一、创建一个table(lapi.c, line:666)
LUA_API void lua_createtable (lua_State *L, int narray, int nrec) {
Table *t;
lua_lock(L);
luaC_checkGC(L);
t = luaH_new(L);
sethvalue(L, L->top, t);
api_incr_top(L);
if (narray > 0 || nrec > 0)
luaH_resize(L, t, narray, nrec);
lua_unlock(L);
}1.luaH_new: 创建一个table(ltable.c, line:368)
Table *luaH_new (lua_State *L) {
Table *t = &luaC_newobj(L, LUA_TTABLE, sizeof(Table), NULL, 0)->h;
t->metatable = NULL;
t->flags = cast_byte(~0);
t->array = NULL;
t->sizearray = 0;
setnodevector(L, t, 0);
return t;
}
初始化下面几个重要属性
1.t->array = NULL; /*数组为空*/
2.t->sizearray = 0; /*数组长度为0*/
3.t->node = cast(Node *, dummynode); /* use common `dummynode' */
4.t->lsizenode = cast_byte(lsize); /*hash 节点链表长度为0 */
5.t->lastfree = gnode(t, size); /* all positions are free */
2.luaH_resize(ltable.c, line:304): 根据narray和nrec的长度来决定是否要resize
a.resize分两部分：array和hash部分
array部分：
如果需要扩大，则在最后部分增加空节点；
如果需要减少，把超出新的总量部分的不为空的节点插入到hash部分里，再减少数量。
hash部分：
把先保存一下旧的节点列表头指针，设置hash列表部分的大小后，重新把旧的节目插入到hash部分。
注意：
调用luaM_reallocvector时，实际调用的是void * frealloc (void *ud, void *ptr, size_t osize, size_t nsize)
frealloc是初始化是在lua_State *L = lua_newstate(l_alloc, NULL)，l_alloc为frealloc最后调用分配的地方
1.会创建一个大小为nsize的数据块，而不管osize是什么。
2.如果nsize为0，则释放这个数据块
3.如果osize和nsize都为0，则什么都不做
void luaH_resize (lua_State *L, Table *t, int nasize, int nhsize) {
int i;
int oldasize = t->sizearray;
int oldhsize = t->lsizenode;
Node *nold = t->node; /* save old hash ... */
if (nasize > oldasize) /* array part must grow? */
setarrayvector(L, t, nasize);
/* create new hash part with appropriate size */
setnodevector(L, t, nhsize);
if (nasize < oldasize) { /* array part must shrink? */
t->sizearray = nasize;
/* re-insert elements from vanishing slice */
/* 如果数组为{1,2,3,nil,5,6}，会把5和6设置到hash部分去*/
for (i=nasize; i<oldasize; i++) {
if (!ttisnil(&t->array[i]))
luaH_setint(L, t, i + 1, &t->array[i]);
}
/* shrink array */
luaM_reallocvector(L, t->array, oldasize, nasize, TValue);
}
/* re-insert elements from hash part */
for (i = twoto(oldhsize) - 1; i >= 0; i--) {
Node *old = nold+i;
if (!ttisnil(gval(old))) {
/* doesn't need barrier/invalidate cache, as entry was
already present in the table */
setobjt2t(L, luaH_set(L, t, gkey(old)), gval(old));
}
}
if (!isdummy(nold))
luaM_freearray(L, nold, cast(size_t, twoto(oldhsize))); /* free old array */
}
/* 重置array部分大小，变长部分的节点全部置为nil */
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;
} /* 重置hash部分大小,大小使用log底数来存，最后根据底数计算2的幂，设置大小和最后一个空的节点 */
static void setnodevector (lua_State *L, Table *t, int size) {
int lsize;
if (size == 0) { /* no elements to hash part? */
t->node = cast(Node *, dummynode); /* use common `dummynode' */
lsize = 0;
}
else {
int i;
lsize = luaO_ceillog2(size);
if (lsize > MAXBITS)
luaG_runerror(L, "table overflow");
size = twoto(lsize);
t->node = luaM_newvector(L, size, Node);
for (i=0; i<size; i++) {
Node *n = gnode(t, i);
gnext(n) = NULL;
setnilvalue(gkey(n));
setnilvalue(gval(n));
}
}
t->lsizenode = cast_byte(lsize);
t->lastfree = gnode(t, size); /* all positions are free */
}
二、设置key和value(lapi.c, line:741)
LUA_API void lua_settable (lua_State *L, int idx) {
StkId t;
lua_lock(L);
api_checknelems(L, 2);
t = index2adr(L, idx);
api_checkvalidindex(L, t);
luaV_settable(L, t, L->top - 2, L->top - 1);
L->top -= 2; /* pop index and value */
lua_unlock(L);
}1.luaV_settable(lvm.c, line:141):根据key和value设置
void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
int loop;
TValue temp;
for (loop = 0; loop < MAXTAGLOOP; loop++) {
const TValue *tm;
if (ttistable(t)) { /* `t' is a table? */
Table *h = hvalue(t);
TValue *oldval = luaH_set(L, h, key); /* do a primitive set */
if (!ttisnil(oldval) || /* result is no nil? */
(tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL) { /* or no TM? */
setobj2t(L, oldval, val);
h->flags = 0;
luaC_barriert(L, h, val);
return;
}
/* else will try the tag method */
}
else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_NEWINDEX)))
luaG_typeerror(L, t, "index");
if (ttisfunction(tm)) {
callTM(L, tm, t, key, val);
return;
}
/* else repeat with `tm' */
setobj(L, &temp, tm); /* avoid pointing inside table (may rehash) */
t = &temp;
}
luaG_runerror(L, "loop in settable");
}2.luaH_set(ltable.c, line:510)：设置前,先get,检查是否已经存在,存在即返回;如果不存在，则通过newkey创建一个新key并返回新的节点
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);
}三、根据key值获取内容luaH_get(ltable.c, line:481)
const TValue *luaH_get (Table *t, const TValue *key) {
switch (ttype(key)) {
case LUA_TNIL: return luaO_nilobject;
case LUA_TSHRSTR: return luaH_getstr(t, rawtsvalue(key));
case 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_getint(t, k); /* use specialized version */
/* else go through */
}
default: {
Node *n = mainposition(t, key);
do { /* check whether `key' is somewhere in the chain */
if (luaV_rawequalobj(gkey(n), key))
return gval(n); /* that's it */
else n = gnext(n);
} while (n);
return luaO_nilobject;
}
}
}1.luaH_getstr(ltable.c, line:466)
当key为LUA_TSHRSTR时，调用luaH_getstr
对于hash部分，需要在node的链表里搜索是否存在；
如果不存在，看看能否在链表中是否有空的位置；
如果有返回；否则需要rehash再找合适位置存储；
/*
** search function for short strings
*/
const TValue *luaH_getstr (Table *t, TString *key) {
Node *n = hashstr(t, key);
lua_assert(key->tsv.tt == LUA_TSHRSTR);
do { /* check whether `key' is somewhere in the chain */
if (ttisshrstring(gkey(n)) && eqshrstr(rawtsvalue(gkey(n)), key))
return gval(n); /* that's it */
else n = gnext(n);
} while (n);
return luaO_nilobject;
}2.luaH_getint(ltable.c, line:446)
当key为LUA_TNUMBER时，调用luaH_getint
如果key的值大于1并且小于数组部分长度，就在数组部分查找并返回
否则，就去hash部分查找
/*
** search function for integers
*/
const TValue *luaH_getint (Table *t, int key) {
/* (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;
}
}3.数组下标的hash值计算
先把n转换为double，把n的内存结构前后各半拆开做加法得到的就是为hash值
#define luai_hashnum(i,n) \
{ volatile union luai_Cast u; u.l_d = (n) + 1.0; /* avoid -0 */ \
(i) = u.l_p[0]; (i) += u.l_p[1]; } /* add double bits for his hash */
/*
** hash for lua_Numbers
*/
static Node *hashnum (const Table *t, lua_Number n) {
int i;
luai_hashnum(i, n);
if (i < 0) {
if (cast(unsigned int, i) == 0u - i) /* use unsigned to avoid overflows */
i = 0; /* handle INT_MIN */
i = -i; /* must be a positive value */
}
return hashmod(t, i);
}
4.当key都不是LUA_TSHRSTR，LUA_TNIL，LUA_TNUMBER时，就调用mainposition获取它的地址
四、luaH_newkey(ltable.c, line:405)，这个篇幅比较大，具体参考另一篇文章：Lua源码之Table - 细说Hash部分
创建一个新的key(对于新的key,会调用2次luaH_set:第一次是在luaV_settable，第二次是在newkey函数rehash后)
TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
Node *mp;
if (ttisnil(key)) luaG_runerror(L, "table index is nil");
else if (ttisnumber(key) && luai_numisnan(L, nvalue(key)))
luaG_runerror(L, "table index is NaN");
mp = mainposition(t, key);
if (!ttisnil(gval(mp)) || isdummy(mp)) { /* main position is taken? */
Node *othern;
Node *n = getfreepos(t); /* get a free place */
if (n == NULL) { /* cannot find a free place? */
rehash(L, t, key); /* grow table */
/* whatever called 'newkey' take care of TM cache and GC barrier */
return luaH_set(L, t, key); /* insert key into grown table */
}
lua_assert(!isdummy(n));
othern = mainposition(t, gkey(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_barrierback(L, obj2gco(t), key);
lua_assert(ttisnil(gval(mp)));
return gval(mp);
}