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Diffstat (limited to 'src/contrib/qp-trie/trie.h')
| -rw-r--r-- | src/contrib/qp-trie/trie.h | 280 |
1 files changed, 280 insertions, 0 deletions
diff --git a/src/contrib/qp-trie/trie.h b/src/contrib/qp-trie/trie.h new file mode 100644 index 0000000..d479d3e --- /dev/null +++ b/src/contrib/qp-trie/trie.h @@ -0,0 +1,280 @@ +/* Copyright (C) 2019 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz> + Copyright (C) 2018 Tony Finch <dot@dotat.at> + + 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, see <https://www.gnu.org/licenses/>. + */ + +#pragma once + +#include <stdbool.h> +#include <stdint.h> + +#include "libknot/mm_ctx.h" + +/*! + * \brief Native API of QP-tries: + * + * - keys are uint8_t strings, not necessarily zero-terminated, + * the structure copies the contents of the passed keys + * - values are void* pointers, typically you get an ephemeral pointer to it + * - key lengths are limited by 2^32-1 ATM + */ + +/*! \brief Element value. */ +typedef void* trie_val_t; +/*! \brief Key for indexing tries. Sign could be flipped easily. */ +typedef uint8_t trie_key_t; + +/*! \brief Opaque structure holding a QP-trie. */ +typedef struct trie trie_t; + +/*! \brief Opaque type for holding a QP-trie iterator. */ +typedef struct trie_it trie_it_t; + +/*! \brief Callback for cloning trie values. */ +typedef trie_val_t (*trie_dup_cb)(const trie_val_t val, knot_mm_t *mm); + +/*! \brief Callback for performing actions on a trie leaf + * + * Used during copy-on-write transactions + * + * \param val The value of the element to be altered + * \param key The key of the element to be altered + * \param len The length of key + * \param d Additional user data + */ +typedef void trie_cb(trie_val_t val, const trie_key_t *key, size_t len, void *d); + +/*! \brief Opaque type for holding the copy-on-write state for a QP-trie. */ +typedef struct trie_cow trie_cow_t; + +/*! \brief Create a trie instance. */ +trie_t* trie_create(knot_mm_t *mm); + +/*! \brief Free a trie instance. */ +void trie_free(trie_t *tbl); + +/*! \brief Clear a trie instance (make it empty). */ +void trie_clear(trie_t *tbl); + +/*! \brief Create a clone of existing trie. */ +trie_t* trie_dup(const trie_t *orig, trie_dup_cb dup_cb, knot_mm_t *mm); + +/*! \brief Return the number of keys in the trie. */ +size_t trie_weight(const trie_t *tbl); + +/*! \brief Search the trie, returning NULL on failure. */ +trie_val_t* trie_get_try(trie_t *tbl, const trie_key_t *key, uint32_t len); + +/*! \brief Search the trie including DNS wildcard semantics, returning NULL on failure. + * + * \note We assume the key is in knot_dname_lf() format, i.e. labels are ordered + * from root to leaf and separated by zero bytes (and no other zeros are allowed). + * \note Beware that DNS wildcard matching is not exactly what normal people would expect. + */ +trie_val_t* trie_get_try_wildcard(trie_t *tbl, const trie_key_t *key, uint32_t len); + +/*! \brief Search the trie, inserting NULL trie_val_t on failure. */ +trie_val_t* trie_get_ins(trie_t *tbl, const trie_key_t *key, uint32_t len); + +/*! + * \brief Search for less-or-equal element. + * + * \param tbl Trie. + * \param key Searched key. + * \param len Key length. + * \param val (optional) Value found; it will be set to NULL if not found or errored. + * \return KNOT_EOK for exact match, 1 for previous, KNOT_ENOENT for not-found, + * or KNOT_E*. + */ +int trie_get_leq(trie_t *tbl, const trie_key_t *key, uint32_t len, trie_val_t **val); + +/*! + * \brief Apply a function to every trie_val_t, in order. + * + * \return KNOT_EOK if success or KNOT_E* if error. + */ +int trie_apply(trie_t *tbl, int (*f)(trie_val_t *, void *), void *d); + +/*! + * \brief Remove an item, returning KNOT_EOK if succeeded or KNOT_ENOENT if not found. + * + * If val!=NULL and deletion succeeded, the deleted value is set. + */ +int trie_del(trie_t *tbl, const trie_key_t *key, uint32_t len, trie_val_t *val); + + +/*! \brief Create a new iterator pointing to the first element (if any). + * + * trie_it_* functions deal with these iterators capable of walking and jumping + * over the trie. Note that any modification to key-set stored by the trie + * will in general invalidate all iterators and you will need to begin anew. + * (It won't be detected - you may end up reading freed memory, etc.) + */ +trie_it_t* trie_it_begin(trie_t *tbl); + +/*! \brief Test if the iterator has gone "past the end" (and points nowhere). */ +bool trie_it_finished(trie_it_t *it); + +/*! \brief Free any resources of the iterator. It's OK to call it on NULL. */ +void trie_it_free(trie_it_t *it); + +/*! \brief Copy the iterator. See the warning in trie_it_begin(). */ +trie_it_t *trie_it_clone(const trie_it_t *it); + +/*! + * \brief Return pointer to the key of the current element. + * + * \note The len is uint32_t internally but size_t is better for our usage + * as it is without an additional type conversion. + */ +const trie_key_t* trie_it_key(trie_it_t *it, size_t *len); + +/*! \brief Return pointer to the value of the current element (writable). */ +trie_val_t* trie_it_val(trie_it_t *it); + +/*! + * \brief Advance the iterator to the next element. + * + * Iteration is in ascending lexicographical order. + * In particular, the empty string would be considered as the very first. + * + * \TODO: in most iterator operations, ENOMEM is very unlikely + * but it leads to a _finished() iterator (silently). + * Perhaps the functions should simply return KNOT_E* + */ +void trie_it_next(trie_it_t *it); +/*! \brief Advance the iterator to the previous element. See trie_it_next(). */ +void trie_it_prev(trie_it_t *it); + +/*! \brief Advance iterator to the next element, looping to first after last. */ +void trie_it_next_loop(trie_it_t *it); +/*! \brief Advance iterator to the previous element, looping to last after first. */ +void trie_it_prev_loop(trie_it_t *it); + +/*! \brief Advance iterator to the next element while ignoring the subtree. + * + * \note Another formulation: skip keys that are prefixed by the current key. + * \TODO: name, maybe _unprefixed? The thing is that in the "subtree" meaning + * doesn't correspond to how the pointers go in the implementation, + * but we may not care much for implementation in the API... + */ +void trie_it_next_nosub(trie_it_t *it); + +/*! \brief Advance iterator to the longest prefix of the current key. + * + * \TODO: name, maybe _prefix? Arguments similar to _nosub vs. _unprefixed. + */ +void trie_it_parent(trie_it_t *it); + +/*! \brief trie_get_leq() but with an iterator. */ +int trie_it_get_leq(trie_it_t *it, const trie_key_t *key, uint32_t len); + +/*! \brief Remove the current element. The iterator will get trie_it_finished() */ +void trie_it_del(trie_it_t *it); + + +/*! \brief Start a COW transaction + * + * A copy-on-write transaction starts by obtaining a write lock (in + * your application code) followed by a call to trie_cow(). This + * creates a shared clone of the trie and saves both old and new roots + * in the COW context. + * + * During the COW transaction, you call trie_cow_ins() or + * trie_cow_del() as necessary. These calls ensure that the relevant + * parts of the (new) trie are copied so that they can be modified + * freely. + * + * Your trie_val_t objects must be able to distinguish their + * reachability, either shared, or old-only, or new-only. Before a COW + * transaction the reachability of your objects is indeterminate. + * During a transaction, any trie_val_t objects that might be affected + * (because they are adjacent to a trie_get_cow() or trie_del_cow()) + * are first marked as shared using the callback you pass to + * trie_cow(). + * + * When the transaction is complete, to commit, call trie_cow_new() to + * get the new root, swap the old and new trie roots (e.g. with + * rcu_xchg_pointer()), wait for readers to finish with the old trie + * (e.g. using synchronize_rcu()), then call trie_cow_commit(). For a + * rollback, you can just call trie_cow_rollback() without waiting + * since that doesn't conflict with readers. After trie_cow_commit() + * or trie_cow_rollback() have finished, you can release your write + * lock. + * + * Concurrent reading of the old trie is allowed during a transaction + * provided that it is known when all readers have finished with the + * old version, e.g. using rcu_read_lock() and rcu_read_unlock(). + * There must be only one write transaction at a time. + * + * \param old the old trie + * \param mark_shared callback to mark a leaf as shared (can be NULL) + * \param d extra data for the callback + * \return a pointer to a COW context, + * or NULL if there was a failure + */ +trie_cow_t* trie_cow(trie_t *old, trie_cb *mark_shared, void *d); + +/*! \brief get the new trie from a COW context */ +trie_t* trie_cow_new(trie_cow_t *cow); + +/*! \brief variant of trie_get_ins() for use during COW transactions + * + * As necessary, this copies path from the root of the trie to the + * leaf, so that it is no longer shared. Any leaves adjacent to this + * path are marked as shared using the mark_shared callback passed to + * trie_cow(). + * + * It is your responsibility to COW your trie_val_t objects. If you copy an + * object you must change the original's reachability from shared to old-only. + * New objects (including copies) must have new-only reachability. + */ +trie_val_t* trie_get_cow(trie_cow_t *cow, const trie_key_t *key, uint32_t len); + +/*! + * \brief variant of trie_del() for use during COW transactions + * + * The mark_shared callback is invoked as necessary, in the same way + * as trie_get_cow(). + * + * Returns KNOT_EOK if the key was removed or KNOT_ENOENT if not found. + * If val!=NULL and deletion succeeded, the *val is set to the deleted + * value pointer. + */ +int trie_del_cow(trie_cow_t *cow, const trie_key_t *key, uint32_t len, trie_val_t *val); + +/*! \brief clean up the old trie after committing a COW transaction + * + * Your callback is invoked for any trie_val_t objects that might need + * cleaning up; you must free any objects you have marked as old-only + * and retain objects with shared reachability. + * + * \note The callback can be NULL. + * + * The cow object is free()d, and the new trie root is returned. + */ +trie_t* trie_cow_commit(trie_cow_t *cow, trie_cb *cb, void *d); + +/*! \brief clean up the new trie after rolling back a COW transaction + * + * Your callback is invoked for any trie_val_t objects that might need + * cleaning up; you must free any objects you have marked as new-only + * and retain objects with shared reachability. + * + * \note The callback can be NULL. + * + * The cow object is free()d, and the old trie root is returned. + */ +trie_t* trie_cow_rollback(trie_cow_t *cow, trie_cb *cb, void *d); |