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785969a047
This will be used in ldconfig to reduce the ld.so.cache size slightly. Tail merging is an optimization where a pointer points into another string if the first string is a suffix of the second string. The hash function FNV-1a was chosen because it is simple and achieves good dispersion even for short strings (so that the hash table bucket count can be a power of two). It is clearly superior to the hsearch hash and the ELF hash in this regard. The hash table uses chaining for collision resolution. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
65 lines
2.4 KiB
C
65 lines
2.4 KiB
C
/* String tables for ld.so.cache construction.
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Copyright (C) 2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published
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by the Free Software Foundation; version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <https://www.gnu.org/licenses/>. */
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#ifndef _STRINGTABLE_H
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#define _STRINGTABLE_H
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#include <stddef.h>
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#include <stdint.h>
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/* An entry in the string table. Only the length and string fields are
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expected to be used outside the string table code. */
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struct stringtable_entry
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{
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struct stringtable_entry *next; /* For collision resolution. */
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uint32_t length; /* Length of then string. */
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uint32_t offset; /* From start of finalized table. */
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char string[]; /* Null-terminated string. */
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};
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/* A string table. Zero-initialization produces a valid atable. */
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struct stringtable
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{
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struct stringtable_entry **entries; /* Array of hash table buckets. */
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uint32_t count; /* Number of elements in the table. */
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uint32_t allocated; /* Length of the entries array. */
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};
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/* Adds STRING to TABLE. May return the address of an existing entry. */
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struct stringtable_entry *stringtable_add (struct stringtable *table,
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const char *string);
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/* Result of stringtable_finalize. SIZE bytes at STRINGS should be
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written to the file. */
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struct stringtable_finalized
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{
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char *strings;
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size_t size;
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};
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/* Assigns offsets to string table entries and computes the serialized
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form of the string table. */
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void stringtable_finalize (struct stringtable *table,
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struct stringtable_finalized *result);
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/* Deallocate the string table (but not the TABLE pointer itself).
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(The table can be re-used for adding more strings without
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initialization.) */
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void stringtable_free (struct stringtable *table);
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#endif /* _STRINGTABLE_H */
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