670 lines
19 KiB
C++
670 lines
19 KiB
C++
/*
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** $Id: ltable.c,v 2.118 2016/11/07 12:38:35 roberto Exp $
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** Lua tables (hash)
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** See Copyright Notice in lua.h
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*/
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#define ltable_c
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#define LUA_CORE
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#include "ltable.h"
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#include "lprefix.h"
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/*
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** Implementation of tables (aka arrays, objects, or hash tables).
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** Tables keep its elements in two parts: an array part and a hash part.
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** Non-negative integer keys are all candidates to be kept in the array
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** part. The actual size of the array is the largest 'n' such that
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** more than half the slots between 1 and n are in use.
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** Hash uses a mix of chained scatter table with Brent's variation.
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** A main invariant of these tables is that, if an element is not
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** in its main position (i.e. the 'original' position that its hash gives
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** to it), then the colliding element is in its own main position.
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** Hence even when the load factor reaches 100%, performance remains good.
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*/
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#include <math.h>
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#include <limits.h>
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#include "lua.h"
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#include "ldebug.h"
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#include "ldo.h"
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#include "lgc.h"
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#include "lmem.h"
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#include "lobject.h"
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#include "lstate.h"
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#include "lstring.h"
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#include "lvm.h"
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namespace NS_SLUA {
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/*
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** Maximum size of array part (MAXASIZE) is 2^MAXABITS. MAXABITS is
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** the largest integer such that MAXASIZE fits in an unsigned int.
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*/
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#define MAXABITS cast_int(sizeof(int) * CHAR_BIT - 1)
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#define MAXASIZE (1u << MAXABITS)
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/*
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** Maximum size of hash part is 2^MAXHBITS. MAXHBITS is the largest
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** integer such that 2^MAXHBITS fits in a signed int. (Note that the
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** maximum number of elements in a table, 2^MAXABITS + 2^MAXHBITS, still
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** fits comfortably in an unsigned int.)
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*/
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#define MAXHBITS (MAXABITS - 1)
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#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
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#define hashstr(t,str) hashpow2(t, (str)->hash)
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#define hashboolean(t,p) hashpow2(t, p)
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#define hashint(t,i) hashpow2(t, i)
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/*
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** for some types, it is better to avoid modulus by power of 2, as
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** they tend to have many 2 factors.
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*/
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#define hashmod(t,n) (gnode(t, ((n) % ((sizenode(t)-1)|1))))
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#define hashpointer(t,p) hashmod(t, point2uint(p))
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#define dummynode (&dummynode_)
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static const Node dummynode_ = {
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{NILCONSTANT}, /* value */
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{{NILCONSTANT, 0}} /* key */
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};
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/*
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** Hash for floating-point numbers.
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** The main computation should be just
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** n = frexp(n, &i); return (n * INT_MAX) + i
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** but there are some numerical subtleties.
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** In a two-complement representation, INT_MAX does not has an exact
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** representation as a float, but INT_MIN does; because the absolute
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** value of 'frexp' is smaller than 1 (unless 'n' is inf/NaN), the
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** absolute value of the product 'frexp * -INT_MIN' is smaller or equal
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** to INT_MAX. Next, the use of 'unsigned int' avoids overflows when
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** adding 'i'; the use of '~u' (instead of '-u') avoids problems with
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** INT_MIN.
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*/
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#if !defined(l_hashfloat)
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static int l_hashfloat (lua_Number n) {
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int i;
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lua_Integer ni;
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n = l_mathop(frexp)(n, &i) * -cast_num(INT_MIN);
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if (!lua_numbertointeger(n, &ni)) { /* is 'n' inf/-inf/NaN? */
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lua_assert(luai_numisnan(n) || l_mathop(fabs)(n) == cast_num(HUGE_VAL));
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return 0;
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}
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else { /* normal case */
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unsigned int u = cast(unsigned int, i) + cast(unsigned int, ni);
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return cast_int(u <= cast(unsigned int, INT_MAX) ? u : ~u);
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}
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}
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#endif
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/*
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** returns the 'main' position of an element in a table (that is, the index
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** of its hash value)
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*/
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static Node *mainposition (const Table *t, const TValue *key) {
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switch (ttype(key)) {
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case LUA_TNUMINT:
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return hashint(t, ivalue(key));
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case LUA_TNUMFLT:
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return hashmod(t, l_hashfloat(fltvalue(key)));
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case LUA_TSHRSTR:
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return hashstr(t, tsvalue(key));
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case LUA_TLNGSTR:
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return hashpow2(t, luaS_hashlongstr(tsvalue(key)));
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case LUA_TBOOLEAN:
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return hashboolean(t, bvalue(key));
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case LUA_TLIGHTUSERDATA:
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return hashpointer(t, pvalue(key));
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case LUA_TLCF:
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return hashpointer(t, fvalue(key));
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default:
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lua_assert(!ttisdeadkey(key));
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return hashpointer(t, gcvalue(key));
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}
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}
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/*
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** returns the index for 'key' if 'key' is an appropriate key to live in
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** the array part of the table, 0 otherwise.
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*/
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static unsigned int arrayindex (const TValue *key) {
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if (ttisinteger(key)) {
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lua_Integer k = ivalue(key);
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if (0 < k && (lua_Unsigned)k <= MAXASIZE)
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return cast(unsigned int, k); /* 'key' is an appropriate array index */
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}
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return 0; /* 'key' did not match some condition */
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}
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/*
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** returns the index of a 'key' for table traversals. First goes all
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** elements in the array part, then elements in the hash part. The
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** beginning of a traversal is signaled by 0.
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*/
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static unsigned int findindex (lua_State *L, Table *t, StkId key) {
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unsigned int i;
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if (ttisnil(key)) return 0; /* first iteration */
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i = arrayindex(key);
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if (i != 0 && i <= t->sizearray) /* is 'key' inside array part? */
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return i; /* yes; that's the index */
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else {
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int nx;
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Node *n = mainposition(t, key);
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for (;;) { /* check whether 'key' is somewhere in the chain */
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/* key may be dead already, but it is ok to use it in 'next' */
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if (luaV_rawequalobj(gkey(n), key) ||
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(ttisdeadkey(gkey(n)) && iscollectable(key) &&
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deadvalue(gkey(n)) == gcvalue(key))) {
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i = cast_int(n - gnode(t, 0)); /* key index in hash table */
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/* hash elements are numbered after array ones */
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return (i + 1) + t->sizearray;
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}
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nx = gnext(n);
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if (nx == 0)
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luaG_runerror(L, "invalid key to 'next'"); /* key not found */
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else n += nx;
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}
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}
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}
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int luaH_next (lua_State *L, Table *t, StkId key) {
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unsigned int i = findindex(L, t, key); /* find original element */
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for (; i < t->sizearray; i++) { /* try first array part */
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if (!ttisnil(&t->array[i])) { /* a non-nil value? */
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setivalue(key, i + 1);
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setobj2s(L, key+1, &t->array[i]);
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return 1;
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}
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}
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for (i -= t->sizearray; cast_int(i) < sizenode(t); i++) { /* hash part */
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if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
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setobj2s(L, key, gkey(gnode(t, i)));
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setobj2s(L, key+1, gval(gnode(t, i)));
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return 1;
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}
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}
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return 0; /* no more elements */
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}
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/*
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** {=============================================================
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** Rehash
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** ==============================================================
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*/
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/*
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** Compute the optimal size for the array part of table 't'. 'nums' is a
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** "count array" where 'nums[i]' is the number of integers in the table
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** between 2^(i - 1) + 1 and 2^i. 'pna' enters with the total number of
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** integer keys in the table and leaves with the number of keys that
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** will go to the array part; return the optimal size.
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*/
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static unsigned int computesizes (unsigned int nums[], unsigned int *pna) {
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int i;
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unsigned int twotoi; /* 2^i (candidate for optimal size) */
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unsigned int a = 0; /* number of elements smaller than 2^i */
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unsigned int na = 0; /* number of elements to go to array part */
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unsigned int optimal = 0; /* optimal size for array part */
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/* loop while keys can fill more than half of total size */
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for (i = 0, twotoi = 1; *pna > twotoi / 2; i++, twotoi *= 2) {
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if (nums[i] > 0) {
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a += nums[i];
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if (a > twotoi/2) { /* more than half elements present? */
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optimal = twotoi; /* optimal size (till now) */
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na = a; /* all elements up to 'optimal' will go to array part */
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}
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}
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}
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lua_assert((optimal == 0 || optimal / 2 < na) && na <= optimal);
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*pna = na;
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return optimal;
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}
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static int countint (const TValue *key, unsigned int *nums) {
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unsigned int k = arrayindex(key);
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if (k != 0) { /* is 'key' an appropriate array index? */
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nums[luaO_ceillog2(k)]++; /* count as such */
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return 1;
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}
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else
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return 0;
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}
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/*
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** Count keys in array part of table 't': Fill 'nums[i]' with
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** number of keys that will go into corresponding slice and return
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** total number of non-nil keys.
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*/
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static unsigned int numusearray (const Table *t, unsigned int *nums) {
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int lg;
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unsigned int ttlg; /* 2^lg */
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unsigned int ause = 0; /* summation of 'nums' */
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unsigned int i = 1; /* count to traverse all array keys */
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/* traverse each slice */
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for (lg = 0, ttlg = 1; lg <= MAXABITS; lg++, ttlg *= 2) {
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unsigned int lc = 0; /* counter */
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unsigned int lim = ttlg;
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if (lim > t->sizearray) {
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lim = t->sizearray; /* adjust upper limit */
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if (i > lim)
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break; /* no more elements to count */
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}
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/* count elements in range (2^(lg - 1), 2^lg] */
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for (; i <= lim; i++) {
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if (!ttisnil(&t->array[i-1]))
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lc++;
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}
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nums[lg] += lc;
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ause += lc;
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}
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return ause;
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}
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static int numusehash (const Table *t, unsigned int *nums, unsigned int *pna) {
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int totaluse = 0; /* total number of elements */
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int ause = 0; /* elements added to 'nums' (can go to array part) */
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int i = sizenode(t);
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while (i--) {
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Node *n = &t->node[i];
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if (!ttisnil(gval(n))) {
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ause += countint(gkey(n), nums);
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totaluse++;
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}
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}
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*pna += ause;
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return totaluse;
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}
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static void setarrayvector (lua_State *L, Table *t, unsigned int size) {
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unsigned int i;
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luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
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for (i=t->sizearray; i<size; i++)
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setnilvalue(&t->array[i]);
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t->sizearray = size;
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}
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static void setnodevector (lua_State *L, Table *t, unsigned int size) {
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if (size == 0) { /* no elements to hash part? */
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t->node = cast(Node *, dummynode); /* use common 'dummynode' */
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t->lsizenode = 0;
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t->lastfree = NULL; /* signal that it is using dummy node */
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}
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else {
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int i;
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int lsize = luaO_ceillog2(size);
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if (lsize > MAXHBITS)
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luaG_runerror(L, "table overflow");
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size = twoto(lsize);
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t->node = luaM_newvector(L, size, Node);
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for (i = 0; i < (int)size; i++) {
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Node *n = gnode(t, i);
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gnext(n) = 0;
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setnilvalue(wgkey(n));
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setnilvalue(gval(n));
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}
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t->lsizenode = cast_byte(lsize);
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t->lastfree = gnode(t, size); /* all positions are free */
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}
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}
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void luaH_resize (lua_State *L, Table *t, unsigned int nasize,
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unsigned int nhsize) {
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unsigned int i;
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int j;
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unsigned int oldasize = t->sizearray;
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int oldhsize = allocsizenode(t);
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Node *nold = t->node; /* save old hash ... */
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if (nasize > oldasize) /* array part must grow? */
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setarrayvector(L, t, nasize);
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/* create new hash part with appropriate size */
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setnodevector(L, t, nhsize);
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if (nasize < oldasize) { /* array part must shrink? */
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t->sizearray = nasize;
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/* re-insert elements from vanishing slice */
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for (i=nasize; i<oldasize; i++) {
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if (!ttisnil(&t->array[i]))
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luaH_setint(L, t, i + 1, &t->array[i]);
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}
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/* shrink array */
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luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
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}
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/* re-insert elements from hash part */
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for (j = oldhsize - 1; j >= 0; j--) {
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Node *old = nold + j;
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if (!ttisnil(gval(old))) {
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/* doesn't need barrier/invalidate cache, as entry was
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already present in the table */
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setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
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}
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}
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if (oldhsize > 0) /* not the dummy node? */
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luaM_freearray(L, nold, cast(size_t, oldhsize)); /* free old hash */
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}
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void luaH_resizearray (lua_State *L, Table *t, unsigned int nasize) {
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int nsize = allocsizenode(t);
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luaH_resize(L, t, nasize, nsize);
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}
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/*
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** nums[i] = number of keys 'k' where 2^(i - 1) < k <= 2^i
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*/
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static void rehash (lua_State *L, Table *t, const TValue *ek) {
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unsigned int asize; /* optimal size for array part */
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unsigned int na; /* number of keys in the array part */
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unsigned int nums[MAXABITS + 1];
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int i;
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int totaluse;
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for (i = 0; i <= MAXABITS; i++) nums[i] = 0; /* reset counts */
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na = numusearray(t, nums); /* count keys in array part */
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totaluse = na; /* all those keys are integer keys */
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totaluse += numusehash(t, nums, &na); /* count keys in hash part */
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/* count extra key */
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na += countint(ek, nums);
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totaluse++;
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/* compute new size for array part */
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asize = computesizes(nums, &na);
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/* resize the table to new computed sizes */
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luaH_resize(L, t, asize, totaluse - na);
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}
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/*
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** }=============================================================
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*/
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Table *luaH_new (lua_State *L) {
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GCObject *o = luaC_newobj(L, LUA_TTABLE, sizeof(Table));
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Table *t = gco2t(o);
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t->metatable = NULL;
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t->flags = cast_byte(~0);
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t->array = NULL;
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t->sizearray = 0;
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setnodevector(L, t, 0);
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return t;
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}
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void luaH_free (lua_State *L, Table *t) {
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if (!isdummy(t))
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luaM_freearray(L, t->node, cast(size_t, sizenode(t)));
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luaM_freearray(L, t->array, t->sizearray);
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luaM_free(L, t);
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}
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static Node *getfreepos (Table *t) {
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if (!isdummy(t)) {
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while (t->lastfree > t->node) {
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t->lastfree--;
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if (ttisnil(gkey(t->lastfree)))
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return t->lastfree;
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}
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}
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return NULL; /* could not find a free place */
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}
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/*
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** inserts a new key into a hash table; first, check whether key's main
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** position is free. If not, check whether colliding node is in its main
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** position or not: if it is not, move colliding node to an empty place and
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** put new key in its main position; otherwise (colliding node is in its main
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** position), new key goes to an empty position.
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*/
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TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
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Node *mp;
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TValue aux;
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if (ttisnil(key)) luaG_runerror(L, "table index is nil");
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else if (ttisfloat(key)) {
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lua_Integer k;
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if (luaV_tointeger(key, &k, 0)) { /* does index fit in an integer? */
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setivalue(&aux, k);
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key = &aux; /* insert it as an integer */
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}
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else if (luai_numisnan(fltvalue(key)))
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luaG_runerror(L, "table index is NaN");
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}
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mp = mainposition(t, key);
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if (!ttisnil(gval(mp)) || isdummy(t)) { /* main position is taken? */
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Node *othern;
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Node *f = getfreepos(t); /* get a free place */
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if (f == NULL) { /* cannot find a free place? */
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rehash(L, t, key); /* grow table */
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/* whatever called 'newkey' takes care of TM cache */
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return luaH_set(L, t, key); /* insert key into grown table */
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}
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lua_assert(!isdummy(t));
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othern = mainposition(t, gkey(mp));
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if (othern != mp) { /* is colliding node out of its main position? */
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/* yes; move colliding node into free position */
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while (othern + gnext(othern) != mp) /* find previous */
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othern += gnext(othern);
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gnext(othern) = cast_int(f - othern); /* rechain to point to 'f' */
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*f = *mp; /* copy colliding node into free pos. (mp->next also goes) */
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if (gnext(mp) != 0) {
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gnext(f) += cast_int(mp - f); /* correct 'next' */
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gnext(mp) = 0; /* now 'mp' is free */
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}
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setnilvalue(gval(mp));
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|
}
|
|
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 int unbound_search (Table *t, unsigned int j) {
|
|
unsigned int 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 > cast(unsigned int, MAX_INT)/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) {
|
|
unsigned int 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).
|
|
*/
|
|
int 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
|
|
|
|
} // end NS_SLUA
|