186 lines
7.2 KiB
C
186 lines
7.2 KiB
C
/*
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* Copyright (C) 2022-2024 Jordan Bancino <@jordan:bancino.net>
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation files
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* (the "Software"), to deal in the Software without restriction,
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* including without limitation the rights to use, copy, modify, merge,
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* publish, distribute, sublicense, and/or sell copies of the Software,
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* and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#ifndef CYTOPLASM_HASHMAP_H
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#define CYTOPLASM_HASHMAP_H
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/***
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* @Nm HashMap
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* @Nd A simple hash map implementation.
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* @Dd October 11 2022
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* @Xr Array Queue
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*
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* This is the public interface for Cytoplasm's hash map
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* implementation. This hash map is designed to be simple,
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* well-documented, and generally readable and understandable, yet also
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* performant enough to be useful, because it is used extensively
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* throughout the project.
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* .Pp
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* Fundamentally, this is an entirely generic map implementation. It
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* can be used for many general purposes, but it is designed only to
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* implement the features Cytoplasm needs to be functional. One
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* example of a Cytoplasm-specific feature is that keys cannot be
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* arbitrary data; they are NULL-terminated C strings.
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*/
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#include <stddef.h>
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#include "Array.h"
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/**
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* These functions operate on an opaque structure, which the caller
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* has no knowledge about.
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*/
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typedef struct HashMap HashMap;
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/**
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* Create a new hash map that is ready to be used with the rest of the
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* functions defined here.
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*/
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extern HashMap * HashMapCreate(void);
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/**
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* Free the specified hash map such that it becomes invalid and any
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* future use results in undefined behavior. Note that this function
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* does not free the values stored in the hash map, but since it stores
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* the keys internally, it will free the keys. You should use
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* .Fn HashMapIterate
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* to free the values stored in this map appropriately before calling
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* this function.
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*/
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extern void HashMapFree(HashMap *);
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/**
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* Control the maximum load of the hash map before it is expanded.
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* When the hash map reaches the given capacity, it is grown. You
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* don't want to only grow hash maps when they are full, because that
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* makes them perform very poorly. The maximum load value is a
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* percentage of how full the hash map is, and it should be between
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* 0 and 1, where 0 means that no elements will cause the map to be
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* expanded, and 1 means that the hash map must be completely full
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* before it is expanded. The default maximum load on a new hash map
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* is 0.75, which should be good enough for most purposes, however,
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* this function exists specifically so that the maximum load can be
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* fine-tuned.
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*/
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extern void HashMapMaxLoadSet(HashMap *, float);
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/**
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* Use a custom hashing function with the given hash map. New hash
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* maps have a sane hashing function that should work okay for most
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* use cases, but if you have a better hashing function, it can be
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* specified this way. Do not change the hash function after keys have
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* been added; doing so results in undefined behavior. Only set a new
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* hash function immediately after constructing a new hash map, before
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* anything has been added to it.
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* .Pp
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* The hash function takes a pointer to a C string, and is expected
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* to return a fairly unique numerical hash value which will be
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* converted into an array index.
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*/
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extern void
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HashMapFunctionSet(HashMap *, unsigned long (*) (const char *));
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/**
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* Set the given string key to the given value. Note that the key is
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* copied into the hash map's own memory space, but the value is not.
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* It is the caller's job to ensure that the value pointer remains
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* valid for the life of the hash map, and are freed when no longer
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* needed.
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*/
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extern void * HashMapSet(HashMap *, char *, void *);
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/**
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* Retrieve the value for the given key, or return NULL if no such
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* key exists in the hash map.
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*/
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extern void * HashMapGet(HashMap *, const char *);
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/**
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* Remove a value specified by the given key from the hash map, and
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* return it to the caller to deal with. This function returns NULL
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* if no such key exists.
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*/
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extern void * HashMapDelete(HashMap *, const char *);
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/**
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* Iterate over all the keys and values of a hash map. This function
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* works very similarly to
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* .Xr getopt 3 ,
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* where calls are repeatedly made in a while loop until there are no
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* more items to go over. The difference is that this function does not
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* rely on globals; it takes pointer pointers, and stores all
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* necessary state inside the hash map itself.
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* .Pp
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* Note that this function is not thread-safe; two threads cannot be
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* iterating over any given hash map at the same time, though they
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* can each be iterating over different hash maps.
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* .Pp
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* This function can be tricky to use in some scenarios, as it
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* continues where it left off on each call, until there are no more
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* elements to go through in the hash map. If you are not iterating
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* over the entire map in one go, and happen to break the loop, then
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* the next time you attempt to iterate the hash map, you'll start
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* somewhere in the middle, which is most likely not the intended
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* behavior. Thus, it is always recommended to iterate over the entire
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* hash map if you're going to use this function.
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* .Pp
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* Also note that the behavior of this function is undefined if
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* insertions or deletions occur during the iteration. This
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* functionality has not been tested, and will likely not work.
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*/
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extern bool HashMapIterate(HashMap *, char **, void **);
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/**
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* A reentrant version of
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* .Fn HashMapIterate
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* that allows the caller to overcome the flaws of that function by
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* storing the cursor outside of the hash map structure itself. This
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* allows multiple threads to iterate over the same hash map at the
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* same time, and it allows the iteration to be halted midway through
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* without causing any unintended side effects.
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* .Pp
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* The cursor should be initialized to 0 at the start of iteration.
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*/
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extern bool
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HashMapIterateReentrant(HashMap *, char **, void **, size_t *);
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/**
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* Collect the string keys of a hash map and return them as an array.
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* The returned array holds pointers to the strings stored in the
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* hash map, so the strings should NOT be freed; it is sufficient to
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* free the array itself. Likewise, once the hash map is freed, the
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* array elements are invalid and the array should be freed.
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*/
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extern Array * HashMapKeys(HashMap *);
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/**
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* Collect the values of a hash map and return them as an array. The
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* returned array holds the same pointers to the values as the hash
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* map.
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*/
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extern Array * HashMapValues(HashMap *);
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#endif /* CYTOPLASM_HASHMAP_H */
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