lobject.c（5.3.4）解析

/*** $Id: lobject.c,v 2.113 2016/12/22 13:08:50 roberto Exp $** Some generic functions over Lua objects** See Copyright Notice in lua.h*/#define lobject_c#define LUA_CORE#include "lprefix.h"#include <locale.h>#include <math.h>#include <stdarg.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include "lua.h"#include "lctype.h"#include "ldebug.h"#include "ldo.h"#include "lmem.h"#include "lobject.h"#include "lstate.h"#include "lstring.h"#include "lvm.h"LUAI_DDEF const TValue luaO_nilobject_ = {NILCONSTANT};/*** converts an integer to a "floating point byte", represented as** (eeeeexxx), where the real value is (1xxx) * 2^(eeeee - 1) if** eeeee != 0 and (xxx) otherwise.*/// 使用浮点数的方法扩充整数范围（0 ~ 15 * 2^30）// e代表指数// 如果传进来的x没有超出三位尾数的范围那么就直接返回int luaO_int2fb (unsigned int x) {  int e = 0;  /* exponent */  if (x < 8) return x;  while (x >= (8 << 4)) {  /* coarse steps */    x = (x + 0xf) >> 4;  /* x = ceil(x / 16) */    e += 4;  }  while (x >= (8 << 1)) {  /* fine steps */    x = (x + 1) >> 1;  /* x = ceil(x / 2) */    e++;  }  return ((e+1) << 3) | (cast_int(x) - 8);}/* converts back */int luaO_fb2int (int x) {  return (x < 8) ? x : ((x & 7) + 8) << ((x >> 3) - 1);}/*** Computes ceil(log2(x))*/// 解释一下这个函数，作用是计算 ceil(log2(x)),也就是求出x的以2为底的对数，在对结果进行向上取整// 函数的大意就是，先把x转换成2^n的形式，然后求出n就可以了// 打个比方说传进来的是256，那么就是2^8 这里的log_2数组之所以这么写，就是为了按照这种思想求n// 如果传进来的数字在128和256之间  那么也用8来作为n的结果。目的就是实现ceil的向上取整// 如果x大于256，就让x除以256，然后把结果加上8int luaO_ceillog2 (unsigned int x) {  static const lu_byte log_2[256] = {  /* log_2[i] = ceil(log2(i - 1)) */    0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,    6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8  };  int l = 0;  x--;  while (x >= 256) { l += 8; x >>= 8; }  return l + log_2[x];}// 两个整数之间的运算// op是传进来的操作码，定义在lua.h中，LUA_OPADD是0，LUA_OPBNOT是13// intop和luaV_mod等算术操作定义在lvm.h中，都是基于堆栈的算术操作，到那里再具体分析// LUA_OPADD：加法操作// LUA_OPSUB：减法操作// LUA_OPMUL：乘法操作// LUA_OPMOD：取摸操作// LUA_OPIDIV：向下取整的除法操作// LUA_OPBAND：按位与操作// LUA_OPBOR：按位或操作// LUA_OPBXOR：按位异或操作// LUA_OPSHL：左移操作// LUA_OPSHR：右移操作// LUA_OPUNM：取负操作（就是沿用的减法操作，第一个操作数为0）// LUA_OPBNOT：按位取反操作static lua_Integer intarith (lua_State *L, int op, lua_Integer v1,                                                   lua_Integer v2) {  switch (op) {    case LUA_OPADD: return intop(+, v1, v2);    case LUA_OPSUB:return intop(-, v1, v2);    case LUA_OPMUL:return intop(*, v1, v2);    case LUA_OPMOD: return luaV_mod(L, v1, v2);    case LUA_OPIDIV: return luaV_div(L, v1, v2);    case LUA_OPBAND: return intop(&, v1, v2);    case LUA_OPBOR: return intop(|, v1, v2);    case LUA_OPBXOR: return intop(^, v1, v2);    case LUA_OPSHL: return luaV_shiftl(v1, v2);    case LUA_OPSHR: return luaV_shiftl(v1, -v2);    case LUA_OPUNM: return intop(-, 0, v1);    case LUA_OPBNOT: return intop(^, ~l_castS2U(0), v1);    default: lua_assert(0); return 0;  }}// 两个number之间的运算// luai_numadd等方法定义在llimits.h中，内部操作依靠+-*等操作，取摸等复杂操作则调用C函数// LUA_OPADD：加法操作// LUA_OPSUB：减法操作// LUA_OPMUL：乘法操作// LUA_OPDIV：普通的除法操作// LUA_OPPOW：幂操作// LUA_OPIDIV：向下取整的除法操作// LUA_OPUNM：取负操作// LUA_OPMOD：取摸操作static lua_Number numarith (lua_State *L, int op, lua_Number v1,                                                  lua_Number v2) {  switch (op) {    case LUA_OPADD: return luai_numadd(L, v1, v2);    case LUA_OPSUB: return luai_numsub(L, v1, v2);    case LUA_OPMUL: return luai_nummul(L, v1, v2);    case LUA_OPDIV: return luai_numdiv(L, v1, v2);    case LUA_OPPOW: return luai_numpow(L, v1, v2);    case LUA_OPIDIV: return luai_numidiv(L, v1, v2);    case LUA_OPUNM: return luai_numunm(L, v1);    case LUA_OPMOD: {      lua_Number m;      luai_nummod(L, v1, v2, m);      return m;    }    default: lua_assert(0); return 0;  }}// 两个TValue的算术运算// 具体做法是先把TValue的具体值取出来然后再调用上面的两种类型函数进行操作void luaO_arith (lua_State *L, int op, const TValue *p1, const TValue *p2,                 TValue *res) {  switch (op) {    case LUA_OPBAND: case LUA_OPBOR: case LUA_OPBXOR:    case LUA_OPSHL: case LUA_OPSHR:    case LUA_OPBNOT: {  /* operate only on integers */      lua_Integer i1; lua_Integer i2;      if (tointeger(p1, &i1) && tointeger(p2, &i2)) {        setivalue(res, intarith(L, op, i1, i2));        return;      }      else break;  /* go to the end */    }    case LUA_OPDIV: case LUA_OPPOW: {  /* operate only on floats */      lua_Number n1; lua_Number n2;      if (tonumber(p1, &n1) && tonumber(p2, &n2)) {        setfltvalue(res, numarith(L, op, n1, n2));        return;      }      else break;  /* go to the end */    }    default: {  /* other operations */      lua_Number n1; lua_Number n2;      if (ttisinteger(p1) && ttisinteger(p2)) {        setivalue(res, intarith(L, op, ivalue(p1), ivalue(p2)));        return;      }      else if (tonumber(p1, &n1) && tonumber(p2, &n2)) {        setfltvalue(res, numarith(L, op, n1, n2));        return;      }      else break;  /* go to the end */    }  }  /* could not perform raw operation; try metamethod */  lua_assert(L != NULL);  /* should not fail when folding (compile time) */  luaT_trybinTM(L, p1, p2, res, cast(TMS, (op - LUA_OPADD) + TM_ADD));}// lisdigit检查参数是否为十进制数字字符，当c为数字0~9时，返回非零值，否则返回零// 如果c是十进制字符的话，就返回具体的数字// 如果不是的话，ltolower就把字符转成小写字符之后，再减去'a'得到数字，加上10，就等于说16进制的字符变成了数字// 总的来说，luaO_hexavalue的作用就是把能转变成数字的字符变成数字并返回int luaO_hexavalue (int c) {  if (lisdigit(c)) return c - '0';  else return (ltolower(c) - 'a') + 10;}// 获取*s指向的字符是'+'还是'-'// 1代表负,0代表正,并且s向前移一位static int isneg (const char **s) {  if (**s == '-') { (*s)++; return 1; }  else if (**s == '+') (*s)++;  return 0;}/*** {==================================================================** Lua's implementation for 'lua_strx2number'** ===================================================================*/#if !defined(lua_strx2number)/* maximum number of significant digits to read (to avoid overflows   even with single floats) */#define MAXSIGDIG30/*** convert an hexadecimal numeric string to a number, following** C99 specification for 'strtod'*/// 将十六进制数字串转换成数字，下面是关于'strtod'的C99规范// lua_getlocaledecpoint得到本地的小数点号(ascii表示'.'为46)// lisspace主要用于检查参数是否为空格字符,若参数c为空格字符，则返回TRUE，否则返回NULL(0)// 首先s跳过前面的空格,然后neg得到*s的符号,1代表负,0代表正// 然后检测开头的两位字符是不是"0x"或"0X",不然的话就不是16进制,直接返回0// 在循环里面刚开始遇见第一个点就把hasdot赋值1,如果第二次再碰见点的话就跳出循环// lisxdigit检查参数是否为16进制数字,如果是的话返回非0值,不然返回0.参数类型为int,但是可以直接将char 类型数据传入.// sigdig代表有意义数字的数量,nosigdig代表没有意义数字的数量(没有意义的就是字符串开头的0,中间的不算)// luaO_hexavalue把参数转换成十进制数字// 重要的操作是r * cast_num(16.0) 把之前的结果乘以16,就代表16进制往左移了一位,然后再加上新的数// 然后超出MAXSIGDIG限制的字符会被计入e,然后小数点后面如果有字符的话会抵消一部分e// endptr是有效字符的下一位static lua_Number lua_strx2number (const char *s, char **endptr) {  int dot = lua_getlocaledecpoint();  lua_Number r = 0.0;  /* result (accumulator) */  int sigdig = 0;  /* number of significant digits */  int nosigdig = 0;  /* number of non-significant digits */  int e = 0;  /* exponent correction */  int neg;  /* 1 if number is negative */  int hasdot = 0;  /* true after seen a dot */  *endptr = cast(char *, s);  /* nothing is valid yet */  while (lisspace(cast_uchar(*s))) s++;  /* skip initial spaces */  neg = isneg(&s);  /* check signal */  if (!(*s == '0' && (*(s + 1) == 'x' || *(s + 1) == 'X')))  /* check '0x' */    return 0.0;  /* invalid format (no '0x') */  for (s += 2; ; s++) {  /* skip '0x' and read numeral */    if (*s == dot) {      if (hasdot) break;  /* second dot? stop loop */      else hasdot = 1;    }    else if (lisxdigit(cast_uchar(*s))) {      if (sigdig == 0 && *s == '0')  /* non-significant digit (zero)? */        nosigdig++;      else if (++sigdig <= MAXSIGDIG)  /* can read it without overflow? */          r = (r * cast_num(16.0)) + luaO_hexavalue(*s);      else e++; /* too many digits; ignore, but still count for exponent */      if (hasdot) e--;  /* decimal digit? correct exponent */    }    else break;  /* neither a dot nor a digit */  }  if (nosigdig + sigdig == 0)  /* no digits? */    return 0.0;  /* invalid format */  *endptr = cast(char *, s);  /* valid up to here */  e *= 4;  /* each digit multiplies/divides value by 2^4 */  if (*s == 'p' || *s == 'P') {  /* exponent part? */    int exp1 = 0;  /* exponent value */    int neg1;  /* exponent signal */    s++;  /* skip 'p' */    neg1 = isneg(&s);  /* signal */    if (!lisdigit(cast_uchar(*s)))      return 0.0;  /* invalid; must have at least one digit */    while (lisdigit(cast_uchar(*s)))  /* read exponent */      exp1 = exp1 * 10 + *(s++) - '0';    if (neg1) exp1 = -exp1;    e += exp1;    *endptr = cast(char *, s);  /* valid up to here */  }  if (neg) r = -r;  return l_mathop(ldexp)(r, e);}#endif/* }====================================================== *//* maximum length of a numeral */#if !defined (L_MAXLENNUM)#define L_MAXLENNUM200#endif// lua_strx2number把一个十六进制字符转成数字// lua_str2number把一个普通字符转成数字static const char *l_str2dloc (const char *s, lua_Number *result, int mode) {  char *endptr;  *result = (mode == 'x') ? lua_strx2number(s, &endptr)  /* try to convert */                          : lua_str2number(s, &endptr);  if (endptr == s) return NULL;  /* nothing recognized? */  while (lisspace(cast_uchar(*endptr))) endptr++;  /* skip trailing spaces */  return (*endptr == '\0') ? endptr : NULL;  /* OK if no trailing characters */}/*** Convert string 's' to a Lua number (put in 'result'). Return NULL** on fail or the address of the ending '\0' on success.** 'pmode' points to (and 'mode' contains) special things in the string:** - 'x'/'X' means an hexadecimal numeral** - 'n'/'N' means 'inf' or 'nan' (which should be rejected)** - '.' just optimizes the search for the common case (nothing special)** This function accepts both the current locale or a dot as the radix** mark. If the convertion fails, it may mean number has a dot but** locale accepts something else. In that case, the code copies 's'** to a buffer (because 's' is read-only), changes the dot to the** current locale radix mark, and tries to convert again.*/// 把字符串s转换成number数据，在失败时返回NULL或在成功时返回字符串最后一位的地址（就是'\0'的地址）// strpbrk（const char *s1, const char *s2）是在源字符串（s1）中找出最先含有搜索字符串（s2）中任一字符的位置并返回，若找不到则返回空指针。// pmode指向字符串中特殊的字符（'.','x','X','n','N'）// 'x'/'X'意味着十六进制字符// 'n'/'N'意味着无穷大或未定义(它们被直接返回)// 该函数接受当前区域设置或点作为基数标记。如果转换失败,那可能意味着数字是一个点并且本地也接受了其他别的东西// 在这种情况下,代码拷贝了一个s来指向一段缓冲区(因为s是只读的),将点更改为当前区域设置的基数，并尝试再次转换。static const char *l_str2d (const char *s, lua_Number *result) {  const char *endptr;  const char *pmode = strpbrk(s, ".xXnN");  int mode = pmode ? ltolower(cast_uchar(*pmode)) : 0;  if (mode == 'n')  /* reject 'inf' and 'nan' */    return NULL;  endptr = l_str2dloc(s, result, mode);  /* try to convert */  if (endptr == NULL) {  /* failed? may be a different locale */    char buff[L_MAXLENNUM + 1];    const char *pdot = strchr(s, '.');    if (strlen(s) > L_MAXLENNUM || pdot == NULL)      return NULL;  /* string too long or no dot; fail */    strcpy(buff, s);  /* copy string to buffer */    buff[pdot - s] = lua_getlocaledecpoint();  /* correct decimal point */    endptr = l_str2dloc(buff, result, mode);  /* try again */    if (endptr != NULL)      endptr = s + (endptr - buff);  /* make relative to 's' */  }  return endptr;}#define MAXBY10cast(lua_Unsigned, LUA_MAXINTEGER / 10)#define MAXLASTDcast_int(LUA_MAXINTEGER % 10)// 把字符串转换为int，结果保存在result中// 通过lisspace跳过开头的空格字符// 然后isneg获取正负号，1代表负,0代表正,并且s向前移一位// 然后判断是不是十六进制，是的话跳过'0x'，然后lisxdigit检查参数是否为16进制数字,如果是的话返回非0值,不然返回0.参数类型为int,但是可以直接将char 类型数据传入.// 然后将结果*16并加上新得的数字，luaO_hexavalue的作用就是把能转变成数字的字符变成数字并返回// 10进制的话，原理一样，但是多了一个溢出检测，机制就是判断a是不是大于LUA_MAXINTEGER / 10，因为下一步要进行a*10static const char *l_str2int (const char *s, lua_Integer *result) {  lua_Unsigned a = 0;  int empty = 1;  int neg;  while (lisspace(cast_uchar(*s))) s++;  /* skip initial spaces */  neg = isneg(&s);  if (s[0] == '0' &&      (s[1] == 'x' || s[1] == 'X')) {  /* hex? */    s += 2;  /* skip '0x' */    for (; lisxdigit(cast_uchar(*s)); s++) {      a = a * 16 + luaO_hexavalue(*s);      empty = 0;    }  }  else {  /* decimal */    for (; lisdigit(cast_uchar(*s)); s++) {      int d = *s - '0';      if (a >= MAXBY10 && (a > MAXBY10 || d > MAXLASTD + neg))  /* overflow? */        return NULL;  /* do not accept it (as integer) */      a = a * 10 + d;      empty = 0;    }  }  while (lisspace(cast_uchar(*s))) s++;  /* skip trailing spaces */  if (empty || *s != '\0') return NULL;  /* something wrong in the numeral */  else {    *result = l_castU2S((neg) ? 0u - a : a);    return s;  }}// 把一个字符串转换成数字// 首先调用l_str2int看能不能转换成int，可以的话调用setivalue创建一个类型为LUA_TNUMINT的int// 不行的话调用setfltvalue看能不能转换成float类型的数据,可以的话调用setfltvalue创建一个类型为LUA_TNUMFLT的float// 还是不行的就返回0，代表转换失败// 成功的话返回字符串的长度size_t luaO_str2num (const char *s, TValue *o) {  lua_Integer i; lua_Number n;  const char *e;  if ((e = l_str2int(s, &i)) != NULL) {  /* try as an integer */    setivalue(o, i);  }  else if ((e = l_str2d(s, &n)) != NULL) {  /* else try as a float */    setfltvalue(o, n);  }  else    return 0;  /* conversion failed */  return (e - s) + 1;  /* success; return string size */}// 返回x的utf8字节数量// x <= 0x10FFFF，这里x不能超过unicode的最大编码// x < 0x80属于ascii编码，buff的最后一位保存x，并且返回字节数1// 0x80等于十进制的128// 如果不属于ascii范围的话，就需要延长字节// 首先定义一个mfb，因为ascii的范围为0x00 - 0x7f// 大于ascii的范围之后就需要扩充字节了// else部分不太明白int luaO_utf8esc (char *buff, unsigned long x) {  int n = 1;  /* number of bytes put in buffer (backwards) */  lua_assert(x <= 0x10FFFF);  if (x < 0x80)  /* ascii? */    buff[UTF8BUFFSZ - 1] = cast(char, x);  else {  /* need continuation bytes */    unsigned int mfb = 0x3f;  /* maximum that fits in first byte */    do {  /* add continuation bytes */      buff[UTF8BUFFSZ - (n++)] = cast(char, 0x80 | (x & 0x3f));      x >>= 6;  /* remove added bits */      mfb >>= 1;  /* now there is one less bit available in first byte */    } while (x > mfb);  /* still needs continuation byte? */    buff[UTF8BUFFSZ - n] = cast(char, (~mfb << 1) | x);  /* add first byte */  }  return n;}/* maximum length of the conversion of a number to a string */#define MAXNUMBER2STR50/*** Convert a number object to a string*/// 把一个数字对象转换成字符串// lua_integer2str的作用就是把一个整数转换成字符串，定义在luaconf.h中// lua_number2str的作用就是把一个浮点型数据转换成字符串，定义在luaconf.h中// strspn的原型为：size_t strspn (const char *s,const char * accept)// strspn()从参数s 字符串的开头计算连续的字符，而这些字符都完全是accept 所指字符串中的字符。// 简单的说，若strspn()返回的数值为n，则代表字符串s 开头连续有n 个字符都是属于字符串accept内的字符。// 所以这里通过strspn判断是不是转换成了int值// 如果定义了LUA_COMPAT_FLOATSTRING则在字符串结尾加上0（定义在luaconf.h中）// lua_getlocaledecpoint()返回当地的小数点// 然后调用setsvalue2s创建一个LUA_TSTRING类型的TValue压入栈中void luaO_tostring (lua_State *L, StkId obj) {  char buff[MAXNUMBER2STR];  size_t len;  lua_assert(ttisnumber(obj));  if (ttisinteger(obj))    len = lua_integer2str(buff, sizeof(buff), ivalue(obj));  else {    len = lua_number2str(buff, sizeof(buff), fltvalue(obj));#if !defined(LUA_COMPAT_FLOATSTRING)    if (buff[strspn(buff, "-0123456789")] == '\0') {  /* looks like an int? */      buff[len++] = lua_getlocaledecpoint();      buff[len++] = '0';  /* adds '.0' to result */    }#endif  }  setsvalue2s(L, obj, luaS_newlstr(L, buff, len));}// 创建一个字符串，让L->top指向该字符串// luaS_newlstr创建一个字符串，到lstring.c中再分析// 然后调用luaD_inctop，让栈顶指针自增1static void pushstr (lua_State *L, const char *str, size_t l) {  setsvalue2s(L, L->top, luaS_newlstr(L, str, l));  luaD_inctop(L);}/*** this function handles only '%d', '%c', '%f', '%p', and '%s'   conventional formats, plus Lua-specific '%I' and '%U'*/// luaO_pushfstring(L, "%s:%d: %s", buff, line, msg)// luaO_pushvfstring的作用是把luaO_pushfstring传进来的可变参数中的值，一个一个的加入lua栈中// 这个函数仅支持'%d', '%c', '%f', '%p', and '%s'转换格式，外加lua的'%I' and '%U'// strchr作用是找出fmt中首次出现'%'的位置，并返回其指针// 首先，e的位置就是%的位置，然后调用pushstr向栈中=顶压入一个字符串，并栈顶自增1// 下面就是不同格式的参数压入规则了// 如果是's'的话，代表以'\0'结尾的字符串，通过va_arg返回可变的参数，va_arg的第二个参数是你要返回的参数的类型// 如果是'c'的话，代表以int作为的字符，然后lisprint判断是否为可打印字符，是的话直接入栈，不然就（这个地方我还不知道）// 如果是'd'的话，就代表是一个int，直接入栈，然后把这个int转换成字符串// 如果是'I'的话，就代表lua里面的lua_Integer，也是直接入栈，然后把这个lua_Integer转换成字符串// 如果是'f'的话，就代表是一个lua_Number，执行流程和lua_Integer一样// 如果是'p'的话，就代表是一个指针，把argp中的void *类型的参数按照%p的格式转换进buff中，然后返回装入buff中的size，然后入栈// 如果是'U'的话，就代表一个UTF-8序列，计算出序列的字节数，然后入栈const char *luaO_pushvfstring (lua_State *L, const char *fmt, va_list argp) {  int n = 0;  for (;;) {    const char *e = strchr(fmt, '%');    if (e == NULL) break;    pushstr(L, fmt, e - fmt);    switch (*(e+1)) {      case 's': {  /* zero-terminated string */        const char *s = va_arg(argp, char *);        if (s == NULL) s = "(null)";        pushstr(L, s, strlen(s));        break;      }      case 'c': {  /* an 'int' as a character */        char buff = cast(char, va_arg(argp, int));        if (lisprint(cast_uchar(buff)))          pushstr(L, &buff, 1);        else  /* non-printable character; print its code */          luaO_pushfstring(L, "<\\%d>", cast_uchar(buff));        break;      }      case 'd': {  /* an 'int' */        setivalue(L->top, va_arg(argp, int));        goto top2str;      }      case 'I': {  /* a 'lua_Integer' */        setivalue(L->top, cast(lua_Integer, va_arg(argp, l_uacInt)));        goto top2str;      }      case 'f': {  /* a 'lua_Number' */        setfltvalue(L->top, cast_num(va_arg(argp, l_uacNumber)));      top2str:  /* convert the top element to a string */        luaD_inctop(L);        luaO_tostring(L, L->top - 1);        break;      }      case 'p': {  /* a pointer */        char buff[4*sizeof(void *) + 8]; /* should be enough space for a '%p' */        int l = l_sprintf(buff, sizeof(buff), "%p", va_arg(argp, void *));        pushstr(L, buff, l);        break;      }      case 'U': {  /* an 'int' as a UTF-8 sequence */        char buff[UTF8BUFFSZ];        int l = luaO_utf8esc(buff, cast(long, va_arg(argp, long)));        pushstr(L, buff + UTF8BUFFSZ - l, l);        break;      }      case '%': {        pushstr(L, "%", 1);        break;      }      default: {        luaG_runerror(L, "invalid option '%%%c' to 'lua_pushfstring'",                         *(e + 1));      }    }    n += 2;    fmt = e+2;  }  luaD_checkstack(L, 1);  pushstr(L, fmt, strlen(fmt));  if (n > 0) luaV_concat(L, n + 1);  return svalue(L->top - 1);}// luaO_pushfstring的作用是把一个字符串按照固定格式压入L栈中，比如说：// luaO_pushfstring(L, "%s:%d: %s", buff, line, msg)   把一个调试信息格式的打印日志压入L栈中// va_list,va_start,va_end 这些宏定义在stdarg.h中// va_list定义了一个可变参数argp// va_start初始化了argp，第一个参数是argp，第二个参数是fmt（可变参数的前一个参数）const char *luaO_pushfstring (lua_State *L, const char *fmt, ...) {  const char *msg;  va_list argp;  va_start(argp, fmt);  msg = luaO_pushvfstring(L, fmt, argp);  va_end(argp);  return msg;}/* number of chars of a literal string without the ending \0 */#define LL(x)(sizeof(x)/sizeof(char) - 1)#define RETS"..."#define PRE"[string \""#define POS"\"]"#define addstr(a,b,l)( memcpy(a,b,(l) * sizeof(char)), a += (l) )// 看完debug的相关调用后，再回来分析void luaO_chunkid (char *out, const char *source, size_t bufflen) {  size_t l = strlen(source);  if (*source == '=') {  /* 'literal' source */    if (l <= bufflen)  /* small enough? */      memcpy(out, source + 1, l * sizeof(char));    else {  /* truncate it */      addstr(out, source + 1, bufflen - 1);      *out = '\0';    }  }  else if (*source == '@') {  /* file name */    if (l <= bufflen)  /* small enough? */      memcpy(out, source + 1, l * sizeof(char));    else {  /* add '...' before rest of name */      addstr(out, RETS, LL(RETS));      bufflen -= LL(RETS);      memcpy(out, source + 1 + l - bufflen, bufflen * sizeof(char));    }  }  else {  /* string; format as [string "source"] */    const char *nl = strchr(source, '\n');  /* find first new line (if any) */    addstr(out, PRE, LL(PRE));  /* add prefix */    bufflen -= LL(PRE RETS POS) + 1;  /* save space for prefix+suffix+'\0' */    if (l < bufflen && nl == NULL) {  /* small one-line source? */      addstr(out, source, l);  /* keep it */    }    else {      if (nl != NULL) l = nl - source;  /* stop at first newline */      if (l > bufflen) l = bufflen;      addstr(out, source, l);      addstr(out, RETS, LL(RETS));    }    memcpy(out, POS, (LL(POS) + 1) * sizeof(char));  }}