ltable.c
(5.4.6)
/*
** $Id: ltable.c $
** 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"
/*
** MAXABITS is the largest integer such that MAXASIZE fits in an
** unsigned int.
*/
#define MAXABITS cast_int(sizeof(int) * CHAR_BIT - 1)
/*
** MAXASIZE is the maximum size of the array part. It is the minimum
** between 2^MAXABITS and the maximum size that, measured in bytes,
** fits in a 'size_t'.
*/
#define MAXASIZE luaM_limitN(1u << MAXABITS, TValue)
/*
** MAXHBITS is the largest integer such that 2^MAXHBITS fits in a
** signed int.
*/
#define MAXHBITS (MAXABITS - 1)
/*
** MAXHSIZE is the maximum size of the hash part. It is the minimum
** between 2^MAXHBITS and the maximum size such that, measured in bytes,
** it fits in a 'size_t'.
*/
#define MAXHSIZE luaM_limitN(1u << MAXHBITS, Node)
/*
** When the original hash value is good, hashing by a power of 2
** avoids the cost of '%'.
*/
#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
/*
** for other types, it is better to avoid modulo by power of 2, as
** they can have many 2 factors.
*/
#define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
#define hashstr(t,str) hashpow2(t, (str)->hash)
#define hashboolean(t,p) hashpow2(t, p)
#define hashpointer(t,p) hashmod(t, point2uint(p))
#define dummynode (&dummynode_)
static const Node dummynode_ = {
{{NULL}, LUA_VEMPTY, /* value's value and type */
LUA_VNIL, 0, {NULL}} /* key type, next, and key value */
};
static const TValue absentkey = {ABSTKEYCONSTANT};
/*
** Hash for integers. To allow a good hash, use the remainder operator
** ('%'). If integer fits as a non-negative int, compute an int
** remainder, which is faster. Otherwise, use an unsigned-integer
** remainder, which uses all bits and ensures a non-negative result.
*/
static Node *hashint (const Table *t, lua_Integer i) {
lua_Unsigned ui = l_castS2U(i);
if (ui <= cast_uint(INT_MAX))
return hashmod(t, cast_int(ui));
else
return hashmod(t, ui);
}
/*
** 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_uint(i) + cast_uint(ni);
return cast_int(u <= cast_uint(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 *mainpositionTV (const Table *t, const TValue *key) {
switch (ttypetag(key)) {
case LUA_VNUMINT: {
lua_Integer i = ivalue(key);
return hashint(t, i);
}
case LUA_VNUMFLT: {
lua_Number n = fltvalue(key);
return hashmod(t, l_hashfloat(n));
}
case LUA_VSHRSTR: {
TString *ts = tsvalue(key);
return hashstr(t, ts);
}
case LUA_VLNGSTR: {
TString *ts = tsvalue(key);
return hashpow2(t, luaS_hashlongstr(ts));
}
case LUA_VFALSE:
return hashboolean(t, 0);
case LUA_VTRUE:
return hashboolean(t, 1);
case LUA_VLIGHTUSERDATA: {
void *p = pvalue(key);
return hashpointer(t, p);
}
case LUA_VLCF: {
lua_CFunction f = fvalue(key);
return hashpointer(t, f);
}
default: {
GCObject *o = gcvalue(key);
return hashpointer(t, o);
}
}
}
l_sinline Node *mainpositionfromnode (const Table *t, Node *nd) {
TValue key;
getnodekey(cast(lua_State *, NULL), &key, nd);
return mainpositionTV(t, &key);
}
/*
** Check whether key 'k1' is equal to the key in node 'n2'. This
** equality is raw, so there are no metamethods. Floats with integer
** values have been normalized, so integers cannot be equal to
** floats. It is assumed that 'eqshrstr' is simply pointer equality, so
** that short strings are handled in the default case.
** A true 'deadok' means to accept dead keys as equal to their original
** values. All dead keys are compared in the default case, by pointer
** identity. (Only collectable objects can produce dead keys.) Note that
** dead long strings are also compared by identity.
** Once a key is dead, its corresponding value may be collected, and
** then another value can be created with the same address. If this
** other value is given to 'next', 'equalkey' will signal a false
** positive. In a regular traversal, this situation should never happen,
** as all keys given to 'next' came from the table itself, and therefore
** could not have been collected. Outside a regular traversal, we
** have garbage in, garbage out. What is relevant is that this false
** positive does not break anything. (In particular, 'next' will return
** some other valid item on the table or nil.)
*/
static int equalkey (const TValue *k1, const Node *n2, int deadok) {
if ((rawtt(k1) != keytt(n2)) && /* not the same variants? */
!(deadok && keyisdead(n2) && iscollectable(k1)))
return 0; /* cannot be same key */
switch (keytt(n2)) {
case LUA_VNIL: case LUA_VFALSE: case LUA_VTRUE:
return 1;
case LUA_VNUMINT:
return (ivalue(k1) == keyival(n2));
case LUA_VNUMFLT:
return luai_numeq(fltvalue(k1), fltvalueraw(keyval(n2)));
case LUA_VLIGHTUSERDATA:
return pvalue(k1) == pvalueraw(keyval(n2));
case LUA_VLCF:
return fvalue(k1) == fvalueraw(keyval(n2));
case ctb(LUA_VLNGSTR):
return luaS_eqlngstr(tsvalue(k1), keystrval(n2));
default:
return gcvalue(k1) == gcvalueraw(keyval(n2));
}
}
/*
** True if value of 'alimit' is equal to the real size of the array
** part of table 't'. (Otherwise, the array part must be larger than
** 'alimit'.)
*/
#define limitequalsasize(t) (isrealasize(t) || ispow2((t)->alimit))
/*
** Returns the real size of the 'array' array
*/
LUAI_FUNC unsigned int luaH_realasize (const Table *t) {
if (limitequalsasize(t))
return t->alimit; /* this is the size */
else {
unsigned int size = t->alimit;
/* compute the smallest power of 2 not smaller than 'n' */
size |= (size >> 1);
size |= (size >> 2);
size |= (size >> 4);
size |= (size >> 8);
#if (UINT_MAX >> 14) > 3 /* unsigned int has more than 16 bits */
size |= (size >> 16);
#if (UINT_MAX >> 30) > 3
size |= (size >> 32); /* unsigned int has more than 32 bits */
#endif
#endif
size++;
lua_assert(ispow2(size) && size/2 < t->alimit && t->alimit < size);
return size;
}
}
/*
** Check whether real size of the array is a power of 2.
** (If it is not, 'alimit' cannot be changed to any other value
** without changing the real size.)
*/
static int ispow2realasize (const Table *t) {
return (!isrealasize(t) || ispow2(t->alimit));
}
static unsigned int setlimittosize (Table *t) {
t->alimit = luaH_realasize(t);
setrealasize(t);
return t->alimit;
}
#define limitasasize(t) check_exp(isrealasize(t), t->alimit)
/*
** "Generic" get version. (Not that generic: not valid for integers,
** which may be in array part, nor for floats with integral values.)
** See explanation about 'deadok' in function 'equalkey'.
*/
static const TValue *getgeneric (Table *t, const TValue *key, int deadok) {
Node *n = mainpositionTV(t, key);
for (;;) { /* check whether 'key' is somewhere in the chain */
if (equalkey(key, n, deadok))
return gval(n); /* that's it */
else {
int nx = gnext(n);
if (nx == 0)
return &absentkey; /* not found */
n += nx;
}
}
}
/*
** returns the index for 'k' if 'k' is an appropriate key to live in
** the array part of a table, 0 otherwise.
*/
static unsigned int arrayindex (lua_Integer k) {
if (l_castS2U(k) - 1u < MAXASIZE) /* 'k' in [1, MAXASIZE]? */
return cast_uint(k); /* 'key' is an appropriate array index */
else
return 0;
}
/*
** 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, TValue *key,
unsigned int asize) {
unsigned int i;
if (ttisnil(key)) return 0; /* first iteration */
i = ttisinteger(key) ? arrayindex(ivalue(key)) : 0;
if (i - 1u < asize) /* is 'key' inside array part? */
return i; /* yes; that's the index */
else {
const TValue *n = getgeneric(t, key, 1);
if (l_unlikely(isabstkey(n)))
luaG_runerror(L, "invalid key to 'next'"); /* key not found */
i = cast_int(nodefromval(n) - gnode(t, 0)); /* key index in hash table */
/* hash elements are numbered after array ones */
return (i + 1) + asize;
}
}
int luaH_next (lua_State *L, Table *t, StkId key) {
unsigned int asize = luaH_realasize(t);
unsigned int i = findindex(L, t, s2v(key), asize); /* find original key */
for (; i < asize; i++) { /* try first array part */
if (!isempty(&t->array[i])) { /* a non-empty entry? */
setivalue(s2v(key), i + 1);
setobj2s(L, key + 1, &t->array[i]);
return 1;
}
}
for (i -= asize; cast_int(i) < sizenode(t); i++) { /* hash part */
if (!isempty(gval(gnode(t, i)))) { /* a non-empty entry? */
Node *n = gnode(t, i);
getnodekey(L, s2v(key), n);
setobj2s(L, key + 1, gval(n));
return 1;
}
}
return 0; /* no more elements */
}
static void freehash (lua_State *L, Table *t) {
if (!isdummy(t))
luaM_freearray(L, t->node, cast_sizet(sizenode(t)));
}
/*
** {=============================================================
** 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. (The condition
** 'twotoi > 0' in the for loop stops the loop if 'twotoi' overflows.)
*/
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) {
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 (lua_Integer 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 */
unsigned int asize = limitasasize(t); /* real array size */
/* traverse each slice */
for (lg = 0, ttlg = 1; lg <= MAXABITS; lg++, ttlg *= 2) {
unsigned int lc = 0; /* counter */
unsigned int lim = ttlg;
if (lim > asize) {
lim = asize; /* 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 (!isempty(&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 (!isempty(gval(n))) {
if (keyisinteger(n))
ause += countint(keyival(n), nums);
totaluse++;
}
}
*pna += ause;
return totaluse;
}
/*
** Creates an array for the hash part of a table with the given
** size, or reuses the dummy node if size is zero.
** The computation for size overflow is in two steps: the first
** comparison ensures that the shift in the second one does not
** overflow.
*/
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 || (1u << lsize) > MAXHSIZE)
luaG_runerror(L, "table overflow");
size = twoto(lsize);
t->node = luaM_newvector(L, size, Node);
for (i = 0; i < cast_int(size); i++) {
Node *n = gnode(t, i);
gnext(n) = 0;
setnilkey(n);
setempty(gval(n));
}
t->lsizenode = cast_byte(lsize);
t->lastfree = gnode(t, size); /* all positions are free */
}
}
/*
** (Re)insert all elements from the hash part of 'ot' into table 't'.
*/
static void reinsert (lua_State *L, Table *ot, Table *t) {
int j;
int size = sizenode(ot);
for (j = 0; j < size; j++) {
Node *old = gnode(ot, j);
if (!isempty(gval(old))) {
/* doesn't need barrier/invalidate cache, as entry was
already present in the table */
TValue k;
getnodekey(L, &k, old);
luaH_set(L, t, &k, gval(old));
}
}
}
/*
** Exchange the hash part of 't1' and 't2'.
*/
static void exchangehashpart (Table *t1, Table *t2) {
lu_byte lsizenode = t1->lsizenode;
Node *node = t1->node;
Node *lastfree = t1->lastfree;
t1->lsizenode = t2->lsizenode;
t1->node = t2->node;
t1->lastfree = t2->lastfree;
t2->lsizenode = lsizenode;
t2->node = node;
t2->lastfree = lastfree;
}
/*
** Resize table 't' for the new given sizes. Both allocations (for
** the hash part and for the array part) can fail, which creates some
** subtleties. If the first allocation, for the hash part, fails, an
** error is raised and that is it. Otherwise, it copies the elements from
** the shrinking part of the array (if it is shrinking) into the new
** hash. Then it reallocates the array part. If that fails, the table
** is in its original state; the function frees the new hash part and then
** raises the allocation error. Otherwise, it sets the new hash part
** into the table, initializes the new part of the array (if any) with
** nils and reinserts the elements of the old hash back into the new
** parts of the table.
*/
void luaH_resize (lua_State *L, Table *t, unsigned int newasize,
unsigned int nhsize) {
unsigned int i;
Table newt; /* to keep the new hash part */
unsigned int oldasize = setlimittosize(t);
TValue *newarray;
/* create new hash part with appropriate size into 'newt' */
setnodevector(L, &newt, nhsize);
if (newasize < oldasize) { /* will array shrink? */
t->alimit = newasize; /* pretend array has new size... */
exchangehashpart(t, &newt); /* and new hash */
/* re-insert into the new hash the elements from vanishing slice */
for (i = newasize; i < oldasize; i++) {
if (!isempty(&t->array[i]))
luaH_setint(L, t, i + 1, &t->array[i]);
}
t->alimit = oldasize; /* restore current size... */
exchangehashpart(t, &newt); /* and hash (in case of errors) */
}
/* allocate new array */
newarray = luaM_reallocvector(L, t->array, oldasize, newasize, TValue);
if (l_unlikely(newarray == NULL && newasize > 0)) { /* allocation failed? */
freehash(L, &newt); /* release new hash part */
luaM_error(L); /* raise error (with array unchanged) */
}
/* allocation ok; initialize new part of the array */
exchangehashpart(t, &newt); /* 't' has the new hash ('newt' has the old) */
t->array = newarray; /* set new array part */
t->alimit = newasize;
for (i = oldasize; i < newasize; i++) /* clear new slice of the array */
setempty(&t->array[i]);
/* re-insert elements from old hash part into new parts */
reinsert(L, &newt, t); /* 'newt' now has the old hash */
freehash(L, &newt); /* free old hash part */
}
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 */
setlimittosize(t);
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 */
if (ttisinteger(ek))
na += countint(ivalue(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_VTABLE, sizeof(Table));
Table *t = gco2t(o);
t->metatable = NULL;
t->flags = cast_byte(maskflags); /* table has no metamethod fields */
t->array = NULL;
t->alimit = 0;
setnodevector(L, t, 0);
return t;
}
void luaH_free (lua_State *L, Table *t) {
freehash(L, t);
luaM_freearray(L, t->array, luaH_realasize(t));
luaM_free(L, t);
}
static Node *getfreepos (Table *t) {
if (!isdummy(t)) {
while (t->lastfree > t->node) {
t->lastfree--;
if (keyisnil(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.
*/
void luaH_newkey (lua_State *L, Table *t, const TValue *key, TValue *value) {
Node *mp;
TValue aux;
if (l_unlikely(ttisnil(key)))
luaG_runerror(L, "table index is nil");
else if (ttisfloat(key)) {
lua_Number f = fltvalue(key);
lua_Integer k;
if (luaV_flttointeger(f, &k, F2Ieq)) { /* does key fit in an integer? */
setivalue(&aux, k);
key = &aux; /* insert it as an integer */
}
else if (l_unlikely(luai_numisnan(f)))
luaG_runerror(L, "table index is NaN");
}
if (ttisnil(value))
return; /* do not insert nil values */
mp = mainpositionTV(t, key);
if (!isempty(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 */
luaH_set(L, t, key, value); /* insert key into grown table */
return;
}
lua_assert(!isdummy(t));
othern = mainpositionfromnode(t, 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 */
}
setempty(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, key);
luaC_barrierback(L, obj2gco(t), key);
lua_assert(isempty(gval(mp)));
setobj2t(L, gval(mp), value);
}
/*
** Search function for integers. If integer is inside 'alimit', get it
** directly from the array part. Otherwise, if 'alimit' is not equal to
** the real size of the array, key still can be in the array part. In
** this case, try to avoid a call to 'luaH_realasize' when key is just
** one more than the limit (so that it can be incremented without
** changing the real size of the array).
*/
const TValue *luaH_getint (Table *t, lua_Integer key) {
if (l_castS2U(key) - 1u < t->alimit) /* 'key' in [1, t->alimit]? */
return &t->array[key - 1];
else if (!limitequalsasize(t) && /* key still may be in the array part? */
(l_castS2U(key) == t->alimit + 1 ||
l_castS2U(key) - 1u < luaH_realasize(t))) {
t->alimit = cast_uint(key); /* probably '#t' is here now */
return &t->array[key - 1];
}
else {
Node *n = hashint(t, key);
for (;;) { /* check whether 'key' is somewhere in the chain */
if (keyisinteger(n) && keyival(n) == key)
return gval(n); /* that's it */
else {
int nx = gnext(n);
if (nx == 0) break;
n += nx;
}
}
return &absentkey;
}
}
/*
** search function for short strings
*/
const TValue *luaH_getshortstr (Table *t, TString *key) {
Node *n = hashstr(t, key);
lua_assert(key->tt == LUA_VSHRSTR);
for (;;) { /* check whether 'key' is somewhere in the chain */
if (keyisshrstr(n) && eqshrstr(keystrval(n), key))
return gval(n); /* that's it */
else {
int nx = gnext(n);
if (nx == 0)
return &absentkey; /* not found */
n += nx;
}
}
}
const TValue *luaH_getstr (Table *t, TString *key) {
if (key->tt == LUA_VSHRSTR)
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, 0);
}
}
/*
** main search function
*/
const TValue *luaH_get (Table *t, const TValue *key) {
switch (ttypetag(key)) {
case LUA_VSHRSTR: return luaH_getshortstr(t, tsvalue(key));
case LUA_VNUMINT: return luaH_getint(t, ivalue(key));
case LUA_VNIL: return &absentkey;
case LUA_VNUMFLT: {
lua_Integer k;
if (luaV_flttointeger(fltvalue(key), &k, F2Ieq)) /* integral index? */
return luaH_getint(t, k); /* use specialized version */
/* else... */
} /* FALLTHROUGH */
default:
return getgeneric(t, key, 0);
}
}
/*
** Finish a raw "set table" operation, where 'slot' is where the value
** should have been (the result of a previous "get table").
** Beware: when using this function you probably need to check a GC
** barrier and invalidate the TM cache.
*/
void luaH_finishset (lua_State *L, Table *t, const TValue *key,
const TValue *slot, TValue *value) {
if (isabstkey(slot))
luaH_newkey(L, t, key, value);
else
setobj2t(L, cast(TValue *, slot), value);
}
/*
** beware: when using this function you probably need to check a GC
** barrier and invalidate the TM cache.
*/
void luaH_set (lua_State *L, Table *t, const TValue *key, TValue *value) {
const TValue *slot = luaH_get(t, key);
luaH_finishset(L, t, key, slot, value);
}
void luaH_setint (lua_State *L, Table *t, lua_Integer key, TValue *value) {
const TValue *p = luaH_getint(t, key);
if (isabstkey(p)) {
TValue k;
setivalue(&k, key);
luaH_newkey(L, t, &k, value);
}
else
setobj2t(L, cast(TValue *, p), value);
}
/*
** Try to find a boundary in the hash part of table 't'. From the
** caller, we know that 'j' is zero or present and that 'j + 1' is
** present. We want to find a larger key that is absent from the
** table, so that we can do a binary search between the two keys to
** find a boundary. We keep doubling 'j' until we get an absent index.
** If the doubling would overflow, we try LUA_MAXINTEGER. If it is
** absent, we are ready for the binary search. ('j', being max integer,
** is larger or equal to 'i', but it cannot be equal because it is
** absent while 'i' is present; so 'j > i'.) Otherwise, 'j' is a
** boundary. ('j + 1' cannot be a present integer key because it is
** not a valid integer in Lua.)
*/
static lua_Unsigned hash_search (Table *t, lua_Unsigned j) {
lua_Unsigned i;
if (j == 0) j++; /* the caller ensures 'j + 1' is present */
do {
i = j; /* 'i' is a present index */
if (j <= l_castS2U(LUA_MAXINTEGER) / 2)
j *= 2;
else {
j = LUA_MAXINTEGER;
if (isempty(luaH_getint(t, j))) /* t[j] not present? */
break; /* 'j' now is an absent index */
else /* weird case */
return j; /* well, max integer is a boundary... */
}
} while (!isempty(luaH_getint(t, j))); /* repeat until an absent t[j] */
/* i < j && t[i] present && t[j] absent */
while (j - i > 1u) { /* do a binary search between them */
lua_Unsigned m = (i + j) / 2;
if (isempty(luaH_getint(t, m))) j = m;
else i = m;
}
return i;
}
static unsigned int binsearch (const TValue *array, unsigned int i,
unsigned int j) {
while (j - i > 1u) { /* binary search */
unsigned int m = (i + j) / 2;
if (isempty(&array[m - 1])) 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 present and t[i+1] is absent, or 0 if t[1] is absent
** and 'maxinteger' if t[maxinteger] is present.)
** (In the next explanation, we use Lua indices, that is, with base 1.
** The code itself uses base 0 when indexing the array part of the table.)
** The code starts with 'limit = t->alimit', a position in the array
** part that may be a boundary.
**
** (1) If 't[limit]' is empty, there must be a boundary before it.
** As a common case (e.g., after 't[#t]=nil'), check whether 'limit-1'
** is present. If so, it is a boundary. Otherwise, do a binary search
** between 0 and limit to find a boundary. In both cases, try to
** use this boundary as the new 'alimit', as a hint for the next call.
**
** (2) If 't[limit]' is not empty and the array has more elements
** after 'limit', try to find a boundary there. Again, try first
** the special case (which should be quite frequent) where 'limit+1'
** is empty, so that 'limit' is a boundary. Otherwise, check the
** last element of the array part. If it is empty, there must be a
** boundary between the old limit (present) and the last element
** (absent), which is found with a binary search. (This boundary always
** can be a new limit.)
**
** (3) The last case is when there are no elements in the array part
** (limit == 0) or its last element (the new limit) is present.
** In this case, must check the hash part. If there is no hash part
** or 'limit+1' is absent, 'limit' is a boundary. Otherwise, call
** 'hash_search' to find a boundary in the hash part of the table.
** (In those cases, the boundary is not inside the array part, and
** therefore cannot be used as a new limit.)
*/
lua_Unsigned luaH_getn (Table *t) {
unsigned int limit = t->alimit;
if (limit > 0 && isempty(&t->array[limit - 1])) { /* (1)? */
/* there must be a boundary before 'limit' */
if (limit >= 2 && !isempty(&t->array[limit - 2])) {
/* 'limit - 1' is a boundary; can it be a new limit? */
if (ispow2realasize(t) && !ispow2(limit - 1)) {
t->alimit = limit - 1;
setnorealasize(t); /* now 'alimit' is not the real size */
}
return limit - 1;
}
else { /* must search for a boundary in [0, limit] */
unsigned int boundary = binsearch(t->array, 0, limit);
/* can this boundary represent the real size of the array? */
if (ispow2realasize(t) && boundary > luaH_realasize(t) / 2) {
t->alimit = boundary; /* use it as the new limit */
setnorealasize(t);
}
return boundary;
}
}
/* 'limit' is zero or present in table */
if (!limitequalsasize(t)) { /* (2)? */
/* 'limit' > 0 and array has more elements after 'limit' */
if (isempty(&t->array[limit])) /* 'limit + 1' is empty? */
return limit; /* this is the boundary */
/* else, try last element in the array */
limit = luaH_realasize(t);
if (isempty(&t->array[limit - 1])) { /* empty? */
/* there must be a boundary in the array after old limit,
and it must be a valid new limit */
unsigned int boundary = binsearch(t->array, t->alimit, limit);
t->alimit = boundary;
return boundary;
}
/* else, new limit is present in the table; check the hash part */
}
/* (3) 'limit' is the last element and either is zero or present in table */
lua_assert(limit == luaH_realasize(t) &&
(limit == 0 || !isempty(&t->array[limit - 1])));
if (isdummy(t) || isempty(luaH_getint(t, cast(lua_Integer, limit + 1))))
return limit; /* 'limit + 1' is absent */
else /* 'limit + 1' is also present */
return hash_search(t, limit);
}
#if defined(LUA_DEBUG)
/* export these functions for the test library */
Node *luaH_mainposition (const Table *t, const TValue *key) {
return mainpositionTV(t, key);
}
#endif