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/* hash.c -- hash table routines for BFD Copyright 1993, 1994, 1995, 1997, 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007 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 = 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 (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; new = objalloc_alloc ((struct objalloc *) table->memory, len + 1); if (!new) { bfd_set_error (bfd_error_no_memory); return NULL; } memcpy (new, string, len + 1); string = new; } 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 = 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 = 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 = 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; } /* Free a strtab. */ void _bfd_stringtab_free (struct bfd_strtab_hash *table) { bfd_hash_table_free (&table->table); free (table); } /* Get the index of a string in a strtab, adding it if it is not already present. If HASH is FALSE, we don't really use the hash table, and we don't eliminate duplicate strings. */ bfd_size_type _bfd_stringtab_add (struct bfd_strtab_hash *tab, const char *str, bfd_boolean hash, bfd_boolean copy) { struct strtab_hash_entry *entry; if (hash) { entry = strtab_hash_lookup (tab, str, TRUE, copy); if (entry == NULL) return (bfd_size_type) -1; } else { entry = bfd_hash_allocate (&tab->table, sizeof (* entry)); if (entry == NULL) return (bfd_size_type) -1; if (! copy) entry->root.string = str; else { char *n; n = bfd_hash_allocate (&tab->table, strlen (str) + 1); if (n == NULL) return (bfd_size_type) -1; entry->root.string = n; } entry->index = (bfd_size_type) -1; entry->next = NULL; } if (entry->index == (bfd_size_type) -1) { entry->index = tab->size; tab->size += strlen (str) + 1; if (tab->xcoff) { entry->index += 2; tab->size += 2; } if (tab->first == NULL) tab->first = entry; else tab->last->next = entry; tab->last = entry; } return entry->index; } /* Get the number of bytes in a strtab. */ bfd_size_type _bfd_stringtab_size (struct bfd_strtab_hash *tab) { return tab->size; } /* Write out a strtab. ABFD must already be at the right location in the file. */ bfd_boolean _bfd_stringtab_emit (bfd *abfd, struct bfd_strtab_hash *tab) { bfd_boolean xcoff; struct strtab_hash_entry *entry; xcoff = tab->xcoff; for (entry = tab->first; entry != NULL; entry = entry->next) { const char *str; size_t len; str = entry->root.string; len = strlen (str) + 1; if (xcoff) { bfd_byte buf[2]; /* The output length includes the null byte. */ bfd_put_16 (abfd, (bfd_vma) len, buf); if (bfd_bwrite ((void *) buf, (bfd_size_type) 2, abfd) != 2) return FALSE; } if (bfd_bwrite ((void *) str, (bfd_size_type) len, abfd) != len) return FALSE; } return TRUE; }
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