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nodemcu-firmware/app/lua/ltable.c

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/*
** $Id: ltable.c,v 2.32.1.2 2007/12/28 15:32:23 roberto Exp $
** Lua tables (hash)
** See Copyright Notice in lua.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 at
** least half the slots between 0 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.
*/
#define ltable_c
#define LUA_CORE
#include "lua.h"
#include <math.h>
#include <string.h>
#include "ldebug.h"
#include "ldo.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "ltable.h"
#include "lstring.h"
/*
** max size of array part is 2^MAXBITS
*/
#if LUAI_BITSINT > 26
#define MAXBITS 26
#else
#define MAXBITS (LUAI_BITSINT-2)
#endif
#define MAXASIZE (1 << MAXBITS)
#define hashpow2(t,n) (gnode(t, lmod((n), sizenode(t))))
#define hashstr(t,str) hashpow2(t, (str)->tsv.hash)
#define hashboolean(t,p) hashpow2(t, p)
/*
** 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, IntPoint(p))
/*
** number of ints inside a lua_Number
*/
#define numints cast_int(sizeof(lua_Number)/sizeof(int))
static const TValue* rotable_findentry(ROTable *rotable, TString *key, unsigned *ppos);
static void rotable_next_helper(lua_State *L, ROTable *pentries, int pos,
TValue *key, TValue *val);
static void rotable_next(lua_State *L, ROTable *rotable, TValue *key, TValue *val);
#define dummynode (&dummynode_)
static const Node dummynode_ = {
{LUA_TVALUE_NIL}, /* value */
{LUA_TKEY_NIL} /* key */
};
/*
** hash for lua_Numbers
*/
static Node *hashnum (const Table *t, lua_Number n) {
unsigned int a[numints];
int i;
if (luai_numeq(n, 0)) /* avoid problems with -0 */
return gnode(t, 0);
memcpy(a, &n, sizeof(a));
for (i = 1; i < numints; i++) a[0] += a[i];
return hashmod(t, a[0]);
}
/*
** 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_TNUMBER:
return hashnum(t, nvalue(key));
case LUA_TSTRING:
return hashstr(t, rawtsvalue(key));
case LUA_TBOOLEAN:
return hashboolean(t, bvalue(key));
case LUA_TLIGHTUSERDATA:
case LUA_TLIGHTFUNCTION:
return hashpointer(t, pvalue(key));
case LUA_TROTABLE:
return hashpointer(t, hvalue(key));
default:
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, -1 otherwise.
*/
static int arrayindex (const TValue *key) {
if (ttisnumber(key)) {
lua_Number n = nvalue(key);
int k;
lua_number2int(k, n);
if (luai_numeq(cast_num(k), n))
return k;
}
return -1; /* `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 signalled by -1.
*/
static int findindex (lua_State *L, Table *t, StkId key) {
int i;
if (ttisnil(key)) return -1; /* first iteration */
i = arrayindex(key);
if (0 < i && i <= t->sizearray) /* is `key' inside array part? */
return i-1; /* yes; that's the index (corrected to C) */
else {
Node *n = mainposition(t, key);
do { /* check whether `key' is somewhere in the chain */
/* key may be dead already, but it is ok to use it in `next' */
if (luaO_rawequalObj(key2tval(n), key) ||
(ttype(gkey(n)) == LUA_TDEADKEY && iscollectable(key) &&
gcvalue(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 + t->sizearray;
}
else n = gnext(n);
} while (n);
luaG_runerror(L, "invalid key to " LUA_QL("next")); /* key not found */
return 0; /* to avoid warnings */
}
}
int luaH_next (lua_State *L, Table *t, StkId key) {
int i;
if (isrotable(t)) {
rotable_next(L, (ROTable *) t, key, key+1);
return ttisnil(key) ? 0 : 1;
}
i = findindex(L, t, key); /* find original element */
for (i++; i < t->sizearray; i++) { /* try first array part */
if (!ttisnil(&t->array[i])) { /* a non-nil value? */
setnvalue(key, cast_num(i+1));
setobj2s(L, key+1, &t->array[i]);
return 1;
}
}
for (i -= t->sizearray; i < sizenode(t); i++) { /* then hash part */
if (!ttisnil(gval(gnode(t, i)))) { /* a non-nil value? */
setobj2s(L, key, key2tval(gnode(t, i)));
setobj2s(L, key+1, gval(gnode(t, i)));
return 1;
}
}
return 0; /* no more elements */
}
/*
** {=============================================================
** Rehash
** ==============================================================
*/
static int computesizes (int nums[], int *narray) {
int i;
int twotoi; /* 2^i */
int a = 0; /* number of elements smaller than 2^i */
int na = 0; /* number of elements to go to array part */
int n = 0; /* optimal size for array part */
for (i = 0, twotoi = 1; twotoi/2 < *narray; i++, twotoi *= 2) {
if (nums[i] > 0) {
a += nums[i];
if (a > twotoi/2) { /* more than half elements present? */
n = twotoi; /* optimal size (till now) */
na = a; /* all elements smaller than n will go to array part */
}
}
if (a == *narray) break; /* all elements already counted */
}
*narray = n;
lua_assert(*narray/2 <= na && na <= *narray);
return na;
}
static int countint (const TValue *key, int *nums) {
int k = arrayindex(key);
if (0 < k && k <= MAXASIZE) { /* is `key' an appropriate array index? */
nums[ceillog2(k)]++; /* count as such */
return 1;
}
else
return 0;
}
static int numusearray (const Table *t, int *nums) {
int lg;
int ttlg; /* 2^lg */
int ause = 0; /* summation of `nums' */
int i = 1; /* count to traverse all array keys */
for (lg=0, ttlg=1; lg<=MAXBITS; lg++, ttlg*=2) { /* for each slice */
int lc = 0; /* counter */
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, int *nums, int *pnasize) {
int totaluse = 0; /* total number of elements */
int ause = 0; /* summation of `nums' */
int i = sizenode(t);
while (i--) {
Node *n = &t->node[i];
if (!ttisnil(gval(n))) {
ause += countint(key2tval(n), nums);
totaluse++;
}
}
*pnasize += ause;
return totaluse;
}
static void setarrayvector (lua_State *L, Table *t, int size) {
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 Node *getfreepos (Table *t) {
while (t->lastfree-- > t->node) {
if (ttisnil(gkey(t->lastfree)))
return t->lastfree;
}
return NULL; /* could not find a free place */
}
static void resizenodevector (lua_State *L, Table *t, int oldsize, int newsize) {
int lsize;
if (newsize == 0) { /* no elements to hash part? */
t->node = cast(Node *, dummynode); /* use common `dummynode' */
lsize = 0;
}
else {
Node *node = t->node;
int i;
lsize = ceillog2(newsize);
if (lsize > MAXBITS)
luaG_runerror(L, "table overflow");
newsize = twoto(lsize);
if (node == dummynode) {
oldsize = 0;
node = NULL; /* don't try to realloc `dummynode' pointer. */
}
luaM_reallocvector(L, node, oldsize, newsize, Node);
t->node = node;
for (i=oldsize; i<newsize; i++) {
Node *n = gnode(t, i);
gnext(n) = NULL;
setnilvalue(gkey(n));
setnilvalue(gval(n));
}
}
t->lsizenode = cast_byte(lsize);
t->lastfree = gnode(t, newsize); /* reset lastfree to end of table. */
}
static Node *find_prev_node(Node *mp, Node *next) {
Node *prev = mp;
while (prev != NULL && gnext(prev) != next) prev = gnext(prev);
return prev;
}
/*
** move a node from it's old position to it's new position during a rehash;
** first, check whether the moving node'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 moving node in its main position; otherwise
** (colliding node is in its main position), moving node goes to an empty position.
*/
static int move_node (lua_State *L, Table *t, Node *node) {
(void)L;
Node *mp = mainposition(t, key2tval(node));
/* if node is in it's main position, don't need to move node. */
if (mp == node) return 1;
/* if node is in it's main position's chain, don't need to move node. */
if (find_prev_node(mp, node) != NULL) return 1;
/* is main position is free? */
if (!ttisnil(gval(mp)) || mp == dummynode) {
/* no; move main position node if it is out of its main position */
Node *othermp;
othermp = mainposition(t, key2tval(mp));
if (othermp != mp) { /* is colliding node out of its main position? */
/* yes; swap colliding node with the node that is being moved. */
Node *prev;
Node tmp;
tmp = *node;
prev = find_prev_node(othermp, mp); /* find previous */
if (prev != NULL) gnext(prev) = node; /* redo the chain with `n' in place of `mp' */
*node = *mp; /* copy colliding node into free pos. (mp->next also goes) */
*mp = tmp;
return (prev != NULL) ? 1 : 0; /* is colliding node part of its main position chain? */
}
else { /* colliding node is in its own main position */
/* add node to main position's chain. */
gnext(node) = gnext(mp); /* chain new position */
gnext(mp) = node;
}
}
else { /* main position is free, move node */
*mp = *node;
gnext(node) = NULL;
setnilvalue(gkey(node));
setnilvalue(gval(node));
}
return 1;
}
static int move_number (lua_State *L, Table *t, Node *node) {
(void)L;
int key;
lua_Number n = nvalue(key2tval(node));
lua_number2int(key, n);
if (luai_numeq(cast_num(key), nvalue(key2tval(node)))) {/* index is int? */
/* (1 <= key && key <= t->sizearray) */
if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray)) {
setobjt2t(L, &t->array[key-1], gval(node));
setnilvalue(gkey(node));
setnilvalue(gval(node));
return 1;
}
}
return 0;
}
static void resize_hashpart (lua_State *L, Table *t, int nhsize) {
int i;
int lsize=0;
int oldhsize = (t->node != dummynode) ? twoto(t->lsizenode) : 0;
if (nhsize > 0) { /* round new hashpart size up to next power of two. */
lsize=ceillog2(nhsize);
if (lsize > MAXBITS)
luaG_runerror(L, "table overflow");
}
nhsize = twoto(lsize);
/* grow hash part to new size. */
if (oldhsize < nhsize)
resizenodevector(L, t, oldhsize, nhsize);
else { /* hash part might be shrinking */
if (nhsize > 0) {
t->lsizenode = cast_byte(lsize);
t->lastfree = gnode(t, nhsize); /* reset lastfree back to end of table. */
}
else { /* new hashpart size is zero. */
resizenodevector(L, t, oldhsize, nhsize);
return;
}
}
/* break old chains, try moving int keys to array part and compact keys into new hashpart */
for (i = 0; i < oldhsize; i++) {
Node *old = gnode(t, i);
gnext(old) = NULL;
if (ttisnil(gval(old))) { /* clear nodes with nil values. */
setnilvalue(gkey(old));
continue;
}
if (ttisnumber(key2tval(old))) { /* try moving the int keys into array part. */
if(move_number(L, t, old))
continue;
}
if (i >= nhsize) { /* move all valid keys to indices < nhsize. */
Node *n = getfreepos(t); /* get a free place */
lua_assert(n != dummynode && n != NULL);
*n = *old;
}
}
/* shrink hash part */
if (oldhsize > nhsize)
resizenodevector(L, t, oldhsize, nhsize);
/* move nodes to their new mainposition and re-create node chains */
for (i = 0; i < nhsize; i++) {
Node *curr = gnode(t, i);
if (!ttisnil(gval(curr)))
while (move_node(L, t, curr) == 0);
}
}
static void resize (lua_State *L, Table *t, int nasize, int nhsize) {
int i;
int oldasize = t->sizearray;
if (nasize > oldasize) /* array part must grow? */
setarrayvector(L, t, nasize);
if (t->node != dummynode || nhsize>0)
resize_hashpart(L, t, nhsize);
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]))
setobjt2t(L, luaH_setnum(L, t, i+1), &t->array[i]);
}
/* shrink array */
luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
}
}
void luaH_resizearray (lua_State *L, Table *t, int nasize) {
int nsize = (t->node == dummynode) ? 0 : sizenode(t);
resize(L, t, nasize, nsize);
}
static void rehash (lua_State *L, Table *t, const TValue *ek) {
int nasize, na;
int nums[MAXBITS+1]; /* nums[i] = number of keys between 2^(i-1) and 2^i */
int i;
int totaluse;
for (i=0; i<=MAXBITS; i++) nums[i] = 0; /* reset counts */
nasize = numusearray(t, nums); /* count keys in array part */
totaluse = nasize; /* all those keys are integer keys */
totaluse += numusehash(t, nums, &nasize); /* count keys in hash part */
/* count extra key */
nasize += countint(ek, nums);
totaluse++;
/* compute new size for array part */
na = computesizes(nums, &nasize);
/* resize the table to new computed sizes */
resize(L, t, nasize, totaluse - na);
}
/*
** }=============================================================
*/
Table *luaH_new (lua_State *L, int narray, int nhash) {
Table *t = luaM_new(L, Table);
luaC_link(L, obj2gco(t), LUA_TTABLE);
sethvalue2s(L, L->top, t); /* put table on stack */
incr_top(L);
t->metatable = NULL;
t->flags = cast_byte(~0);
/* temporary values (kept only if some malloc fails) */
t->array = NULL;
t->sizearray = 0;
t->lsizenode = 0;
t->node = cast(Node *, dummynode);
setarrayvector(L, t, narray);
resizenodevector(L, t, 0, nhash);
L->top--; /* remove table from stack */
return t;
}
void luaH_free (lua_State *L, Table *t) {
if (t->node != dummynode)
luaM_freearray(L, t->node, sizenode(t), Node);
luaM_freearray(L, t->array, t->sizearray, TValue);
luaM_free(L, t);
}
/*
** 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.
*/
static TValue *newkey (lua_State *L, Table *t, const TValue *key) {
Node *mp = mainposition(t, key);
if (!ttisnil(gval(mp)) || mp == dummynode) {
Node *othern;
Node *n = getfreepos(t); /* get a free place */
if (n == NULL) { /* cannot find a free place? */
rehash(L, t, key); /* grow table */
return luaH_set(L, t, key); /* re-insert key into grown table */
}
lua_assert(n != dummynode);
othern = mainposition(t, key2tval(mp));
if (othern != mp) { /* is colliding node out of its main position? */
/* yes; move colliding node into free position */
while (gnext(othern) != mp) othern = gnext(othern); /* find previous */
gnext(othern) = n; /* redo the chain with `n' in place of `mp' */
*n = *mp; /* copy colliding node into free pos. (mp->next also goes) */
gnext(mp) = NULL; /* now `mp' is free */
setnilvalue(gval(mp));
}
else { /* colliding node is in its own main position */
/* new node will go into free position */
gnext(n) = gnext(mp); /* chain new position */
gnext(mp) = n;
mp = n;
}
}
setobj2t(L, gkey(mp), key);
luaC_barriert(L, t, key);
lua_assert(ttisnil(gval(mp)));
return gval(mp);
}
/*
** search function for integers
*/
const TValue *luaH_getnum (Table *t, int key) {
if (isrotable(t))
return luaO_nilobject;
/* (1 <= key && key <= t->sizearray) */
if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
return &t->array[key-1];
else {
lua_Number nk = cast_num(key);
Node *n = hashnum(t, nk);
do { /* check whether `key' is somewhere in the chain */
if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
return gval(n); /* that's it */
else n = gnext(n);
} while (n);
return luaO_nilobject;
}
}
/*
** search function for strings
*/
const TValue *luaH_getstr (Table *t, TString *key) {
if (isrotable(t)) {
if (key->tsv.len>LUA_MAX_ROTABLE_NAME)
return luaO_nilobject;
return rotable_findentry((ROTable*) t, key, NULL);
}
Node *n = hashstr(t, key);
do { /* check whether `key' is somewhere in the chain */
if (ttisstring(gkey(n)) && rawtsvalue(gkey(n)) == key)
return gval(n); /* that's it */
else n = gnext(n);
} while (n);
return luaO_nilobject;
}
/*
** main search function
*/
const TValue *luaH_get (Table *t, const TValue *key) {
int type = ttype(key);
if (type == LUA_TNIL)
return luaO_nilobject;
if (type == LUA_TSTRING)
return luaH_getstr(t, rawtsvalue(key));
if (isrotable(t))
return luaO_nilobject;
if (type == LUA_TNUMBER) {
int k;
lua_Number n = nvalue(key);
lua_number2int(k, n);
if (luai_numeq(cast_num(k), nvalue(key))) /* index is int? */
return luaH_getnum(t, k); /* use specialized version */
}
/* default */
Node *n = mainposition(t, key);
do { /* check whether `key' is somewhere in the chain */
if (luaO_rawequalObj(key2tval(n), key))
return gval(n); /* that's it */
else n = gnext(n);
} while (n);
return luaO_nilobject;
}
TValue *luaH_set (lua_State *L, Table *t, const TValue *key) {
const TValue *p;
if (isrotable(t))
luaG_runerror(L, "table is readonly");
p = luaH_get(t, key);
t->flags = 0;
if (p != luaO_nilobject)
return cast(TValue *, p);
else {
if (ttisnil(key)) luaG_runerror(L, "table index is nil");
else if (ttisnumber(key) && luai_numisnan(nvalue(key)))
luaG_runerror(L, "table index is NaN");
return newkey(L, t, key);
}
}
TValue *luaH_setnum (lua_State *L, Table *t, int key) {
const TValue *p;
if (isrotable(t))
luaG_runerror(L, "table is readonly");
p = luaH_getnum(t, key);
if (p != luaO_nilobject)
return cast(TValue *, p);
else {
TValue k;
setnvalue(&k, cast_num(key));
return newkey(L, t, &k);
}
}
TValue *luaH_setstr (lua_State *L, Table *t, TString *key) {
const TValue *p;
if (isrotable(t))
luaG_runerror(L, "table is readonly");
p = luaH_getstr(t, key);
if (p != luaO_nilobject)
return cast(TValue *, p);
else {
TValue k;
setsvalue(L, &k, key);
return newkey(L, t, &k);
}
}
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_getnum(t, j))) {
i = j;
j *= 2;
if (j > cast(unsigned int, MAX_INT)) { /* overflow? */
/* table was built with bad purposes: resort to linear search */
i = 1;
while (!ttisnil(luaH_getnum(t, i))) i++;
return i - 1;
}
}
/* now do a binary search between them */
while (j - i > 1) {
unsigned int m = (i+j)/2;
if (ttisnil(luaH_getnum(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;
if(isrotable(t))
return 0;
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 (t->node == dummynode) /* hash part is empty? */
return j; /* that is easy... */
else return unbound_search(t, j);
}
int luaH_isdummy (Node *n) { return n == dummynode; }
/*
** All keyed ROTable access passes through rotable_findentry(). ROTables
** are simply a list of <key><TValue value> pairs.
**
** The global KeyCache is used to avoid a relatively expensive Flash memory
** vector scan. A simple hash on the key's TString addr and the ROTable
** addr selects the cache line. The line's slots are then scanned for a
** hit.
**
** Unlike the standard hast which uses a prime line count therefore requires
** the use of modulus operation which is expensive on an IoT processor
** without H/W divide. This hash is power of 2 based which might not be
** quite so uniform but can be calcuated without using H/W-based instructions.
**
** If a match is found and the table addresses match, then this entry is
** probed first. In practice the hit-rate here is over 99% so the code
** rarely fails back to doing the linear scan in ROM.
** Note that this hash does a couple of prime multiples and a modulus 2^X
** with is all evaluated in H/W, and adequately randomizes the lookup.
*/
#define LA_LINES 32
#define LA_SLOTS 4
static size_t cache [LA_LINES][LA_SLOTS];
#define HASH(a,b) ((((29*(size_t)(a)) ^ (37*((b)->tsv.hash)))>>4) % LA_LINES)
#define NDX_SHFT 24
#define ADDR_MASK (((size_t) 1<<24)-1)
/*
* Find a string key entry in a rotable and return it. Note that this internally
* uses a null key to denote a metatable search.
*/
static const TValue* rotable_findentry(ROTable *t, TString *key, unsigned *ppos) {
const ROTable_entry *e = cast(const ROTable_entry *, t->entry);
const int tl = getlsizenode(t);
const char *strkey = getstr(key);
size_t *cl = cache[HASH(t, key)];
int i, j = 1, l;
if (!e || gettt(key) != LUA_TSTRING)
return luaO_nilobject;
l = key->tsv.len;
/* scan the ROTable lookaside cache and return if hit found */
for (i=0; i<LA_SLOTS; i++) {
int cl_ndx = cl[i] >> NDX_SHFT;
if ((((size_t)t - cl[i]) & ADDR_MASK) == 0 && cl_ndx < tl &&
strcmp(e[cl_ndx].key, strkey) == 0) {
if (ppos)
*ppos = cl_ndx;
return &e[cl_ndx].value;
}
}
/*
* A lot of search misses are metavalues, but tables typically only have at
* most a couple of them, so these are always put at the front of the table
* in ascending order and the metavalue scan short circuits using a straight
* strcmp()
*/
lu_int32 name4 = *(lu_int32 *) strkey;
if (*(char*)&name4 == '_') {
for(i = 0; i < tl; i++) {
j = strcmp(e[i].key, strkey);
if (j>=0)
break;
}
} else {
/*
* Ordinary (non-meta) keys can be unsorted. This is for legacy compatiblity,
* plus misses are pretty rare in this case. The masked name4 comparison is
* safe 4-byte comparison that nearly always avoids the more costly strcmp()
* for an actual hit validation.
*/
lu_int32 mask4 = l > 2 ? (~0u) : (~0u)>>((3-l)*8);
for(i = 0; i < tl; i++) {
if (((*(lu_int32 *)e[i].key ^ name4) & mask4) != 0)
continue;
j = strcmp(e[i].key, strkey);
if (j==0)
break;
}
}
if (j)
return luaO_nilobject;
if (ppos)
*ppos = i;
/* In the case of a hit, update the lookaside cache */
for (j = LA_SLOTS-1; j>0; j--)
cl[j] = cl[j-1];
cl[0] = ((size_t)t & ADDR_MASK) + (i << NDX_SHFT);
return &e[i].value;
}
static void rotable_next_helper(lua_State *L, ROTable *t, int pos,
TValue *key, TValue *val) {
const ROTable_entry *e = cast(const ROTable_entry *, t->entry);
if (pos < getlsizenode(t)) {
/* Found an entry */
setsvalue(L, key, luaS_new(L, e[pos].key));
setobj2s(L, val, &e[pos].value);
} else {
setnilvalue(key);
setnilvalue(val);
}
}
/* next (used for iteration) */
static void rotable_next(lua_State *L, ROTable *t, TValue *key, TValue *val) {
unsigned keypos = getlsizenode(t);
/* Special case: if key is nil, return the first element of the rotable */
if (ttisnil(key))
rotable_next_helper(L, t, 0, key, val);
else if (ttisstring(key)) {
/* Find the previous key again */
if (ttisstring(key)) {
rotable_findentry(t, rawtsvalue(key), &keypos);
}
/* Advance to next key */
rotable_next_helper(L, t, ++keypos, key, val);
}
}
#if defined(LUA_DEBUG)
Node *luaH_mainposition (const Table *t, const TValue *key) {
return mainposition(t, key);
}
#endif
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