Lua源码学习-lapi.c-优快云博客

本文链接：https://blog.youkuaiyun.com/pyf09/article/details/106963273

/*
** $Id: lapi.c,v 2.257 2015/11/02 18:48:07 roberto Exp $
** Lua API
** See Copyright Notice in lua.h
*/

#define lapi_c
#define LUA_CORE

#include "lprefix.h"

#include <stdarg.h>
#include <string.h>

#include "lua.h"

#include "lapi.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lundump.h"
#include "lvm.h"

/* 使用了字符串自动连接的特性 */
const char lua_ident[] =
"$LuaVersion: " LUA_COPYRIGHT " $"
"$LuaAuthors: " LUA_AUTHORS " $";

/* value at a non-valid index */
#define NONVALIDVALUE cast(TValue *, luaO_nilobject)

/* corresponding(一致) test */
#define isvalid(o) ((o) != luaO_nilobject)

/*
* test for pseudo(伪) index
* 看LUA_REGISTRYINDEX的宏定义便一目了然
*/
#define ispseudo(i) ((i) <= LUA_REGISTRYINDEX)

/* test for upvalue */
#define isupvalue(i) ((i) < LUA_REGISTRYINDEX)

/* test for valid but not pseudo index */
#define isstackindex(i, o) (isvalid(o) && !ispseudo(i))

#define api_checkvalidindex(l,o) api_check(l, isvalid(o), "invalid index")

#define api_checkstackindex(l, i, o) \
api_check(l, isstackindex(i, o), "index not in the stack")

/*
* 按索引值范围解析出对应的slot
* 不同于C的地址索引从0开始，Lua的从1开始
* 可以从这个函数看出一些Lua的设计点
*/
static TValue *index2addr (lua_State *L, int idx) {
CallInfo *ci = L->ci;
if (idx > 0) {
TValue *o = ci->func + idx; /* idx>=1可以推断出ci->func保存了被调用的函数指针 */

/* 下面这个判断，按照正常的来说不应该是idx <= ((ci->top - (ci->func + 1)) + 1)么，
** 为什么没有加1呢，拿笔纸出来画一下就知道top指针可能指向类似数值最后一个元素的下一个元素了哦
** ci->func+1指向第一个数据类的slot, ci->func则是保存了被调用的函数的指针？
*/
api_check(L, idx <= ci->top - (ci->func + 1), "unacceptable index");

//这里说明了L->top这个是一个阈值，实际上不可解析
if (o >= L->top) return NONVALIDVALUE;
else return o;
} else if (!ispseudo(idx)) { /* negative index idx>LUA_REGISTRYINDEX pseudo:伪装，匿名 */
/* 这里用的是L->top和上面的ci->top不一样哦 */
api_check(L, idx != 0 && -idx <= L->top - (ci->func + 1), "invalid index");
return L->top + idx;
} else if (idx == LUA_REGISTRYINDEX) { //预留给C的一个特定slot(注册表(全局表？))
return &G(L)->l_registry;
} else { /* upvalues */
idx = LUA_REGISTRYINDEX - idx;
api_check(L, idx <= MAXUPVAL + 1, "upvalue index too large");
if (ttislcf(ci->func)) /* light C function? */
return NONVALIDVALUE; /* it has no upvalues */
else {
CClosure *func = clCvalue(ci->func);
return (idx <= func->nupvalues) ? &func->upvalue[idx-1] : NONVALIDVALUE;
}
}
}

/*
** to be called by 'lua_checkstack' in protected mode, to grow stack
** capturing memory errors
** 在不超过堆栈尺寸限制的情况下修改堆栈尺寸信息
*/
static void growstack (lua_State *L, void *ud) {
int size = *(int *)ud;
luaD_growstack(L, size);
}

/* 调整堆栈的大小确保空闲的slot数量>=n */
LUA_API int lua_checkstack (lua_State *L, int n) {
int res;
CallInfo *ci = L->ci;
lua_lock(L);
api_check(L, n >= 0, "negative 'n'");
if (L->stack_last - L->top > n) /* stack large enough? */
res = 1; /* yes; check is OK */
else { /* no; need to grow stack */
int inuse = cast_int(L->top - L->stack) + EXTRA_STACK;
if (inuse + n > LUAI_MAXSTACK) /* n值太大了 */
//if (inuse > LUAI_MAXSTACK - n) /* can grow without overflow? */
res = 0; /* no */
else /* try to grow stack */
res = (luaD_rawrunprotected(L, &growstack, &n) == LUA_OK);
}
if (res && ci->top < L->top + n)
ci->top = L->top + n; /* adjust frame top */
lua_unlock(L);
return res;
}

/*
* 从堆栈from移动N个元素到to上
* form,to必须指向同一个虚拟机
*/
LUA_API void lua_xmove (lua_State *from, lua_State *to, int n) {
int i;
if (from == to) return;
lua_lock(to);
api_checknelems(from, n);
api_check(from, G(from) == G(to), "moving among independent states");
api_check(from, to->ci->top - to->top >= n, "stack overflow");
from->top -= n;
for (i = 0; i < n; i++) {
setobj2s(to, to->top, from->top + i);
to->top++; /* stack already checked by previous 'api_check' */
}
lua_unlock(to);
}

/*
* 设置"异常"处理句柄
* 这里返回了可能的旧句柄，这是一个好习惯
*/
LUA_API lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf) {
lua_CFunction old;
lua_lock(L);
old = G(L)->panic;
G(L)->panic = panicf;
lua_unlock(L);
return old;
}

/* 返回全局的版本器或自己的版本器 */
LUA_API const lua_Number *lua_version (lua_State *L) {
static const lua_Number version = LUA_VERSION_NUM;
if (L == NULL)
return &version; /* 避免静态库的N份的链接问题，这里返回地址，用于调用者对比 */
else
return G(L)->version;
}

/*
** basic stack manipulation
*/

/*
** convert an acceptable stack index into an absolute index
** 拿笔和纸划一下堆栈图就知道了，这是求有效的idx
*/
LUA_API int lua_absindex (lua_State *L, int idx) {
return (idx > 0 || ispseudo(idx))
? idx
: cast_int(L->top - L->ci->func) + idx;
}

/* 求栈内元素个数
* 仔细揣摩下这里的top和L->ci->func+1
* L->ci->func这个slot存放的是回跳地址么？(ps:本栈结束后，上一个栈的基地址),top:又指代什么
* 普通的[n,m]区间的slot个数计算公式是m-n+1,这里是m-n-1,差了2，一头一尾
*/
LUA_API int lua_gettop (lua_State *L) {
return cast_int(L->top - (L->ci->func + 1));
}

/* 调整栈顶指针，扩大(填nil)或缩小栈
** idx>=0表示留下多少个slot,
** <0表示,保留到哪一个元素，-1：表示保留到最后一个元素，等于做无用功，-2：表示保留到倒数第二个元素，等于剔除一个元素,依次类推
*/
LUA_API void lua_settop (lua_State *L, int idx) {
StkId func = L->ci->func;
lua_lock(L);
if (idx >= 0) {
api_check(L, idx <= L->stack_last - (func + 1), "new top too large");
while (L->top < (func + 1) + idx) /* 补充扩充的slot,填nil */
setnilvalue(L->top++);
L->top = (func + 1) + idx;
} else {
api_check(L, -(idx+1) <= (L->top - (func + 1)), "invalid new top");
L->top += idx+1; /* 'subtract' index (index is negative) */
}
lua_unlock(L);
}

/*
** Reverse the stack segment from 'from' to 'to'
** (auxiliary(辅助) to 'lua_rotate(旋转)')
** 交换slot中的值
*/
static void reverse (lua_State *L, StkId from, StkId to) {
for (; from < to; from++, to--) {
TValue temp;
setobj(L, &temp, from);
setobjs2s(L, from, to);
setobj2s(L, to, &temp);
}
}

/*
** Let x = AB, where A is a prefix of length 'n'. Then,
** rotate(旋转) x n == BA. But BA == (A^r . B^r)^r.
*/
LUA_API void lua_rotate (lua_State *L, int idx, int n) {
StkId p, t, m;
lua_lock(L);
t = L->top - 1; /* end of stack segment being rotated */
p = index2addr(L, idx); /* start of segment */
api_checkstackindex(L, idx, p);
api_check(L, (n >= 0 ? n : -n) <= (t - p + 1), "invalid 'n'");
m = (n >= 0 ? t - n : p - n - 1); /* end of prefix */
reverse(L, p, m); /* reverse the prefix with length 'n' */
reverse(L, m + 1, t); /* reverse the suffix */
reverse(L, p, t); /* reverse the entire segment */
lua_unlock(L);
}

LUA_API void lua_copy (lua_State *L, int fromidx, int toidx) {
TValue *fr, *to;
lua_lock(L);
fr = index2addr(L, fromidx);
to = index2addr(L, toidx);
api_checkvalidindex(L, to);
setobj(L, to, fr);
if (isupvalue(toidx)) /* function upvalue? */
luaC_barrier(L, clCvalue(L->ci->func), fr);
/* LUA_REGISTRYINDEX does not need gc barrier
(collector revisits it before finishing collection) */
lua_unlock(L);
}

//将idx指定的slot中的值CP一份到栈顶，并且修正L->top指针,而没有修正L->ci->top指针
LUA_API void lua_pushvalue (lua_State *L, int idx) {
lua_lock(L);
setobj2s(L, L->top, index2addr(L, idx));
api_incr_top(L);
lua_unlock(L);
}

/*
** access functions (stack -> C)
*/

//仅考虑bit[0, 3]的类型，不考虑 [4,5]的类型
//eg:数字类型，而不具体区分是double还是int
LUA_API int lua_type (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
return (isvalid(o) ? ttnov(o) : LUA_TNONE);
}

/* 返回大类型名(number而不是interget) */
LUA_API const char *lua_typename (lua_State *L, int t) {
UNUSED(L);
api_check(L, LUA_TNONE <= t && t < LUA_NUMTAGS, "invalid tag");
return ttypename(t);
}

LUA_API int lua_iscfunction (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
return (ttislcf(o) || (ttisCclosure(o)));
}

LUA_API int lua_isinteger (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
return ttisinteger(o);
}

LUA_API int lua_isnumber (lua_State *L, int idx) {
lua_Number n;
const TValue *o = index2addr(L, idx);
return tonumber(o, &n);
}

LUA_API int lua_isstring (lua_State *L, int idx) {
const TValue *o = index2addr(L, idx);
return (ttisstring(o) || cvt2str(o));
}

LUA_API int lua_isuserdata (lua_State *L, int idx) {
const TValue *o = index2addr(L, idx);
return (ttisfulluserdata(o) || ttislightuserdata(o));
}

/* 不用元方法的裸比 */
LUA_API int lua_rawequal (lua_State *L, int index1, int index2) {
StkId o1 = index2addr(L, index1);
StkId o2 = index2addr(L, index2);
return (isvalid(o1) && isvalid(o2)) ? luaV_rawequalobj(o1, o2) : 0;
}

/* 进行某种运算 */
LUA_API void lua_arith (lua_State *L, int op) {
lua_lock(L);
if (op != LUA_OPUNM && op != LUA_OPBNOT)
api_checknelems(L, 2); /* all other operations expect two operands */
else { /* for unary operations, add fake 2nd operand */
api_checknelems(L, 1);
setobjs2s(L, L->top, L->top - 1);   /* 将最后一个slot元素拷贝一份到栈顶，并++top，以便形成2个参数 */
api_incr_top(L);
}

/*
** first operand at top - 2, second at top - 1; result go to top - 2
** 仔细仔细读上面的这句话，可以看出val1+val2,运行完毕后，保留了结果，弹出了所有的操作数
** 一般的计算机都会这样干哦？
*/
luaO_arith(L, op, L->top - 2, L->top - 1, L->top - 2);
L->top--; /* remove second operand */

lua_unlock(L);
}

LUA_API int lua_compare (lua_State *L, int index1, int index2, int op) {
StkId o1, o2;
int i = 0;
lua_lock(L); /* may call tag method */
o1 = index2addr(L, index1);
o2 = index2addr(L, index2);
if (isvalid(o1) && isvalid(o2)) {
switch (op) {
case LUA_OPEQ: i = luaV_equalobj(L, o1, o2); break;
case LUA_OPLT: i = luaV_lessthan(L, o1, o2); break;
case LUA_OPLE: i = luaV_lessequal(L, o1, o2); break;
default: api_check(L, 0, "invalid option");
}
}
lua_unlock(L);
return i;
}

/* 会被 tonumber()函数调用到哦 */
LUA_API size_t lua_stringtonumber (lua_State *L, const char *s) {
size_t sz = luaO_str2num(s, L->top);
if (sz != 0) // 这里要先判断下转换结果
api_incr_top(L);
return sz;
}

LUA_API lua_Number lua_tonumberx (lua_State *L, int idx, int *pisnum) {
lua_Number n;
const TValue *o = index2addr(L, idx);
int isnum = tonumber(o, &n);
if (!isnum)
n = 0; /* call to 'tonumber' may change 'n' even if it fails */
if (pisnum) *pisnum = isnum;
return n;
}

//将idx指定的参数转换为整数，
//pisnum:转换是否成功的标志位
LUA_API lua_Integer lua_tointegerx (lua_State *L, int idx, int *pisnum) {
lua_Integer res;
const TValue *o = index2addr(L, idx);
int isnum = tointeger(o, &res);
if (!isnum)
res = 0; /* call to 'tointeger' may change 'n' even if it fails */
if (pisnum) *pisnum = isnum;
return res;
}

LUA_API int lua_toboolean (lua_State *L, int idx) {
const TValue *o = index2addr(L, idx);
return !l_isfalse(o);
}

LUA_API const char *lua_tolstring (lua_State *L, int idx, size_t *len) {
StkId o = index2addr(L, idx);
if (!ttisstring(o)) {
if (!cvt2str(o)) { /* not convertible? */
if (len != NULL) *len = 0;
return NULL;
}
lua_lock(L); /* 'luaO_tostring' may create a new string */
luaC_checkGC(L);
o = index2addr(L, idx); /* previous call may reallocate the stack */
luaO_tostring(L, o);
lua_unlock(L);
}
if (len != NULL)
*len = vslen(o);
return svalue(o);
}

/* 计算字符串,userdata,table的长度 */
LUA_API size_t lua_rawlen (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
switch (ttype(o)) {
case LUA_TSHRSTR: return tsvalue(o)->shrlen;
case LUA_TLNGSTR: return tsvalue(o)->u.lnglen;
case LUA_TUSERDATA: return uvalue(o)->len;
case LUA_TTABLE: return luaH_getn(hvalue(o));
default: return 0;
}
}

LUA_API lua_CFunction lua_tocfunction (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
if (ttislcf(o)) return fvalue(o); /* light C function */
else if (ttisCclosure(o)) /* C closure */
return clCvalue(o)->f;
else return NULL; /* not a C function */
}

LUA_API void *lua_touserdata (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
switch (ttnov(o)) {
case LUA_TUSERDATA: return getudatamem(uvalue(o));
case LUA_TLIGHTUSERDATA: return pvalue(o);-
default: return NULL;
}
}

LUA_API lua_State *lua_tothread (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
return (!ttisthread(o)) ? NULL : thvalue(o);
}

LUA_API const void *lua_topointer (lua_State *L, int idx) {
StkId o = index2addr(L, idx);
switch (ttype(o)) {
case LUA_TTABLE: return hvalue(o);
case LUA_TLCL: return clLvalue(o);
case LUA_TCCL: return clCvalue(o);
case LUA_TLCF: return cast(void *, cast(size_t, fvalue(o)));
case LUA_TTHREAD: return thvalue(o);
case LUA_TUSERDATA: return getudatamem(uvalue(o));
case LUA_TLIGHTUSERDATA: return pvalue(o);
default: return NULL;
}
}

/*
** push functions (C -> stack)
*/

LUA_API void lua_pushnil (lua_State *L) {
lua_lock(L);

/* 看的出这里的L->top指向下一个可用的slot,而不是上一个被填满的slot，这边要适应
* 压入值后，要手动top++，下同。
*/
setnilvalue(L->top);
api_incr_top(L);

lua_unlock(L);
}

LUA_API void lua_pushnumber (lua_State *L, lua_Number n) {
lua_lock(L);
setfltvalue(L->top, n);
api_incr_top(L);
lua_unlock(L);
}

LUA_API void lua_pushinteger (lua_State *L, lua_Integer n) {
lua_lock(L);
setivalue(L->top, n);
api_incr_top(L);
lua_unlock(L);
}

/*
** Pushes on the stack a string with given length. Avoid using 's' when
** 'len' == 0 (as 's' can be NULL in that case), due to later use of
** 'memcmp' and 'memcpy'.
*/
LUA_API const char *lua_pushlstring (lua_State *L, const char *s, size_t len) {
TString *ts;
lua_lock(L);
luaC_checkGC(L);
ts = (len == 0) ? luaS_new(L, "") : luaS_newlstr(L, s, len);
setsvalue2s(L, L->top, ts);
api_incr_top(L);
lua_unlock(L);
return getstr(ts);
}

/* 将C的s字符串转换为String，压入栈顶 */
LUA_API const char *lua_pushstring (lua_State *L, const char *s) {
lua_lock(L);
if (s == NULL)
setnilvalue(L->top);
else {
TString *ts;
luaC_checkGC(L);
ts = luaS_new(L, s);
setsvalue2s(L, L->top, ts);
s = getstr(ts); /* internal copy's address */
}
api_incr_top(L);
lua_unlock(L);
return s;
}

LUA_API const char *lua_pushvfstring (lua_State *L, const char *fmt,
va_list argp) {
const char *ret;
lua_lock(L);
luaC_checkGC(L);
ret = luaO_pushvfstring(L, fmt, argp);
lua_unlock(L);
return ret;
}

LUA_API const char *lua_pushfstring (lua_State *L, const char *fmt, ...) {
const char *ret;
va_list argp;
lua_lock(L);
luaC_checkGC(L);
va_start(argp, fmt);
ret = luaO_pushvfstring(L, fmt, argp);
va_end(argp);
lua_unlock(L);
return ret;
}

//创建一个闭包
//若上值个数为0，则创建一个简单的闭包即可
//若有N个上值，则创建一个闭包，将栈顶上的上值填入闭包中，最后弹出上值，压入新构建的闭包
LUA_API void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n) {
lua_lock(L);
if (n == 0) { //简单的CFunction
setfvalue(L->top, fn);
}
else {
CClosure *cl;
api_checknelems(L, n);
api_check(L, n <= MAXUPVAL, "upvalue index too large");
luaC_checkGC(L);
cl = luaF_newCclosure(L, n);
cl->f = fn;
L->top -= n;
while (n--) {
setobj2n(L, &cl->upvalue[n], L->top + n); //复制上值
/* does not need barrier because closure is white */
}
setclCvalue(L, L->top, cl); //压入构建好的闭包到栈顶
}
api_incr_top(L);
lua_unlock(L);
}

LUA_API void lua_pushboolean (lua_State *L, int b) {
lua_lock(L);
setbvalue(L->top, (b != 0)); /* ensure that true is 1 */
api_incr_top(L);
lua_unlock(L);
}

LUA_API void lua_pushlightuserdata (lua_State *L, void *p) {
lua_lock(L);
setpvalue(L->top, p);
api_incr_top(L);
lua_unlock(L);
}

LUA_API int lua_pushthread (lua_State *L) {
lua_lock(L);
setthvalue(L, L->top, L);
api_incr_top(L);
lua_unlock(L);
return (G(L)->mainthread == L);
}

/*
** get functions (Lua -> stack)
*/

static int auxgetstr (lua_State *L, const TValue *t, const char *k) {
const TValue *aux;

/* 将外部的const chant *k指针转换为Lua内部的TString */
TString *str = luaS_new(L, k);

if (luaV_fastget(L, t, str, aux, luaH_getstr)) { /* 在table中找到了key的值 */
setobj2s(L, L->top, aux);
api_incr_top(L);
} else {
setsvalue2s(L, L->top, str);
api_incr_top(L);
luaV_finishget(L, t, L->top - 1, L->top - 1, aux);
}
lua_unlock(L);
return ttnov(L->top - 1);
}

LUA_API int lua_getglobal (lua_State *L, const char *name) {
Table *reg = hvalue(&G(L)->l_registry);
lua_lock(L);
return auxgetstr(L, luaH_getint(reg, LUA_RIDX_GLOBALS), name);
}

/* 查找由idx指定的table中L->top-1指定的key的val值，并把结果放到L->top-1上 */
LUA_API int lua_gettable (lua_State *L, int idx) {
StkId t;
lua_lock(L);
t = index2addr(L, idx);
luaV_gettable(L, t, L->top - 1, L->top - 1);
lua_unlock(L);
return ttnov(L->top - 1);
}

/*
* 获取位于idx指定的表的key域的值(返回到栈顶上)
* top = T(idx)[key]
*/
LUA_API int lua_getfield (lua_State *L, int idx, const char *k) {
lua_lock(L);
return auxgetstr(L, index2addr(L, idx), k);
}

//上面函数的type(key)==int的版
LUA_API int lua_geti (lua_State *L, int idx, lua_Integer n) {
StkId t;
const TValue *aux;
lua_lock(L);
t = index2addr(L, idx);
if (luaV_fastget(L, t, n, aux, luaH_getint)) {
setobj2s(L, L->top, aux);
api_incr_top(L);
}
else {
setivalue(L->top, n);
api_incr_top(L);
luaV_finishget(L, t, L->top - 1, L->top - 1, aux);
}
lua_unlock(L);
return ttnov(L->top - 1);
}

LUA_API int lua_rawget (lua_State *L, int idx) {
StkId t;
lua_lock(L);
t = index2addr(L, idx);
api_check(L, ttistable(t), "table expected");
setobj2s(L, L->top - 1, luaH_get(hvalue(t), L->top - 1));
lua_unlock(L);
return ttnov(L->top - 1);
}

//提取idx指定的表的key==n的值
LUA_API int lua_rawgeti (lua_State *L, int idx, lua_Integer n) {
StkId t;
lua_lock(L);
t = index2addr(L, idx);
api_check(L, ttistable(t), "table expected");
setobj2s(L, L->top, luaH_getint(hvalue(t), n));
api_incr_top(L);
lua_unlock(L);
return ttnov(L->top - 1);
}

//get light userdata
LUA_API int lua_rawgetp (lua_State *L, int idx, const void *p) {
StkId t;
TValue k;
lua_lock(L);
t = index2addr(L, idx);
api_check(L, ttistable(t), "table expected");
setpvalue(&k, cast(void *, p));
setobj2s(L, L->top, luaH_get(hvalue(t), &k));
api_incr_top(L);
lua_unlock(L);
return ttnov(L->top - 1);
}

/*
** 构建一个narray,nrec的表
** 之后压入栈顶
*/
LUA_API void lua_createtable (lua_State *L, int narray, int nrec) {
Table *t;
lua_lock(L);
luaC_checkGC(L);
t = luaH_new(L); /* 先构建一个zero的表 */
sethvalue(L, L->top, t);
api_incr_top(L);
if (narray > 0 || nrec > 0)
luaH_resize(L, t, narray, nrec); /* 这里再扩展array或rec区域 */
lua_unlock(L);
}

//提取Table, UserData等的元表
LUA_API int lua_getmetatable (lua_State *L, int objindex) {
const TValue *obj;
Table *mt;
int res = 0;
lua_lock(L);
obj = index2addr(L, objindex);
switch (ttnov(obj)) {
case LUA_TTABLE:
mt = hvalue(obj)->metatable;
break;
case LUA_TUSERDATA:
mt = uvalue(obj)->metatable;
break;
default: /* 这里看的出，其它类型的，直接读全局表 */
mt = G(L)->mt[ttnov(obj)];
break;
}
if (mt != NULL) {
sethvalue(L, L->top, mt); //将结果压栈
api_incr_top(L);
res = 1;
}
lua_unlock(L);
return res;
}

LUA_API int lua_getuservalue (lua_State *L, int idx) {
StkId o;
lua_lock(L);
o = index2addr(L, idx);
api_check(L, ttisfulluserdata(o), "full userdata expected");
getuservalue(L, uvalue(o), L->top);
api_incr_top(L);
lua_unlock(L);
return ttnov(L->top - 1);
}

/*
** set functions (stack -> Lua)
**
** t[k] = value at the top of the stack (where 'k' is a string)
** 看代码，值已经放到L->top-1的slot栈位置
*/
static void auxsetstr (lua_State *L, const TValue *t, const char *k) {
const TValue *aux;

TString *str = luaS_new(L, k);   /* 这里将k指向的字符串先转为内部的TString */

api_checknelems(L, 1);
if (luaV_fastset(L, t, str, aux, luaH_getstr, L->top - 1))
L->top--; /* pop value */
else {
setsvalue2s(L, L->top, str); /* push 'str' (to make it a TValue) */
api_incr_top(L);

luaV_finishset(L, t, L->top - 1, L->top - 2, aux);
L->top -= 2; /* pop value and key */
}
lua_unlock(L); /* lock done by caller */
}

/* 类似上面的函数，不过表是全局注册表了 */
LUA_API void lua_setglobal (lua_State *L, const char *name) {
Table *reg = hvalue(&G(L)->l_registry);
lua_lock(L); /* unlock done in 'auxsetstr' */
auxsetstr(L, luaH_getint(reg, LUA_RIDX_GLOBALS), name);
}

/* key，value已放到了栈顶对应的slot，这里idx来确定表 */
LUA_API void lua_settable (lua_State *L, int idx) {
StkId t;
lua_lock(L);
api_checknelems(L, 2);
t = index2addr(L, idx);
luaV_settable(L, t, L->top - 2, L->top - 1);
L->top -= 2; /* pop index and value */
lua_unlock(L);
}

//idx["k"] = top,之后将top弹出栈,表由idx指定
LUA_API void lua_setfield (lua_State *L, int idx, const char *k) {
lua_lock(L); /* unlock done in 'auxsetstr' */
auxsetstr(L, index2addr(L, idx), k);
}

//idx[n] = top,之后将top弹出栈
LUA_API void lua_seti (lua_State *L, int idx, lua_Integer n) {
StkId t;
const TValue *aux;
lua_lock(L);
api_checknelems(L, 1);
t = index2addr(L, idx);
if (luaV_fastset(L, t, n, aux, luaH_getint, L->top - 1)) {
L->top--; /* pop value */
} else {
setivalue(L->top, n);
api_incr_top(L);
luaV_finishset(L, t, L->top - 1, L->top - 2, aux);
L->top -= 2; /* pop value and key */
}
lua_unlock(L);
}

//将idx指定的tbl进行tbl[top-2] = *(top-1)
LUA_API void lua_rawset (lua_State *L, int idx) {
StkId o;
TValue *slot;
lua_lock(L);
api_checknelems(L, 2);
o = index2addr(L, idx);
api_check(L, ttistable(o), "table expected");
slot = luaH_set(L, hvalue(o), L->top - 2);
setobj2t(L, slot, L->top - 1);
invalidateTMcache(hvalue(o));
luaC_barrierback(L, hvalue(o), L->top-1);
L->top -= 2;
lua_unlock(L);
}

//idx'Table [n] = top
LUA_API void lua_rawseti (lua_State *L, int idx, lua_Integer n) {
StkId o;
lua_lock(L);
api_checknelems(L, 1);
o = index2addr(L, idx);
api_check(L, ttistable(o), "table expected");
luaH_setint(L, hvalue(o), n, L->top - 1);
luaC_barrierback(L, hvalue(o), L->top-1);
L->top--;
lua_unlock(L);
}

//set light userdata
LUA_API void lua_rawsetp (lua_State *L, int idx, const void *p) {
StkId o;
TValue k, *slot;
lua_lock(L);
api_checknelems(L, 1);
o = index2addr(L, idx);
api_check(L, ttistable(o), "table expected");
setpvalue(&k, cast(void *, p));
slot = luaH_set(L, hvalue(o), &k);
setobj2t(L, slot, L->top - 1);
luaC_barrierback(L, hvalue(o), L->top - 1);
L->top--;
lua_unlock(L);
}

/*
** statck[top]->table.meatetable = objindex
** 仔细看完这个函数，switch中三种情况的处理
** statck[objindex].metatable = statck[top]
*/
LUA_API int lua_setmetatable (lua_State *L, int objindex) {
TValue *obj;
Table *mt;
lua_lock(L);
api_checknelems(L, 1);

if (ttisnil(L->top - 1))   /* 空值相当于取消原表 */
mt = NULL;
else {
api_check(L, ttistable(L->top - 1), "table expected");   /* 这里可以看到，非空时，必须是张表 */
mt = hvalue(L->top - 1);
}

obj = index2addr(L, objindex);   /* 确定被设置原表的对象 */
switch (ttnov(obj)) {
case LUA_TTABLE: {
hvalue(obj)->metatable = mt;
if (mt) {
luaC_objbarrier(L, gcvalue(obj), mt);
luaC_checkfinalizer(L, gcvalue(obj), mt);
}
break;
}
case LUA_TUSERDATA: {
uvalue(obj)->metatable = mt;
if (mt) {
luaC_objbarrier(L, uvalue(obj), mt);
luaC_checkfinalizer(L, gcvalue(obj), mt);
}
break;
}
default: {
G(L)->mt[ttnov(obj)] = mt; /* 厉害了哦,这里可以对基础类型的原表进行覆盖处理,没必要，必要进行此操作吧 */
break;
}
}
L->top--;
lua_unlock(L);
return 1;   /* 这里返回1有啥意义？ */
}

/* statck[idx] = top */
LUA_API void lua_setuservalue (lua_State *L, int idx) {
StkId o;
lua_lock(L);
api_checknelems(L, 1);
o = index2addr(L, idx);
api_check(L, ttisfulluserdata(o), "full userdata expected");
setuservalue(L, uvalue(o), L->top - 1);
luaC_barrier(L, gcvalue(o), L->top - 1);
L->top--;
lua_unlock(L);
}

/*
** 'load' and 'call' functions (run Lua code)
*/

#define checkresults(L,na,nr) \
api_check(L, (nr) == LUA_MULTRET || (L->ci->top - L->top >= (nr) - (na)), \
"results from function overflow current stack size")

/* KEY-FUN
** 多看看此函数，目前还没有看懂 2020/05/13
*/
LUA_API void lua_callk (lua_State *L, int nargs, int nresults,
lua_KContext ctx, lua_KFunction k) {
StkId func;
lua_lock(L); /* 考虑下：上面定义变量和这一行的lock调用的前后顺序调换下位置对性能而言有啥区别？ */

api_check(L, k == NULL || !isLua(L->ci),
"cannot use continuations inside hooks");
api_checknelems(L, nargs+1);
api_check(L, L->status == LUA_OK, "cannot do calls on non-normal thread");
checkresults(L, nargs, nresults);

/* 函数指针在这里,另外看的出参数放到了函数指针的"上面" */
func = L->top - (nargs+1);

if (k != NULL && L->nny == 0) { /* need to prepare continuation? */
L->ci->u.c.k = k; /* save continuation */
L->ci->u.c.ctx = ctx; /* save context */
luaD_call(L, func, nresults); /* do the call */
}
else /* no continuation or no yieldable */
luaD_callnoyield(L, func, nresults); /* just do the call */

adjustresults(L, nresults);
lua_unlock(L);
}

/*
** Execute a protected call.
*/
struct CallS { /* data to 'f_call' */
StkId func;
int nresults;
};

static void f_call (lua_State *L, void *ud) {
struct CallS *c = cast(struct CallS *, ud);
luaD_callnoyield(L, c->func, c->nresults);
}

/*
** 带保护模式下调用函数？，看不懂，后面遇到了再多看几次吧
*/
LUA_API int lua_pcallk (lua_State *L, int nargs, int nresults, int errfunc,
lua_KContext ctx, lua_KFunction k) {
struct CallS c;
int status;
ptrdiff_t func;
lua_lock(L);
api_check(L, k == NULL || !isLua(L->ci),
"cannot use continuations inside hooks");
api_checknelems(L, nargs+1);
api_check(L, L->status == LUA_OK, "cannot do calls on non-normal thread");
checkresults(L, nargs, nresults);
if (errfunc == 0)
func = 0;
else {
StkId o = index2addr(L, errfunc);
api_checkstackindex(L, errfunc, o);
func = savestack(L, o);
}
c.func = L->top - (nargs+1); /* function to be called */
if (k == NULL || L->nny > 0) { /* no continuation or no yieldable? */
c.nresults = nresults; /* do a 'conventional' protected call */
status = luaD_pcall(L, f_call, &c, savestack(L, c.func), func);
}
else { /* prepare continuation (call is already protected by 'resume') */
CallInfo *ci = L->ci;
ci->u.c.k = k; /* save continuation */
ci->u.c.ctx = ctx; /* save context */
/* save information for error recovery */
ci->extra = savestack(L, c.func);
ci->u.c.old_errfunc = L->errfunc;
L->errfunc = func;
setoah(ci->callstatus, L->allowhook); /* save value of 'allowhook' */
ci->callstatus |= CIST_YPCALL; /* function can do error recovery */
luaD_call(L, c.func, nresults); /* do the call */
ci->callstatus &= ~CIST_YPCALL;
L->errfunc = ci->u.c.old_errfunc;
status = LUA_OK; /* if it is here, there were no errors */
}
adjustresults(L, nresults);
lua_unlock(L);
return status;
}

/* KEY-FUNCTION
** 加载一段字符串，生成闭包。
** 没有完全看懂(gc)，遇到再看。
*/
LUA_API int lua_load (lua_State *L, lua_Reader reader, void *data,
const char *chunkname, const char *mode) {
ZIO z;
int status;
lua_lock(L);
if (!chunkname) chunkname = "?";

luaZ_init(L, &z, reader, data);   /* 初始化读结构体 */

status = luaD_protectedparser(L, &z, chunkname, mode);   /* 调用parser进行处理，是不是觉得这个单词很面熟，对的,编译原理走起来。。。 */

if (status == LUA_OK) { /* no errors? */
LClosure *f = clLvalue(L->top - 1); /* get newly created function */
if (f->nupvalues >= 1) { /* does it have an upvalue? */

/* get global table from registry */
Table *reg = hvalue(&G(L)->l_registry);
const TValue *gt = luaH_getint(reg, LUA_RIDX_GLOBALS);

/* set global table as 1st upvalue of 'f' (may be LUA_ENV) */
setobj(L, f->upvals[0]->v, gt);
luaC_upvalbarrier(L, f->upvals[0]);
}
}
lua_unlock(L);
return status;
}

LUA_API int lua_dump (lua_State *L, lua_Writer writer, void *data, int strip) {
int status;
TValue *o;
lua_lock(L);
api_checknelems(L, 1);
o = L->top - 1;
if (isLfunction(o))
status = luaU_dump(L, getproto(o), writer, data, strip);
else
status = 1;
lua_unlock(L);
return status;
}

/* 纯粹的API函数 */
LUA_API int lua_status (lua_State *L) {
return L->status;
}

/*
** Garbage-collection function
*/

LUA_API int lua_gc (lua_State *L, int what, int data) {
int res = 0;
global_State *g;
lua_lock(L);
g = G(L);
switch (what) {
case LUA_GCSTOP: {
g->gcrunning = 0;
break;
}
case LUA_GCRESTART: {
luaE_setdebt(g, 0);
g->gcrunning = 1;
break;
}
case LUA_GCCOLLECT: {
luaC_fullgc(L, 0);
break;
}
case LUA_GCCOUNT: {
/* GC values are expressed in Kbytes: #bytes/2^10 */
res = cast_int(gettotalbytes(g) >> 10);
break;
}
case LUA_GCCOUNTB: { /* 0x3ff:用bits画下 */
res = cast_int(gettotalbytes(g) & 0x3ff);
break;
}
case LUA_GCSTEP: {
l_mem debt = 1; /* =1 to signal that it did an actual step */
lu_byte oldrunning = g->gcrunning;
g->gcrunning = 1; /* allow GC to run */
if (data == 0) {
luaE_setdebt(g, -GCSTEPSIZE); /* to do a "small" step */
luaC_step(L);
}
else { /* add 'data' to total debt */
debt = cast(l_mem, data) * 1024 + g->GCdebt;
luaE_setdebt(g, debt);
luaC_checkGC(L);
}
g->gcrunning = oldrunning; /* restore previous state */
if (debt > 0 && g->gcstate == GCSpause) /* end of cycle? */
res = 1; /* signal it */
break;
}
case LUA_GCSETPAUSE: {
res = g->gcpause;
g->gcpause = data;
break;
}
case LUA_GCSETSTEPMUL: {
res = g->gcstepmul;
if (data < 40) data = 40; /* avoid ridiculous low values (and 0) */
g->gcstepmul = data;
break;
}
case LUA_GCISRUNNING: {
res = g->gcrunning;
break;
}
default: res = -1; /* invalid option */
}
lua_unlock(L);
return res;
}

/*
** miscellaneous(杂) functions
*/

LUA_API int lua_error (lua_State *L) {
lua_lock(L);
api_checknelems(L, 1);
luaG_errormsg(L);
/* code unreachable; will unlock when control actually leaves the kernel */
return 0; /* to avoid warnings */
}

/* table == statck[idx], key==top-1的下一对key<-->value */
LUA_API int lua_next (lua_State *L, int idx) {
StkId t;
int more;
lua_lock(L);

t = index2addr(L, idx);   /* 找到表 */
api_check(L, ttistable(t), "table expected");   /* 参数必须是个表 */

more = luaH_next(L, hvalue(t), L->top - 1);
if (more) {
api_incr_top(L);   /* 找到了，且返回了key对应的value,所以这里堆栈要增长以便存下value */
}
else /* no more elements */
L->top -= 1; /* remove key */

lua_unlock(L);
return more;
}

LUA_API void lua_concat (lua_State *L, int n) {
lua_lock(L);
api_checknelems(L, n);
if (n >= 2) {
luaC_checkGC(L);
luaV_concat(L, n);
}
else if (n == 0) { /* push empty string */
setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));
api_incr_top(L);
}
/* else n == 1; nothing to do */
lua_unlock(L);
}

/* 求"变量"的长度 */
LUA_API void lua_len (lua_State *L, int idx) {
StkId t;
lua_lock(L);
t = index2addr(L, idx);
luaV_objlen(L, L->top, t);
api_incr_top(L);
lua_unlock(L);
}

LUA_API lua_Alloc lua_getallocf (lua_State *L, void **ud) {
lua_Alloc f;
lua_lock(L);
if (ud) *ud = G(L)->ud;
f = G(L)->frealloc;
lua_unlock(L);
return f;
}

LUA_API void lua_setallocf (lua_State *L, lua_Alloc f, void *ud) {
lua_lock(L);
G(L)->ud = ud;
G(L)->frealloc = f;
lua_unlock(L);
}

//构建一个User'Data并压栈，返回UData中私有数据地址
LUA_API void *lua_newuserdata (lua_State *L, size_t size) {
Udata *u;
lua_lock(L);
luaC_checkGC(L);

/* 构建一份UserData数据 */
u = luaS_newudata(L, size);

/* 将上述构建的UserData压入栈顶 */
setuvalue(L, L->top, u);
api_incr_top(L);

lua_unlock(L);
return getudatamem(u);   /* 返回私有地址 */
}

/* 不太明白这个函数的作用 */
static const char *aux_upvalue (StkId fi, int n, TValue **val,
CClosure **owner, UpVal **uv) {
switch (ttype(fi)) {
case LUA_TCCL: { /* C closure */
CClosure *f = clCvalue(fi);
if (!(1 <= n && n <= f->nupvalues)) return NULL;
*val = &f->upvalue[n-1];
if (owner) *owner = f;
return "";
}
case LUA_TLCL: { /* Lua closure */
LClosure *f = clLvalue(fi);
TString *name;
Proto *p = f->p;
if (!(1 <= n && n <= p->sizeupvalues)) return NULL;
*val = f->upvals[n-1]->v;
if (uv) *uv = f->upvals[n - 1];
name = p->upvalues[n-1].name;
return (name == NULL) ? "(*no name)" : getstr(name);
}
default: return NULL; /* not a closure */
}
}

/* 获取某个upvalue ? */
LUA_API const char *lua_getupvalue (lua_State *L, int funcindex, int n) {
const char *name;
TValue *val = NULL; /* to avoid warnings */
lua_lock(L);
name = aux_upvalue(index2addr(L, funcindex), n, &val, NULL, NULL);
if (name) {
setobj2s(L, L->top, val);
api_incr_top(L);
}
lua_unlock(L);
return name;
}

/* 设置某个upvalue? */
LUA_API const char *lua_setupvalue (lua_State *L, int funcindex, int n) {
const char *name;
TValue *val = NULL; /* to avoid warnings */
CClosure *owner = NULL;
UpVal *uv = NULL;
StkId fi;
lua_lock(L);
fi = index2addr(L, funcindex);
api_checknelems(L, 1);
name = aux_upvalue(fi, n, &val, &owner, &uv);
if (name) {
L->top--;
setobj(L, val, L->top);
if (owner) { luaC_barrier(L, owner, L->top); }
else if (uv) { luaC_upvalbarrier(L, uv); }
}
lua_unlock(L);
return name;
}

static UpVal **getupvalref (lua_State *L, int fidx, int n, LClosure **pf) {
LClosure *f;
StkId fi = index2addr(L, fidx);
api_check(L, ttisLclosure(fi), "Lua function expected");
f = clLvalue(fi);
api_check(L, (1 <= n && n <= f->p->sizeupvalues), "invalid upvalue index");
if (pf) *pf = f;
return &f->upvals[n - 1]; /* get its upvalue pointer */
}

LUA_API void *lua_upvalueid (lua_State *L, int fidx, int n) {
StkId fi = index2addr(L, fidx);
switch (ttype(fi)) {
case LUA_TLCL: { /* lua closure */
return *getupvalref(L, fidx, n, NULL);
}
case LUA_TCCL: { /* C closure */
CClosure *f = clCvalue(fi);
api_check(L, 1 <= n && n <= f->nupvalues, "invalid upvalue index");
return &f->upvalue[n - 1];
}
default: {
api_check(L, 0, "closure expected");
return NULL;
}
}
}

LUA_API void lua_upvaluejoin (lua_State *L, int fidx1, int n1,
int fidx2, int n2) {
LClosure *f1;
UpVal **up1 = getupvalref(L, fidx1, n1, &f1);
UpVal **up2 = getupvalref(L, fidx2, n2, NULL);
luaC_upvdeccount(L, *up1);
*up1 = *up2;
(*up1)->refcount++;
if (upisopen(*up1)) (*up1)->u.open.touched = 1;
luaC_upvalbarrier(L, *up1);
}