *table; |
| 423 | const char *string; |
| 424 | { |
| 425 | if (entry == (struct bfd_hash_entry *) NULL) |
| 426 | entry = ((struct bfd_hash_entry *) |
| 427 | bfd_hash_allocate (table, sizeof (struct bfd_hash_entry))); |
| 428 | return entry; |
| 429 | } |
| 430 | |
| 431 | /* Allocate space in a hash table. */ |
| 432 | |
| 433 | PTR |
| 434 | bfd_hash_allocate (table, size) |
| 435 | struct bfd_hash_table *table; |
| 436 | unsigned int size; |
| 437 | { |
| 438 | return obstack_alloc (&table->memory, size); |
| 439 | } |
| 440 | |
| 441 | /* Traverse a hash table. */ |
| 442 | |
| 443 | void |
| 444 | bfd_hash_traverse (table, func, info) |
| 445 | struct bfd_hash_table *table; |
| 446 | boolean (*func) PARAMS ((struct bfd_hash_entry *, PTR)); |
| 447 | PTR info; |
| 448 | { |
| 449 | unsigned int i; |
| 450 | |
| 451 | for (i = 0; i < table->size; i++) |
| 452 | { |
| 453 | struct bfd_hash_entry *p; |
| 454 | |
| 455 | for (p = table->table[i]; p != NULL; p = p->next) |
| 456 | { |
| 457 | if (! (*func) (p, info)) |
| 458 | return; |
| 459 | } |
| 460 | } |
| 461 | } |