| |
| /* index.c: module index file shared functions for modprobe and depmod |
| Copyright (C) 2008 Alan Jenkins <alan-jenkins@tuffmail.co.uk>. |
| |
| These programs are 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 2 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 these programs. If not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #ifndef MODINITTOOLS_INDEX_H |
| #define MODINITTOOLS_INDEX_H |
| |
| #include <stdint.h> |
| |
| /* Integers are stored as 32 bit unsigned in "network" order, i.e. MSB first. |
| All files start with a magic number. |
| |
| Magic spells "BOOTFAST". Second one used on newer versioned binary files. |
| */ |
| /* #define INDEX_MAGIC_OLD 0xB007FA57 */ |
| #define INDEX_MAGIC 0xB007F457 |
| |
| /* We use a version string to keep track of changes to the binary format |
| * This is stored in the form: INDEX_MAJOR (hi) INDEX_MINOR (lo) just in |
| * case we ever decide to have minor changes that are not incompatible. |
| */ |
| |
| #define INDEX_VERSION_MAJOR 0x0002 |
| #define INDEX_VERSION_MINOR 0x0001 |
| #define INDEX_VERSION ((INDEX_VERSION_MAJOR<<16)|INDEX_VERSION_MINOR) |
| |
| /* The index file maps keys to values. Both keys and values are ASCII strings. |
| Each key can have multiple values. Values are sorted by an integer priority. |
| |
| The reader also implements a wildcard search (including range expressions) |
| where the keys in the index are treated as patterns. |
| This feature is required for module aliases. |
| */ |
| |
| /* Implementation is based on a radix tree, or "trie". |
| Each arc from parent to child is labelled with a character. |
| Each path from the root represents a string. |
| |
| == Example strings == |
| |
| ask |
| ate |
| on |
| once |
| one |
| |
| == Key == |
| + Normal node |
| * Marked node, representing a key and it's values. |
| |
| + |
| |-a-+-s-+-k-* |
| | | |
| | `-t-+-e-* |
| | |
| `-o-+-n-*-c-+-e-* |
| | |
| `-e-* |
| |
| Naive implementations tend to be very space inefficient; child pointers |
| are stored in arrays indexed by character, but most child pointers are null. |
| |
| Our implementation uses a scheme described by Wikipedia as a Patrica trie, |
| |
| "easiest to understand as a space-optimized trie where |
| each node with only one child is merged with its child" |
| |
| + |
| |-a-+-sk-* |
| | | |
| | `-te-* |
| | |
| `-on-*-ce-* |
| | |
| `-e-* |
| |
| We still use arrays of child pointers indexed by a single character; |
| the remaining characters of the label are stored as a "prefix" in the child. |
| |
| The paper describing the original Patrica trie works on individiual bits - |
| each node has a maximum of two children, which increases space efficiency. |
| However for this application it is simpler to use the ASCII character set. |
| Since the index file is read-only, it can be compressed by omitting null |
| child pointers at the start and end of arrays. |
| */ |
| |
| #define INDEX_PRIORITY_MIN UINT32_MAX |
| |
| struct index_value { |
| struct index_value *next; |
| unsigned int priority; |
| char value[0]; |
| }; |
| |
| /* In-memory index (depmod only) */ |
| |
| #define INDEX_CHILDMAX 128 |
| struct index_node { |
| char *prefix; /* path compression */ |
| struct index_value *values; |
| unsigned char first; /* range of child nodes */ |
| unsigned char last; |
| struct index_node *children[INDEX_CHILDMAX]; /* indexed by character */ |
| }; |
| |
| /* Disk format: |
| |
| uint32_t magic = INDEX_MAGIC; |
| uint32_t version = INDEX_VERSION; |
| uint32_t root_offset; |
| |
| (node_offset & INDEX_NODE_MASK) specifies the file offset of nodes: |
| |
| char[] prefix; // nul terminated |
| |
| char first; |
| char last; |
| uint32_t children[last - first + 1]; |
| |
| uint32_t value_count; |
| struct { |
| uint32_t priority; |
| char[] value; // nul terminated |
| } values[value_count]; |
| |
| (node_offset & INDEX_NODE_FLAGS) indicates which fields are present. |
| Empty prefixes are ommitted, leaf nodes omit the three child-related fields. |
| |
| This could be optimised further by adding a sparse child format |
| (indicated using a new flag). |
| */ |
| |
| /* Format of node offsets within index file */ |
| enum node_offset { |
| INDEX_NODE_FLAGS = 0xF0000000, /* Flags in high nibble */ |
| INDEX_NODE_PREFIX = 0x80000000, |
| INDEX_NODE_VALUES = 0x40000000, |
| INDEX_NODE_CHILDS = 0x20000000, |
| |
| INDEX_NODE_MASK = 0x0FFFFFFF, /* Offset value */ |
| }; |
| |
| struct index_file; |
| |
| struct index_node *index_create(void); |
| void index_destroy(struct index_node *node); |
| int index_insert(struct index_node *node, const char *key, |
| const char *value, unsigned int priority); |
| void index_write(const struct index_node *node, FILE *out); |
| |
| struct index_file *index_file_open(const char *filename); |
| void index_file_close(struct index_file *index); |
| |
| /* Dump all strings in index as lines in a plain text file |
| (prefix is prepended to each line) |
| */ |
| void index_dump(struct index_file *in, FILE *out, const char *prefix); |
| |
| /* Return value for first matching key. |
| Keys must be exactly equal to match - i.e. there are no wildcard patterns |
| */ |
| char *index_search(struct index_file *index, const char *key); |
| |
| /* Return values for all matching keys. |
| The keys in the index are treated as wildcard patterns using fnmatch() |
| */ |
| struct index_value *index_searchwild(struct index_file *index, const char *key); |
| |
| void index_values_free(struct index_value *values); |
| |
| #endif /* MODINITTOOLS_INDEX_H */ |