ltable.c
(5.3.6)
/*
** $Id: ltable.c,v 2.118.1.4 2018/06/08 16:22:51 roberto Exp $
** Lua tables (hash)
** See Copyright Notice in lua.h
*/
#define ltable_c
#define LUA_CORE
#include "lprefix.h"
/*
** Implementation of tables (aka arrays, objects, or hash tables).
** Tables keep its elements in two parts: an array part and a hash part.
** Non-negative integer keys are all candidates to be kept in the array
** part. The actual size of the array is the largest 'n' such that
** more than half the slots between 1 and n are in use.
** Hash uses a mix of chained scatter table with Brent's variation.
** A main invariant of these tables is that, if an element is not
** in its main position (i.e. the 'original' position that its hash gives
** to it), then the colliding element is in its own main position.
** Hence even when the load factor reaches 100%, performance remains good.
*/
#include <math.h>
#include <limits.h>
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "lvm.h"
/*
** Maximum size of array part (MAXASIZE) is 2^MAXABITS. MAXABITS is
** the largest integer such that MAXASIZE fits in an unsigned int.
*/
#define MAXABITS cast_int(sizeof(int) * CHAR_BIT - 1)
#define MAXASIZE (1u << MAXABITS)
/*
** Maximum size of hash part is 2^MAXHBITS. MAXHBITS is the largest
** integer such that 2^MAXHBITS fits in a signed int. (Note that the
** maximum number of elements in a table, 2^MAXABITS + 2^MAXHBITS, still
** fits comfortably in an unsigned int.)
*/
#define MAXHBITS (MAXABITS - 1)
#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
#define hashstr(t,str) hashpow2(t, (str)->hash)
#define hashboolean(t,p) hashpow2(t, p)
#define hashint(t,i) hashpow2(t, i)
/*
** for some types, it is better to avoid modulus by power of 2, as
** they tend to have many 2 factors.
*/
#define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
#define hashpointer(t,p) hashmod(t, point2uint(p))
#define dummynode (&dummynode_)
static const Node dummynode_ = {
{NILCONSTANT}, /* value */
{{NILCONSTANT, 0}} /* key */
};
/*
** Hash for floating-point numbers.
** The main computation should be just
** n = frexp(n, &i); return (n * INT_MAX) + i
** but there are some numerical subtleties.
** In a two-complement representation, INT_MAX does not has an exact
** representation as a float, but INT_MIN does; because the absolute
** value of 'frexp' is smaller than 1 (unless 'n' is inf/NaN), the
** absolute value of the product 'frexp * -INT_MIN' is smaller or equal
** to INT_MAX. Next, the use of 'unsigned int' avoids overflows when
** adding 'i'; the use of '~u' (instead of '-u') avoids problems with
** INT_MIN.
*/
#if !defined(l_hashfloat)
static int l_hashfloat (lua_Number n) {
int i;
lua_Integer ni;
n = l_mathop(frexp)(n, &i) * -cast_num(INT_MIN);
if (!lua_numbertointeger(n, &ni)) { /* is 'n' inf/-inf/NaN? */
lua_assert(luai_numisnan(n) || l_mathop(fabs)(n) == cast_num(HUGE_VAL));
return 0;
}
else { /* normal case */
unsigned int u = cast(unsigned int, i) + cast(unsigned int, ni);
return cast_int(u <= cast(unsigned int, INT_MAX) ? u : ~u);
}
}
#endif
/*
** returns the 'main' position of an element in a table (that is, the index
** of its hash value)
*/
static Node *mainposition (const Table *t, const TValue *key) {
switch (ttype(key)) {
case LUA_TNUMINT:
return hashint(t, ivalue(key));
case LUA_TNUMFLT:
return hashmod(t, l_hashfloat(fltvalue(key)));
case LUA_TSHRSTR:
return hashstr(t, tsvalue(key));
case LUA_TLNGSTR:
return hashpow2(t, luaS_hashlongstr(tsvalue(key)));
case LUA_TBOOLEAN:
return hashboolean(t, bvalue(key));
case LUA_TLIGHTUSERDATA:
return hashpointer(t, pvalue(key));
case LUA_TLCF:
return hashpointer(t, fvalue(key));
default:
lua_assert(!ttisdeadkey(key));
return hashpointer(t, gcvalue(key));
}
}
/*
** returns the index for 'key' if 'key' is an appropriate key to live in
** the array part of the table, 0 otherwise.
*/
static unsigned int arrayindex (const TValue *key) {
if (ttisinteger(key)) {
lua_Integer k = ivalue(key);
if (0 < k && (lua_Unsigned)k <= MAXASIZE)
return cast(unsigned int, k); /* 'key' is an appropriate array index */
}
return 0; /* 'key' did not match some condition */
}
/*
** returns the index of a 'key' for table traversals. First goes all
** elements in the array part, then elements in the hash part. The
** beginning of a traversal is signaled by 0.
*/
static unsigned int findindex (lua_State *L, Table *t, StkId key) {
unsigned int i;
if (ttisnil(key)) return 0; /* first iteration */
i = arrayindex(key);
if (i != 0 && i <= t->sizearray) /* is 'key' inside array part? */
return i; /* yes; that's the index */
else {
int nx;
Node *n = mainposition(t, key);
for (;;) { /* check whether 'key' is somewhere in the chain */
/* key may be dead already, but it is ok to use it in 'next' */
if (luaV_rawequalobj(gkey(n), key) ||
(ttisdeadkey(gkey(n)) && iscollectable(key) &&
deadvalue(gkey(n)) == gcvalue(key))) {
i = cast_int(n - gnode(t, 0)); /* key index in hash table */
/* hash elements are numbered after array ones */
return (i + 1) + t->sizearray;
}
nx = gnext(n);
if (nx == 0)
luaG_runerror(L, "invalid key to 'next'"); /* key not found */
else n += nx;
}
}
}
int luaH_next (lua_State *L, Table *t, StkId key) {
unsigned int i = findindex(L, t, key); /* find original element */
for (; i < t->sizearray; i++) { /* try first array part */
if (!ttisnil(&t->array[i])) { /* a non-nil value? */
setivalue(key, i + 1);
setobj2s(L, key+1, &t->array[i]);
return 1;
}
}
for (i -= t->sizearray; cast_int(i) < sizenode(t); i++) { /* hash part */
if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
setobj2s(L, key, gkey(gnode(t, i)));
setobj2s(L, key+1, gval(gnode(t, i)));
return 1;
}
}
return 0; /* no more elements */
}
/*
** {=============================================================
** Rehash
** ==============================================================
*/
/*
** Compute the optimal size for the array part of table 't'. 'nums' is a
** "count array" where 'nums[i]' is the number of integers in the table
** between 2^(i - 1) + 1 and 2^i. 'pna' enters with the total number of
** integer keys in the table and leaves with the number of keys that
** will go to the array part; return the optimal size.
*/
static unsigned int computesizes (unsigned int nums[], unsigned int *pna) {
int i;
unsigned int twotoi; /* 2^i (candidate for optimal size) */
unsigned int a = 0; /* number of elements smaller than 2^i */
unsigned int na = 0; /* number of elements to go to array part */
unsigned int optimal = 0; /* optimal size for array part */
/* loop while keys can fill more than half of total size */
for (i = 0, twotoi = 1;
twotoi > 0 && *pna > twotoi / 2;
i++, twotoi *= 2) {
if (nums[i] > 0) {
a += nums[i];
if (a > twotoi/2) { /* more than half elements present? */
optimal = twotoi; /* optimal size (till now) */
na = a; /* all elements up to 'optimal' will go to array part */
}
}
}
lua_assert((optimal == 0 || optimal / 2 < na) && na <= optimal);
*pna = na;
return optimal;
}
static int countint (const TValue *key, unsigned int *nums) {
unsigned int k = arrayindex(key);
if (k != 0) { /* is 'key' an appropriate array index? */
nums[luaO_ceillog2(k)]++; /* count as such */
return 1;
}
else
return 0;
}
/*
** Count keys in array part of table 't': Fill 'nums[i]' with
** number of keys that will go into corresponding slice and return
** total number of non-nil keys.
*/
static unsigned int numusearray (const Table *t, unsigned int *nums) {
int lg;
unsigned int ttlg; /* 2^lg */
unsigned int ause = 0; /* summation of 'nums' */
unsigned int i = 1; /* count to traverse all array keys */
/* traverse each slice */
for (lg = 0, ttlg = 1; lg <= MAXABITS; lg++, ttlg *= 2) {
unsigned int lc = 0; /* counter */
unsigned int lim = ttlg;
if (lim > t->sizearray) {
lim = t->sizearray; /* adjust upper limit */
if (i > lim)
break; /* no more elements to count */
}
/* count elements in range (2^(lg - 1), 2^lg] */
for (; i <= lim; i++) {
if (!ttisnil(&t->array[i-1]))
lc++;
}
nums[lg] += lc;
ause += lc;
}
return ause;
}
static int numusehash (const Table *t, unsigned int *nums, unsigned int *pna) {
int totaluse = 0; /* total number of elements */
int ause = 0; /* elements added to 'nums' (can go to array part) */
int i = sizenode(t);
while (i--) {
Node *n = &t->node[i];
if (!ttisnil(gval(n))) {
ause += countint(gkey(n), nums);
totaluse++;
}
}
*pna += ause;
return totaluse;
}
static void setarrayvector (lua_State *L, Table *t, unsigned int size) {
unsigned int i;
luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
for (i=t->sizearray; i<size; i++)
setnilvalue(&t->array[i]);
t->sizearray = size;
}
static void setnodevector (lua_State *L, Table *t, unsigned int size) {
if (size == 0) { /* no elements to hash part? */
t->node = cast(Node *, dummynode); /* use common 'dummynode' */
t->lsizenode = 0;
t->lastfree = NULL; /* signal that it is using dummy node */
}
else {
int i;
int lsize = luaO_ceillog2(size);
if (lsize > MAXHBITS)
luaG_runerror(L, "table overflow");
size = twoto(lsize);
t->node = luaM_newvector(L, size, Node);
for (i = 0; i < (int)size; i++) {
Node *n = gnode(t, i);
gnext(n) = 0;
setnilvalue(wgkey(n));
setnilvalue(gval(n));
}
t->lsizenode = cast_byte(lsize);
t->lastfree = gnode(t, size); /* all positions are free */
}
}
typedef struct {
Table *t;
unsigned int nhsize;
} AuxsetnodeT;
static void auxsetnode (lua_State *L, void *ud) {
AuxsetnodeT *asn = cast(AuxsetnodeT *, ud);
setnodevector(L, asn->t, asn->nhsize);
}
void luaH_resize (lua_State *L, Table *t, unsigned int nasize,
unsigned int nhsize) {
unsigned int i;
int j;
AuxsetnodeT asn;
unsigned int oldasize = t->sizearray;
int oldhsize = allocsizenode(t);
Node *nold = t->node; /* save old hash ... */
if (nasize > oldasize) /* array part must grow? */
setarrayvector(L, t, nasize);
/* create new hash part with appropriate size */
asn.t = t; asn.nhsize = nhsize;
if (luaD_rawrunprotected(L, auxsetnode, &asn) != LUA_OK) { /* mem. error? */
setarrayvector(L, t, oldasize); /* array back to its original size */
luaD_throw(L, LUA_ERRMEM); /* rethrow memory error */
}
if (nasize < oldasize) { /* array part must shrink? */
t->sizearray = nasize;
/* re-insert elements from vanishing slice */
for (i=nasize; i<oldasize; i++) {
if (!ttisnil(&t->array[i]))
luaH_setint(L, t, i + 1, &t->array[i]);
}
/* shrink array */
luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
}
/* re-insert elements from hash part */
for (j = oldhsize - 1; j >= 0; j--) {
Node *old = nold + j;
if (!ttisnil(gval(old))) {
/* doesn't need barrier/invalidate cache, as entry was
already present in the table */
setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
}
}
if (oldhsize > 0) /* not the dummy node? */
luaM_freearray(L, nold, cast(size_t, oldhsize)); /* free old hash */
}
void luaH_resizearray (lua_State *L, Table *t, unsigned int nasize) {
int nsize = allocsizenode(t);
luaH_resize(L, t, nasize, nsize);
}
/*
** nums[i] = number of keys 'k' where 2^(i - 1) < k <= 2^i
*/
static void rehash (lua_State *L, Table *t, const TValue *ek) {
unsigned int asize; /* optimal size for array part */
unsigned int na; /* number of keys in the array part */
unsigned int nums[MAXABITS + 1];
int i;
int totaluse;
for (i = 0; i <= MAXABITS; i++) nums[i] = 0; /* reset counts */
na = numusearray(t, nums); /* count keys in array part */
totaluse = na; /* all those keys are integer keys */
totaluse += numusehash(t, nums, &na); /* count keys in hash part */
/* count extra key */
na += countint(ek, nums);
totaluse++;
/* compute new size for array part */
asize = computesizes(nums, &na);
/* resize the table to new computed sizes */
luaH_resize(L, t, asize, totaluse - na);
}
/*
** }=============================================================
*/
Table *luaH_new (lua_State *L) {
GCObject *o = luaC_newobj(L, LUA_TTABLE, sizeof(Table));
Table *t = gco2t(o);
t->metatable = NULL;
t->flags = cast_byte(~0);
t->array = NULL;
t->sizearray = 0;
setnodevector(L, t, 0);
return t;
}
void luaH_free (lua_State *L, Table *t) {
if (!isdummy(t))
luaM_freearray(L, t->node, cast(size_t, sizenode(t)));
luaM_freearray(L, t->array, t->sizearray);
luaM_free(L, t);
}
static Node *getfreepos (Table *t) {
if (!isdummy(t)) {
while (t->lastfree > t->node) {
t->lastfree--;
if (ttisnil(gkey(t->lastfree)))
return t->lastfree;
}
}
return NULL; /* could not find a free place */
}
/*
** inserts a new key into a hash table; first, check whether key's main
** position is free. If not, check whether colliding node is in its main
** position or not: if it is not, move colliding node to an empty place and
** put new key in its main position; otherwise (colliding node is in its main
** position), new key goes to an empty position.
*/
TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
Node *mp;
TValue aux;
if (ttisnil(key)) luaG_runerror(L, "table index is nil");
else if (ttisfloat(key)) {
lua_Integer k;
if (luaV_tointeger(key, &k, 0)) { /* does index fit in an integer? */
setivalue(&aux, k);
key = &aux; /* insert it as an integer */
}
else if (luai_numisnan(fltvalue(key)))
luaG_runerror(L, "table index is NaN");
}
mp = mainposition(t, key);
if (!ttisnil(gval(mp)) || isdummy(t)) { /* main position is taken? */
Node *othern;
Node *f = getfreepos(t); /* get a free place */
if (f == NULL) { /* cannot find a free place? */
rehash(L, t, key); /* grow table */
/* whatever called 'newkey' takes care of TM cache */
return luaH_set(L, t, key); /* insert key into grown table */
}
lua_assert(!isdummy(t));
othern = mainposition(t, gkey(mp));
if (othern != mp) { /* is colliding node out of its main position? */
/* yes; move colliding node into free position */
while (othern + gnext(othern) != mp) /* find previous */
othern += gnext(othern);
gnext(othern) = cast_int(f - othern); /* rechain to point to 'f' */
*f = *mp; /* copy colliding node into free pos. (mp->next also goes) */
if (gnext(mp) != 0) {
gnext(f) += cast_int(mp - f); /* correct 'next' */
gnext(mp) = 0; /* now 'mp' is free */
}
setnilvalue(gval(mp));
}
else { /* colliding node is in its own main position */
/* new node will go into free position */
if (gnext(mp) != 0)
gnext(f) = cast_int((mp + gnext(mp)) - f); /* chain new position */
else lua_assert(gnext(f) == 0);
gnext(mp) = cast_int(f - mp);
mp = f;
}
}
setnodekey(L, &mp->i_key, key);
luaC_barrierback(L, t, key);
lua_assert(ttisnil(gval(mp)));
return gval(mp);
}
/*
** search function for integers
*/
const TValue *luaH_getint (Table *t, lua_Integer key) {
/* (1 <= key && key <= t->sizearray) */
if (l_castS2U(key) - 1 < t->sizearray)
return &t->array[key - 1];
else {
Node *n = hashint(t, key);
for (;;) { /* check whether 'key' is somewhere in the chain */
if (ttisinteger(gkey(n)) && ivalue(gkey(n)) == key)
return gval(n); /* that's it */
else {
int nx = gnext(n);
if (nx == 0) break;
n += nx;
}
}
return luaO_nilobject;
}
}
/*
** search function for short strings
*/
const TValue *luaH_getshortstr (Table *t, TString *key) {
Node *n = hashstr(t, key);
lua_assert(key->tt == LUA_TSHRSTR);
for (;;) { /* check whether 'key' is somewhere in the chain */
const TValue *k = gkey(n);
if (ttisshrstring(k) && eqshrstr(tsvalue(k), key))
return gval(n); /* that's it */
else {
int nx = gnext(n);
if (nx == 0)
return luaO_nilobject; /* not found */
n += nx;
}
}
}
/*
** "Generic" get version. (Not that generic: not valid for integers,
** which may be in array part, nor for floats with integral values.)
*/
static const TValue *getgeneric (Table *t, const TValue *key) {
Node *n = mainposition(t, key);
for (;;) { /* check whether 'key' is somewhere in the chain */
if (luaV_rawequalobj(gkey(n), key))
return gval(n); /* that's it */
else {
int nx = gnext(n);
if (nx == 0)
return luaO_nilobject; /* not found */
n += nx;
}
}
}
const TValue *luaH_getstr (Table *t, TString *key) {
if (key->tt == LUA_TSHRSTR)
return luaH_getshortstr(t, key);
else { /* for long strings, use generic case */
TValue ko;
setsvalue(cast(lua_State *, NULL), &ko, key);
return getgeneric(t, &ko);
}
}
/*
** main search function
*/
const TValue *luaH_get (Table *t, const TValue *key) {
switch (ttype(key)) {
case LUA_TSHRSTR: return luaH_getshortstr(t, tsvalue(key));
case LUA_TNUMINT: return luaH_getint(t, ivalue(key));
case LUA_TNIL: return luaO_nilobject;
case LUA_TNUMFLT: {
lua_Integer k;
if (luaV_tointeger(key, &k, 0)) /* index is int? */
return luaH_getint(t, k); /* use specialized version */
/* else... */
} /* FALLTHROUGH */
default:
return getgeneric(t, key);
}
}
/*
** beware: when using this function you probably need to check a GC
** barrier and invalidate the TM cache.
*/
TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
const TValue *p = luaH_get(t, key);
if (p != luaO_nilobject)
return cast(TValue *, p);
else return luaH_newkey(L, t, key);
}
void luaH_setint (lua_State *L, Table *t, lua_Integer key, TValue *value) {
const TValue *p = luaH_getint(t, key);
TValue *cell;
if (p != luaO_nilobject)
cell = cast(TValue *, p);
else {
TValue k;
setivalue(&k, key);
cell = luaH_newkey(L, t, &k);
}
setobj2t(L, cell, value);
}
static lua_Unsigned unbound_search (Table *t, lua_Unsigned j) {
lua_Unsigned i = j; /* i is zero or a present index */
j++;
/* find 'i' and 'j' such that i is present and j is not */
while (!ttisnil(luaH_getint(t, j))) {
i = j;
if (j > l_castS2U(LUA_MAXINTEGER) / 2) { /* overflow? */
/* table was built with bad purposes: resort to linear search */
i = 1;
while (!ttisnil(luaH_getint(t, i))) i++;
return i - 1;
}
j *= 2;
}
/* now do a binary search between them */
while (j - i > 1) {
lua_Unsigned m = (i+j)/2;
if (ttisnil(luaH_getint(t, m))) j = m;
else i = m;
}
return i;
}
/*
** Try to find a boundary in table 't'. A 'boundary' is an integer index
** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
*/
lua_Unsigned luaH_getn (Table *t) {
unsigned int j = t->sizearray;
if (j > 0 && ttisnil(&t->array[j - 1])) {
/* there is a boundary in the array part: (binary) search for it */
unsigned int i = 0;
while (j - i > 1) {
unsigned int m = (i+j)/2;
if (ttisnil(&t->array[m - 1])) j = m;
else i = m;
}
return i;
}
/* else must find a boundary in hash part */
else if (isdummy(t)) /* hash part is empty? */
return j; /* that is easy... */
else return unbound_search(t, j);
}
#if defined(LUA_DEBUG)
Node *luaH_mainposition (const Table *t, const TValue *key) {
return mainposition(t, key);
}
int luaH_isdummy (const Table *t) { return isdummy(t); }
#endif