Lua 5.1.4: ltable.c

---

L0001 /*
L0002 ** $Id: ltable.c,v 2.32.1.2 2007年12月28日 15:32:23 roberto Exp $
L0003 ** Lua tables (hash)
L0004 ** See Copyright Notice in lua.h
L0005 */
L0006 
L0007 
L0008 /*
L0009 ** Implementation of tables (aka arrays, objects, or hash tables).
L0010 ** Tables keep its elements in two parts: an array part and a hash part.
L0011 ** Non-negative integer keys are all candidates to be kept in the array
L0012 ** part. The actual size of the array is the largest `n' such that at
L0013 ** least half the slots between 0 and n are in use.
L0014 ** Hash uses a mix of chained scatter table with Brent's variation.
L0015 ** A main invariant of these tables is that, if an element is not
L0016 ** in its main position (i.e. the `original' position that its hash gives
L0017 ** to it), then the colliding element is in its own main position.
L0018 ** Hence even when the load factor reaches 100%, performance remains good.
L0019 */
L0020 
L0021 #include <math.h>
L0022 #include <string.h>
L0023 
L0024 #define ltable_c
L0025 #define LUA_CORE
L0026 
L0027 #include "lua.h"
 L0028 
L0029 #include "ldebug.h"
 L0030 #include "ldo.h"
 L0031 #include "lgc.h"
 L0032 #include "lmem.h"
 L0033 #include "lobject.h"
 L0034 #include "lstate.h"
 L0035 #include "ltable.h"
 L0036 
L0037 
L0038 /*
L0039 ** max size of array part is 2^MAXBITS
L0040 */
L0041 #if LUAI_BITSINT > 26
L0042 #define MAXBITS		26
L0043 #else
L0044 #define MAXBITS		(LUAI_BITSINT-2)
L0045 #endif
L0046 
L0047 #define MAXASIZE	(1 << MAXBITS)
L0048 
L0049 
L0050 #define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
L0051 
L0052 #define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
L0053 #define hashboolean(t,p) hashpow2(t, p)
L0054 
L0055 
L0056 /*
L0057 ** for some types, it is better to avoid modulus by power of 2, as
L0058 ** they tend to have many 2 factors.
L0059 */
L0060 #define hashmod(t,n)	(gnode(t, ((n) % ((sizenode(t)-1)|1))))
L0061 
L0062 
L0063 #define hashpointer(t,p)	hashmod(t, IntPoint(p))
L0064 
L0065 
L0066 /*
L0067 ** number of ints inside a lua_Number
L0068 */
L0069 #define numints		cast_int(sizeof(lua_Number)/sizeof(int))
L0070 
L0071 
L0072 
L0073 #define dummynode		(&dummynode_)
L0074 
L0075 static const Node dummynode_ = {
L0076 {{NULL}, LUA_TNIL}, /* value */
L0077 {{{NULL}, LUA_TNIL, NULL}} /* key */
L0078 };
L0079 
L0080 
L0081 /*
L0082 ** hash for lua_Numbers
L0083 */
L0084 static Node *hashnum (const Table *t, lua_Number n) {
L0085 unsigned int a[numints];
L0086 int i;
L0087 if (luai_numeq(n, 0)) /* avoid problems with -0 */
L0088 return gnode(t, 0);
L0089 memcpy(a, &n, sizeof(a));
L0090 for (i = 1; i < numints; i++) a[0] += a[i];
L0091 return hashmod(t, a[0]);
L0092 }
L0093 
L0094 
L0095 
L0096 /*
L0097 ** returns the `main' position of an element in a table (that is, the index
L0098 ** of its hash value)
L0099 */
L0100 static Node *mainposition (const Table *t, const TValue *key) {
L0101 switch (ttype(key)) {
L0102 case LUA_TNUMBER:
L0103 return hashnum(t, nvalue(key));
L0104 case LUA_TSTRING:
L0105 return hashstr(t, rawtsvalue(key));
L0106 case LUA_TBOOLEAN:
L0107 return hashboolean(t, bvalue(key));
L0108 case LUA_TLIGHTUSERDATA:
L0109 return hashpointer(t, pvalue(key));
L0110 default:
L0111 return hashpointer(t, gcvalue(key));
L0112 }
L0113 }
L0114 
L0115 
L0116 /*
L0117 ** returns the index for `key' if `key' is an appropriate key to live in
L0118 ** the array part of the table, -1 otherwise.
L0119 */
L0120 static int arrayindex (const TValue *key) {
L0121 if (ttisnumber(key)) {
L0122 lua_Number n = nvalue(key);
L0123 int k;
L0124 lua_number2int(k, n);
L0125 if (luai_numeq(cast_num(k), n))
L0126 return k;
L0127 }
L0128 return -1; /* `key' did not match some condition */
L0129 }
L0130 
L0131 
L0132 /*
L0133 ** returns the index of a `key' for table traversals. First goes all
L0134 ** elements in the array part, then elements in the hash part. The
L0135 ** beginning of a traversal is signalled by -1.
L0136 */
L0137 static int findindex (lua_State *L, Table *t, StkId key) {
L0138 int i;
L0139 if (ttisnil(key)) return -1; /* first iteration */
L0140 i = arrayindex(key);
L0141 if (0 < i && i <= t->sizearray) /* is `key' inside array part? */
L0142 return i-1; /* yes; that's the index (corrected to C) */
L0143 else {
L0144 Node *n = mainposition(t, key);
L0145 do { /* check whether `key' is somewhere in the chain */
L0146 /* key may be dead already, but it is ok to use it in `next' */
L0147 if (luaO_rawequalObj(key2tval(n), key) ||
L0148 (ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&
L0149 gcvalue(gkey(n)) == gcvalue(key))) {
L0150 i = cast_int(n - gnode(t, 0)); /* key index in hash table */
L0151 /* hash elements are numbered after array ones */
L0152 return i + t->sizearray;
L0153 }
L0154 else n = gnext(n);
L0155 } while (n);
L0156 luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
L0157 return 0; /* to avoid warnings */
L0158 }
L0159 }
L0160 
L0161 
L0162 int luaH_next (lua_State *L, Table *t, StkId key) {
L0163 int i = findindex(L, t, key); /* find original element */
L0164 for (i++; i < t->sizearray; i++) { /* try first array part */
L0165 if (!ttisnil(&t->array[i])) { /* a non-nil value? */
L0166 setnvalue(key, cast_num(i+1));
L0167 setobj2s(L, key+1, &t->array[i]);
L0168 return 1;
L0169 }
L0170 }
L0171 for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
L0172 if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
L0173 setobj2s(L, key, key2tval(gnode(t, i)));
L0174 setobj2s(L, key+1, gval(gnode(t, i)));
L0175 return 1;
L0176 }
L0177 }
L0178 return 0; /* no more elements */
L0179 }
L0180 
L0181 
L0182 /*
L0183 ** {=============================================================
L0184 ** Rehash
L0185 ** ==============================================================
L0186 */
L0187 
L0188 
L0189 static int computesizes (int nums[], int *narray) {
L0190 int i;
L0191 int twotoi; /* 2^i */
L0192 int a = 0; /* number of elements smaller than 2^i */
L0193 int na = 0; /* number of elements to go to array part */
L0194 int n = 0; /* optimal size for array part */
L0195 for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
L0196 if (nums[i] > 0) {
L0197 a += nums[i];
L0198 if (a > twotoi/2) { /* more than half elements present? */
L0199 n = twotoi; /* optimal size (till now) */
L0200 na = a; /* all elements smaller than n will go to array part */
L0201 }
L0202 }
L0203 if (a == *narray) break; /* all elements already counted */
L0204 }
L0205 *narray = n;
L0206 lua_assert(*narray/2 <= na && na <= *narray);
L0207 return na;
L0208 }
L0209 
L0210 
L0211 static int countint (const TValue *key, int *nums) {
L0212 int k = arrayindex(key);
L0213 if (0 < k && k <= MAXASIZE) { /* is `key' an appropriate array index? */
L0214 nums[ceillog2(k)]++; /* count as such */
L0215 return 1;
L0216 }
L0217 else
L0218 return 0;
L0219 }
L0220 
L0221 
L0222 static int numusearray (const Table *t, int *nums) {
L0223 int lg;
L0224 int ttlg; /* 2^lg */
L0225 int ause = 0; /* summation of `nums' */
L0226 int i = 1; /* count to traverse all array keys */
L0227 for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) { /* for each slice */
L0228 int lc = 0; /* counter */
L0229 int lim = ttlg;
L0230 if (lim > t->sizearray) {
L0231 lim = t->sizearray; /* adjust upper limit */
L0232 if (i > lim)
L0233 break; /* no more elements to count */
L0234 }
L0235 /* count elements in range (2^(lg-1), 2^lg] */
L0236 for (; i <= lim; i++) {
L0237 if (!ttisnil(&t->array[i-1]))
L0238 lc++;
L0239 }
L0240 nums[lg] += lc;
L0241 ause += lc;
L0242 }
L0243 return ause;
L0244 }
L0245 
L0246 
L0247 static int numusehash (const Table *t, int *nums, int *pnasize) {
L0248 int totaluse = 0; /* total number of elements */
L0249 int ause = 0; /* summation of `nums' */
L0250 int i = sizenode(t);
L0251 while (i--) {
L0252 Node *n = &t->node[i];
L0253 if (!ttisnil(gval(n))) {
L0254 ause += countint(key2tval(n), nums);
L0255 totaluse++;
L0256 }
L0257 }
L0258 *pnasize += ause;
L0259 return totaluse;
L0260 }
L0261 
L0262 
L0263 static void setarrayvector (lua_State *L, Table *t, int size) {
L0264 int i;
L0265 luaM_reallocvector(L, t->array, t->sizearray, size, TValue);
L0266 for (i=t->sizearray; i<size; i++)
L0267 setnilvalue(&t->array[i]);
L0268 t->sizearray = size;
L0269 }
L0270 
L0271 
L0272 static void setnodevector (lua_State *L, Table *t, int size) {
L0273 int lsize;
L0274 if (size == 0) { /* no elements to hash part? */
L0275 t->node = cast(Node *, dummynode); /* use common `dummynode' */
L0276 lsize = 0;
L0277 }
L0278 else {
L0279 int i;
L0280 lsize = ceillog2(size);
L0281 if (lsize > MAXBITS)
L0282 luaG_runerror(L, "table overflow");
L0283 size = twoto(lsize);
L0284 t->node = luaM_newvector(L, size, Node);
L0285 for (i=0; i<size; i++) {
L0286 Node *n = gnode(t, i);
L0287 gnext(n) = NULL;
L0288 setnilvalue(gkey(n));
L0289 setnilvalue(gval(n));
L0290 }
L0291 }
L0292 t->lsizenode = cast_byte(lsize);
L0293 t->lastfree = gnode(t, size); /* all positions are free */
L0294 }
L0295 
L0296 
L0297 static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
L0298 int i;
L0299 int oldasize = t->sizearray;
L0300 int oldhsize = t->lsizenode;
L0301 Node *nold = t->node; /* save old hash ... */
L0302 if (nasize > oldasize) /* array part must grow? */
L0303 setarrayvector(L, t, nasize);
L0304 /* create new hash part with appropriate size */
L0305 setnodevector(L, t, nhsize); 
L0306 if (nasize < oldasize) { /* array part must shrink? */
L0307 t->sizearray = nasize;
L0308 /* re-insert elements from vanishing slice */
L0309 for (i=nasize; i<oldasize; i++) {
L0310 if (!ttisnil(&t->array[i]))
L0311 setobjt2t(L, luaH_setnum(L, t, i+1), &t->array[i]);
L0312 }
L0313 /* shrink array */
L0314 luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
L0315 }
L0316 /* re-insert elements from hash part */
L0317 for (i = twoto(oldhsize) - 1; i >= 0; i--) {
L0318 Node *old = nold+i;
L0319 if (!ttisnil(gval(old)))
L0320 setobjt2t(L, luaH_set(L, t, key2tval(old)), gval(old));
L0321 }
L0322 if (nold != dummynode)
L0323 luaM_freearray(L, nold, twoto(oldhsize), Node); /* free old array */
L0324 }
L0325 
L0326 
L0327 void luaH_resizearray (lua_State *L, Table *t, int nasize) {
L0328 int nsize = (t->node == dummynode) ? 0 : sizenode(t);
L0329 resize(L, t, nasize, nsize);
L0330 }
L0331 
L0332 
L0333 static void rehash (lua_State *L, Table *t, const TValue *ek) {
L0334 int nasize, na;
L0335 int nums[MAXBITS +1]; /* nums[i] = number of keys between 2^(i-1) and 2^i */
L0336 int i;
L0337 int totaluse;
L0338 for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* reset counts */
L0339 nasize = numusearray(t, nums); /* count keys in array part */
L0340 totaluse = nasize; /* all those keys are integer keys */
L0341 totaluse += numusehash(t, nums, &nasize); /* count keys in hash part */
L0342 /* count extra key */
L0343 nasize += countint(ek, nums);
L0344 totaluse++;
L0345 /* compute new size for array part */
L0346 na = computesizes(nums, &nasize);
L0347 /* resize the table to new computed sizes */
L0348 resize(L, t, nasize, totaluse - na);
L0349 }
L0350 
L0351 
L0352 
L0353 /*
L0354 ** }=============================================================
L0355 */
L0356 
L0357 
L0358 Table *luaH_new (lua_State *L, int narray, int nhash) {
L0359 Table *t = luaM_new(L, Table);
L0360 luaC_link(L, obj2gco(t), LUA_TTABLE);
L0361 t->metatable = NULL;
L0362 t->flags = cast_byte(~0);
L0363 /* temporary values (kept only if some malloc fails) */
L0364 t->array = NULL;
L0365 t->sizearray = 0;
L0366 t->lsizenode = 0;
L0367 t->node = cast(Node *, dummynode);
L0368 setarrayvector(L, t, narray);
L0369 setnodevector(L, t, nhash);
L0370 return t;
L0371 }
L0372 
L0373 
L0374 void luaH_free (lua_State *L, Table *t) {
L0375 if (t->node != dummynode)
L0376 luaM_freearray(L, t->node, sizenode(t), Node);
L0377 luaM_freearray(L, t->array, t->sizearray, TValue);
L0378 luaM_free(L, t);
L0379 }
L0380 
L0381 
L0382 static Node *getfreepos (Table *t) {
L0383 while (t->lastfree-- > t->node) {
L0384 if (ttisnil(gkey(t->lastfree)))
L0385 return t->lastfree;
L0386 }
L0387 return NULL; /* could not find a free place */
L0388 }
L0389 
L0390 
L0391 
L0392 /*
L0393 ** inserts a new key into a hash table; first, check whether key's main 
L0394 ** position is free. If not, check whether colliding node is in its main 
L0395 ** position or not: if it is not, move colliding node to an empty place and 
L0396 ** put new key in its main position; otherwise (colliding node is in its main 
L0397 ** position), new key goes to an empty position. 
L0398 */
L0399 static TValue *newkey (lua_State *L, Table *t, const TValue *key) {
L0400 Node *mp = mainposition(t, key);
L0401 if (!ttisnil(gval(mp)) || mp == dummynode) {
L0402 Node *othern;
L0403 Node *n = getfreepos(t); /* get a free place */
L0404 if (n == NULL) { /* cannot find a free place? */
L0405 rehash(L, t, key); /* grow table */
L0406 return luaH_set(L, t, key); /* re-insert key into grown table */
L0407 }
L0408 lua_assert(n != dummynode);
L0409 othern = mainposition(t, key2tval(mp));
L0410 if (othern != mp) { /* is colliding node out of its main position? */
L0411 /* yes; move colliding node into free position */
L0412 while (gnext(othern) != mp) othern = gnext(othern); /* find previous */
L0413 gnext(othern) = n; /* redo the chain with `n' in place of `mp' */
L0414 *n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
L0415 gnext(mp) = NULL; /* now `mp' is free */
L0416 setnilvalue(gval(mp));
L0417 }
L0418 else { /* colliding node is in its own main position */
L0419 /* new node will go into free position */
L0420 gnext(n) = gnext(mp); /* chain new position */
L0421 gnext(mp) = n;
L0422 mp = n;
L0423 }
L0424 }
L0425 gkey(mp)->value = key->value; gkey(mp)->tt = key->tt;
L0426 luaC_barriert(L, t, key);
L0427 lua_assert(ttisnil(gval(mp)));
L0428 return gval(mp);
L0429 }
L0430 
L0431 
L0432 /*
L0433 ** search function for integers
L0434 */
L0435 const TValue *luaH_getnum (Table *t, int key) {
L0436 /* (1 <= key && key <= t->sizearray) */
L0437 if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
L0438 return &t->array[key-1];
L0439 else {
L0440 lua_Number nk = cast_num(key);
L0441 Node *n = hashnum(t, nk);
L0442 do { /* check whether `key' is somewhere in the chain */
L0443 if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
L0444 return gval(n); /* that's it */
L0445 else n = gnext(n);
L0446 } while (n);
L0447 return luaO_nilobject;
L0448 }
L0449 }
L0450 
L0451 
L0452 /*
L0453 ** search function for strings
L0454 */
L0455 const TValue *luaH_getstr (Table *t, TString *key) {
L0456 Node *n = hashstr(t, key);
L0457 do { /* check whether `key' is somewhere in the chain */
L0458 if (ttisstring(gkey(n)) && rawtsvalue(gkey(n)) == key)
L0459 return gval(n); /* that's it */
L0460 else n = gnext(n);
L0461 } while (n);
L0462 return luaO_nilobject;
L0463 }
L0464 
L0465 
L0466 /*
L0467 ** main search function
L0468 */
L0469 const TValue *luaH_get (Table *t, const TValue *key) {
L0470 switch (ttype(key)) {
L0471 case LUA_TNIL: return luaO_nilobject;
L0472 case LUA_TSTRING: return luaH_getstr(t, rawtsvalue(key));
L0473 case LUA_TNUMBER: {
L0474 int k;
L0475 lua_Number n = nvalue(key);
L0476 lua_number2int(k, n);
L0477 if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */
L0478 return luaH_getnum(t, k); /* use specialized version */
L0479 /* else go through */
L0480 }
L0481 default: {
L0482 Node *n = mainposition(t, key);
L0483 do { /* check whether `key' is somewhere in the chain */
L0484 if (luaO_rawequalObj(key2tval(n), key))
L0485 return gval(n); /* that's it */
L0486 else n = gnext(n);
L0487 } while (n);
L0488 return luaO_nilobject;
L0489 }
L0490 }
L0491 }
L0492 
L0493 
L0494 TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
L0495 const TValue *p = luaH_get(t, key);
L0496 t->flags = 0;
L0497 if (p != luaO_nilobject)
L0498 return cast(TValue *, p);
L0499 else {
L0500 if (ttisnil(key)) luaG_runerror(L, "table index is nil");
L0501 else if (ttisnumber(key) && luai_numisnan(nvalue(key)))
L0502 luaG_runerror(L, "table index is NaN");
L0503 return newkey(L, t, key);
L0504 }
L0505 }
L0506 
L0507 
L0508 TValue *luaH_setnum (lua_State *L, Table *t, int key) {
L0509 const TValue *p = luaH_getnum(t, key);
L0510 if (p != luaO_nilobject)
L0511 return cast(TValue *, p);
L0512 else {
L0513 TValue k;
L0514 setnvalue(&k, cast_num(key));
L0515 return newkey(L, t, &k);
L0516 }
L0517 }
L0518 
L0519 
L0520 TValue *luaH_setstr (lua_State *L, Table *t, TString *key) {
L0521 const TValue *p = luaH_getstr(t, key);
L0522 if (p != luaO_nilobject)
L0523 return cast(TValue *, p);
L0524 else {
L0525 TValue k;
L0526 setsvalue(L, &k, key);
L0527 return newkey(L, t, &k);
L0528 }
L0529 }
L0530 
L0531 
L0532 static int unbound_search (Table *t, unsigned int j) {
L0533 unsigned int i = j; /* i is zero or a present index */
L0534 j++;
L0535 /* find `i' and `j' such that i is present and j is not */
L0536 while (!ttisnil(luaH_getnum(t, j))) {
L0537 i = j;
L0538 j *= 2;
L0539 if (j > cast(unsigned int, MAX_INT)) { /* overflow? */
L0540 /* table was built with bad purposes: resort to linear search */
L0541 i = 1;
L0542 while (!ttisnil(luaH_getnum(t, i))) i++;
L0543 return i - 1;
L0544 }
L0545 }
L0546 /* now do a binary search between them */
L0547 while (j - i > 1) {
L0548 unsigned int m = (i+j)/2;
L0549 if (ttisnil(luaH_getnum(t, m))) j = m;
L0550 else i = m;
L0551 }
L0552 return i;
L0553 }
L0554 
L0555 
L0556 /*
L0557 ** Try to find a boundary in table `t'. A `boundary' is an integer index
L0558 ** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
L0559 */
L0560 int luaH_getn (Table *t) {
L0561 unsigned int j = t->sizearray;
L0562 if (j > 0 && ttisnil(&t->array[j - 1])) {
L0563 /* there is a boundary in the array part: (binary) search for it */
L0564 unsigned int i = 0;
L0565 while (j - i > 1) {
L0566 unsigned int m = (i+j)/2;
L0567 if (ttisnil(&t->array[m - 1])) j = m;
L0568 else i = m;
L0569 }
L0570 return i;
L0571 }
L0572 /* else must find a boundary in hash part */
L0573 else if (t->node == dummynode) /* hash part is empty? */
L0574 return j; /* that is easy... */
L0575 else return unbound_search(t, j);
L0576 }
L0577 
L0578 
L0579 
L0580 #if defined(LUA_DEBUG)
L0581 
L0582 Node *luaH_mainposition (const Table *t, const TValue *key) {
L0583 return mainposition(t, key);
L0584 }
L0585 
L0586 int luaH_isdummy (Node *n) { return n == dummynode; }
L0587 
L0588 #endif

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