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verstable.h
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/*------------------------------------------------- VERSTABLE v2.1.1 ---------------------------------------------------
Verstable is a C99-compatible, open-addressing hash table using quadratic probing and the following additions:
* All keys that hash (i.e. "belong") to the same bucket (their "home bucket") are linked together by an 11-bit integer
specifying the quadratic displacement, relative to that bucket, of the next key in the chain.
* If a chain of keys exists for a given bucket, then it always begins at that bucket. To maintain this policy, a 1-bit
flag is used to mark whether the key occupying a bucket belongs there. When inserting a new key, if the bucket it
belongs to is occupied by a key that does not belong there, then the occupying key is evicted and the new key takes
the bucket.
* A 4-bit fragment of each key's hash code is also stored.
* The aforementioned metadata associated with each bucket (the 4-bit hash fragment, the 1-bit flag, and the 11-bit link
to the next key in the chain) are stored together in a uint16_t array rather than in the bucket alongside the key and
(optionally) the value.
One way to conceptualize this scheme is as a chained hash table in which overflowing keys are stored not in separate
memory allocations but in otherwise unused buckets. In this regard, it shares similarities with Malte Skarupke's Bytell
hash table (https://www.youtube.com/watch?v=M2fKMP47slQ) and traditional "coalesced hashing".
Advantages of this scheme include:
* Fast lookups impervious to load factor: If the table contains any key belonging to the lookup key's home bucket, then
that bucket contains the first in a traversable chain of all keys belonging to it. Hence, only the home bucket and
other buckets containing keys belonging to it are ever probed. Moreover, the stored hash fragments allow skipping most
non-matching keys in the chain without accessing the actual buckets array or calling the (potentially expensive) key
comparison function.
* Fast insertions: Insertions are faster than they are in other schemes that move keys around (e.g. Robin Hood) because
they only move, at most, one existing key.
* Fast, tombstone-free deletions: Deletions, which usually require tombstones in quadratic-probing hash tables, are
tombstone-free and only move, at most, one existing key.
* Fast iteration: The separate metadata array allows keys in sparsely populated tables to be found without incurring the
frequent cache misses that would result from traversing the buckets array.
Usage example:
+---------------------------------------------------------+----------------------------------------------------------+
| Using the generic macro API (C11 and later): | Using the prefixed functions API (C99 and later): |
|---------------------------------------------------------+----------------------------------------------------------+
| #include <stdio.h> | #include <stdio.h> |
| | |
| // Instantiating a set template. | // Instantiating a set template. |
| #define NAME int_set | #define NAME int_set |
| #define KEY_TY int | #define KEY_TY int |
| #include "verstable.h" | #define HASH_FN vt_hash_integer |
| | #define CMPR_FN vt_cmpr_integer |
| // Instantiating a map template. | #include "verstable.h" |
| #define NAME int_int_map | |
| #define KEY_TY int | // Instantiating a map template. |
| #define VAL_TY int | #define NAME int_int_map |
| #include "verstable.h" | #define KEY_TY int |
| | #define VAL_TY int |
| int main( void ) | #define HASH_FN vt_hash_integer |
| { | #define CMPR_FN vt_cmpr_integer |
| // Set. | #include "verstable.h" |
| | |
| int_set our_set; | int main( void ) |
| vt_init( &our_set ); | { |
| | // Set. |
| // Inserting keys. | |
| for( int i = 0; i < 10; ++i ) | int_set our_set; |
| { | int_set_init( &our_set ); |
| int_set_itr itr = vt_insert( &our_set, i ); | |
| if( vt_is_end( itr ) ) | // Inserting keys. |
| { | for( int i = 0; i < 10; ++i ) |
| // Out of memory, so abort. | { |
| vt_cleanup( &our_set ); | int_set_itr itr = |
| return 1; | int_set_insert( &our_set, i ); |
| } | if( int_set_is_end( itr ) ) |
| } | { |
| | // Out of memory, so abort. |
| // Erasing keys. | int_set_cleanup( &our_set ); |
| for( int i = 0; i < 10; i += 3 ) | return 1; |
| vt_erase( &our_set, i ); | } |
| | } |
| // Retrieving keys. | |
| for( int i = 0; i < 10; ++i ) | // Erasing keys. |
| { | for( int i = 0; i < 10; i += 3 ) |
| int_set_itr itr = vt_get( &our_set, i ); | int_set_erase( &our_set, i ); |
| if( !vt_is_end( itr ) ) | |
| printf( "%d ", itr.data->key ); | // Retrieving keys. |
| } | for( int i = 0; i < 10; ++i ) |
| // Printed: 1 2 4 5 7 8 | { |
| | int_set_itr itr = int_set_get( &our_set, i ); |
| // Iteration. | if( !int_set_is_end( itr ) ) |
| for( | printf( "%d ", itr.data->key ); |
| int_set_itr itr = vt_first( &our_set ); | } |
| !vt_is_end( itr ); | // Printed: 1 2 4 5 7 8 |
| itr = vt_next( itr ) | |
| ) | // Iteration. |
| printf( "%d ", itr.data->key ); | for( |
| // Printed: 2 4 7 1 5 8 | int_set_itr itr = |
| | int_set_first( &our_set ); |
| vt_cleanup( &our_set ); | !int_set_is_end( itr ); |
| | itr = int_set_next( itr ) |
| // Map. | ) |
| | printf( "%d ", itr.data->key ); |
| int_int_map our_map; | // Printed: 2 4 7 1 5 8 |
| vt_init( &our_map ); | |
| | int_set_cleanup( &our_set ); |
| // Inserting keys and values. | |
| for( int i = 0; i < 10; ++i ) | // Map. |
| { | |
| int_int_map_itr itr = | int_int_map our_map; |
| vt_insert( &our_map, i, i + 1 ); | int_int_map_init( &our_map ); |
| if( vt_is_end( itr ) ) | |
| { | // Inserting keys and values. |
| // Out of memory, so abort. | for( int i = 0; i < 10; ++i ) |
| vt_cleanup( &our_map ); | { |
| return 1; | int_int_map_itr itr = |
| } | int_int_map_insert( &our_map, i, i + 1 ); |
| } | if( int_int_map_is_end( itr ) ) |
| | { |
| // Erasing keys and values. | // Out of memory, so abort. |
| for( int i = 0; i < 10; i += 3 ) | int_int_map_cleanup( &our_map ); |
| vt_erase( &our_map, i ); | return 1; |
| | } |
| // Retrieving keys and values. | } |
| for( int i = 0; i < 10; ++i ) | |
| { | // Erasing keys and values. |
| int_int_map_itr itr = vt_get( &our_map, i ); | for( int i = 0; i < 10; i += 3 ) |
| if( !vt_is_end( itr ) ) | int_int_map_erase( &our_map, i ); |
| printf( | |
| "%d:%d ", | // Retrieving keys and values. |
| itr.data->key, | for( int i = 0; i < 10; ++i ) |
| itr.data->val | { |
| ); | int_int_map_itr itr = |
| } | int_int_map_get( &our_map, i ); |
| // Printed: 1:2 2:3 4:5 5:6 7:8 8:9 | if( !int_int_map_is_end( itr ) ) |
| | printf( |
| // Iteration. | "%d:%d ", |
| for( | itr.data->key, |
| int_int_map_itr itr = vt_first( &our_map ); | itr.data->val |
| !vt_is_end( itr ); | ); |
| itr = vt_next( itr ) | } |
| ) | // Printed: 1:2 2:3 4:5 5:6 7:8 8:9 |
| printf( | |
| "%d:%d ", | // Iteration. |
| itr.data->key, | for( |
| itr.data->val | int_int_map_itr itr = |
| ); | int_int_map_first( &our_map ); |
| // Printed: 2:3 4:5 7:8 1:2 5:6 8:9 | !int_int_map_is_end( itr ); |
| | itr = int_int_map_next( itr ) |
| vt_cleanup( &our_map ); | ) |
| } | printf( |
| | "%d:%d ", |
| | itr.data->key, |
| | itr.data->val |
| | ); |
| | // Printed: 2:3 4:5 7:8 1:2 5:6 8:9 |
| | |
| | int_int_map_cleanup( &our_map ); |
| | } |
| | |
+---------------------------------------------------------+----------------------------------------------------------+
API:
Instantiating a hash table template:
Create a new hash table type in the following manner:
#define NAME <your chosen type name>
#define KEY_TY <type>
#include "verstable.h"
The NAME macro specifies the name of hash table type that the library will declare, the prefix for the functions
associated with it, and the prefix for the associated iterator type.
The KEY_TY macro specifies the key type.
In C99, it is also always necessary to define HASH_FN and CMPR_FN (see below) before including the header.
The following macros may also be defined before including the header:
#define VAL_TY <type>
The type of the value associated with each key.
If this macro is defined, the hash table acts as a map associating keys with values.
Otherwise, it acts as a set containing only keys.
#define HASH_FN <function name>
The name of the existing function used to hash each key.
The function should have the signature uint64_t ( KEY_TY key ) and return a 64-bit hash code.
For best performance, the hash function should provide a high level of entropy across all bits.
There are two default hash functions: vt_hash_integer for all integer types up to 64 bits in size, and
vt_hash_string for NULL-terminated strings (i.e. char *).
When KEY_TY is one of such types and the compiler is in C11 mode or later, HASH_FN may be left undefined, in
which case the appropriate default function is inferred from KEY_TY.
Otherwise, HASH_FN must be defined.
#define CMPR_FN <function name>
The name of the existing function used to compare two keys.
The function should have the signature bool ( KEY_TY key_1, KEY_TY key_2 ) and return true if the two keys are
equal.
There are two default comparison functions: vt_cmpr_integer for all integer types up to 64 bits in size, and
vt_cmpr_string for NULL-terminated strings (i.e. char *).
As with the default hash functions, in C11 or later the appropriate default comparison function is inferred if
KEY_TY is one of such types and CMPR_FN is left undefined.
Otherwise, CMPR_FN must be defined.
#define MAX_LOAD <floating point value>
The floating-point load factor at which the hash table automatically doubles the size of its internal buckets
array.
The default is 0.9, i.e. 90%.
#define KEY_DTOR_FN <function name>
The name of the existing destructor function, with the signature void ( KEY_TY key ), called on a key when it is
erased from the table or replaced by a newly inserted key.
The API functions that may call the key destructor are NAME_insert, NAME_erase, NAME_erase_itr, NAME_clear,
and NAME_cleanup.
#define VAL_DTOR_FN <function name>
The name of the existing destructor function, with the signature void ( VAL_TY val ), called on a value when it
is erased from the table or replaced by a newly inserted value.
The API functions that may call the value destructor are NAME_insert, NAME_erase, NAME_erase_itr, NAME_clear,
and NAME_cleanup.
#define CTX_TY <type>
The type of the hash table type's ctx (context) member.
This member only exists if CTX_TY was defined.
It is intended to be used in conjunction with MALLOC_FN and FREE_FN (see below).
#define MALLOC_FN <function name>
The name of the existing function used to allocate memory.
If CTX_TY was defined, the signature should be void *( size_t size, CTX_TY *ctx ), where size is the number of
bytes to allocate and ctx points to the table's ctx member.
Otherwise, the signature should be void *( size_t size ).
The default wraps stdlib.h's malloc.
#define FREE_FN <function name>
The name of the existing function used to free memory.
If CTX_TY was defined, the signature should be void ( void *ptr, size_t size, CTX_TY *ctx ), where ptr points to
the memory to free, size is the number of bytes that were allocated, and ctx points to the table's ctx member.
Otherwise, the signature should be void ( void *ptr, size_t size ).
The default wraps stdlib.h's free.
#define HEADER_MODE
#define IMPLEMENTATION_MODE
By default, all hash table functions are defined as static inline functions, the intent being that a given hash
table template should be instantiated once per translation unit; for best performance, this is the recommended
way to use the library.
However, it is also possible separate the struct definitions and function declarations from the function
definitions such that one implementation can be shared across all translation units (as in a traditional header
and source file pair).
In that case, instantiate a template wherever it is needed by defining HEADER_MODE, along with only NAME,
KEY_TY, and (optionally) VAL_TY, CTX_TY, and header guards, and including the library, e.g.:
#ifndef INT_INT_MAP_H
#define INT_INT_MAP_H
#define NAME int_int_map
#define KEY_TY int
#define VAL_TY int
#define HEADER_MODE
#include "verstable.h"
#endif
In one source file, define IMPLEMENTATION_MODE, along with NAME, KEY_TY, and any of the aforementioned optional
macros, and include the library, e.g.:
#define NAME int_int_map
#define KEY_TY int
#define VAL_TY int
#define HASH_FN vt_hash_integer // C99.
#define CMPR_FN vt_cmpr_integer // C99.
#define MAX_LOAD 0.8
#define IMPLEMENTATION_MODE
#include "verstable.h"
Including the library automatically undefines all the aforementioned macros after they have been used to instantiate
the template.
Functions:
The functions associated with a hash table type are all prefixed with the name the user supplied via the NAME macro.
In C11 and later, the generic "vt_"-prefixed macros may be used to automatically select the correct version of the
specified function based on the arguments.
void NAME_init( NAME *table )
void NAME_init( NAME *table, CTX_TY ctx )
// C11 generic macro: vt_init.
Initializes the table for use.
If CTX_TY was defined, ctx sets the table's ctx member.
bool NAME_init_clone( NAME *table, NAME *source )
bool NAME_init_clone( NAME *table, NAME *source, CTX_TY ctx )
// C11 generic macro: vt_init_clone.
Initializes the table as a shallow copy of the specified source table.
If CTX_TY was defined, ctx sets the table's ctx member.
Returns false in the case of memory allocation failure.
size_t NAME_size( NAME *table ) // C11 generic macro: vt_size.
Returns the number of keys currently in the table.
size_t NAME_bucket_count( NAME *table ) // C11 generic macro: vt_bucket_count.
Returns the table's current bucket count.
NAME_itr NAME_insert( NAME *table, KEY_TY key )
NAME_itr NAME_insert( NAME *table, KEY_TY key, VAL_TY val )
// C11 generic macro: vt_insert.
Inserts the specified key (and value, if VAL_TY was defined) into the hash table.
If the same key already exists, then the new key (and value) replaces the existing key (and value).
Returns an iterator to the new key, or an end iterator in the case of memory allocation failure.
NAME_itr NAME_get_or_insert( NAME *table, KEY_TY key )
NAME_itr NAME_get_or_insert( NAME *table, KEY_TY key, VAL_TY val )
// C11 generic macro: vt_get_or_insert.
Inserts the specified key (and value, if VAL_TY was defined) if it does not already exist in the table.
Returns an iterator to the new key if it was inserted, or an iterator to the existing key, or an end iterator if
the key did not exist but the new key could not be inserted because of memory allocation failure.
Determine whether the key was inserted by comparing the table's size before and after the call.
NAME_itr NAME_get( NAME *table, KEY_TY key ) // C11 generic macro: vt_get.
Returns a iterator to the specified key, or an end iterator if no such key exists.
bool NAME_erase( NAME *table, KEY_TY key ) // C11 generic macro: vt_erase.
Erases the specified key (and associated value, if VAL_TY was defined), if it exists.
Returns true if a key was erased.
NAME_itr NAME_erase_itr( NAME *table, NAME_itr itr ) // C11 generic macro: vt_erase_itr.
Erases the key (and associated value, if VAL_TY was defined) pointed to by the specified iterator.
Returns an iterator to the next key in the table, or an end iterator if the erased key was the last one.
bool NAME_reserve( NAME *table, size_t size ) // C11 generic macro: vt_reserve.
Ensures that the bucket count is large enough to support the specified key count (i.e. size) without rehashing.
Returns false if unsuccessful due to memory allocation failure.
bool NAME_shrink( NAME *table ) // C11 generic macro: vt_shrink.
Shrinks the bucket count to best accommodate the current size.
Returns false if unsuccessful due to memory allocation failure.
NAME_itr NAME_first( NAME *table ) // C11 generic macro: vt_first.
Returns an iterator to the first key in the table, or an end iterator if the table is empty.
bool NAME_is_end( NAME *table, NAME_itr itr ) // C11 generic macro: vt_is_end.
Returns true if the iterator is an end iterator.
NAME_itr NAME_next( NAME_itr itr ) // C11 generic macro: vt_next.
Returns an iterator to the key after the one pointed to by the specified iterator, or an end iterator if the
specified iterator points to the last key in the table.
void NAME_clear( NAME *table ) // C11 generic macro: vt_clear.
Erases all keys (and values, if VAL_TY was defined) in the table.
void NAME_cleanup( NAME *table ) // C11 generic macro: vt_cleanup.
Erases all keys (and values, if VAL_TY was defined) in the table, frees all memory associated with it, and
initializes it for reuse.
Iterators:
Access the key (and value, if VAL_TY was defined) that an iterator points to using the NAME_itr struct's data
member:
itr.data->key
itr.data->val
Functions that may insert new keys (NAME_insert and NAME_get_or_insert), erase keys (NAME_erase and NAME_erase_itr),
or reallocate the internal bucket array (NAME_reserve and NAME_shrink) invalidate all exiting iterators.
To delete keys during iteration and resume iterating, use the return value of NAME_erase_itr.
Version history:
18/06/2024 2.1.1: Fixed a bug affecting iteration on big-endian platforms under MSVC.
27/05/2024 2.1.0: Replaced the Murmur3 mixer with the fast-hash mixer as the default integer hash function.
Fixed a bug that could theoretically cause a crash on rehash (triggerable in testing using
NAME_shrink with a maximum load factor significantly higher than 1.0).
06/02/2024 2.0.0: Improved custom allocator support by introducing the CTX_TY option and allowing user-supplied free
functions to receive the allocation size.
Improved documentation.
Introduced various optimizations, including storing the buckets-array size mask instead of the
bucket count, eliminating empty-table checks, combining the buckets memory and metadata memory into
one allocation, and adding branch prediction macros.
Fixed a bug that caused a key to be used after destruction during erasure.
12/12/2023 1.0.0: Initial release.
License (MIT):
Copyright (c) 2023-2024 Jackson L. Allan
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit
persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/*--------------------------------------------------------------------------------------------------------------------*/
/* Common header section */
/*--------------------------------------------------------------------------------------------------------------------*/
#ifndef VERSTABLE_H
#define VERSTABLE_H
#include <limits.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
// Two-way concatenation macro.
#define VT_CAT_( a, b ) a##b
#define VT_CAT( a, b ) VT_CAT_( a, b )
// Branch optimization macros.
#ifdef __GNUC__
#define VT_LIKELY( expression ) __builtin_expect( (bool)( expression ), true )
#define VT_UNLIKELY( expression ) __builtin_expect( (bool)( expression ), false )
#else
#define VT_LIKELY( expression ) ( expression )
#define VT_UNLIKELY( expression ) ( expression )
#endif
// Masks for manipulating and extracting data from a bucket's uint16_t metadatum.
#define VT_EMPTY 0x0000
#define VT_HASH_FRAG_MASK 0xF000 // 0b1111000000000000.
#define VT_IN_HOME_BUCKET_MASK 0x0800 // 0b0000100000000000.
#define VT_DISPLACEMENT_MASK 0x07FF // 0b0000011111111111, also denotes the displacement limit. Set to VT_LOAD to 1.0
// to test proper handling of encroachment on the displacement limit during
// inserts.
// Extracts a hash fragment from a uint64_t hash code.
// We take the highest four bits so that keys that map (via modulo) to the same bucket have distinct hash fragments.
static inline uint16_t vt_hashfrag( uint64_t hash )
{
return ( hash >> 48 ) & VT_HASH_FRAG_MASK;
}
// Standard quadratic probing formula that guarantees that all buckets are visited when the bucket count is a power of
// two (at least in theory, because the displacement limit could terminate the search early when the bucket count is
// high).
static inline size_t vt_quadratic( uint16_t displacement )
{
return ( (size_t)displacement * displacement + displacement ) / 2;
}
#define VT_MIN_NONZERO_BUCKET_COUNT 8 // Must be a power of two.
// Function to find the left-most non-zero uint16_t in a uint64_t.
// This function is used when we scan four buckets at a time while iterating and relies on compiler intrinsics wherever
// possible.
#if defined( __GNUC__ ) && ULLONG_MAX == 0xFFFFFFFFFFFFFFFF
static inline int vt_first_nonzero_uint16( uint64_t val )
{
const uint16_t endian_checker = 0x0001;
if( *(const char *)&endian_checker ) // Little-endian (the compiler will optimize away the check at -O1 and above).
return __builtin_ctzll( val ) / 16;
return __builtin_clzll( val ) / 16;
}
#elif defined( _MSC_VER ) && ( defined( _M_X64 ) || defined( _M_ARM64 ) )
#include <intrin.h>
#pragma intrinsic(_BitScanForward64)
#pragma intrinsic(_BitScanReverse64)
static inline int vt_first_nonzero_uint16( uint64_t val )
{
unsigned long result;
const uint16_t endian_checker = 0x0001;
if( *(const char *)&endian_checker )
_BitScanForward64( &result, val );
else
{
_BitScanReverse64( &result, val );
result = 63 - result;
}
return result / 16;
}
#else
static inline int vt_first_nonzero_uint16( uint64_t val )
{
int result = 0;
uint32_t half;
memcpy( &half, &val, sizeof( uint32_t ) );
if( !half )
result += 2;
uint16_t quarter;
memcpy( &quarter, (char *)&val + result * sizeof( uint16_t ), sizeof( uint16_t ) );
if( !quarter )
result += 1;
return result;
}
#endif
// When the bucket count is zero, setting the metadata pointer to point to a VT_EMPTY placeholder, rather than NULL,
// allows us to avoid checking for a zero bucket count during insertion and lookup.
static const uint16_t vt_empty_placeholder_metadatum = VT_EMPTY;
// Default hash and comparison functions.
// Fast-hash, as described by https://jonkagstrom.com/bit-mixer-construction and
// https://code.google.com/archive/p/fast-hash.
// In testing, this hash function provided slightly better performance than the Murmur3 mixer.
static inline uint64_t vt_hash_integer( uint64_t key )
{
key ^= key >> 23;
key *= 0x2127599bf4325c37ull;
key ^= key >> 47;
return key;
}
// FNV-1a.
static inline uint64_t vt_hash_string( char *key )
{
uint64_t hash = 0xcbf29ce484222325ull;
while( *key )
hash = ( (unsigned char)*key++ ^ hash ) * 0x100000001b3ull;
return hash;
}
static inline bool vt_cmpr_integer( uint64_t key_1, uint64_t key_2 )
{
return key_1 == key_2;
}
static inline bool vt_cmpr_string( char *key_1, char *key_2 )
{
return strcmp( key_1, key_2 ) == 0;
}
// Default allocation and free functions.
static inline void *vt_malloc( size_t size )
{
return malloc( size );
}
static inline void vt_free( void *ptr, size_t size )
{
(void)size;
free( ptr );
}
static inline void *vt_malloc_with_ctx( size_t size, void *ctx )
{
(void)ctx;
return malloc( size );
}
static inline void vt_free_with_ctx( void *ptr, size_t size, void *ctx )
{
(void)size;
(void)ctx;
free( ptr );
}
// The rest of the common header section pertains to the C11 generic macro API.
// This interface is based on the extendible-_Generic mechanism documented in detail at
// https://github.com/JacksonAllan/CC/blob/main/articles/Better_C_Generics_Part_1_The_Extendible_Generic.md.
// In summary, instantiating a template also defines wrappers for the template's types and functions with names in the
// pattern of vt_table_NNNN and vt_init_NNNN, where NNNN is an automatically generated integer unique to the template
// instance in the current translation unit.
// These wrappers plug in to _Generic-based API macros, which use preprocessor magic to automatically generate _Generic
// slots for every existing template instance.
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L && !defined( VT_NO_C11_GENERIC_API )
// Octal counter that supports up to 511 hash table templates.
#define VT_TEMPLATE_COUNT_D1 0 // Digit 1, i.e. least significant digit.
#define VT_TEMPLATE_COUNT_D2 0
#define VT_TEMPLATE_COUNT_D3 0
// Four-way concatenation macro.
#define VT_CAT_4_( a, b, c, d ) a##b##c##d
#define VT_CAT_4( a, b, c, d ) VT_CAT_4_( a, b, c, d )
// Provides the current value of the counter as a three-digit octal number preceded by 0.
#define VT_TEMPLATE_COUNT VT_CAT_4( 0, VT_TEMPLATE_COUNT_D3, VT_TEMPLATE_COUNT_D2, VT_TEMPLATE_COUNT_D1 )
// _Generic-slot generation macros.
#define VT_GENERIC_SLOT( ty, fn, n ) , VT_CAT( ty, n ): VT_CAT( fn, n )
#define VT_R1_0( ty, fn, d3, d2 )
#define VT_R1_1( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 0 ) )
#define VT_R1_2( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 1 ) ) VT_R1_1( ty, fn, d3, d2 )
#define VT_R1_3( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 2 ) ) VT_R1_2( ty, fn, d3, d2 )
#define VT_R1_4( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 3 ) ) VT_R1_3( ty, fn, d3, d2 )
#define VT_R1_5( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 4 ) ) VT_R1_4( ty, fn, d3, d2 )
#define VT_R1_6( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 5 ) ) VT_R1_5( ty, fn, d3, d2 )
#define VT_R1_7( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 6 ) ) VT_R1_6( ty, fn, d3, d2 )
#define VT_R1_8( ty, fn, d3, d2 ) VT_GENERIC_SLOT( ty, fn, VT_CAT_4( 0, d3, d2, 7 ) ) VT_R1_7( ty, fn, d3, d2 )
#define VT_R2_0( ty, fn, d3 )
#define VT_R2_1( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 0 )
#define VT_R2_2( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 1 ) VT_R2_1( ty, fn, d3 )
#define VT_R2_3( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 2 ) VT_R2_2( ty, fn, d3 )
#define VT_R2_4( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 3 ) VT_R2_3( ty, fn, d3 )
#define VT_R2_5( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 4 ) VT_R2_4( ty, fn, d3 )
#define VT_R2_6( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 5 ) VT_R2_5( ty, fn, d3 )
#define VT_R2_7( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 6 ) VT_R2_6( ty, fn, d3 )
#define VT_R2_8( ty, fn, d3 ) VT_R1_8( ty, fn, d3, 7 ) VT_R2_7( ty, fn, d3 )
#define VT_R3_0( ty, fn )
#define VT_R3_1( ty, fn ) VT_R2_8( ty, fn, 0 )
#define VT_R3_2( ty, fn ) VT_R2_8( ty, fn, 1 ) VT_R3_1( ty, fn )
#define VT_R3_3( ty, fn ) VT_R2_8( ty, fn, 2 ) VT_R3_2( ty, fn )
#define VT_R3_4( ty, fn ) VT_R2_8( ty, fn, 3 ) VT_R3_3( ty, fn )
#define VT_R3_5( ty, fn ) VT_R2_8( ty, fn, 4 ) VT_R3_4( ty, fn )
#define VT_R3_6( ty, fn ) VT_R2_8( ty, fn, 5 ) VT_R3_5( ty, fn )
#define VT_R3_7( ty, fn ) VT_R2_8( ty, fn, 6 ) VT_R3_6( ty, fn )
#define VT_GENERIC_SLOTS( ty, fn ) \
VT_CAT( VT_R1_, VT_TEMPLATE_COUNT_D1 )( ty, fn, VT_TEMPLATE_COUNT_D3, VT_TEMPLATE_COUNT_D2 ) \
VT_CAT( VT_R2_, VT_TEMPLATE_COUNT_D2 )( ty, fn, VT_TEMPLATE_COUNT_D3 ) \
VT_CAT( VT_R3_, VT_TEMPLATE_COUNT_D3 )( ty, fn ) \
// Actual generic API macros.
// vt_init must be handled as a special case because it could take one or two arguments, depending on whether CTX_TY
// was defined.
#define VT_ARG_3( _1, _2, _3, ... ) _3
#define vt_init( ... ) VT_ARG_3( __VA_ARGS__, vt_init_with_ctx, vt_init_without_ctx, )( __VA_ARGS__ )
#define vt_init_without_ctx( table ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_init_ ) )( table )
#define vt_init_with_ctx( table, ... ) _Generic( *( table ) \
VT_GENERIC_SLOTS( vt_table_, vt_init_ ) \
)( table, __VA_ARGS__ ) \
#define vt_init_clone( table, ... ) _Generic( *( table ) \
VT_GENERIC_SLOTS( vt_table_, vt_init_clone_ ) \
)( table, __VA_ARGS__ ) \
#define vt_size( table )_Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_size_ ) )( table )
#define vt_bucket_count( table ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_bucket_count_ ) )( table )
#define vt_is_end( itr ) _Generic( itr VT_GENERIC_SLOTS( vt_table_itr_, vt_is_end_ ) )( itr )
#define vt_insert( table, ... ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_insert_ ) )( table, __VA_ARGS__ )
#define vt_get_or_insert( table, ... ) _Generic( *( table ) \
VT_GENERIC_SLOTS( vt_table_, vt_get_or_insert_ ) \
)( table, __VA_ARGS__ ) \
#define vt_get( table, ... ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_get_ ) )( table, __VA_ARGS__ )
#define vt_erase( table, ... ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_erase_ ) )( table, __VA_ARGS__ )
#define vt_next( itr ) _Generic( itr VT_GENERIC_SLOTS( vt_table_itr_, vt_next_ ) )( itr )
#define vt_erase_itr( table, ... ) _Generic( *( table ) \
VT_GENERIC_SLOTS( vt_table_, vt_erase_itr_ ) \
)( table, __VA_ARGS__ ) \
#define vt_reserve( table, ... ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_reserve_ ) )( table, __VA_ARGS__ )
#define vt_shrink( table ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_shrink_ ) )( table )
#define vt_first( table ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_first_ ) )( table )
#define vt_clear( table ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_clear_ ) )( table )
#define vt_cleanup( table ) _Generic( *( table ) VT_GENERIC_SLOTS( vt_table_, vt_cleanup_ ) )( table )
#endif
#endif
/*--------------------------------------------------------------------------------------------------------------------*/
/* Prefixed structs */
/*--------------------------------------------------------------------------------------------------------------------*/
#ifndef IMPLEMENTATION_MODE
typedef struct
{
KEY_TY key;
#ifdef VAL_TY
VAL_TY val;
#endif
} VT_CAT( NAME, _bucket );
typedef struct
{
VT_CAT( NAME, _bucket ) *data;
uint16_t *metadatum;
uint16_t *metadata_end; // Iterators carry an internal end pointer so that NAME_is_end does not need the table to be
// passed in as an argument.
// This also allows for the zero-bucket-count check to occur once in NAME_first, rather than
// repeatedly in NAME_is_end.
size_t home_bucket; // SIZE_MAX if home bucket is unknown.
} VT_CAT( NAME, _itr );
typedef struct
{
size_t key_count;
size_t buckets_mask; // Rather than storing the bucket count directly, we store the bit mask used to reduce a hash
// code or displacement-derived bucket index to the buckets array, i.e. the bucket count minus
// one.
// Consequently, a zero bucket count (i.e. when .metadata points to the placeholder) constitutes
// a special case, represented by all bits unset (i.e. zero).
VT_CAT( NAME, _bucket ) *buckets;
uint16_t *metadata; // As described above, each metadatum consists of a 4-bit hash-code fragment (X), a 1-bit flag
// indicating whether the key in this bucket begins a chain associated with the bucket (Y), and
// an 11-bit value indicating the quadratic displacement of the next key in the chain (Z):
// XXXXYZZZZZZZZZZZ.
#ifdef CTX_TY
CTX_TY ctx;
#endif
} NAME;
#endif
/*--------------------------------------------------------------------------------------------------------------------*/
/* Function prototypes */
/*--------------------------------------------------------------------------------------------------------------------*/
#if defined( HEADER_MODE ) || defined( IMPLEMENTATION_MODE )
#define VT_API_FN_QUALIFIERS
#else
#define VT_API_FN_QUALIFIERS static inline
#endif
#ifndef IMPLEMENTATION_MODE
VT_API_FN_QUALIFIERS void VT_CAT( NAME, _init )(
NAME *
#ifdef CTX_TY
, CTX_TY
#endif
);
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _init_clone )(
NAME *,
NAME *
#ifdef CTX_TY
, CTX_TY
#endif
);
VT_API_FN_QUALIFIERS size_t VT_CAT( NAME, _size )( NAME * );
VT_API_FN_QUALIFIERS size_t VT_CAT( NAME, _bucket_count )( NAME * );
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _is_end )( VT_CAT( NAME, _itr ) );
VT_API_FN_QUALIFIERS VT_CAT( NAME, _itr ) VT_CAT( NAME, _insert )(
NAME *,
KEY_TY
#ifdef VAL_TY
, VAL_TY
#endif
);
VT_API_FN_QUALIFIERS VT_CAT( NAME, _itr ) VT_CAT( NAME, _get_or_insert )(
NAME *,
KEY_TY
#ifdef VAL_TY
, VAL_TY
#endif
);
VT_API_FN_QUALIFIERS VT_CAT( NAME, _itr ) VT_CAT( NAME, _get )(
NAME *table,
KEY_TY key
);
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _erase )( NAME *, KEY_TY );
VT_API_FN_QUALIFIERS VT_CAT( NAME, _itr ) VT_CAT( NAME, _next )( VT_CAT( NAME, _itr ) );
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _reserve )( NAME *, size_t );
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _shrink )( NAME * );
VT_API_FN_QUALIFIERS VT_CAT( NAME, _itr ) VT_CAT( NAME, _first )( NAME * );
VT_API_FN_QUALIFIERS void VT_CAT( NAME, _clear )( NAME * );
VT_API_FN_QUALIFIERS void VT_CAT( NAME, _cleanup )( NAME * );
// Not an API function, but must be prototyped anyway because it is called by the inline NAME_erase_itr below.
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _erase_itr_raw ) ( NAME *, VT_CAT( NAME, _itr ) );
// Erases the key pointed to by itr and returns an iterator to the next key in the table.
// This function must be inlined to ensure that the compiler optimizes away the NAME_fast_forward call if the returned
// iterator is discarded.
#ifdef __GNUC__
static inline __attribute__((always_inline))
#elif defined( _MSC_VER )
static __forceinline
#else
static inline
#endif
VT_CAT( NAME, _itr ) VT_CAT( NAME, _erase_itr )( NAME *table, VT_CAT( NAME, _itr ) itr )
{
if( VT_CAT( NAME, _erase_itr_raw )( table, itr ) )
return VT_CAT( NAME, _next )( itr );
return itr;
}
#endif
/*--------------------------------------------------------------------------------------------------------------------*/
/* Function implementations */
/*--------------------------------------------------------------------------------------------------------------------*/
#ifndef HEADER_MODE
// Default settings.
#ifndef MAX_LOAD
#define MAX_LOAD 0.9
#endif
#if !defined( MALLOC ) || !defined( FREE )
#include <stdlib.h>
#endif
#ifndef MALLOC_FN
#ifdef CTX_TY
#define MALLOC_FN vt_malloc_with_ctx
#else
#define MALLOC_FN vt_malloc
#endif
#endif
#ifndef FREE_FN
#ifdef CTX_TY
#define FREE_FN vt_free_with_ctx
#else
#define FREE_FN vt_free
#endif
#endif
#ifndef HASH_FN
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
#ifdef _MSC_VER // In MSVC, the compound literal in the _Generic triggers a warning about unused local variables at /W4.
#define HASH_FN \
_Pragma( "warning( push )" ) \
_Pragma( "warning( disable: 4189 )" ) \
_Generic( ( KEY_TY ){ 0 }, char *: vt_hash_string, default: vt_hash_integer ) \
_Pragma( "warning( pop )" )
#else
#define HASH_FN _Generic( ( KEY_TY ){ 0 }, char *: vt_hash_string, default: vt_hash_integer )
#endif
#else
#error Hash function inference is only available in C11 and later. In C99, you need to define HASH_FN manually to \
vt_hash_integer, vt_hash_string, or your own custom function with the signature uint64_t ( KEY_TY ).
#endif
#endif
#ifndef CMPR_FN
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
#ifdef _MSC_VER
#define CMPR_FN \
_Pragma( "warning( push )" ) \
_Pragma( "warning( disable: 4189 )" ) \
_Generic( ( KEY_TY ){ 0 }, char *: vt_cmpr_string, default: vt_cmpr_integer ) \
_Pragma( "warning( pop )" )
#else
#define CMPR_FN _Generic( ( KEY_TY ){ 0 }, char *: vt_cmpr_string, default: vt_cmpr_integer )
#endif
#else
#error Comparison function inference is only available in C11 and later. In C99, you need to define CMPR_FN manually \
to vt_cmpr_integer, vt_cmpr_string, or your own custom function with the signature bool ( KEY_TY, KEY_TY ).
#endif
#endif
VT_API_FN_QUALIFIERS void VT_CAT( NAME, _init )(
NAME *table
#ifdef CTX_TY
, CTX_TY ctx
#endif
)
{
table->key_count = 0;
table->buckets_mask = 0x0000000000000000ull;
table->buckets = NULL;
table->metadata = (uint16_t *)&vt_empty_placeholder_metadatum;
#ifdef CTX_TY
table->ctx = ctx;
#endif
}
// For efficiency, especially in the case of a small table, the buckets array and metadata share the same dynamic memory
// allocation:
// +-----------------------------+-----+----------------+--------+
// | Buckets | Pad | Metadata | Excess |
// +-----------------------------+-----+----------------+--------+
// Any allocated metadata array requires four excess elements to ensure that iteration functions, which read four
// metadata at a time, never read beyond the end of it.
// This function returns the offset of the beginning of the metadata, i.e. the size of the buckets array plus the
// (usually zero) padding.
// It assumes that the bucket count is not zero.
static inline size_t VT_CAT( NAME, _metadata_offset )( NAME *table )
{
// Use sizeof, rather than alignof, for C99 compatibility.
return ( ( ( table->buckets_mask + 1 ) * sizeof( VT_CAT( NAME, _bucket ) ) + sizeof( uint16_t ) - 1 ) /
sizeof( uint16_t ) ) * sizeof( uint16_t );
}
// Returns the total allocation size, including the buckets array, padding, metadata, and excess metadata.
// As above, this function assumes that the bucket count is not zero.
static inline size_t VT_CAT( NAME, _total_alloc_size )( NAME *table )
{
return VT_CAT( NAME, _metadata_offset )( table ) + ( table->buckets_mask + 1 + 4 ) * sizeof( uint16_t );
}
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _init_clone )(
NAME *table,
NAME *source
#ifdef CTX_TY
, CTX_TY ctx
#endif
)
{
table->key_count = source->key_count;
table->buckets_mask = source->buckets_mask;
#ifdef CTX_TY
table->ctx = ctx;
#endif
if( !source->buckets_mask )
{
table->metadata = (uint16_t *)&vt_empty_placeholder_metadatum;
table->buckets = NULL;
return true;
}
void *allocation = MALLOC_FN(
VT_CAT( NAME, _total_alloc_size )( table )
#ifdef CTX_TY
, &table->ctx
#endif
);
if( VT_UNLIKELY( !allocation ) )
return false;
table->buckets = (VT_CAT( NAME, _bucket ) *)allocation;
table->metadata = (uint16_t *)( (unsigned char *)allocation + VT_CAT( NAME, _metadata_offset )( table ) );
memcpy( allocation, source->buckets, VT_CAT( NAME, _total_alloc_size )( table ) );
return true;
}
VT_API_FN_QUALIFIERS size_t VT_CAT( NAME, _size )( NAME *table )
{
return table->key_count;
}
VT_API_FN_QUALIFIERS size_t VT_CAT( NAME, _bucket_count )( NAME *table )
{
// If the bucket count is zero, buckets_mask will be zero, not the bucket count minus one.
// We account for this special case by adding (bool)buckets_mask rather than one.
return table->buckets_mask + (bool)table->buckets_mask;
}
VT_API_FN_QUALIFIERS bool VT_CAT( NAME, _is_end )( VT_CAT( NAME, _itr ) itr )
{
return itr.metadatum == itr.metadata_end;