The Flat Hash Map Interface. More...

#include "impl/impl_flat_hash_map.h"
#include "types.h"

Include dependency graph for flat_hash_map.h:

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Initialization Interface
Initialize the container with memory, callbacks, and permissions.
#define	ccc_fhm_init(memory_ptr, capacity, fhash_elem_field, key_field, alloc_fn, hash_fn, key_eq_fn, aux_data)
	Initialize a map with a buffer of types at compile time or runtime.

ccc_result	ccc_fhm_copy (ccc_flat_hash_map dst, ccc_flat_hash_map const src, ccc_alloc_fn *fn)
	Copy the map at source to destination.

Entry Interface
Obtain and operate on container entries for efficient queries when non-trivial control flow is needed.
#define	ccc_fhm_insert_r(flat_hash_map_ptr, out_handle_ptr)
	Invariantly inserts the key value wrapping out_handle_ptr.

#define	ccc_fhm_remove_r(flat_hash_map_ptr, out_handle_ptr)
	Removes the key value in the map storing the old value, if present, in the struct containing out_handle_ptr provided by the user.

#define	ccc_fhm_try_insert_r(flat_hash_map_ptr, key_val_handle_ptr)
	Attempts to insert the key value wrapping key_val_handle_ptr.

#define	ccc_fhm_try_insert_w(flat_hash_map_ptr, key, lazy_value...)
	lazily insert lazy_value into the map at key if key is absent.

#define	ccc_fhm_insert_or_assign_r(flat_hash_map_ptr, key_val_handle_ptr)
	Invariantly inserts or overwrites a user struct into the table.

#define	ccc_fhm_insert_or_assign_w(flat_hash_map_ptr, key, lazy_value...)
	Inserts a new key value pair or overwrites the existing entry.

#define	ccc_fhm_entry_r(flat_hash_map_ptr, key_ptr)
	Obtains an entry for the provided key in the table for future use.

#define	ccc_fhm_and_modify_w(flat_hash_map_entry_ptr, type_name, closure_over_T...)
	Modify an Occupied entry with a closure over user type T.

#define	ccc_fhm_or_insert_w(flat_hash_map_entry_ptr, lazy_key_value...) ccc_impl_fhm_or_insert_w(flat_hash_map_entry_ptr, lazy_key_value)
	lazily insert the desired key value into the entry if it is Vacant.

#define	ccc_fhm_insert_entry_w(flat_hash_map_entry_ptr, lazy_key_value...) ccc_impl_fhm_insert_entry_w(flat_hash_map_entry_ptr, lazy_key_value)
	write the contents of the compound literal lazy_key_value to a slot.

#define	ccc_fhm_remove_entry_r(flat_hash_map_entry_ptr)
	Remove the entry from the table if Occupied.

ccc_entry	ccc_fhm_insert (ccc_flat_hash_map h, ccc_fhmap_elem out_handle)
	Invariantly inserts the key value wrapping out_handle.

ccc_entry	ccc_fhm_remove (ccc_flat_hash_map h, ccc_fhmap_elem out_handle)
	Removes the key value in the map storing the old value, if present, in the struct containing out_handle provided by the user.

ccc_entry	ccc_fhm_try_insert (ccc_flat_hash_map h, ccc_fhmap_elem key_val_handle)
	Attempts to insert the key value wrapping key_val_handle.

ccc_entry	ccc_fhm_insert_or_assign (ccc_flat_hash_map h, ccc_fhmap_elem key_val_handle)
	Invariantly inserts or overwrites a user struct into the table.

ccc_fhmap_entry	ccc_fhm_entry (ccc_flat_hash_map h, void const key)
	Obtains an entry for the provided key in the table for future use.

ccc_fhmap_entry *	ccc_fhm_and_modify (ccc_fhmap_entry e, ccc_update_fn fn)
	Modifies the provided entry if it is Occupied.

ccc_fhmap_entry *	ccc_fhm_and_modify_aux (ccc_fhmap_entry e, ccc_update_fn fn, void *aux)
	Modifies the provided entry if it is Occupied.

void *	ccc_fhm_or_insert (ccc_fhmap_entry const e, ccc_fhmap_elem elem)
	Inserts the struct with handle elem if the entry is Vacant.

void *	ccc_fhm_insert_entry (ccc_fhmap_entry const e, ccc_fhmap_elem elem)
	Inserts the provided entry invariantly.

ccc_entry	ccc_fhm_remove_entry (ccc_fhmap_entry const *e)
	Remove the entry from the table if Occupied.

void *	ccc_fhm_unwrap (ccc_fhmap_entry const *e)
	Unwraps the provided entry to obtain a view into the table element.

bool	ccc_fhm_occupied (ccc_fhmap_entry const *e)
	Returns the Vacant or Occupied status of the entry.

bool	ccc_fhm_insert_error (ccc_fhmap_entry const *e)
	Provides the status of the entry should an insertion follow.

ccc_entry_status	ccc_fhm_entry_status (ccc_fhmap_entry const *e)
	Obtain the entry status from a container entry.

Container Types
Types available in the container interface.
typedef struct ccc_fhmap_	ccc_flat_hash_map
	A container for storing key-value structures defined by the user in a contiguous buffer.

typedef struct ccc_fhmap_elem_	ccc_fhmap_elem
	An intrusive element for a user provided type.

typedef union ccc_fhmap_entry_	ccc_fhmap_entry
	A container specific entry used to implement the Entry Interface.

Membership Interface
Test membership or obtain references to stored user types directly.
bool	ccc_fhm_contains (ccc_flat_hash_map h, void const key)
	Searches the table for the presence of key.

void *	ccc_fhm_get_key_val (ccc_flat_hash_map h, void const key)
	Returns a reference into the table at entry key.

Deallocation Interface
Destroy the container.
ccc_result	ccc_fhm_clear (ccc_flat_hash_map h, ccc_destructor_fn fn)
	Frees all slots in the table for use without affecting capacity.

ccc_result	ccc_fhm_clear_and_free (ccc_flat_hash_map h, ccc_destructor_fn fn)
	Frees all slots in the table and frees the underlying buffer.

Iterator Interface
Obtain and manage iterators over the container.
void *	ccc_fhm_begin (ccc_flat_hash_map const *h)
	Obtains a pointer to the first element in the table.

void *	ccc_fhm_next (ccc_flat_hash_map const h, ccc_fhmap_elem const iter)
	Advances the iterator to the next occupied table slot.

void *	ccc_fhm_end (ccc_flat_hash_map const *h)
	Check the current iterator against the end for loop termination.

State Interface
Obtain the container state.
bool	ccc_fhm_is_empty (ccc_flat_hash_map const *h)
	Returns the size status of the table.

size_t	ccc_fhm_size (ccc_flat_hash_map const *h)
	Returns the size of the table.

size_t	ccc_fhm_next_prime (size_t n)
	Helper to find a prime number if needed.

size_t	ccc_fhm_capacity (ccc_flat_hash_map const *h)
	Return the full capacity of the backing storage.

void *	ccc_fhm_data (ccc_flat_hash_map const *h)
	Return a reference to the base of backing array. O(1).

bool	ccc_fhm_validate (ccc_flat_hash_map const *h)
	Validation of invariants for the hash table.

Detailed Description

The Flat Hash Map Interface.

A Flat Hash Map stores elements by hash value and allows the user to retrieve them by key in amortized O(1). Elements in the table may be copied and moved so no pointer stability is available in this implementation. If pointer stability is needed, store and hash pointers to those elements in this table.

A flat hash map requires the user to provide a struct with known key and flat hash element fields as well as a hash function and key comparator function. The hash function should be well tailored to the key being stored in the table to prevent collisions. Currently, the flat hash map does not offer any default hash functions or hash strengthening algorithms so strong hash functions should be obtained by the user for the data set.

To shorten names in the interface, define the following preprocessor directive at the top of your file.

#define FLAT_HASH_MAP_USING_NAMESPACE_CCC

All types and functions can then be written without the ccc_ prefix.

Macro Definition Documentation

◆ ccc_fhm_and_modify_w

#define ccc_fhm_and_modify_w	(	flat_hash_map_entry_ptr,
		type_name,
		closure_over_T...
	)

Value:

    &(ccc_fhmap_entry)                                                         \
    {                                                                          \
        ccc_impl_fhm_and_modify_w(flat_hash_map_entry_ptr, type_name,          \
                                  closure_over_T)                              \
    }

Modify an Occupied entry with a closure over user type T.

Parameters

[in]	flat_hash_map_entry_ptr	a pointer to the obtained entry.
[in]	type_name	the name of the user type stored in the container.
[in]	closure_over_T	the code to be run on the reference to user type T, if Occupied. This may be a semicolon separated list of statements to execute on T or a section of code wrapped in braces {code here} which may be preferred for formatting.

Returns: a compound literal reference to the modified entry if it was occupied or a vacant entry if it was vacant.

Note: T is a reference to the user type stored in the entry guaranteed to be non-NULL if the closure executes.

#define FLAT_HASH_MAP_USING_NAMESPACE_CCC
// Increment the key k if found otherwise do nothing.
fhm_entry *e = fhm_and_modify_w(entry_r(&fhm, &k), word, T->cnt++;);
 
// Increment the key k if found otherwise insert a default value.
word *w = fhm_or_insert_w(fhm_and_modify_w(entry_r(&fhm, &k), word,
                                           { T->cnt++; }),
                          (word){.key = k, .cnt = 1});

Note that any code written is only evaluated if the entry is Occupied and the container can deliver the user type T. This means any function calls are lazily evaluated in the closure scope.

◆ ccc_fhm_entry_r

#define ccc_fhm_entry_r	(	flat_hash_map_ptr,
		key_ptr
	)

Value:

    &(ccc_fhmap_entry)                                                         \
    {                                                                          \
        ccc_fhm_entry((flat_hash_map_ptr), (key_ptr)).impl_                    \
    }

Obtains an entry for the provided key in the table for future use.

Parameters

[in]	flat_hash_map_ptr	the hash table to be searched.
[in]	key_ptr	the key used to search the table matching the stored key type.

Returns: a compound literal reference to a specialized hash entry for use with other functions in the Entry Interface.

Warning: the contents of an entry should not be examined or modified. Use the provided functions, only.

An entry is a search result that provides either an Occupied or Vacant entry in the table. An occupied entry signifies that the search was successful. A Vacant entry means the search was not successful but we now have a handle to where in the table such an element should be inserted.

An entry is most often passed in a functional style to subsequent calls in the Entry Interface.

◆ ccc_fhm_init

#define ccc_fhm_init	(	memory_ptr,
		capacity,
		fhash_elem_field,
		key_field,
		alloc_fn,
		hash_fn,
		key_eq_fn,
		aux_data
	)

Value:

ccc_impl_fhm_init(memory_ptr, capacity, fhash_elem_field, key_field, \

alloc_fn, hash_fn, key_eq_fn, aux_data)

Initialize a map with a buffer of types at compile time or runtime.

Parameters

[in]	memory_ptr	the pointer to the backing buffer array of user types. May be NULL if the user provides a allocation function. The buffer will be interpreted in units of type size that the user intends to store.
[in]	capacity	the starting capacity of the provided buffer or 0 if no buffer is provided and an allocation function is given.
[in]	fhash_elem_field	the name of the fhmap_elem field.
[in]	key_field	the field of the struct used for key storage.
[in]	alloc_fn	the allocation function for resizing or NULL if no resizing is allowed.
[in]	hash_fn	the ccc_hash_fn function the user desires for the table.
[in]	key_eq_fn	the ccc_key_eq_fn the user intends to use.
[in]	aux_data	auxiliary data that is needed for hashing or comparison.

Returns: the flat hash map directly initialized on the right hand side of the equality operator (i.e. ccc_flat_hash_map fh = ccc_fhm_init(...);)

◆ ccc_fhm_insert_entry_w

#define ccc_fhm_insert_entry_w	(	flat_hash_map_entry_ptr,
		lazy_key_value...
	)	ccc_impl_fhm_insert_entry_w(flat_hash_map_entry_ptr, lazy_key_value)

write the contents of the compound literal lazy_key_value to a slot.

Parameters

[in]	flat_hash_map_entry_ptr	a pointer to the obtained entry.
[in]	lazy_key_value	the compound literal to write to a new slot.

Returns: a reference to the newly inserted or overwritten user type. NULL is returned if resizing is required but fails or is not allowed.

◆ ccc_fhm_insert_or_assign_r

#define ccc_fhm_insert_or_assign_r	(	flat_hash_map_ptr,
		key_val_handle_ptr
	)

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_fhm_insert_or_assign((flat_hash_map_ptr), (key_val_handle)).impl_  \
    }

Invariantly inserts or overwrites a user struct into the table.

Parameters

[in]	flat_hash_map_ptr	a pointer to the flat hash map.
[in]	key_val_handle_ptr	the handle to the wrapping user struct key value.

Returns: a compound literal reference to the entry. If Occupied an entry was overwritten by the new key value. If Vacant no prior table entry existed.

Note that this function can be used when the old user type is not needed but the information regarding its presence is helpful.

◆ ccc_fhm_insert_or_assign_w

#define ccc_fhm_insert_or_assign_w	(	flat_hash_map_ptr,
		key,
		lazy_value...
	)

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_impl_fhm_insert_or_assign_w(flat_hash_map_ptr, key, lazy_value)    \
    }

Inserts a new key value pair or overwrites the existing entry.

Parameters

[in]	flat_hash_map_ptr	the pointer to the flat hash map.
[in]	key	the key to be searched in the table.
[in]	lazy_value	the compound literal to insert or use for overwrite.

Returns: a compound literal reference to the entry of the existing or newly inserted value. Occupied indicates the key existed, Vacant indicates the key was absent. Unwrapping in any case provides the current value unless an error occurs that prevents insertion. An insertion error will flag such a case.

Note that for brevity and convenience the user need not write the key to the lazy value compound literal as well. This function ensures the key in the compound literal matches the searched key.

◆ ccc_fhm_insert_r

#define ccc_fhm_insert_r	(	flat_hash_map_ptr,
		out_handle_ptr
	)

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_fhm_insert((flat_hash_map_ptr), (out_handle_ptr)).impl_            \
    }

Invariantly inserts the key value wrapping out_handle_ptr.

Parameters

[in]	flat_hash_map_ptr	the pointer to the flat hash map.
[out]	out_handle_ptr	the handle to the user type wrapping fhash elem.

Returns: a compound literal reference to the entry. If Vacant, no prior element with key existed and the type wrapping out_handle_ptr remains unchanged. If Occupied the old value is written to the type wrapping out_handle_ptr and may be unwrapped to view. If more space is needed but allocation fails or has been forbidden, an insert error is set.

Note that this function may write to the struct containing the second parameter and wraps it in an entry to provide information about the old value.

◆ ccc_fhm_or_insert_w

#define ccc_fhm_or_insert_w	(	flat_hash_map_entry_ptr,
		lazy_key_value...
	)	ccc_impl_fhm_or_insert_w(flat_hash_map_entry_ptr, lazy_key_value)

lazily insert the desired key value into the entry if it is Vacant.

Parameters

[in]	flat_hash_map_entry_ptr	a pointer to the obtained entry.
[in]	lazy_key_value	the compound literal to construct in place if the entry is Vacant.

Returns: a reference to the unwrapped user type in the entry, either the unmodified reference if the entry was Occupied or the newly inserted element if the entry was Vacant. NULL is returned if resizing is required but fails or is not allowed.

Note that if the compound literal uses any function calls to generate values or other data, such functions will not be called if the entry is Occupied.

◆ ccc_fhm_remove_entry_r

#define ccc_fhm_remove_entry_r ( flat_hash_map_entry_ptr )

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_fhm_remove_entry((flat_hash_map_entry_ptr)).impl_                  \
    }

Remove the entry from the table if Occupied.

Parameters

[in] flat_hash_map_entry_ptr a pointer to the table entry.

Returns: an entry containing NULL. If Occupied an entry in the table existed and was removed. If Vacant, no prior entry existed to be removed.

◆ ccc_fhm_remove_r

#define ccc_fhm_remove_r	(	flat_hash_map_ptr,
		out_handle_ptr
	)

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_fhm_remove((flat_hash_map_ptr), (out_handle_ptr)).impl_            \
    }

Removes the key value in the map storing the old value, if present, in the struct containing out_handle_ptr provided by the user.

Parameters

[in]	flat_hash_map_ptr	the pointer to the flat hash map.
[out]	out_handle_ptr	the handle to the user type wrapping fhash elem.

Returns: a compound literal reference to the removed entry. If Occupied it may be unwrapped to obtain the old key value pair. If Vacant the key value pair was not stored in the map. If bad input is provided an input error is set.

Note that this function may write to the struct containing the second parameter and wraps it in an entry to provide information about the old value.

◆ ccc_fhm_try_insert_r

#define ccc_fhm_try_insert_r	(	flat_hash_map_ptr,
		key_val_handle_ptr
	)

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_fhm_try_insert((flat_hash_map_ptr), (key_val_handle_ptr)).impl_    \
    }

Attempts to insert the key value wrapping key_val_handle_ptr.

Parameters

[in]	flat_hash_map_ptr	the pointer to the flat hash map.
[in]	key_val_handle_ptr	the handle to the user type wrapping fhash elem.

Returns: a compound literal reference to the entry. If Occupied, the entry contains a reference to the key value user type in the table and may be unwrapped. If Vacant the entry contains a reference to the newly inserted entry in the table. If more space is needed but allocation fails or has been forbidden, an insert error is set.

Warning: because this function returns a reference to a user type in the table any subsequent insertions or deletions invalidate this reference.

◆ ccc_fhm_try_insert_w

#define ccc_fhm_try_insert_w	(	flat_hash_map_ptr,
		key,
		lazy_value...
	)

Value:

    &(ccc_entry)                                                               \
    {                                                                          \
        ccc_impl_fhm_try_insert_w(flat_hash_map_ptr, key, lazy_value)          \
    }

lazily insert lazy_value into the map at key if key is absent.

Parameters

[in]	flat_hash_map_ptr	a pointer to the flat hash map.
[in]	key	the direct key r-value.
[in]	lazy_value	the compound literal specifying the value.

Returns: a compound literal reference to the entry of the existing or newly inserted value. Occupied indicates the key existed, Vacant indicates the key was absent. Unwrapping in any case provides the current value unless an error occurs that prevents insertion. An insertion error will flag such a case.

Warning: ensure the key type matches the type stored in table as your key. For example, if your key is of type int and you pass a size_t variable to the key argument, you will overwrite adjacent bytes of your struct.

Note that for brevity and convenience the user need not write the key to the lazy value compound literal as well. This function ensures the key in the compound literal matches the searched key.

Typedef Documentation

◆ ccc_fhmap_elem

typedef struct ccc_fhmap_elem_ ccc_fhmap_elem

An intrusive element for a user provided type.

Because the hash map is flat, data is always copied from the provided type into the table.

◆ ccc_fhmap_entry

typedef union ccc_fhmap_entry_ ccc_fhmap_entry

A container specific entry used to implement the Entry Interface.

The Entry Interface offers efficient search and subsequent insertion, deletion, or value update based on the needs of the user.

◆ ccc_flat_hash_map

typedef struct ccc_fhmap_ ccc_flat_hash_map

A container for storing key-value structures defined by the user in a contiguous buffer.

A flat hash map can be initialized on the stack, heap, or data segment at runtime.

Function Documentation

◆ ccc_fhm_and_modify()

ccc_fhmap_entry * ccc_fhm_and_modify	(	ccc_fhmap_entry *	e,
		ccc_update_fn *	fn
	)

Modifies the provided entry if it is Occupied.

Parameters

[in]	e	the entry obtained from an entry function or macro.
[in]	fn	an update function in which the auxiliary argument is unused.

Returns: the updated entry if it was Occupied or the unmodified vacant entry.

This function is intended to make the function chaining in the Entry Interface more succinct if the entry will be modified in place based on its own value without the need of the auxiliary argument a ccc_update_fn can provide.

◆ ccc_fhm_and_modify_aux()

ccc_fhmap_entry * ccc_fhm_and_modify_aux	(	ccc_fhmap_entry *	e,
		ccc_update_fn *	fn,
		void *	aux
	)

Modifies the provided entry if it is Occupied.

Parameters

[in]	e	the entry obtained from an entry function or macro.
[in]	fn	an update function that requires auxiliary data.
[in]	aux	auxiliary data required for the update.

Returns: the updated entry if it was Occupied or the unmodified vacant entry.

This function makes full use of a ccc_update_fn capability, meaning a complete ccc_update object will be passed to the update function callback.

◆ ccc_fhm_begin()

void * ccc_fhm_begin ( ccc_flat_hash_map const * h )

Obtains a pointer to the first element in the table.

Parameters

[in] h the table to iterate through.

Returns: a pointer that can be cast directly to the user type that is stored.

Warning: erasing or inserting during iteration may invalidate iterators if resizing occurs which would lead to undefined behavior. O(capacity).

Iteration starts from index 0 by capacity of the table so iteration order is not obvious to the user, nor should any specific order be relied on.

◆ ccc_fhm_capacity()

size_t ccc_fhm_capacity ( ccc_flat_hash_map const * h )

Return the full capacity of the backing storage.

Parameters

[in] h the hash table.

Returns: the capacity.

◆ ccc_fhm_clear()

ccc_result ccc_fhm_clear	(	ccc_flat_hash_map *	h,
		ccc_destructor_fn *	fn
	)

Frees all slots in the table for use without affecting capacity.

Parameters

[in]	h	the table to be cleared.
[in]	fn	the destructor for each element. NULL can be passed if no maintenance is required on the elements in the table before their slots are forfeit.

If NULL is passed as the destructor function time is O(1), else O(capacity).

◆ ccc_fhm_clear_and_free()

ccc_result ccc_fhm_clear_and_free	(	ccc_flat_hash_map *	h,
		ccc_destructor_fn *	fn
	)

Frees all slots in the table and frees the underlying buffer.

Parameters

[in]	h	the table to be cleared.
[in]	fn	the destructor for each element. NULL can be passed if no maintenance is required on the elements in the table before their slots are forfeit.

Returns: the result of free operation. If no alloc function is provided it is an error to attempt to free the buffer and a memory error is returned. Otherwise, an OK result is returned.

◆ ccc_fhm_contains()

bool ccc_fhm_contains	(	ccc_flat_hash_map *	h,
		void const *	key
	)

Searches the table for the presence of key.

Parameters

[in]	h	the flat hash table to be searched.
[in]	key	pointer to the key matching the key type of the user struct.

Returns: true if the struct containing key is stored, false if not.

◆ ccc_fhm_copy()

ccc_result ccc_fhm_copy	(	ccc_flat_hash_map *	dst,
		ccc_flat_hash_map const *	src,
		ccc_alloc_fn *	fn
	)

Copy the map at source to destination.

Parameters

[in]	dst	the initialized destination for the copy of the src map.
[in]	src	the initialized source of the map.
[in]	fn	the optional allocation function if resizing is needed.

Returns: the result of the copy operation. If the destination capacity is less than the source capacity and no allocation function is provided an input error is returned. If resizing is required and resizing of dst fails a memory error is returned.

Note: dst must have capacity greater than or equal to src. If dst capacity is less than src, an allocation function must be provided with the fn argument.

Note that there are two ways to copy data from source to destination: provide sufficient memory and pass NULL as fn, or allow the copy function to take care of allocation for the copy.

Manual memory management with no allocation function provided.

#define FLAT_HASH_MAP_USING_NAMESPACE_CCC
struct val
{
    fhmap_elem e;
    int key;
    int val;
};
static flat_hash_map src
    = fhm_static_init((static struct val[11]){}, key, e, fhmap_int_to_u64,
                      fhmap_id_eq, NULL);
insert_rand_vals(&src);
static flat_hash_map dst
    = fhm_static_init((static struct val[13]){}, key, e, fhmap_int_to_u64,
                      fhmap_id_eq, NULL);
ccc_result res = fhm_copy(&dst, &src, NULL);

The above requires dst capacity be greater than or equal to src capacity. Here is memory management handed over to the copy function.

#define FLAT_HASH_MAP_USING_NAMESPACE_CCC
struct val
{
    fhmap_elem e;
    int key;
    int val;
};
static flat_hash_map src = fhm_zero_init(
    struct val, key, e, std_alloc, fhmap_int_to_u64, fhmap_id_eq, NULL);
insert_rand_vals(&src);
static flat_hash_map dst = fhm_zero_init(
    struct val, key, e, std_alloc, fhmap_int_to_u64, fhmap_id_eq, NULL);
ccc_result res = fhm_copy(&dst, &src, std_alloc);

The above allows dst to have a capacity less than that of the src as long as copy has been provided an allocation function to resize dst. Note that this would still work if copying to a destination that the user wants as a fixed size map.

#define FLAT_HASH_MAP_USING_NAMESPACE_CCC
struct val
{
    fhmap_elem e;
    int key;
    int val;
};
static flat_hash_map src = fhm_zero_init(
    struct val, key, e, std_alloc, fhmap_int_to_u64, fhmap_id_eq, NULL);
insert_rand_vals(&src);
static flat_hash_map dst = fhm_zero_init(
    struct val, key, e, NULL, fhmap_int_to_u64, fhmap_id_eq, NULL);
ccc_result res = fhm_copy(&dst, &src, std_alloc);

The above sets up dst with fixed size while src is a dynamic map. Because an allocation function is provided, the dst is resized once for the copy and retains its fixed size after the copy is complete. This would require the user to manually free the underlying buffer at dst eventually if this method is used. Usually it is better to allocate the memory explicitly before the copy if copying between maps without allocation permission.

These options allow users to stay consistent across containers with their memory management strategies.

◆ ccc_fhm_data()

void * ccc_fhm_data ( ccc_flat_hash_map const * h )

Return a reference to the base of backing array. O(1).

Parameters

[in] h a pointer to the map.

Returns: a reference to the base of the backing array.

Note: the reference is to the base of the backing array at index 0 with no consideration for the organization of map.

Warning: it is the users responsibility to ensure that access to any data is within the capacity of the backing buffer.

◆ ccc_fhm_end()

void * ccc_fhm_end ( ccc_flat_hash_map const * h )

Check the current iterator against the end for loop termination.

Parameters

[in] h the table being iterated upon.

Returns: the end address of the hash table.

Warning: It is undefined behavior to access or modify the end address.

◆ ccc_fhm_entry()

ccc_fhmap_entry ccc_fhm_entry	(	ccc_flat_hash_map *	h,
		void const *	key
	)

Obtains an entry for the provided key in the table for future use.

Parameters

[in]	h	the hash table to be searched.
[in]	key	the key used to search the table matching the stored key type.

Returns: a specialized hash entry for use with other functions in the Entry Interface.

Warning: the contents of an entry should not be examined or modified. Use the provided functions, only.

An entry is a search result that provides either an Occupied or Vacant entry in the table. An occupied entry signifies that the search was successful. A Vacant entry means the search was not successful but we now have a handle to where in the table such an element should be inserted.

An entry is rarely useful on its own. It should be passed in a functional style to subsequent calls in the Entry Interface.

◆ ccc_fhm_entry_status()

ccc_entry_status ccc_fhm_entry_status ( ccc_fhmap_entry const * e )

Obtain the entry status from a container entry.

Parameters

[in] e a pointer to the entry.

Returns: the status stored in the entry after the required action on the container completes. If e is NULL an entry input error is returned so ensure e is non-NULL to avoid an inaccurate status returned.

Note that this function can be useful for debugging or if more detailed messages are needed for logging purposes. See ccc_entry_status_msg() in ccc/types.h for more information on detailed entry statuses.

◆ ccc_fhm_get_key_val()

void * ccc_fhm_get_key_val	(	ccc_flat_hash_map *	h,
		void const *	key
	)

Returns a reference into the table at entry key.

Parameters

[in]	h	the flat hash map to search.
[in]	key	the key to search matching stored key type.

Returns: a view of the table entry if it is present, else NULL.

◆ ccc_fhm_insert()

ccc_entry ccc_fhm_insert	(	ccc_flat_hash_map *	h,
		ccc_fhmap_elem *	out_handle
	)

Invariantly inserts the key value wrapping out_handle.

Parameters

[in]	h	the pointer to the flat hash map.
[out]	out_handle	the handle to the user type wrapping fhash elem.

Returns: an entry. If Vacant, no prior element with key existed and the type wrapping out_handle remains unchanged. If Occupied the old value is written to the type wrapping out_handle and may be unwrapped to view. If more space is needed but allocation fails or has been forbidden, an insert error is set.

Note that this function may write to the struct containing the second parameter and wraps it in an entry to provide information about the old value.

◆ ccc_fhm_insert_entry()

void * ccc_fhm_insert_entry	(	ccc_fhmap_entry const *	e,
		ccc_fhmap_elem *	elem
	)

Inserts the provided entry invariantly.

Parameters

[in]	e	the entry returned from a call obtaining an entry.
[in]	elem	a handle to the struct the user intends to insert.

Returns: a pointer to the inserted element or NULL upon a memory error in which the load factor would be exceeded when no allocation policy is defined or resizing failed to find more memory.

This method can be used when the old value in the table does not need to be preserved. See the regular insert method if the old value is of interest. If an error occurs during the insertion process due to memory limitations or a search error NULL is returned. Otherwise insertion should not fail.

◆ ccc_fhm_insert_error()

bool ccc_fhm_insert_error ( ccc_fhmap_entry const * e )

Provides the status of the entry should an insertion follow.

Parameters

[in] e the entry from a query to the table via function or macro.

Returns: true if the next insertion of a new element will cause an error.

Table resizing occurs upon calls to entry functions/macros or when trying to insert a new element directly. This is to provide stable entries from the time they are obtained to the time they are used in functions they are passed to (i.e. the idiomatic or_insert(entry(...)...)).

However, if a Vacant entry is returned and then a subsequent insertion function is used, it will not work if resizing has failed and the return of those functions will indicate such a failure. One can also confirm an insertion error will occur from an entry with this function. For example, leaving this function in an assert for debug builds can be a helpful sanity check if the heap should correctly resize by default and errors are not usually expected.

◆ ccc_fhm_insert_or_assign()

ccc_entry ccc_fhm_insert_or_assign	(	ccc_flat_hash_map *	h,
		ccc_fhmap_elem *	key_val_handle
	)

Invariantly inserts or overwrites a user struct into the table.

Parameters

[in]	h	a pointer to the flat hash map.
[in]	key_val_handle	the handle to the wrapping user struct key value.

Returns: an entry. If Occupied an entry was overwritten by the new key value. If Vacant no prior table entry existed.

Note that this function can be used when the old user type is not needed but the information regarding its presence is helpful.

◆ ccc_fhm_is_empty()

bool ccc_fhm_is_empty ( ccc_flat_hash_map const * h )

Returns the size status of the table.

Parameters

[in] h the hash table.

Returns: true if empty else false.

◆ ccc_fhm_next()

void * ccc_fhm_next	(	ccc_flat_hash_map const *	h,
		ccc_fhmap_elem const *	iter
	)

Advances the iterator to the next occupied table slot.

Parameters

[in]	h	the table being iterated upon.
[in]	iter	the previous iterator.

Returns: a pointer that can be cast directly to the user type that is stored.

Warning: erasing or inserting during iteration may invalidate iterators if resizing occurs which would lead to undefined behavior. O(capacity).

◆ ccc_fhm_next_prime()

size_t ccc_fhm_next_prime ( size_t n )

Helper to find a prime number if needed.

Parameters

[in] n the input that may or may not be prime.

Returns: the next larger prime number.

It is possible to use this hash table without an allocator by providing the buffer to be used for the underlying storage and preventing allocation. If such a backing store is used it would be best to ensure it is a prime number size to mitigate hash collisions.

◆ ccc_fhm_occupied()

bool ccc_fhm_occupied ( ccc_fhmap_entry const * e )

Returns the Vacant or Occupied status of the entry.

Parameters

[in] e the entry from a query to the table via function or macro.

Returns: true if the entry is occupied, false if not.

◆ ccc_fhm_or_insert()

void * ccc_fhm_or_insert	(	ccc_fhmap_entry const *	e,
		ccc_fhmap_elem *	elem
	)

Inserts the struct with handle elem if the entry is Vacant.

Parameters

[in]	e	the entry obtained via function or macro call.
[in]	elem	the handle to the struct to be inserted to a Vacant entry.

Returns: a pointer to entry in the table invariantly. NULL on error.

Because this functions takes an entry and inserts if it is Vacant, the only reason NULL shall be returned is when an insertion error will occur, usually due to a resizing memory error. This can happen if the table is not allowed to resize because no allocation function is provided.

◆ ccc_fhm_remove()

ccc_entry ccc_fhm_remove	(	ccc_flat_hash_map *	h,
		ccc_fhmap_elem *	out_handle
	)

Removes the key value in the map storing the old value, if present, in the struct containing out_handle provided by the user.

Parameters

[in]	h	the pointer to the flat hash map.
[out]	out_handle	the handle to the user type wrapping fhash elem.

Returns: the removed entry. If Occupied it may be unwrapped to obtain the old key value pair. If Vacant the key value pair was not stored in the map. If bad input is provided an input error is set.

Note that this function may write to the struct containing the second parameter and wraps it in an entry to provide information about the old value.

◆ ccc_fhm_remove_entry()

ccc_entry ccc_fhm_remove_entry ( ccc_fhmap_entry const * e )

Remove the entry from the table if Occupied.

Parameters

[in] e a pointer to the table entry.

Returns: an entry containing NULL. If Occupied an entry in the table existed and was removed. If Vacant, no prior entry existed to be removed.

◆ ccc_fhm_size()

size_t ccc_fhm_size ( ccc_flat_hash_map const * h )

Returns the size of the table.

Parameters

[in] h the hash table.

Returns: the size_t size.

◆ ccc_fhm_try_insert()

ccc_entry ccc_fhm_try_insert	(	ccc_flat_hash_map *	h,
		ccc_fhmap_elem *	key_val_handle
	)

Attempts to insert the key value wrapping key_val_handle.

Parameters

[in]	h	the pointer to the flat hash map.
[in]	key_val_handle	the handle to the user type wrapping fhash elem.

Returns: an entry. If Occupied, the entry contains a reference to the key value user type in the table and may be unwrapped. If Vacant the entry contains a reference to the newly inserted entry in the table. If more space is needed but allocation fails or has been forbidden, an insert error is set.

Warning: because this function returns a reference to a user type in the table any subsequent insertions or deletions invalidate this reference.

◆ ccc_fhm_unwrap()

void * ccc_fhm_unwrap ( ccc_fhmap_entry const * e )

Unwraps the provided entry to obtain a view into the table element.

Parameters

[in] e the entry from a query to the table via function or macro.

Returns: an view into the table entry if one is present, or NULL.

◆ ccc_fhm_validate()

bool ccc_fhm_validate ( ccc_flat_hash_map const * h )

Validation of invariants for the hash table.

Parameters

[in] h the table to validate.

Returns: true if all invariants hold, false if corruption occurs.

Initialization Interface

Entry Interface

Container Types

Membership Interface

Deallocation Interface

Iterator Interface

State Interface

Detailed Description

Macro Definition Documentation

◆ ccc_fhm_and_modify_w

◆ ccc_fhm_entry_r

◆ ccc_fhm_init

◆ ccc_fhm_insert_entry_w

◆ ccc_fhm_insert_or_assign_r

◆ ccc_fhm_insert_or_assign_w

◆ ccc_fhm_insert_r

◆ ccc_fhm_or_insert_w

◆ ccc_fhm_remove_entry_r

◆ ccc_fhm_remove_r

◆ ccc_fhm_try_insert_r

◆ ccc_fhm_try_insert_w

Typedef Documentation

◆ ccc_fhmap_elem

◆ ccc_fhmap_entry

◆ ccc_flat_hash_map

Function Documentation

◆ ccc_fhm_and_modify()

◆ ccc_fhm_and_modify_aux()

◆ ccc_fhm_begin()

◆ ccc_fhm_capacity()

◆ ccc_fhm_clear()

◆ ccc_fhm_clear_and_free()

◆ ccc_fhm_contains()

◆ ccc_fhm_copy()

◆ ccc_fhm_data()

◆ ccc_fhm_end()

◆ ccc_fhm_entry()

◆ ccc_fhm_entry_status()

◆ ccc_fhm_get_key_val()

◆ ccc_fhm_insert()

◆ ccc_fhm_insert_entry()

◆ ccc_fhm_insert_error()

◆ ccc_fhm_insert_or_assign()

◆ ccc_fhm_is_empty()

◆ ccc_fhm_next()

◆ ccc_fhm_next_prime()

◆ ccc_fhm_occupied()

◆ ccc_fhm_or_insert()

◆ ccc_fhm_remove()

◆ ccc_fhm_remove_entry()

◆ ccc_fhm_size()

◆ ccc_fhm_try_insert()

◆ ccc_fhm_unwrap()

◆ ccc_fhm_validate()