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st.c
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/* This is a public domain general purpose hash table package
originally written by Peter Moore @ UCB.
The hash table data structures were redesigned and the package was
rewritten by Vladimir Makarov <[email protected]>. */
/* The original package implemented classic bucket-based hash tables
with entries doubly linked for an access by their insertion order.
To decrease pointer chasing and as a consequence to improve a data
locality the current implementation is based on storing entries in
an array and using hash tables with open addressing. The current
entries are more compact in comparison with the original ones and
this also improves the data locality.
The hash table has two arrays called *bins* and *entries*.
bins:
-------
| | entries array:
|-------| --------------------------------
| index | | | entry: | | |
|-------| | | | | |
| ... | | ... | hash | ... | ... |
|-------| | | key | | |
| empty | | | record | | |
|-------| --------------------------------
| ... | ^ ^
|-------| |_ entries start |_ entries bound
|deleted|
-------
o The entry array contains table entries in the same order as they
were inserted.
When the first entry is deleted, a variable containing index of
the current first entry (*entries start*) is changed. In all
other cases of the deletion, we just mark the entry as deleted by
using a reserved hash value.
Such organization of the entry storage makes operations of the
table shift and the entries traversal very fast.
o The bins provide access to the entries by their keys. The
key hash is mapped to a bin containing *index* of the
corresponding entry in the entry array.
The bin array size is always power of two, it makes mapping very
fast by using the corresponding lower bits of the hash.
Generally it is not a good idea to ignore some part of the hash.
But alternative approach is worse. For example, we could use a
modulo operation for mapping and a prime number for the size of
the bin array. Unfortunately, the modulo operation for big
64-bit numbers are extremely slow (it takes more than 100 cycles
on modern Intel CPUs).
Still other bits of the hash value are used when the mapping
results in a collision. In this case we use a secondary hash
value which is a result of a function of the collision bin
index and the original hash value. The function choice
guarantees that we can traverse all bins and finally find the
corresponding bin as after several iterations the function
becomes a full cycle linear congruential generator because it
satisfies requirements of the Hull-Dobell theorem.
When an entry is removed from the table besides marking the
hash in the corresponding entry described above, we also mark
the bin by a special value in order to find entries which had
a collision with the removed entries.
There are two reserved values for the bins. One denotes an
empty bin, another one denotes a bin for a deleted entry.
o The length of the bin array is at least two times more than the
entry array length. This keeps the table load factor healthy.
The trigger of rebuilding the table is always a case when we can
not insert an entry anymore at the entries bound. We could
change the entries bound too in case of deletion but than we need
a special code to count bins with corresponding deleted entries
and reset the bin values when there are too many bins
corresponding deleted entries
Table rebuilding is done by creation of a new entry array and
bins of an appropriate size. We also try to reuse the arrays
in some cases by compacting the array and removing deleted
entries.
o To save memory very small tables have no allocated arrays
bins. We use a linear search for an access by a key.
o To save more memory we use 8-, 16-, 32- and 64- bit indexes in
bins depending on the current hash table size.
o The implementation takes into account that the table can be
rebuilt during hashing or comparison functions. It can happen if
the functions are implemented in Ruby and a thread switch occurs
during their execution.
This implementation speeds up the Ruby hash table benchmarks in
average by more 40% on Intel Haswell CPU.
*/
#ifdef NOT_RUBY
#include "regint.h"
#include "st.h"
#else
#include "internal.h"
#endif
#include <stdio.h>
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include <string.h>
#include <assert.h>
#ifdef __GNUC__
#define PREFETCH(addr, write_p) __builtin_prefetch(addr, write_p)
#define EXPECT(expr, val) __builtin_expect(expr, val)
#define ATTRIBUTE_UNUSED __attribute__((unused))
#else
#define PREFETCH(addr, write_p)
#define EXPECT(expr, val) (expr)
#define ATTRIBUTE_UNUSED
#endif
#ifdef ST_DEBUG
#define st_assert assert
#else
#define st_assert(cond) ((void)(0 && (cond)))
#endif
/* The type of hashes. */
typedef st_index_t st_hash_t;
struct st_table_entry {
st_hash_t hash;
st_data_t key;
st_data_t record;
};
#define type_numhash st_hashtype_num
static const struct st_hash_type st_hashtype_num = {
st_numcmp,
st_numhash,
};
static int st_strcmp(st_data_t, st_data_t);
static st_index_t strhash(st_data_t);
static const struct st_hash_type type_strhash = {
st_strcmp,
strhash,
};
static int st_locale_insensitive_strcasecmp_i(st_data_t lhs, st_data_t rhs);
static st_index_t strcasehash(st_data_t);
static const struct st_hash_type type_strcasehash = {
st_locale_insensitive_strcasecmp_i,
strcasehash,
};
/* Value used to catch uninitialized entries/bins during debugging.
There is a possibility for a false alarm, but its probability is
extremely small. */
#define ST_INIT_VAL 0xafafafafafafafaf
#define ST_INIT_VAL_BYTE 0xafa
#ifdef RUBY
#undef malloc
#undef realloc
#undef calloc
#undef free
#define malloc ruby_xmalloc
#define calloc ruby_xcalloc
#define realloc ruby_xrealloc
#define free ruby_xfree
#endif
#define EQUAL(tab,x,y) ((x) == (y) || (*(tab)->type->compare)((x),(y)) == 0)
#define PTR_EQUAL(tab, ptr, hash_val, key_) \
((ptr)->hash == (hash_val) && EQUAL((tab), (key_), (ptr)->key))
/* As PRT_EQUAL only its result is returned in RES. REBUILT_P is set
up to TRUE if the table is rebuilt during the comparison. */
#define DO_PTR_EQUAL_CHECK(tab, ptr, hash_val, key, res, rebuilt_p) \
do { \
unsigned int _old_rebuilds_num = (tab)->rebuilds_num; \
res = PTR_EQUAL(tab, ptr, hash_val, key); \
rebuilt_p = _old_rebuilds_num != (tab)->rebuilds_num; \
} while (FALSE)
/* Features of a table. */
struct st_features {
/* Power of 2 used for number of allocated entries. */
unsigned char entry_power;
/* Power of 2 used for number of allocated bins. Depending on the
table size, the number of bins is 2-4 times more than the
number of entries. */
unsigned char bin_power;
/* Enumeration of sizes of bins (8-bit, 16-bit etc). */
unsigned char size_ind;
/* Bins are packed in words of type st_index_t. The following is
a size of bins counted by words. */
st_index_t bins_words;
};
/* Features of all possible size tables. */
#if SIZEOF_ST_INDEX_T == 8
#define MAX_POWER2 62
static const struct st_features features[] = {
{0, 1, 0, 0x0},
{1, 2, 0, 0x1},
{2, 3, 0, 0x1},
{3, 4, 0, 0x2},
{4, 5, 0, 0x4},
{5, 6, 0, 0x8},
{6, 7, 0, 0x10},
{7, 8, 0, 0x20},
{8, 9, 1, 0x80},
{9, 10, 1, 0x100},
{10, 11, 1, 0x200},
{11, 12, 1, 0x400},
{12, 13, 1, 0x800},
{13, 14, 1, 0x1000},
{14, 15, 1, 0x2000},
{15, 16, 1, 0x4000},
{16, 17, 2, 0x10000},
{17, 18, 2, 0x20000},
{18, 19, 2, 0x40000},
{19, 20, 2, 0x80000},
{20, 21, 2, 0x100000},
{21, 22, 2, 0x200000},
{22, 23, 2, 0x400000},
{23, 24, 2, 0x800000},
{24, 25, 2, 0x1000000},
{25, 26, 2, 0x2000000},
{26, 27, 2, 0x4000000},
{27, 28, 2, 0x8000000},
{28, 29, 2, 0x10000000},
{29, 30, 2, 0x20000000},
{30, 31, 2, 0x40000000},
{31, 32, 2, 0x80000000},
{32, 33, 3, 0x200000000},
{33, 34, 3, 0x400000000},
{34, 35, 3, 0x800000000},
{35, 36, 3, 0x1000000000},
{36, 37, 3, 0x2000000000},
{37, 38, 3, 0x4000000000},
{38, 39, 3, 0x8000000000},
{39, 40, 3, 0x10000000000},
{40, 41, 3, 0x20000000000},
{41, 42, 3, 0x40000000000},
{42, 43, 3, 0x80000000000},
{43, 44, 3, 0x100000000000},
{44, 45, 3, 0x200000000000},
{45, 46, 3, 0x400000000000},
{46, 47, 3, 0x800000000000},
{47, 48, 3, 0x1000000000000},
{48, 49, 3, 0x2000000000000},
{49, 50, 3, 0x4000000000000},
{50, 51, 3, 0x8000000000000},
{51, 52, 3, 0x10000000000000},
{52, 53, 3, 0x20000000000000},
{53, 54, 3, 0x40000000000000},
{54, 55, 3, 0x80000000000000},
{55, 56, 3, 0x100000000000000},
{56, 57, 3, 0x200000000000000},
{57, 58, 3, 0x400000000000000},
{58, 59, 3, 0x800000000000000},
{59, 60, 3, 0x1000000000000000},
{60, 61, 3, 0x2000000000000000},
{61, 62, 3, 0x4000000000000000},
{62, 63, 3, 0x8000000000000000},
};
#else
#define MAX_POWER2 30
static const struct st_features features[] = {
{0, 1, 0, 0x1},
{1, 2, 0, 0x1},
{2, 3, 0, 0x2},
{3, 4, 0, 0x4},
{4, 5, 0, 0x8},
{5, 6, 0, 0x10},
{6, 7, 0, 0x20},
{7, 8, 0, 0x40},
{8, 9, 1, 0x100},
{9, 10, 1, 0x200},
{10, 11, 1, 0x400},
{11, 12, 1, 0x800},
{12, 13, 1, 0x1000},
{13, 14, 1, 0x2000},
{14, 15, 1, 0x4000},
{15, 16, 1, 0x8000},
{16, 17, 2, 0x20000},
{17, 18, 2, 0x40000},
{18, 19, 2, 0x80000},
{19, 20, 2, 0x100000},
{20, 21, 2, 0x200000},
{21, 22, 2, 0x400000},
{22, 23, 2, 0x800000},
{23, 24, 2, 0x1000000},
{24, 25, 2, 0x2000000},
{25, 26, 2, 0x4000000},
{26, 27, 2, 0x8000000},
{27, 28, 2, 0x10000000},
{28, 29, 2, 0x20000000},
{29, 30, 2, 0x40000000},
{30, 31, 2, 0x80000000},
};
#endif
/* The reserved hash value and its substitution. */
#define RESERVED_HASH_VAL (~(st_hash_t) 0)
#define RESERVED_HASH_SUBSTITUTION_VAL ((st_hash_t) 0)
const st_hash_t st_reserved_hash_val = RESERVED_HASH_VAL;
const st_hash_t st_reserved_hash_substitution_val = RESERVED_HASH_SUBSTITUTION_VAL;
/* Return hash value of KEY for table TAB. */
static inline st_hash_t
do_hash(st_data_t key, st_table *tab)
{
st_hash_t hash = (st_hash_t)(tab->type->hash)(key);
/* RESERVED_HASH_VAL is used for a deleted entry. Map it into
another value. Such mapping should be extremely rare. */
return hash == RESERVED_HASH_VAL ? RESERVED_HASH_SUBSTITUTION_VAL : hash;
}
/* Power of 2 defining the minimal number of allocated entries. */
#define MINIMAL_POWER2 2
#if MINIMAL_POWER2 < 2
#error "MINIMAL_POWER2 should be >= 2"
#endif
/* If the power2 of the allocated `entries` is less than the following
value, don't allocate bins and use a linear search. */
#define MAX_POWER2_FOR_TABLES_WITHOUT_BINS 4
/* Return smallest n >= MINIMAL_POWER2 such 2^n > SIZE. */
static int
get_power2(st_index_t size)
{
unsigned int n = ST_INDEX_BITS - nlz_intptr(size);
if (n <= MAX_POWER2)
return n < MINIMAL_POWER2 ? MINIMAL_POWER2 : n;
#ifndef NOT_RUBY
/* Ran out of the table entries */
rb_raise(rb_eRuntimeError, "st_table too big");
#endif
/* should raise exception */
return -1;
}
/* Return value of N-th bin in array BINS of table with bins size
index S. */
static inline st_index_t
get_bin(st_index_t *bins, int s, st_index_t n)
{
return (s == 0 ? ((unsigned char *) bins)[n]
: s == 1 ? ((unsigned short *) bins)[n]
: s == 2 ? ((unsigned int *) bins)[n]
: ((st_index_t *) bins)[n]);
}
/* Set up N-th bin in array BINS of table with bins size index S to
value V. */
static inline void
set_bin(st_index_t *bins, int s, st_index_t n, st_index_t v)
{
if (s == 0) ((unsigned char *) bins)[n] = (unsigned char) v;
else if (s == 1) ((unsigned short *) bins)[n] = (unsigned short) v;
else if (s == 2) ((unsigned int *) bins)[n] = (unsigned int) v;
else ((st_index_t *) bins)[n] = v;
}
/* These macros define reserved values for empty table bin and table
bin which contains a deleted entry. We will never use such values
for an entry index in bins. */
#define EMPTY_BIN 0
#define DELETED_BIN 1
/* Base of a real entry index in the bins. */
#define ENTRY_BASE 2
/* Mark I-th bin of table TAB as empty, in other words not
corresponding to any entry. */
#define MARK_BIN_EMPTY(tab, i) (set_bin((tab)->bins, get_size_ind(tab), i, EMPTY_BIN))
/* Values used for not found entry and bin with given
characteristics. */
#define UNDEFINED_ENTRY_IND (~(st_index_t) 0)
#define UNDEFINED_BIN_IND (~(st_index_t) 0)
/* Entry and bin values returned when we found a table rebuild during
the search. */
#define REBUILT_TABLE_ENTRY_IND (~(st_index_t) 1)
#define REBUILT_TABLE_BIN_IND (~(st_index_t) 1)
/* Mark I-th bin of table TAB as corresponding to a deleted table
entry. Update number of entries in the table and number of bins
corresponding to deleted entries. */
#define MARK_BIN_DELETED(tab, i) \
do { \
st_assert(i != UNDEFINED_BIN_IND); \
st_assert(! IND_EMPTY_OR_DELETED_BIN_P(tab, i)); \
set_bin((tab)->bins, get_size_ind(tab), i, DELETED_BIN); \
} while (0)
/* Macros to check that value B is used empty bins and bins
corresponding deleted entries. */
#define EMPTY_BIN_P(b) ((b) == EMPTY_BIN)
#define DELETED_BIN_P(b) ((b) == DELETED_BIN)
#define EMPTY_OR_DELETED_BIN_P(b) ((b) <= DELETED_BIN)
/* Macros to check empty bins and bins corresponding to deleted
entries. Bins are given by their index I in table TAB. */
#define IND_EMPTY_BIN_P(tab, i) (EMPTY_BIN_P(get_bin((tab)->bins, get_size_ind(tab), i)))
#define IND_DELETED_BIN_P(tab, i) (DELETED_BIN_P(get_bin((tab)->bins, get_size_ind(tab), i)))
#define IND_EMPTY_OR_DELETED_BIN_P(tab, i) (EMPTY_OR_DELETED_BIN_P(get_bin((tab)->bins, get_size_ind(tab), i)))
/* Macros for marking and checking deleted entries given by their
pointer E_PTR. */
#define MARK_ENTRY_DELETED(e_ptr) ((e_ptr)->hash = RESERVED_HASH_VAL)
#define DELETED_ENTRY_P(e_ptr) ((e_ptr)->hash == RESERVED_HASH_VAL)
/* Return bin size index of table TAB. */
static inline unsigned int
get_size_ind(const st_table *tab)
{
return tab->size_ind;
}
/* Return the number of allocated bins of table TAB. */
static inline st_index_t
get_bins_num(const st_table *tab)
{
return ((st_index_t) 1)<<tab->bin_power;
}
/* Return mask for a bin index in table TAB. */
static inline st_index_t
bins_mask(const st_table *tab)
{
return get_bins_num(tab) - 1;
}
/* Return the index of table TAB bin corresponding to
HASH_VALUE. */
static inline st_index_t
hash_bin(st_hash_t hash_value, st_table *tab)
{
return hash_value & bins_mask(tab);
}
/* Return the number of allocated entries of table TAB. */
static inline st_index_t
get_allocated_entries(const st_table *tab)
{
return ((st_index_t) 1)<<tab->entry_power;
}
/* Return size of the allocated bins of table TAB. */
static inline st_index_t
bins_size(const st_table *tab)
{
return features[tab->entry_power].bins_words * sizeof (st_index_t);
}
/* Mark all bins of table TAB as empty. */
static void
initialize_bins(st_table *tab)
{
memset(tab->bins, 0, bins_size(tab));
}
/* Make table TAB empty. */
static void
make_tab_empty(st_table *tab)
{
tab->num_entries = 0;
tab->entries_start = tab->entries_bound = 0;
if (tab->bins != NULL)
initialize_bins(tab);
}
#ifdef ST_DEBUG
#define st_assert_notinitial(ent) \
do { \
st_assert(ent.hash != (st_hash_t) ST_INIT_VAL); \
st_assert(ent.key != ST_INIT_VAL); \
st_assert(ent.record != ST_INIT_VAL); \
} while (0)
/* Check the table T consistency. It can be extremely slow. So use
it only for debugging. */
static void
st_check(st_table *tab)
{
st_index_t d, e, i, n, p;
for (p = get_allocated_entries(tab), i = 0; p > 1; i++, p>>=1)
;
p = i;
st_assert(p >= MINIMAL_POWER2);
st_assert(tab->entries_bound <= get_allocated_entries(tab));
st_assert(tab->entries_start <= tab->entries_bound);
n = 0;
return;
if (tab->entries_bound != 0)
for (i = tab->entries_start; i < tab->entries_bound; i++) {
st_assert_notinitial(tab->entries[i]);
if (! DELETED_ENTRY_P(&tab->entries[i]))
n++;
}
st_assert(n == tab->num_entries);
if (tab->bins == NULL)
st_assert(p <= MAX_POWER2_FOR_TABLES_WITHOUT_BINS);
else {
st_assert(p > MAX_POWER2_FOR_TABLES_WITHOUT_BINS);
for (n = d = i = 0; i < get_bins_num(tab); i++) {
st_assert(get_bin(tab->bins, tab->size_ind, i) != ST_INIT_VAL);
if (IND_DELETED_BIN_P(tab, i)) {
d++;
continue;
}
else if (IND_EMPTY_BIN_P(tab, i))
continue;
n++;
e = get_bin(tab->bins, tab->size_ind, i) - ENTRY_BASE;
st_assert(tab->entries_start <= e && e < tab->entries_bound);
st_assert(! DELETED_ENTRY_P(&tab->entries[e]));
st_assert_notinitial(tab->entries[e]);
}
st_assert(n == tab->num_entries);
st_assert(n + d < get_bins_num(tab));
}
}
#endif
#ifdef HASH_LOG
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
static struct {
int all, total, num, str, strcase;
} collision;
/* Flag switching off output of package statistics at the end of
program. */
static int init_st = 0;
/* Output overall number of table searches and collisions into a
temporary file. */
static void
stat_col(void)
{
char fname[10+sizeof(long)*3];
FILE *f;
if (!collision.total) return;
f = fopen((snprintf(fname, sizeof(fname), "/tmp/col%ld", (long)getpid()), fname), "w");
if (f == NULL)
return;
fprintf(f, "collision: %d / %d (%6.2f)\n", collision.all, collision.total,
((double)collision.all / (collision.total)) * 100);
fprintf(f, "num: %d, str: %d, strcase: %d\n", collision.num, collision.str, collision.strcase);
fclose(f);
}
#endif
/* Create and return table with TYPE which can hold at least SIZE
entries. The real number of entries which the table can hold is
the nearest power of two for SIZE. */
st_table *
st_init_table_with_size(const struct st_hash_type *type, st_index_t size)
{
st_table *tab;
int n;
#ifdef HASH_LOG
#if HASH_LOG+0 < 0
{
const char *e = getenv("ST_HASH_LOG");
if (!e || !*e) init_st = 1;
}
#endif
if (init_st == 0) {
init_st = 1;
atexit(stat_col);
}
#endif
n = get_power2(size);
#ifndef RUBY
if (n < 0)
return NULL;
#endif
tab = (st_table *) malloc(sizeof (st_table));
#ifndef RUBY
if (tab == NULL)
return NULL;
#endif
tab->type = type;
tab->entry_power = n;
tab->bin_power = features[n].bin_power;
tab->size_ind = features[n].size_ind;
if (n <= MAX_POWER2_FOR_TABLES_WITHOUT_BINS)
tab->bins = NULL;
else {
tab->bins = (st_index_t *) malloc(bins_size(tab));
#ifndef RUBY
if (tab->bins == NULL) {
free(tab);
return NULL;
}
#endif
}
tab->entries = (st_table_entry *) malloc(get_allocated_entries(tab)
* sizeof(st_table_entry));
#ifndef RUBY
if (tab->entries == NULL) {
st_free_table(tab);
return NULL;
}
#endif
#ifdef ST_DEBUG
memset(tab->entries, ST_INIT_VAL_BYTE,
get_allocated_entries(tab) * sizeof(st_table_entry));
if (tab->bins != NULL)
memset(tab->bins, ST_INIT_VAL_BYTE, bins_size(tab));
#endif
make_tab_empty(tab);
tab->rebuilds_num = 0;
#ifdef ST_DEBUG
st_check(tab);
#endif
return tab;
}
/* Create and return table with TYPE which can hold a minimal number
of entries (see comments for get_power2). */
st_table *
st_init_table(const struct st_hash_type *type)
{
return st_init_table_with_size(type, 0);
}
/* Create and return table which can hold a minimal number of
numbers. */
st_table *
st_init_numtable(void)
{
return st_init_table(&type_numhash);
}
/* Create and return table which can hold SIZE numbers. */
st_table *
st_init_numtable_with_size(st_index_t size)
{
return st_init_table_with_size(&type_numhash, size);
}
/* Create and return table which can hold a minimal number of
strings. */
st_table *
st_init_strtable(void)
{
return st_init_table(&type_strhash);
}
/* Create and return table which can hold SIZE strings. */
st_table *
st_init_strtable_with_size(st_index_t size)
{
return st_init_table_with_size(&type_strhash, size);
}
/* Create and return table which can hold a minimal number of strings
whose character case is ignored. */
st_table *
st_init_strcasetable(void)
{
return st_init_table(&type_strcasehash);
}
/* Create and return table which can hold SIZE strings whose character
case is ignored. */
st_table *
st_init_strcasetable_with_size(st_index_t size)
{
return st_init_table_with_size(&type_strcasehash, size);
}
/* Make table TAB empty. */
void
st_clear(st_table *tab)
{
make_tab_empty(tab);
tab->rebuilds_num++;
#ifdef ST_DEBUG
st_check(tab);
#endif
}
/* Free table TAB space. */
void
st_free_table(st_table *tab)
{
if (tab->bins != NULL)
free(tab->bins);
free(tab->entries);
free(tab);
}
/* Return byte size of memory allocated for table TAB. */
size_t
st_memsize(const st_table *tab)
{
return(sizeof(st_table)
+ (tab->bins == NULL ? 0 : bins_size(tab))
+ get_allocated_entries(tab) * sizeof(st_table_entry));
}
static st_index_t
find_table_entry_ind(st_table *tab, st_hash_t hash_value, st_data_t key);
static st_index_t
find_table_bin_ind(st_table *tab, st_hash_t hash_value, st_data_t key);
static st_index_t
find_table_bin_ind_direct(st_table *table, st_hash_t hash_value, st_data_t key);
static st_index_t
find_table_bin_ptr_and_reserve(st_table *tab, st_hash_t *hash_value,
st_data_t key, st_index_t *bin_ind);
#ifdef HASH_LOG
static void
count_collision(const struct st_hash_type *type)
{
collision.all++;
if (type == &type_numhash) {
collision.num++;
}
else if (type == &type_strhash) {
collision.strcase++;
}
else if (type == &type_strcasehash) {
collision.str++;
}
}
#define COLLISION (collision_check ? count_collision(tab->type) : (void)0)
#define FOUND_BIN (collision_check ? collision.total++ : (void)0)
#define collision_check 0
#else
#define COLLISION
#define FOUND_BIN
#endif
/* If the number of entries in the table is at least REBUILD_THRESHOLD
times less than the entry array length, decrease the table
size. */
#define REBUILD_THRESHOLD 4
#if REBUILD_THRESHOLD < 2
#error "REBUILD_THRESHOLD should be >= 2"
#endif
/* Rebuild table TAB. Rebuilding removes all deleted bins and entries
and can change size of the table entries and bins arrays.
Rebuilding is implemented by creation of a new table or by
compaction of the existing one. */
static void
rebuild_table(st_table *tab)
{
st_index_t i, ni, bound;
unsigned int size_ind;
st_table *new_tab;
st_table_entry *entries, *new_entries;
st_table_entry *curr_entry_ptr;
st_index_t *bins;
st_index_t bin_ind;
st_assert(tab != NULL);
bound = tab->entries_bound;
entries = tab->entries;
if ((2 * tab->num_entries <= get_allocated_entries(tab)
&& REBUILD_THRESHOLD * tab->num_entries > get_allocated_entries(tab))
|| tab->num_entries < (1 << MINIMAL_POWER2)) {
/* Compaction: */
tab->num_entries = 0;
if (tab->bins != NULL)
initialize_bins(tab);
new_tab = tab;
new_entries = entries;
}
else {
new_tab = st_init_table_with_size(tab->type,
2 * tab->num_entries - 1);
new_entries = new_tab->entries;
}
ni = 0;
bins = new_tab->bins;
size_ind = get_size_ind(new_tab);
for (i = tab->entries_start; i < bound; i++) {
curr_entry_ptr = &entries[i];
PREFETCH(entries + i + 1, 0);
if (EXPECT(DELETED_ENTRY_P(curr_entry_ptr), 0))
continue;
if (&new_entries[ni] != curr_entry_ptr)
new_entries[ni] = *curr_entry_ptr;
if (EXPECT(bins != NULL, 1)) {
bin_ind = find_table_bin_ind_direct(new_tab, curr_entry_ptr->hash,
curr_entry_ptr->key);
st_assert(bin_ind != UNDEFINED_BIN_IND);
st_assert(tab == new_tab || new_tab->rebuilds_num == 0);
st_assert(IND_EMPTY_BIN_P(new_tab, bin_ind));
set_bin(bins, size_ind, bin_ind, ni + ENTRY_BASE);
}
new_tab->num_entries++;
ni++;
}
if (new_tab != tab) {
tab->entry_power = new_tab->entry_power;
tab->bin_power = new_tab->bin_power;
tab->size_ind = new_tab->size_ind;
st_assert(tab->num_entries == ni);
st_assert(new_tab->num_entries == ni);
if (tab->bins != NULL)
free(tab->bins);
tab->bins = new_tab->bins;
free(tab->entries);
tab->entries = new_tab->entries;
free(new_tab);
}
tab->entries_start = 0;
tab->entries_bound = tab->num_entries;
tab->rebuilds_num++;
#ifdef ST_DEBUG
st_check(tab);
#endif
}
/* Return the next secondary hash index for table TAB using previous
index IND and PERTERB. Finally modulo of the function becomes a
full *cycle linear congruential generator*, in other words it
guarantees traversing all table bins in extreme case.
According the Hull-Dobell theorem a generator
"Xnext = (a*Xprev + c) mod m" is a full cycle generator iff
o m and c are relatively prime
o a-1 is divisible by all prime factors of m
o a-1 is divisible by 4 if m is divisible by 4.
For our case a is 5, c is 1, and m is a power of two. */
static inline st_index_t
secondary_hash(st_index_t ind, st_table *tab, st_index_t *perterb)
{
*perterb >>= 11;
ind = (ind << 2) + ind + *perterb + 1;
return hash_bin(ind, tab);
}
/* Find an entry with HASH_VALUE and KEY in TABLE using a linear
search. Return the index of the found entry in array `entries`.
If it is not found, return UNDEFINED_ENTRY_IND. If the table was
rebuilt during the search, return REBUILT_TABLE_ENTRY_IND. */
static inline st_index_t
find_entry(st_table *tab, st_hash_t hash_value, st_data_t key)
{
int eq_p, rebuilt_p;
st_index_t i, bound;
st_table_entry *entries;
bound = tab->entries_bound;
entries = tab->entries;
for (i = tab->entries_start; i < bound; i++) {
DO_PTR_EQUAL_CHECK(tab, &entries[i], hash_value, key, eq_p, rebuilt_p);
if (EXPECT(rebuilt_p, 0))
return REBUILT_TABLE_ENTRY_IND;
if (eq_p)
return i;
}
return UNDEFINED_ENTRY_IND;
}
/* Use the quadratic probing. The method has a better data locality
but more collisions than the current approach. In average it
results in a bit slower search. */
/*#define QUADRATIC_PROBE*/
/* Return index of entry with HASH_VALUE and KEY in table TAB. If
there is no such entry, return UNDEFINED_ENTRY_IND. If the table
was rebuilt during the search, return REBUILT_TABLE_ENTRY_IND. */
static st_index_t
find_table_entry_ind(st_table *tab, st_hash_t hash_value, st_data_t key)
{
int eq_p, rebuilt_p;
st_index_t ind;
#ifdef QUADRATIC_PROBE
st_index_t d;
#else
st_index_t peterb;
#endif
st_index_t bin;
st_table_entry *entries = tab->entries;
st_assert(tab != NULL);
st_assert(tab->bins != NULL);
ind = hash_bin(hash_value, tab);
#ifdef QUADRATIC_PROBE
d = 1;
#else
peterb = hash_value;
#endif
FOUND_BIN;
for (;;) {
bin = get_bin(tab->bins, get_size_ind(tab), ind);
if (! EMPTY_OR_DELETED_BIN_P(bin)) {
DO_PTR_EQUAL_CHECK(tab, &entries[bin - ENTRY_BASE], hash_value, key, eq_p, rebuilt_p);
if (EXPECT(rebuilt_p, 0))
return REBUILT_TABLE_ENTRY_IND;
if (eq_p)
break;
} else if (EMPTY_BIN_P(bin))
return UNDEFINED_ENTRY_IND;
#ifdef QUADRATIC_PROBE
ind = hash_bin(ind + d, tab);
d++;
#else
ind = secondary_hash(ind, tab, &peterb);
#endif
COLLISION;
}
return bin;
}
/* Find and return index of table TAB bin corresponding to an entry
with HASH_VALUE and KEY. If there is no such bin, return
UNDEFINED_BIN_IND. If the table was rebuilt during the search,
return REBUILT_TABLE_BIN_IND. */
static st_index_t
find_table_bin_ind(st_table *tab, st_hash_t hash_value, st_data_t key)
{
int eq_p, rebuilt_p;
st_index_t ind;
#ifdef QUADRATIC_PROBE
st_index_t d;
#else
st_index_t peterb;
#endif
st_index_t bin;
st_table_entry *entries = tab->entries;
st_assert(tab != NULL);
st_assert(tab->bins != NULL);
ind = hash_bin(hash_value, tab);
#ifdef QUADRATIC_PROBE
d = 1;
#else
peterb = hash_value;
#endif
FOUND_BIN;
for (;;) {
bin = get_bin(tab->bins, get_size_ind(tab), ind);
if (! EMPTY_OR_DELETED_BIN_P(bin)) {
DO_PTR_EQUAL_CHECK(tab, &entries[bin - ENTRY_BASE], hash_value, key, eq_p, rebuilt_p);
if (EXPECT(rebuilt_p, 0))
return REBUILT_TABLE_BIN_IND;
if (eq_p)
break;
} else if (EMPTY_BIN_P(bin))
return UNDEFINED_BIN_IND;
#ifdef QUADRATIC_PROBE
ind = hash_bin(ind + d, tab);
d++;
#else
ind = secondary_hash(ind, tab, &peterb);
#endif
COLLISION;
}
return ind;
}
/* Find and return index of table TAB bin corresponding to an entry
with HASH_VALUE and KEY. The entry should be in the table
already. */
static st_index_t
find_table_bin_ind_direct(st_table *tab, st_hash_t hash_value, st_data_t key)
{
st_index_t ind;
#ifdef QUADRATIC_PROBE
st_index_t d;
#else
st_index_t peterb;
#endif
st_index_t bin;