JakeHillion/drgn
1
0
Fork 0
mirror of https://github.com/JakeHillion/drgn.git synced 2024-12-22 17:23:06 +00:00
Code Issues Packages Projects Releases Wiki Activity
cbdf6094b7
drgn/libdrgn/hash_table.h
Omar Sandoval 558aa52d86 libdrgn: hash_table: sanity check integer sizes more 
Check that size_t makes sense and make sure int_key_hash_pair() doesn't
get an integer type larger than it supports. I can't imagine either of
these failing in practice, but make our assumptions explicit.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2022-04-12 16:18:46 -07:00

1797 lines
58 KiB
C
Raw Blame History

// Copyright (c) Meta Platforms, Inc. and affiliates.
// SPDX-License-Identifier: GPL-3.0-or-later
/**
* @file
*
* High performance generic hash tables.
*
* See @ref HashTables.
*/
#ifndef DRGN_HASH_TABLE_H
#define DRGN_HASH_TABLE_H
#ifdef __SSE2__
#include <emmintrin.h> // IWYU pragma: keep
#endif
#ifdef __SSE4_2__
#include <nmmintrin.h>
#endif
#include <stdalign.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include "bitops.h"
#include "cityhash.h"
#include "minmax.h"
#include "nstring.h" // IWYU pragma: export
#include "util.h"
/**
* @ingroup Internals
*
* @defgroup HashTables Hash tables
*
* High performance generic hash tables.
*
* This is an implementation of Facebook's <a
* href="https://github.com/facebook/folly/blob/master/folly/container/F14.md">
* F14</a>, which provides both high performance and good memory efficiency by
* using SIMD instructions to allow for a high load factor.
*
* These hash tables are generic, strongly typed (i.e., keys and values have
* static types rather than <tt>void *</tt>), and don't have any function
* pointer overhead.
*
* On non-x86 platforms, this falls back to a slower implementation that doesn't
* use SIMD.
*
* Abstractly, a hash table stores @em entries which can be looked up by @em
* key. A hash table is defined with @ref DEFINE_HASH_TABLE() (or the
* higher-level wrappers, @ref DEFINE_HASH_MAP() and @ref DEFINE_HASH_SET()).
* Each generated hash table interface is prefixed with a given name; the
* interface documented here uses the example name @c hash_table, which could be
* generated with this example code:
*
* @code{.c}
* key_type entry_to_key(const entry_type *entry);
* struct hash_pair hash_func(const key_type *key);
* bool eq_func(const key_type *a, const key_type *b);
* DEFINE_HASH_TABLE(hash_table, entry_type, entry_to_key, hash_func, eq_func)
* @endcode
*
* @sa BinarySearchTrees
*
* @{
*/
/**
* Double hash.
*
* @sa HashTableHelpers
*/
struct hash_pair {
/**
* First hash.
*
* F14 uses this to select the chunk.
*/
size_t first;
/**
* Second hash.
*
* F14 uses this as the tag within the chunk and as the probe stride
* when a chunk overflows.
*
* Only the 8 least-significant bits of this are used; the rest are zero
* (the folly implementation insists that storing this as @c size_t
* generates better code). The 8th bit is always set. This is derived
* from @ref hash_pair::first; see @ref
* hash_pair_from_avalanching_hash() and @ref
* hash_pair_from_non_avalanching_hash().
*/
size_t second;
};
#ifdef DOXYGEN
/**
* @struct hash_table
*
* Hash table instance.
*
* There are no requirements on how this is allocated; it may be global, on the
* stack, allocated by @c malloc(), embedded in another structure, etc.
*/
struct hash_table;
/**
* Hash table iterator.
*
* Several functions return an iterator or take one as an argument. This
* iterator has a reference to an entry, which can be @c NULL to indicate that
* there is no such entry. It also contains private bookkeeping which should not
* be used.
*
* An iterator remains valid until the table is rehashed or the entry or one
* before it is deleted.
*/
struct hash_table_iterator {
/** Pointer to the entry in the hash table. */
entry_type *entry;
};
/**
* Compute the hash for a given key.
*
* Note that this function is simply a wrapper around the hash function that was
* passed when defining the hash table. It is provided for convenience.
*/
struct hash_pair hash_table_hash(const key_type *key);
/**
* Initialize a @ref hash_table.
*
* The new hash table is empty. It must be deinitialized with @ref
* hash_table_deinit().
*
* @sa HASH_TABLE_INIT
*/
void hash_table_init(struct hash_table *table);
/**
* Free memory allocated by a @ref hash_table.
*
* After this is called, the hash table must not be used unless it is
* reinitialized with @ref hash_table_init(). Note that this only frees memory
* allocated by the hash table implementation; if the keys, values, or the hash
* table structure itself are dynamically allocated, those must be freed
* separately.
*/
void hash_table_deinit(struct hash_table *table);
/**
* Return whether a @ref hash_table has no entries.
*
* This is O(1).
*/
bool hash_table_empty(struct hash_table *table);
/**
* Return the number of entries in a @ref hash_table.
*
* This is O(1).
*/
size_t hash_table_size(struct hash_table *table);
/**
* Delete all entries in a @ref hash_table.
*
* This does not necessarily free memory used by the hash table.
*/
void hash_table_clear(struct hash_table *table);
/**
* Reserve entries in a @ref hash_table.
*
* This allocates space up front and rehashes the table to ensure that it will
* not be rehashed until it contains the given number of entries.
*
* @return @c true on success, @c false on failure.
*/
bool hash_table_reserve(struct hash_table *table, size_t capacity);
/**
* Insert an entry in a @ref hash_table.
*
* If an entry with the same key is already in the hash table, the entry is @em
* not inserted.
*
* @param[out] it_ret If not @c NULL, a returned iterator pointing to the newly
* inserted entry or the existing entry with the same key.
* @return 1 if the entry was inserted, 0 if the key already existed, -1 if
* allocating memory for a rehash failed.
*/
int hash_table_insert(struct hash_table *table, const entry_type *entry,
struct hash_table_iterator *it_ret);
/**
* Insert an entry in a @ref hash_table with a precomputed hash.
*
* Like @ref hash_table_insert(), but the hash was already computed. This saves
* recomputing the hash when doing multiple operations with the same key.
*/
int hash_table_insert_hashed(struct hash_table *table, const entry_type *entry,
struct hash_pair hp,
struct hash_table_iterator *it_ret);
/**
* Insert an entry in a @ref hash_table which is not in the table.
*
* Like @ref hash_table_insert_hashed(), but a search was previously done and
* the key is not already in the table. This saves doing a redundant search in
* that case but is unsafe otherwise.
*/
int hash_table_insert_searched(struct hash_table *table,
const entry_type *entry, struct hash_pair hp,
struct hash_table_iterator *it_ret);
/**
* Search for an entry in a @ref hash_table.
*
* @return An iterator pointing to the entry with the given key, or an iterator
* with <tt>entry == NULL</tt> if the key was not found.
*/
struct hash_table_iterator hash_table_search(struct hash_table *table,
const key_type *key);
/**
* Search for an entry in a @ref hash_table with a precomputed hash.
*
* Like @ref hash_table_search(), but the hash was already computed. This saves
* recomputing the hash when doing multiple operations with the same key.
*/
struct hash_table_iterator hash_table_search_hashed(struct hash_table *table,
const key_type *key,
struct hash_pair hp);
/**
* Delete an entry in a @ref hash_table.
*
* This deletes the entry with the given key. It will never rehash the table.
*
* @return @c true if the entry was found and deleted, @c false if not.
*/
bool hash_table_delete(struct hash_table *table, const key_type *key);
/**
* Delete an entry in a @ref hash_table with a precomputed hash.
*
* Like @ref hash_table_delete(), but the hash was already computed. This saves
* recomputing the hash when doing multiple operations with the same key.
*/
bool hash_table_delete_hashed(struct hash_table *table, struct hash_pair hp);
/**
* Delete an entry given by an iterator in a @ref hash_table.
*
* This deletes the entry pointed to by the iterator. It will never rehash the
* table.
*
* @return An iterator pointing to the next entry in the table. See @ref
* hash_table_next().
*/
struct hash_table_iterator
hash_table_delete_iterator(struct hash_table *table,
struct hash_table_iterator it);
/**
* Delete an entry given by an iterator in a @ref hash_table with a precomputed
* hash.
*
* Like @ref hash_table_delete_iterator(), but the hash was already computed.
* This saves recomputing the hash when doing multiple operations with the same
* key.
*/
struct hash_table_iterator
hash_table_delete_iterator_hashed(struct hash_table *table,
struct hash_table_iterator it,
struct hash_pair hp);
/**
* Get an iterator pointing to the first entry in a @ref hash_table.
*
* The first entry is arbitrary.
*
* @return An iterator pointing to the first entry, or an iterator with
* <tt>entry == NULL</tt> if the table is empty.
*/
struct hash_table_iterator hash_table_first(struct hash_table *table);
/**
* Get an iterator pointing to the next entry in a @ref hash_table.
*
* The order of entries is arbitrary.
*
* @return An iterator pointing to the next entry, or an iterator with <tt>entry
* == NULL</tt> if there are no more entries.
*/
struct hash_table_iterator hash_table_next(struct hash_table_iterator it);
#endif
enum {
hash_table_chunk_alignment = max_iconst(alignof(max_align_t),
(size_t)16),
};
static inline size_t hash_table_probe_delta(struct hash_pair hp)
{
return 2 * hp.second + 1;
}
static const uint8_t hosted_overflow_count_inc = 0x10;
static const uint8_t hosted_overflow_count_dec = -0x10;
/*
* We could represent an empty hash table with chunks set to NULL. However, then
* we would need a branch to check for this in insert, search, and delete. We
* could avoid this by allocating an empty chunk, but that is wasteful since it
* will never actually be used. Instead, we have a special empty chunk which is
* used by all tables.
*/
extern const uint8_t hash_table_empty_chunk_header[];
#define hash_table_empty_chunk (void *)hash_table_empty_chunk_header
#ifdef __SSE2__
#define HASH_TABLE_CHUNK_MATCH(table) \
static inline unsigned int table##_chunk_match(struct table##_chunk *chunk, \
size_t needle) \
{ \
__m128i tag_vec = _mm_load_si128((__m128i *)chunk); \
__m128i needle_vec = _mm_set1_epi8((uint8_t)needle); \
__m128i eq_vec = _mm_cmpeq_epi8(tag_vec, needle_vec); \
return _mm_movemask_epi8(eq_vec) & table##_chunk_full_mask; \
}
#define HASH_TABLE_CHUNK_OCCUPIED(table) \
static inline unsigned int table##_chunk_occupied(struct table##_chunk *chunk) \
{ \
__m128i tag_vec = _mm_load_si128((__m128i *)chunk); \
return _mm_movemask_epi8(tag_vec) & table##_chunk_full_mask; \
}
#else
#define HASH_TABLE_CHUNK_MATCH(table) \
static inline unsigned int table##_chunk_match(struct table##_chunk *chunk, \
size_t needle) \
{ \
unsigned int mask, i; \
for (mask = 0, i = 0; i < table##_chunk_capacity; i++) { \
if (chunk->tags[i] == needle) \
mask |= 1U << i; \
} \
return mask; \
}
#define HASH_TABLE_CHUNK_OCCUPIED(table) \
static inline unsigned int table##_chunk_occupied(struct table##_chunk *chunk) \
{ \
unsigned int mask, i; \
for (mask = 0, i = 0; i < table##_chunk_capacity; i++) { \
if (chunk->tags[i]) \
mask |= 1U << i; \
} \
return mask; \
}
#endif
/**
* Define a hash table type without defining its functions.
*
* This is useful when the hash table type must be defined in one place (e.g., a
* header) but the interface is defined elsewhere (e.g., a source file) with
* @ref DEFINE_HASH_TABLE_FUNCTIONS(). Otherwise, just use @ref
* DEFINE_HASH_TABLE().
*
* @sa DEFINE_HASH_TABLE()
*/
#define DEFINE_HASH_TABLE_TYPE(table, entry_type) \
typedef typeof(entry_type) table##_entry_type; \
\
enum { \
/* \
* Whether this table uses the vector storage policy. \
* \
* The vector policy provides the best performance and memory \
* efficiency for medium and large entries. \
*/ \
table##_vector_policy = sizeof(table##_entry_type) >= 24, \
}; \
\
struct table { \
struct table##_chunk *chunks; \
struct { \
/* \
* The vector storage policy stores 32-bit indices, so we only \
* need 32-bit sizes. \
*/ \
uint32_t chunk_mask; \
uint32_t size; \
/* Allocated together with chunks. */ \
table##_entry_type *entries; \
} vector[table##_vector_policy]; \
struct { \
size_t chunk_mask; \
size_t size; \
uintptr_t first_packed; \
} basic[!table##_vector_policy]; \
};
/*
* Common search function implementation returning an item iterator. This is
* shared by key lookups and index lookups.
*/
#define HASH_TABLE_SEARCH_IMPL(table, func, key_type, item_to_key, eq_func) \
static struct table##_iterator table##_##func(struct table *table, \
const key_type *key, \
struct hash_pair hp) \
{ \
const size_t delta = hash_table_probe_delta(hp); \
size_t index = hp.first; \
for (size_t tries = 0; tries <= table##_chunk_mask(table); tries++) { \
struct table##_chunk *chunk = \
&table->chunks[index & table##_chunk_mask(table)]; \
if (sizeof(*chunk) > 64) \
__builtin_prefetch(&chunk->items[8]); \
unsigned int mask = table##_chunk_match(chunk, hp.second), i; \
for_each_bit(i, mask) { \
table##_item_type *item = &chunk->items[i]; \
key_type item_key = item_to_key(table, item); \
if (likely(eq_func(key, &item_key))) { \
return (struct table##_iterator){ \
.item = item, \
.index = i, \
}; \
} \
} \
if (likely(chunk->outbound_overflow_count == 0)) \
break; \
index += delta; \
} \
return (struct table##_iterator){}; \
}
#define HASH_TABLE_SEARCH_BY_INDEX_ITEM_TO_KEY(table, item) (*(item)->index)
/**
* Define the functions for a hash table.
*
* The hash table type must have already been defined with @ref
* DEFINE_HASH_TABLE_TYPE().
*
* Unless the type and function definitions must be in separate places, use @ref
* DEFINE_HASH_TABLE() instead.
*/
#define DEFINE_HASH_TABLE_FUNCTIONS(table, entry_to_key, hash_func, eq_func) \
typedef typeof(entry_to_key((table##_entry_type *)0)) table##_key_type; \
\
static inline table##_key_type \
table##_entry_to_key(const table##_entry_type *entry) \
{ \
return entry_to_key(entry); \
} \
\
/* \
* Item stored in a chunk. \
* \
* When using the basic policy, the entry is stored directly in the item. When \
* using the vector policy, the item is an index to an out-of-band vector of \
* entries. \
* \
* C doesn't make it easy to define a type conditionally, so we use a nasty \
* hack: the member for the used policy is an array of length 1, and the unused \
* member is an array of length 0. We also have to force the struct to be \
* aligned only for the used member. \
*/ \
typedef struct { \
uint32_t index[table##_vector_policy]; \
table##_entry_type entry[!table##_vector_policy]; \
} __attribute__((__packed__, \
__aligned__(table##_vector_policy ? \
alignof(uint32_t) : alignof(table##_entry_type)))) \
table##_item_type; \
\
enum { \
/* \
* The number of items per chunk. 14 is the most space efficient, but \
* if an item is 4 bytes, 12 items makes a chunk exactly one cache \
* line. \
*/ \
table##_chunk_capacity = sizeof(table##_item_type) == 4 ? 12 : 14, \
/* The maximum load factor in terms of items per chunk. */ \
table##_chunk_desired_capacity = table##_chunk_capacity - 2, \
/* \
* If an item is 16 bytes, add an extra 16 bytes of padding to make a \
* chunk exactly four cache lines. \
*/ \
table##_chunk_allocated_capacity = \
(table##_chunk_capacity + \
(sizeof(table##_item_type) == 16 ? 1 : 0)), \
/* \
* If the chunk capacity is 12, we can use tags 12 and 13 for 16 bits. \
* Otherwise, we only get 4 from control. \
*/ \
table##_capacity_scale_bits = table##_chunk_capacity == 12 ? 16 : 4, \
table##_capacity_scale_shift = table##_capacity_scale_bits - 4, \
table##_chunk_full_mask = (1 << table##_chunk_capacity) - 1, \
}; \
\
struct table##_chunk { \
uint8_t tags[14]; \
/* \
* The lower 4 bits are capacity_scale: for the first chunk, this is \
* the scaling factor between the chunk count and the capacity; for \
* other chunks, this is zero. \
* \
* The upper 4 bits are hosted_overflow_count: the number of entries in \
* this chunk that overflowed their desired chunk. \
*/ \
uint8_t control; \
/* \
* The number of entries that would have been in this chunk if it were \
* not full. This value saturates if it hits 255, after which it will \
* not be updated. \
*/ \
uint8_t outbound_overflow_count; \
table##_item_type items[table##_chunk_allocated_capacity]; \
} __attribute__((__aligned__(hash_table_chunk_alignment))); \
\
/* \
* This may be a "public iterator" (used by the public interface to refer to an \
* entry) or an "item iterator" (used by certain internal functions to refer to \
* an item regardless of the storage policy). \
*/ \
struct table##_iterator { \
union { \
/* Entry if public iterator. */ \
table##_entry_type *entry; \
/* \
* Item if item iterator. Interchangable with entry when using \
* the basic storage policy. \
*/ \
table##_item_type *item; \
}; \
union { \
/* \
* Lowest entry if public iterator and using the vector storage \
* policy (i.e., table->vector->entries). \
*/ \
table##_entry_type *lowest; \
/* \
* Index of item in its containing chunk if item iterator or \
* using the basic storage policy. \
*/ \
size_t index; \
}; \
}; \
\
static inline struct hash_pair table##_hash(const table##_key_type *key) \
{ \
return hash_func(key); \
} \
\
static inline table##_entry_type * \
table##_item_to_entry(struct table *table, table##_item_type *item) \
{ \
if (table##_vector_policy) { \
return &table->vector->entries[*item->index]; \
} else { \
/* \
* Returning item->entry directly results in a false positive \
* -Waddress-of-packed-member warning. \
*/ \
void *entry = item->entry; \
return entry; \
} \
} \
\
static inline table##_key_type \
table##_item_to_key(struct table *table, table##_item_type *item) \
{ \
return table##_entry_to_key(table##_item_to_entry(table, item)); \
} \
\
/* \
* We cache the first position in the table as a tagged pointer: we steal the \
* bottom bits of the chunk pointer for the entry index. We can do this because \
* chunks are aligned to 16 bytes and the index is always less than 16. \
* \
* The folly implementation mentions this strategy but uses a more complicated \
* scheme in order to avoid computing the chunk pointer from an entry pointer. \
* We always have the chunk pointer readily available when we want to pack an \
* entry, so we can use this much simpler scheme. \
*/ \
static inline uintptr_t table##_pack_iterator(struct table##_chunk *chunk, \
size_t index) \
{ \
return (uintptr_t)chunk | (uintptr_t)index; \
} \
\
static inline struct table##_chunk *table##_unpack_chunk(uintptr_t packed) \
{ \
return (struct table##_chunk *)(packed & ~(uintptr_t)0xf); \
} \
\
static inline size_t table##_unpack_index(uintptr_t packed) \
{ \
return packed & 0xf; \
} \
\
static inline struct table##_iterator table##_unpack_iterator(uintptr_t packed) \
{ \
struct table##_chunk *chunk = table##_unpack_chunk(packed); \
size_t index = table##_unpack_index(packed); \
return (struct table##_iterator) { \
.item = chunk ? &chunk->items[index] : NULL, \
.index = index, \
}; \
} \
\
static inline struct table##_chunk * \
table##_iterator_chunk(struct table##_iterator it) \
{ \
return container_of(it.item - it.index, struct table##_chunk, items[0]);\
} \
\
HASH_TABLE_CHUNK_MATCH(table) \
HASH_TABLE_CHUNK_OCCUPIED(table) \
\
static inline unsigned int \
table##_chunk_first_empty(struct table##_chunk *chunk) \
{ \
unsigned int mask = \
table##_chunk_occupied(chunk) ^ table##_chunk_full_mask; \
return mask ? ctz(mask) : (unsigned int)-1; \
} \
\
static inline unsigned int \
table##_chunk_last_occupied(struct table##_chunk *chunk) \
{ \
unsigned int mask = table##_chunk_occupied(chunk); \
return mask ? fls(mask) - 1 : (unsigned int)-1; \
} \
\
static inline size_t \
table##_chunk_hosted_overflow_count(struct table##_chunk *chunk) \
{ \
return chunk->control >> 4; \
} \
\
static inline void \
table##_chunk_adjust_hosted_overflow_count(struct table##_chunk *chunk, \
size_t op) \
{ \
chunk->control += op; \
} \
\
static inline size_t table##_chunk_capacity_scale(struct table##_chunk *chunk) \
{ \
if (table##_capacity_scale_bits == 4) { \
return chunk->control & 0xf; \
} else { \
uint16_t val; \
memcpy(&val, &chunk->tags[12], 2); \
return val; \
} \
} \
\
static inline bool table##_chunk_eof(struct table##_chunk *chunk) \
{ \
return table##_chunk_capacity_scale(chunk) != 0; \
} \
\
static inline void table##_chunk_mark_eof(struct table##_chunk *chunk, \
size_t capacity_scale) \
{ \
if (table##_capacity_scale_bits == 4) { \
chunk->control = capacity_scale; \
} else { \
uint16_t val = capacity_scale; \
memcpy(&chunk->tags[12], &val, 2); \
} \
} \
\
static inline void \
table##_chunk_inc_outbound_overflow_count(struct table##_chunk *chunk) \
{ \
if (chunk->outbound_overflow_count != UINT8_MAX) \
chunk->outbound_overflow_count++; \
} \
\
static inline void \
table##_chunk_dec_outbound_overflow_count(struct table##_chunk *chunk) \
{ \
if (chunk->outbound_overflow_count != UINT8_MAX) \
chunk->outbound_overflow_count--; \
} \
\
__attribute__((__unused__)) \
static void table##_init(struct table *table) \
{ \
table->chunks = hash_table_empty_chunk; \
if (table##_vector_policy) { \
table->vector->chunk_mask = 0; \
table->vector->size = 0; \
table->vector->entries = NULL; \
} else { \
table->basic->chunk_mask = 0; \
table->basic->size = 0; \
table->basic->first_packed = 0; \
} \
} \
\
__attribute__((__unused__)) \
static void table##_deinit(struct table *table) \
{ \
if (table->chunks != hash_table_empty_chunk) \
free(table->chunks); \
} \
\
static inline size_t table##_size(struct table *table) \
{ \
if (table##_vector_policy) \
return table->vector->size; \
else \
return table->basic->size; \
} \
\
static inline void table##_set_size(struct table *table, size_t size) \
{ \
if (table##_vector_policy) \
table->vector->size = size; \
else \
table->basic->size = size; \
} \
\
static inline size_t table##_chunk_mask(struct table *table) \
{ \
if (table##_vector_policy) \
return table->vector->chunk_mask; \
else \
return table->basic->chunk_mask; \
} \
\
static inline void table##_set_chunk_mask(struct table *table, \
size_t chunk_mask) \
{ \
if (table##_vector_policy) \
table->vector->chunk_mask = chunk_mask; \
else \
table->basic->chunk_mask = chunk_mask; \
} \
\
__attribute__((__unused__)) \
static inline bool table##_empty(struct table *table) \
{ \
return table##_size(table) == 0; \
} \
\
static table##_item_type *table##_allocate_tag(struct table *table, \
uint8_t *fullness, \
struct hash_pair hp) \
{ \
const size_t delta = hash_table_probe_delta(hp); \
size_t index = hp.first; \
struct table##_chunk *chunk; \
uint8_t hosted_op = 0; \
for (;;) { \
index &= table##_chunk_mask(table); \
chunk = &table->chunks[index]; \
if (likely(fullness[index] < table##_chunk_capacity)) \
break; \
table##_chunk_inc_outbound_overflow_count(chunk); \
hosted_op = hosted_overflow_count_inc; \
index += delta; \
} \
size_t item_index = fullness[index]++; \
chunk->tags[item_index] = hp.second; \
table##_chunk_adjust_hosted_overflow_count(chunk, hosted_op); \
return &chunk->items[item_index]; \
} \
\
static size_t table##_compute_capacity(size_t chunk_count, size_t scale) \
{ \
return (((chunk_count - 1) >> table##_capacity_scale_shift) + 1) * scale;\
} \
\
static bool \
table##_compute_chunk_count_and_scale(size_t capacity, \
bool continuous_single_chunk_capacity, \
bool continuous_multi_chunk_capacity, \
size_t *chunk_count_ret, \
size_t *scale_ret) \
{ \
if (capacity <= table##_chunk_capacity) { \
if (!continuous_single_chunk_capacity) { \
if (capacity <= 2) \
capacity = 2; \
else if (capacity <= 6) \
capacity = 6; \
else \
capacity = table##_chunk_capacity; \
} \
*chunk_count_ret = 1; \
*scale_ret = capacity; \
} else { \
size_t min_chunks = \
(capacity - 1) / table##_chunk_desired_capacity + 1; \
size_t chunk_pow = fls(min_chunks - 1); \
if (chunk_pow == 8 * sizeof(size_t)) \
return false; \
size_t chunk_count = (size_t)1 << chunk_pow; \
size_t ss = (chunk_pow >= table##_capacity_scale_shift ? \
chunk_pow - table##_capacity_scale_shift : 0); \
size_t scale = \
continuous_multi_chunk_capacity ? \
((capacity - 1) >> ss) + 1 : \
table##_chunk_desired_capacity << (chunk_pow - ss); \
if (table##_vector_policy && \
table##_compute_capacity(chunk_count, scale) > UINT32_MAX) \
return false; \
*chunk_count_ret = chunk_count; \
*scale_ret = scale; \
} \
return true; \
} \
\
static inline size_t table##_chunk_alloc_size(size_t chunk_count, \
size_t capacity_scale) \
{ \
/* \
* Small hash tables are common, so for capacities of less than a full \
* chunk, we only allocate the required items. \
*/ \
if (chunk_count == 1) { \
return (offsetof(struct table##_chunk, items) + \
table##_compute_capacity(1, capacity_scale) * \
sizeof(table##_item_type)); \
} else { \
return chunk_count * sizeof(struct table##_chunk); \
} \
} \
\
static bool table##_rehash(struct table *table, size_t orig_chunk_count, \
size_t orig_capacity_scale, size_t new_chunk_count, \
size_t new_capacity_scale) \
{ \
size_t chunk_alloc_size = table##_chunk_alloc_size(new_chunk_count, \
new_capacity_scale); \
size_t alloc_size, entries_offset; \
if (table##_vector_policy) { \
entries_offset = chunk_alloc_size; \
if (alignof(table##_entry_type) > alignof(table##_item_type)) { \
entries_offset = -(-entries_offset & \
~(alignof(table##_entry_type) - 1)); \
} \
size_t new_capacity = \
table##_compute_capacity(new_chunk_count, \
new_capacity_scale); \
alloc_size = (entries_offset + \
new_capacity * sizeof(table##_entry_type)); \
} else { \
alloc_size = chunk_alloc_size; \
} \
\
void *new_chunks; \
if (posix_memalign(&new_chunks, hash_table_chunk_alignment, alloc_size))\
return false; \
\
struct table##_chunk *orig_chunks = table->chunks; \
table->chunks = new_chunks; \
table##_entry_type *orig_entries; \
if (table##_vector_policy) { \
orig_entries = table->vector->entries; \
table->vector->entries = new_chunks + entries_offset; \
if (table##_size(table) > 0) { \
memcpy(table->vector->entries, orig_entries, \
table##_size(table) * \
sizeof(table##_entry_type)); \
} \
} \
\
memset(table->chunks, 0, chunk_alloc_size); \
table##_chunk_mark_eof(table->chunks, new_capacity_scale); \
table##_set_chunk_mask(table, new_chunk_count - 1); \
\
if (table##_size(table) == 0) { \
/* Nothing to do. */ \
} else if (orig_chunk_count == 1 && new_chunk_count == 1) { \
struct table##_chunk *src = orig_chunks; \
struct table##_chunk *dst = table->chunks; \
size_t src_i = 0, dst_i = 0; \
while (dst_i < table##_size(table)) { \
if (likely(src->tags[src_i])) { \
dst->tags[dst_i] = src->tags[src_i]; \
memcpy(&dst->items[dst_i], &src->items[src_i], \
sizeof(dst->items[dst_i])); \
dst_i++; \
} \
src_i++; \
} \
if (!table##_vector_policy) { \
table->basic->first_packed = \
table##_pack_iterator(dst, dst_i - 1); \
} \
} else { \
uint8_t stack_fullness[256]; \
uint8_t *fullness; \
if (new_chunk_count <= sizeof(stack_fullness)) { \
memset(stack_fullness, 0, sizeof(stack_fullness)); \
fullness = stack_fullness; \
} else { \
fullness = calloc(new_chunk_count, 1); \
if (!fullness) \
goto err; \
} \
\
struct table##_chunk *src = &orig_chunks[orig_chunk_count - 1]; \
size_t remaining = table##_size(table); \
while (remaining) { \
unsigned int mask = table##_chunk_occupied(src), i; \
if (table##_vector_policy) { \
unsigned int pmask = mask; \
for_each_bit(i, pmask) \
__builtin_prefetch(&src->items[i]); \
} \
for_each_bit(i, mask) { \
remaining--; \
\
table##_item_type *src_item = &src->items[i]; \
table##_key_type key = \
table##_item_to_key(table, src_item); \
struct hash_pair hp = table##_hash(&key); \
table##_item_type *dst_item = \
table##_allocate_tag(table, fullness, \
hp); \
memcpy(dst_item, src_item, sizeof(*dst_item)); \
} \
src--; \
} \
\
if (!table##_vector_policy) { \
size_t i = table##_chunk_mask(table); \
while (fullness[i] == 0) \
i--; \
table->basic->first_packed = \
table##_pack_iterator(&table->chunks[i], \
fullness[i] - 1); \
} \
\
if (fullness != stack_fullness) \
free(fullness); \
} \
\
if (orig_chunks != hash_table_empty_chunk) \
free(orig_chunks); \
return true; \
\
err: \
free(table->chunks); \
table->chunks = orig_chunks; \
table##_set_chunk_mask(table, orig_chunk_count - 1); \
if (table##_vector_policy) \
table->vector->entries = orig_entries; \
return false; \
} \
\
static void table##_do_clear(struct table *table, bool reset) \
{ \
if (table->chunks == hash_table_empty_chunk) \
return; \
\
size_t chunk_count = table##_chunk_mask(table) + 1; \
/* Always reset large tables. */ \
if (chunk_count >= 16) \
reset = true; \
if (!table##_empty(table)) { \
if (!reset) { \
size_t capacity_scale = \
table##_chunk_capacity_scale(table->chunks); \
memset(table->chunks, 0, \
table##_chunk_alloc_size(chunk_count, \
capacity_scale)); \
table##_chunk_mark_eof(table->chunks, capacity_scale); \
} \
if (!table##_vector_policy) \
table->basic->first_packed = 0; \
table##_set_size(table, 0); \
} \
if (reset) { \
free(table->chunks); \
table->chunks = hash_table_empty_chunk; \
table##_set_chunk_mask(table, 0); \
if (table##_vector_policy) \
table->vector->entries = NULL; \
} \
} \
\
__attribute__((__unused__)) \
static bool table##_reserve(struct table *table, size_t capacity) \
{ \
capacity = max(capacity, table##_size(table)); \
if (!capacity) { \
table##_do_clear(table, true); \
return true; \
} \
\
size_t orig_chunk_count = table##_chunk_mask(table) + 1; \
size_t orig_capacity_scale = table##_chunk_capacity_scale(table->chunks);\
size_t orig_capacity = table##_compute_capacity(orig_chunk_count, \
orig_capacity_scale); \
\
/* \
* To avoid pathological behavior, ignore decreases that aren't at \
* least a 1/8 decrease, and double for increases that aren't at least \
* a 1/8 increase. \
*/ \
if (capacity <= orig_capacity && \
capacity >= orig_capacity - orig_capacity / 8) \
return true; \
bool attempt_exact = !(capacity > orig_capacity && \
capacity < orig_capacity + orig_capacity / 8); \
\
size_t new_chunk_count; \
size_t new_capacity_scale; \
if (!table##_compute_chunk_count_and_scale(capacity, attempt_exact, \
table##_vector_policy && \
attempt_exact, \
&new_chunk_count, \
&new_capacity_scale)) \
return false; \
size_t new_capacity = table##_compute_capacity(new_chunk_count, \
new_capacity_scale); \
if (new_capacity == orig_capacity) \
return true; \
return table##_rehash(table, orig_chunk_count, orig_capacity_scale, \
new_chunk_count, new_capacity_scale); \
} \
\
__attribute__((__unused__)) \
static void table##_clear(struct table *table) \
{ \
table##_do_clear(table, false); \
} \
\
\
HASH_TABLE_SEARCH_IMPL(table, search_by_key, table##_key_type, \
table##_item_to_key, eq_func) \
HASH_TABLE_SEARCH_IMPL(table, search_by_index, uint32_t, \
HASH_TABLE_SEARCH_BY_INDEX_ITEM_TO_KEY, scalar_key_eq) \
\
\
static struct table##_iterator \
table##_search_hashed(struct table *table, const table##_key_type *key, \
struct hash_pair hp) \
{ \
struct table##_iterator it = table##_search_by_key(table, key, hp); \
/* Convert the item iterator to a public iterator. */ \
if (table##_vector_policy && it.item) { \
it.entry = table##_item_to_entry(table, it.item); \
it.lowest = table->vector->entries; \
} \
return it; \
} \
\
__attribute__((__unused__)) \
static struct table##_iterator \
table##_search(struct table *table, const table##_key_type *key) \
{ \
return table##_search_hashed(table, key, table##_hash(key)); \
} \
\
static bool table##_reserve_for_insert(struct table *table) \
{ \
size_t orig_chunk_count = table##_chunk_mask(table) + 1; \
size_t orig_capacity_scale = table##_chunk_capacity_scale(table->chunks);\
size_t orig_capacity = table##_compute_capacity(orig_chunk_count, \
orig_capacity_scale); \
size_t capacity = table##_size(table) + 1; \
if (capacity <= orig_capacity) \
return true; \
/* Grow by at least orig_capacity * 2^0.5. */ \
size_t min_growth = (orig_capacity + \
(orig_capacity >> 2) + \
(orig_capacity >> 3) + \
(orig_capacity >> 5)); \
capacity = max(capacity, min_growth); \
size_t new_chunk_count, new_capacity_scale; \
if (!table##_compute_chunk_count_and_scale(capacity, false, false, \
&new_chunk_count, \
&new_capacity_scale)) \
return false; \
return table##_rehash(table, orig_chunk_count, orig_capacity_scale, \
new_chunk_count, new_capacity_scale); \
} \
\
static void \
table##_adjust_size_and_first_after_insert(struct table *table, \
struct table##_chunk *chunk, \
size_t index) \
{ \
if (!table##_vector_policy) { \
uintptr_t first_packed = table##_pack_iterator(chunk, index); \
if (first_packed > table->basic->first_packed) \
table->basic->first_packed = first_packed; \
} \
table##_set_size(table, table##_size(table) + 1); \
} \
\
static int table##_insert_searched(struct table *table, \
const table##_entry_type *entry, \
struct hash_pair hp, \
struct table##_iterator *it_ret) \
{ \
if (!table##_reserve_for_insert(table)) \
return -1; \
\
size_t index = hp.first; \
struct table##_chunk *chunk = \
&table->chunks[index & table##_chunk_mask(table)]; \
unsigned int first_empty = table##_chunk_first_empty(chunk); \
if (first_empty == (unsigned int)-1) { \
size_t delta = hash_table_probe_delta(hp); \
do { \
table##_chunk_inc_outbound_overflow_count(chunk); \
index += delta; \
chunk = &table->chunks[index & table##_chunk_mask(table)];\
first_empty = table##_chunk_first_empty(chunk); \
} while (first_empty == (unsigned int)-1); \
table##_chunk_adjust_hosted_overflow_count(chunk, \
hosted_overflow_count_inc);\
} \
chunk->tags[first_empty] = hp.second; \
if (table##_vector_policy) { \
*chunk->items[first_empty].index = table##_size(table); \
memcpy(&table->vector->entries[table##_size(table)], entry, \
sizeof(*entry)); \
} else { \
memcpy(&chunk->items[first_empty], entry, sizeof(*entry)); \
} \
table##_adjust_size_and_first_after_insert(table, chunk, first_empty); \
if (it_ret) { \
if (table##_vector_policy) { \
it_ret->entry = \
&table->vector->entries[table##_size(table) - 1];\
it_ret->lowest = table->vector->entries; \
} else { \
it_ret->item = &chunk->items[first_empty]; \
it_ret->index = first_empty; \
} \
} \
return 1; \
} \
\
static int table##_insert_hashed(struct table *table, \
const table##_entry_type *entry, \
struct hash_pair hp, \
struct table##_iterator *it_ret) \
{ \
table##_key_type key = table##_entry_to_key(entry); \
struct table##_iterator it = table##_search_hashed(table, &key, hp); \
if (it.entry) { \
if (it_ret) \
*it_ret = it; \
return 0; \
} else { \
return table##_insert_searched(table, entry, hp, it_ret); \
} \
} \
\
__attribute__((__unused__)) \
static int table##_insert(struct table *table, \
const table##_entry_type *entry, \
struct table##_iterator *it_ret) \
{ \
table##_key_type key = table##_entry_to_key(entry); \
return table##_insert_hashed(table, entry, table##_hash(&key), it_ret); \
} \
\
/* Similar to table##_next_impl() but for the cached first position. */ \
static void table##_advance_first_packed(struct table *table) \
{ \
uintptr_t packed = table->basic->first_packed; \
struct table##_chunk *chunk = table##_unpack_chunk(packed); \
size_t index = table##_unpack_index(packed); \
while (index > 0) { \
index--; \
if (chunk->tags[index]) { \
table->basic->first_packed = \
table##_pack_iterator(chunk, index); \
return; \
} \
} \
\
/* \
* This is only called when there is another entry in the table, so we \
* don't need to check if we hit the end. \
*/ \
for (;;) { \
chunk--; \
unsigned int last = table##_chunk_last_occupied(chunk); \
if (last != (unsigned int)-1) { \
table->basic->first_packed = \
table##_pack_iterator(chunk, last); \
return; \
} \
} \
} \
\
static void \
table##_adjust_size_and_first_before_delete(struct table *table, \
struct table##_chunk *chunk, \
size_t index) \
{ \
table##_set_size(table, table##_size(table) - 1); \
if (!table##_vector_policy && \
table##_pack_iterator(chunk, index) == table->basic->first_packed) {\
if (table##_empty(table)) \
table->basic->first_packed = 0; \
else \
table##_advance_first_packed(table); \
} \
} \
\
/* \
* We want this inlined so that the whole function call can be optimized away \
* in the likely_dead case, and so that the counter can be optimized away in \
* the not likely_dead case. \
*/ \
__attribute__((__always_inline__)) \
static inline struct table##_iterator \
table##_next_impl(struct table##_iterator it, bool likely_dead) \
{ \
struct table##_chunk *chunk = table##_iterator_chunk(it); \
while (it.index > 0) { \
it.index--; \
it.entry--; \
if (likely(chunk->tags[it.index])) \
return it; \
} \
\
/* \
* This hack is copied from the folly implementation: this is dead code \
* if the return value is not used (e.g., the return value of \
* table##_delete_iterator() is often ignored), but the compiler needs \
* some help proving that the following loop terminates. \
*/ \
for (size_t i = 1; !likely_dead || i != 0; i++) { \
if (unlikely(table##_chunk_eof(chunk))) \
break; \
\
chunk--; \
unsigned int last = table##_chunk_last_occupied(chunk); \
if (!likely_dead) \
__builtin_prefetch(chunk - 1); \
if (likely(last != (unsigned int)-1)) { \
it.index = last; \
it.item = &chunk->items[last]; \
return it; \
} \
} \
return (struct table##_iterator){}; \
} \
\
static void table##_delete_impl(struct table *table, \
struct table##_iterator item_it, \
struct hash_pair hp) \
{ \
struct table##_chunk *it_chunk = table##_iterator_chunk(item_it); \
it_chunk->tags[item_it.index] = 0; \
\
table##_adjust_size_and_first_before_delete(table, it_chunk, \
item_it.index); \
\
if (table##_chunk_hosted_overflow_count(it_chunk)) { \
const size_t delta = hash_table_probe_delta(hp); \
size_t index = hp.first; \
uint8_t hosted_op = 0; \
for (;;) { \
struct table##_chunk *chunk = \
&table->chunks[index & table##_chunk_mask(table)];\
if (chunk == it_chunk) { \
table##_chunk_adjust_hosted_overflow_count(chunk,\
hosted_op);\
break; \
} \
table##_chunk_dec_outbound_overflow_count(chunk); \
hosted_op = hosted_overflow_count_dec; \
index += delta; \
} \
} \
} \
\
static void table##_vector_delete_impl(struct table *table, \
struct table##_iterator item_it, \
struct hash_pair hp) \
{ \
/* Delete the index from the table. */ \
uint32_t index = *item_it.item->index; \
table##_delete_impl(table, item_it, hp); \
\
/* Replace it with the last entry and update its index in the table. */ \
uint32_t tail_index = table##_size(table); \
if (tail_index != index) { \
table##_entry_type *tail = \
&table->vector->entries[tail_index]; \
table##_key_type tail_key = table##_entry_to_key(tail); \
item_it = table##_search_by_index(table, &tail_index, \
table##_hash(&tail_key)); \
*item_it.item->index = index; \
memcpy(&table->vector->entries[index], tail, sizeof(*tail)); \
} \
} \
\
/* \
* We want this inlined so that the call to table##_next_impl() can be \
* optimized away. \
*/ \
__attribute__((__always_inline__)) \
static inline struct table##_iterator \
table##_delete_iterator_hashed(struct table *table, struct table##_iterator it, \
struct hash_pair hp) \
{ \
if (table##_vector_policy) { \
uint32_t index = it.entry - it.lowest; \
struct table##_iterator item_it = \
table##_search_by_index(table, &index, hp); \
table##_vector_delete_impl(table, item_it, hp); \
if (index == 0) { \
return (struct table##_iterator){}; \
} else { \
it.entry--; \
return it; \
} \
} else { \
table##_delete_impl(table, it, hp); \
return table##_next_impl(it, true); \
} \
} \
\
__attribute__((__always_inline__, __unused__)) \
static inline struct table##_iterator \
table##_delete_iterator(struct table *table, struct table##_iterator it) \
{ \
struct hash_pair hp = {}; \
/* \
* The basic policy only needs the hash if the chunk hosts an \
* overflowed entry. \
*/ \
if (table##_vector_policy || \
table##_chunk_hosted_overflow_count(table##_iterator_chunk(it))) { \
table##_key_type key = table##_entry_to_key(it.entry); \
hp = table##_hash(&key); \
} \
return table##_delete_iterator_hashed(table, it, hp); \
} \
\
static bool table##_delete_hashed(struct table *table, \
const table##_key_type *key, \
struct hash_pair hp) \
{ \
struct table##_iterator item_it = table##_search_by_key(table, key, hp);\
if (!item_it.item) \
return false; \
if (table##_vector_policy) \
table##_vector_delete_impl(table, item_it, hp); \
else \
table##_delete_impl(table, item_it, hp); \
return true; \
} \
\
__attribute__((__unused__)) \
static bool table##_delete(struct table *table, const table##_key_type *key) \
{ \
return table##_delete_hashed(table, key, table##_hash(key)); \
} \
\
__attribute__((__unused__)) \
static struct table##_iterator table##_first(struct table *table) \
{ \
if (table##_vector_policy) { \
table##_entry_type *entry; \
if (table##_empty(table)) \
entry = NULL; \
else \
entry = &table->vector->entries[table##_size(table) - 1];\
return (struct table##_iterator){ \
.entry = entry, \
.lowest = table->vector->entries, \
}; \
} else { \
return table##_unpack_iterator(table->basic->first_packed); \
} \
} \
\
__attribute__((__unused__)) \
static struct table##_iterator table##_next(struct table##_iterator it) \
{ \
if (table##_vector_policy) { \
if (it.entry == it.lowest) { \
return (struct table##_iterator){}; \
} else { \
it.entry--; \
return it; \
} \
} else { \
return table##_next_impl(it, false); \
} \
}
/**
* Define a hash table interface.
*
* This macro defines a hash table type along with its functions.
*
* @param[in] table Name of the type to define. This is prefixed to all of the
* types and functions defined for that type.
* @param[in] entry_type Type of entries in the table.
* @param[in] entry_to_key Name of function or macro which is passed a <tt>const
* entry_type *</tt> and returns the key for that entry. The return type is the
* @c key_type of the hash table. The passed entry is never @c NULL.
* @param[in] hash_func Hash function which takes a <tt>const key_type *</tt>
* and returns a @ref hash_pair.
* @param[in] eq_func Comparison function which takes two <tt>const key_type
* *</tt> and returns a @c bool.
*/
#define DEFINE_HASH_TABLE(table, entry_type, entry_to_key, hash_func, eq_func) \
DEFINE_HASH_TABLE_TYPE(table, entry_type) \
DEFINE_HASH_TABLE_FUNCTIONS(table, entry_to_key, hash_func, eq_func)
/**
* Define a hash map type without defining its functions.
*
* The functions are defined with @ref DEFINE_HASH_MAP_FUNCTIONS().
*
* @sa DEFINE_HASH_MAP(), DEFINE_HASH_TABLE_TYPE()
*/
#define DEFINE_HASH_MAP_TYPE(table, key_type, value_type) \
struct table##_entry { \
typeof(key_type) key; \
typeof(value_type) value; \
}; \
DEFINE_HASH_TABLE_TYPE(table, struct table##_entry)
#define HASH_MAP_ENTRY_TO_KEY(entry) ((entry)->key)
/**
* Define the functions for a hash map.
*
* The hash map type must have already been defined with @ref
* DEFINE_HASH_MAP_TYPE().
*
* Unless the type and function definitions must be in separate places, use @ref
* DEFINE_HASH_MAP() instead.
*
* @sa DEFINE_HASH_TABLE_FUNCTIONS
*/
#define DEFINE_HASH_MAP_FUNCTIONS(table, hash_func, eq_func) \
DEFINE_HASH_TABLE_FUNCTIONS(table, HASH_MAP_ENTRY_TO_KEY, hash_func, eq_func)
/**
* Define a hash map interface.
*
* This is a higher-level wrapper for @ref DEFINE_HASH_TABLE() with entries of
* the following type (with the example name @c hash_map):
*
* @code{.c}
* struct hash_map_entry {
* key_type key;
* value_type value;
* };
* @endcode
*
* @param[in] table Name of the map type to define. This is prefixed to all of
* the types and functions defined for that type.
* @param[in] key_type Type of keys in the map.
* @param[in] value_type Type of values in the map.
* @param[in] hash_func See @ref DEFINE_HASH_TABLE().
* @param[in] eq_func See @ref DEFINE_HASH_TABLE().
*/
#define DEFINE_HASH_MAP(table, key_type, value_type, hash_func, eq_func) \
DEFINE_HASH_MAP_TYPE(table, key_type, value_type) \
DEFINE_HASH_MAP_FUNCTIONS(table, hash_func, eq_func)
/**
* Define a hash set type without defining its functions.
*
* The functions are defined with @ref DEFINE_HASH_SET_FUNCTIONS().
*
* @sa DEFINE_HASH_SET(), DEFINE_HASH_TABLE_TYPE()
*/
#define DEFINE_HASH_SET_TYPE DEFINE_HASH_TABLE_TYPE
#define HASH_SET_ENTRY_TO_KEY(entry) (*(entry))
/**
* Define the functions for a hash set.
*
* The hash set type must have already been defined with @ref
* DEFINE_HASH_SET_TYPE().
*
* Unless the type and function definitions must be in separate places, use @ref
* DEFINE_HASH_SET() instead.
*
* @sa DEFINE_HASH_TABLE_FUNCTIONS
*/
#define DEFINE_HASH_SET_FUNCTIONS(table, hash_func, eq_func) \
DEFINE_HASH_TABLE_FUNCTIONS(table, HASH_SET_ENTRY_TO_KEY, hash_func, eq_func)
/**
* Define a hash set interface.
*
* This is a higher-level wrapper for @ref DEFINE_HASH_TABLE() where @p
* entry_type is the same as @p key_type.
*
* @param[in] table Name of the set type to define. This is prefixed to all of
* the types and functions defined for that type.
* @param[in] key_type Type of keys in the set.
* @param[in] hash_func See @ref DEFINE_HASH_TABLE().
* @param[in] eq_func See @ref DEFINE_HASH_TABLE().
*/
#define DEFINE_HASH_SET(table, key_type, hash_func, eq_func) \
DEFINE_HASH_SET_TYPE(table, key_type) \
DEFINE_HASH_SET_FUNCTIONS(table, hash_func, eq_func)
/**
* Empty hash table initializer.
*
* This can be used to initialize a hash table when declaring it.
*
* @sa hash_table_init()
*/
#define HASH_TABLE_INIT { hash_table_empty_chunk }
/**
* @defgroup HashTableHelpers Hash table helpers
*
* Hash functions and comparators for use with @ref HashTables.
*
* F14 resolves collisions by double hashing. Rather than using two independent
* hash functions, this provides two options for efficiently deriving a pair of
* hashes from a single input hash function depending on whether the hash
* function is _avalanching_. See @ref hash_pair_from_avalanching_hash() and
* @ref hash_pair_from_non_avalanching_hash().
*
* This provides:
* * Functions for double hashing common key types: `*_hash_pair()`.
* * Primitives for double hashing more complicated key types.
* * Equality functions for common key types: `*_eq()`.
*
* @{
*/
/**
* Split an avalanching hash into a @ref hash_pair.
*
* A hash function is avalanching if each bit of the hash value has a 50% chance
* of being the same for different inputs. This is true for cryptographic hash
* functions as well as certain non-cryptographic hash functions including
* CityHash, MurmurHash, SipHash, and xxHash. Simple hashes like DJBX33A, ad-hoc
* combinations like `53 * x + y`, and the identity function are not
* avalanching.
*
* We use the input hash value as the first hash and the upper bits of the input
* hash value as the second hash (which would otherwise be discarded when
* masking to select the bucket).
*/
static inline struct hash_pair hash_pair_from_avalanching_hash(size_t hash)
{
return (struct hash_pair){
.first = hash,
.second = (hash >> (8 * sizeof(hash) - 8)) | 0x80,
};
}
/**
* Mix a non-avalanching hash and split it into a @ref hash_pair.
*
* This is architecture-dependent.
*/
static inline struct hash_pair hash_pair_from_non_avalanching_hash(size_t hash)
{
#if SIZE_MAX == 0xffffffffffffffff
_Static_assert(sizeof(size_t) == sizeof(uint64_t),
"size_t/SIZE_MAX doesn't make sense");
#ifdef __SSE4_2__
/* 64-bit with SSE4.2 uses CRC32 */
size_t c = _mm_crc32_u64(0, hash);
return (struct hash_pair){
.first = hash + c,
.second = (c >> 24) | 0x80,
};
#else
/* 64-bit without SSE4.2 uses a 128-bit multiplication-based mixer */
static const uint64_t multiplier = UINT64_C(0xc4ceb9fe1a85ec53);
uint64_t hi = ((unsigned __int128)hash * multiplier) >> 64;
uint64_t lo = hash * multiplier;
hash = hi ^ lo;
hash *= multiplier;
return (struct hash_pair){
.first = hash >> 22,
.second = ((hash >> 15) & 0x7f) | 0x80,
};
#endif
#elif SIZE_MAX == 0xffffffff
_Static_assert(sizeof(size_t) == sizeof(uint32_t),
"size_t/SIZE_MAX doesn't make sense");
#ifdef __SSE4_2__
/* 32-bit with SSE4.2 uses CRC32 */
size_t c = _mm_crc32_u32(0, hash);
return (struct hash_pair){
.first = hash + c,
.second = (uint8_t)(~(c >> 25)),
};
#else
/* 32-bit without SSE4.2 uses the 32-bit Murmur2 finalizer */
hash ^= hash >> 13;
hash *= 0x5bd1e995;
hash ^= hash >> 15;
return (struct hash_pair){
.first = hash,
.second = (uint8_t)(~(hash >> 25)),
};
#endif
#else
#error "unsupported SIZE_MAX"
#endif
}
#ifdef DOXYGEN
/**
* Double hash an integral key.
*
* This can be used for any integer key type.
*/
struct hash_pair int_key_hash_pair(const T *key);
#else
#if SIZE_MAX == 0xffffffffffffffff
static inline uint64_t hash_128_to_64(unsigned __int128 hash)
{
return cityhash_128_to_64(hash, hash >> 64);
}
#define int_key_hash_pair(key) ({ \
__auto_type _key = *(key); \
_Static_assert(sizeof(_key) <= sizeof(unsigned __int128), \
"unsupported integer size"); \
sizeof(_key) > sizeof(size_t) ? \
hash_pair_from_avalanching_hash(hash_128_to_64(_key)) : \
hash_pair_from_non_avalanching_hash(_key); \
})
#else
/* Thomas Wang downscaling hash function. */
static inline uint32_t hash_64_to_32(uint64_t hash)
{
hash = (~hash) + (hash << 18);
hash = hash ^ (hash >> 31);
hash = hash * 21;
hash = hash ^ (hash >> 11);
hash = hash + (hash << 6);
hash = hash ^ (hash >> 22);
return hash;
}
#define int_key_hash_pair(key) ({ \
__auto_type _key = *(key); \
_Static_assert(sizeof(_key) <= sizeof(uint64_t), \
"unsupported integer size"); \
sizeof(_key) > sizeof(size_t) ? \
hash_pair_from_avalanching_hash(hash_64_to_32(_key)) : \
hash_pair_from_non_avalanching_hash(_key); \
})
#endif
#endif
#ifdef DOXYGEN
/**
* Double hash a pointer key.
*
* This can be used when the key is a pointer value (rather than the
* dereferenced value).
*/
struct hash_pair ptr_key_hash_pair(T * const *key);
#else
#define ptr_key_hash_pair(key) ({ \
uintptr_t _ptr = (uintptr_t)*(key); \
int_key_hash_pair(&_ptr); \
})
#endif
#ifdef DOXYGEN
/**
* Return whether two scalar keys are equal.
*
* This can be used as the key comparison function for any scalar key type
* (e.g., integers, floating-point numbers, pointers).
*/
bool scalar_key_eq(const T *a, const T *b);
#else
#define scalar_key_eq(a, b) ((bool)(*(a) == *(b)))
#endif
/**
* Hash two integers.
*
* This is an avalanching hash function. It can be used for any integer types.
* The two integers can have different types.
*
* This can be used to combine input hash functions in order to hash records
* with multiple fields (e.g., structures or arrays). For example:
*
* ```
* struct point3d {
* int x, y, z;
* };
*
* static struct hash_pair point3d_key_hash_pair(const struct point3d *key)
* {
* return hash_pair_from_avalanching_hash(hash_combine(hash_combine(key->x, key->y), key->z));
* }
* ```
*
* Note that the input hash functions need not be avalanching; the output will
* be avalanching regardless.
*/
#ifdef DOXYGEN
size_t hash_combine(T1 a, T2 b);
#else
#if SIZE_MAX == 0xffffffffffffffff
#define hash_combine(a, b) ({ \
_Static_assert(sizeof(a) <= sizeof(unsigned __int128) && \
sizeof(b) <= sizeof(unsigned __int128), \
"unsupported integer size"); \
size_t _a = sizeof(a) > sizeof(size_t) ? hash_128_to_64(a) : (a); \
size_t _b = sizeof(b) > sizeof(size_t) ? hash_128_to_64(b) : (b); \
cityhash_128_to_64(_b, _a); \
})
#else
#define hash_combine(a, b) ({ \
_Static_assert(sizeof(a) <= sizeof(uint64_t) && \
sizeof(b) <= sizeof(uint64_t), \
"unsupported integer size"); \
size_t _a = sizeof(a) > sizeof(size_t) ? hash_64_to_32(a) : (a); \
size_t _b = sizeof(b) > sizeof(size_t) ? hash_64_to_32(b) : (b); \
hash_64_to_32(((uint64_t)_a << 32) | _b); \
})
#endif
#endif
/**
* Hash a byte buffer.
*
* This is an avalanching hash function.
*/
static inline size_t hash_bytes(const void *data, size_t len)
{
return cityhash_size_t(data, len);
}
/**
* Hash a null-terminated string.
*
* This is an avalanching hash function.
*/
static inline size_t hash_c_string(const char *s)
{
return hash_bytes(s, strlen(s));
}
#ifdef DOXYGEN
/** Double hash a null-terminated string key. */
struct hash_pair c_string_key_hash_pair(const char * const *key);
#else
/* This is a macro so that it works with char * and const char * keys. */
#define c_string_key_hash_pair(key) \
hash_pair_from_avalanching_hash(hash_c_string(*(key)))
#endif
#ifdef DOXYGEN
/** Compare two null-terminated string keys for equality. */
bool c_string_key_eq(const char * const *a, const char * const *b);
#else
#define c_string_key_eq(a, b) ((bool)(strcmp(*(a), *(b)) == 0))
#endif
/** Double hash a @ref nstring. */
static inline struct hash_pair nstring_hash_pair(const struct nstring *key)
{
return hash_pair_from_avalanching_hash(hash_bytes(key->str, key->len));
}
/** @} */
/** @} */
#endif /* DRGN_HASH_TABLE_H */
Reference in New Issue View Git Blame Copy Permalink