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* libkmod - interface to kernel module operations
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* Copyright (C) 2011 ProFUSION embedded systems
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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* This library 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 GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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#ifndef _LIBKMOD_INDEX_H
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#define _LIBKMOD_INDEX_H
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/* Integers are stored as 32 bit unsigned in "network" order, i.e. MSB first.
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All files start with a magic number.
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Magic spells "BOOTFAST". Second one used on newer versioned binary files.
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/* #define INDEX_MAGIC_OLD 0xB007FA57 */
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#define INDEX_MAGIC 0xB007F457
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/* We use a version string to keep track of changes to the binary format
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* This is stored in the form: INDEX_MAJOR (hi) INDEX_MINOR (lo) just in
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* case we ever decide to have minor changes that are not incompatible.
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#define INDEX_VERSION_MAJOR 0x0002
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#define INDEX_VERSION_MINOR 0x0001
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#define INDEX_VERSION ((INDEX_VERSION_MAJOR<<16)|INDEX_VERSION_MINOR)
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/* The index file maps keys to values. Both keys and values are ASCII strings.
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Each key can have multiple values. Values are sorted by an integer priority.
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The reader also implements a wildcard search (including range expressions)
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where the keys in the index are treated as patterns.
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This feature is required for module aliases.
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/* Implementation is based on a radix tree, or "trie".
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Each arc from parent to child is labelled with a character.
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Each path from the root represents a string.
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* Marked node, representing a key and it's values.
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Naive implementations tend to be very space inefficient; child pointers
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are stored in arrays indexed by character, but most child pointers are null.
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Our implementation uses a scheme described by Wikipedia as a Patrica trie,
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"easiest to understand as a space-optimized trie where
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each node with only one child is merged with its child"
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We still use arrays of child pointers indexed by a single character;
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the remaining characters of the label are stored as a "prefix" in the child.
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The paper describing the original Patrica trie works on individiual bits -
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each node has a maximum of two children, which increases space efficiency.
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However for this application it is simpler to use the ASCII character set.
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Since the index file is read-only, it can be compressed by omitting null
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child pointers at the start and end of arrays.
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#define INDEX_PRIORITY_MIN UINT32_MAX
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struct index_value *next;
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unsigned int priority;
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/* In-memory index (depmod only) */
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struct index_file *index_file_open(const char *filename);
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void index_file_close(struct index_file *idx);
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char *index_search(struct index_file *idx, const char *key);
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struct index_value *index_searchwild(struct index_file *idx, const char *key);
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void index_values_free(struct index_value *values);
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/* Implementation using mmap */
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struct index_mm *index_mm_open(struct kmod_ctx *ctx, const char *filename,
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bool populate, unsigned long long *stamp);
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void index_mm_close(struct index_mm *index);
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char *index_mm_search(struct index_mm *idx, const char *key);
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struct index_value *index_mm_searchwild(struct index_mm *idx, const char *key);
added
removed
libkmod/libkmod-index.h
