/*** $Id: lstrlib.c,v 1.132.1.5 2010/05/14 15:34:19 roberto Exp $** Standard library for string Operations and pattern-matching** See Copyright Notice in lua.h*/#include <ctype.h>#include <stddef.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#define lstrlib_c#define LUA_LIB#include "lua.h"#include "lauxlib.h"#include "lualib.h"/* macro to `unsign' a character */#define uchar(c)        ((unsigned char)(c))//獲取字符串的長度static int str_len (lua_State *L) {  size_t l;  luaL_checklstring(L, 1, &l);//判斷所得到的值是否為字符串，是的話返回字符串，并修改l為字符串長度  lua_pushinteger(L, l);  return 1;}//ptrdiff_t是C/C++標準庫中定義的一個與機器相關的數據類型。ptrdiff_t類型變量通常用來保存兩個指針減法操作的結果//ptrdiff_t定義在stddef.h（cstddef）這個文件內// 在lua里面索引是從1開始的，-1是從后面開始的，這個函數的作用就是，提供以負數這種方式，// 來訪問堆棧以及字符串、table等。其原理還是根據下面的函數把負數根據長度轉換成整數的形式，其本質和正數是一樣的// （這個函數不是用來讓lua代碼直接調用的，而是實現給C代碼調用的，所以這個函數的書寫形式不同于平常的被Lua調用的C代碼）static ptrdiff_t posrelat (ptrdiff_t pos, size_t len) {  /* relative string position: negative means back from end */  if (pos < 0) pos += (ptrdiff_t)len + 1;  return (pos >= 0) ? pos : 0;}// 截取字符串static int str_sub (lua_State *L) {  size_t l;  const char *s = luaL_checklstring(L, 1, &l);  ptrdiff_t start = posrelat(luaL_checkinteger(L, 2), l);  ptrdiff_t end = posrelat(luaL_optinteger(L, 3, -1), l);  if (start < 1) start = 1;  if (end > (ptrdiff_t)l) end = (ptrdiff_t)l;  if (start <= end)    lua_pushlstring(L, s+start-1, end-start+1);  else lua_pushliteral(L, "");  return 1;}// 翻轉字符串// luaL_Buffer創建一個允許C代碼編譯的Lua字符串塊，它的使用模式如下：// 1、首先定義一個luaL_Buffer類型的變量// 2、然后用luaL_buffinit(L, &b)初始化一下// 3、然后用luaL_addchar(&b, s[l])來add一下string// 4、最后用luaL_pushresult(&b)來壓入棧頂static int str_reverse (lua_State *L) {  size_t l;  luaL_Buffer b;  const char *s = luaL_checklstring(L, 1, &l);  luaL_buffinit(L, &b);  while (l--) luaL_addchar(&b, s[l]);  luaL_pushresult(&b);  return 1;}// 字符串轉換小寫static int str_lower (lua_State *L) {  size_t l;  size_t i;  luaL_Buffer b;  const char *s = luaL_checklstring(L, 1, &l);  luaL_buffinit(L, &b);  for (i=0; i<l; i++)    luaL_addchar(&b, tolower(uchar(s[i])));  luaL_pushresult(&b);  return 1;}// 字符串轉換大寫static int str_upper (lua_State *L) {  size_t l;  size_t i;  luaL_Buffer b;  const char *s = luaL_checklstring(L, 1, &l);  luaL_buffinit(L, &b);  for (i=0; i<l; i++)    luaL_addchar(&b, toupper(uchar(s[i])));  luaL_pushresult(&b);  return 1;}// 復制n段字符串static int str_rep (lua_State *L) {  size_t l;  luaL_Buffer b;  const char *s = luaL_checklstring(L, 1, &l);  int n = luaL_checkint(L, 2);  luaL_buffinit(L, &b);  while (n-- > 0)    luaL_addlstring(&b, s, l);  luaL_pushresult(&b);  return 1;}// 返回某個字符的內部數值表示static int str_byte (lua_State *L) {  size_t l;  const char *s = luaL_checklstring(L, 1, &l);  ptrdiff_t posi = posrelat(luaL_optinteger(L, 2, 1), l);  ptrdiff_t pose = posrelat(luaL_optinteger(L, 3, posi), l);  int n, i;  if (posi <= 0) posi = 1;  if ((size_t)pose > l) pose = l;  if (posi > pose) return 0;  /* empty interval; return no values */  n = (int)(pose -  posi + 1);  if (posi + n <= pose)  /* overflow? */    luaL_error(L, "string slice too long");  luaL_checkstack(L, n, "string slice too long");  for (i=0; i<n; i++)    lua_pushinteger(L, uchar(s[posi+i-1]));  return n;}// 將整數轉換為字符// luaL_argcheck檢查參數是否滿足條件，不滿足的話拋出一條錯誤// #define uchar(c)        ((unsigned char)(c)) 這個宏將整數轉換為字符static int str_char (lua_State *L) {  int n = lua_gettop(L);  /* number of arguments */  int i;  luaL_Buffer b;  luaL_buffinit(L, &b);  for (i=1; i<=n; i++) {    int c = luaL_checkint(L, i);    luaL_argcheck(L, uchar(c) == c, i, "invalid value");    luaL_addchar(&b, uchar(c));  }  luaL_pushresult(&b);  return 1;}static int writer (lua_State *L, const void* b, size_t size, void* B) {  (void)L;  luaL_addlstring((luaL_Buffer*) B, (const char *)b, size);  return 0;} // lua_settop(L, 1);把棧頂位置設置為1static int str_dump (lua_State *L) {  luaL_Buffer b;  luaL_checktype(L, 1, LUA_TFUNCTION);  lua_settop(L, 1);  luaL_buffinit(L,&b);  if (lua_dump(L, writer, &b) != 0)    luaL_error(L, "unable to dump given function");  luaL_pushresult(&b);  return 1;}/*** {======================================================** PATTERN MATCHING** =======================================================*/#define CAP_UNFINISHED	(-1)#define CAP_POSITION	(-2)typedef struct MatchState {  const char *src_init;  /* init of source string */  const char *src_end;  /* end (`/0') of source string */  lua_State *L;  int level;  /* total number of captures (finished or unfinished) */  struct {    const char *init;    ptrdiff_t len;  } capture[LUA_MAXCAPTURES];} MatchState;#define L_ESC		'%'#define SPECIALS	"^$*+?.([%-"static int check_capture (MatchState *ms, int l) {  l -= '1';  if (l < 0 || l >= ms->level || ms->capture[l].len == CAP_UNFINISHED)    return luaL_error(ms->L, "invalid capture index");  return l;}static int capture_to_close (MatchState *ms) {  int level = ms->level;  for (level--; level>=0; level--)    if (ms->capture[level].len == CAP_UNFINISHED) return level;  return luaL_error(ms->L, "invalid pattern capture");}static const char *classend (MatchState *ms, const char *p) {  switch (*p++) {    case L_ESC: {      if (*p == '/0')        luaL_error(ms->L, "malformed pattern (ends with " LUA_QL("%%") ")");      return p+1;    }    case '[': {      if (*p == '^') p++;      do {  /* look for a `]' */        if (*p == '/0')          luaL_error(ms->L, "malformed pattern (missing " LUA_QL("]") ")");        if (*(p++) == L_ESC && *p != '/0')          p++;  /* skip escapes (e.g. `%]') */      } while (*p != ']');      return p+1;    }    default: {      return p;    }  }}static int match_class (int c, int cl) {  int res;  switch (tolower(cl)) {    case 'a' : res = isalpha(c); break;    case 'c' : res = iscntrl(c); break;    case 'd' : res = isdigit(c); break;    case 'l' : res = islower(c); break;    case 'p' : res = ispunct(c); break;    case 's' : res = isspace(c); break;    case 'u' : res = isupper(c); break;    case 'w' : res = isalnum(c); break;    case 'x' : res = isxdigit(c); break;    case 'z' : res = (c == 0); break;    default: return (cl == c);  }  return (islower(cl) ? res : !res);}static int matchbracketclass (int c, const char *p, const char *ec) {  int sig = 1;  if (*(p+1) == '^') {    sig = 0;    p++;  /* skip the `^' */  }  while (++p < ec) {    if (*p == L_ESC) {      p++;      if (match_class(c, uchar(*p)))        return sig;    }    else if ((*(p+1) == '-') && (p+2 < ec)) {      p+=2;      if (uchar(*(p-2)) <= c && c <= uchar(*p))        return sig;    }    else if (uchar(*p) == c) return sig;  }  return !sig;}static int singlematch (int c, const char *p, const char *ep) {  switch (*p) {    case '.': return 1;  /* matches any char */    case L_ESC: return match_class(c, uchar(*(p+1)));    case '[': return matchbracketclass(c, p, ep-1);    default:  return (uchar(*p) == c);  }}static const char *match (MatchState *ms, const char *s, const char *p);static const char *matchbalance (MatchState *ms, const char *s,                                   const char *p) {  if (*p == 0 || *(p+1) == 0)    luaL_error(ms->L, "unbalanced pattern");  if (*s != *p) return NULL;  else {    int b = *p;    int e = *(p+1);    int cont = 1;    while (++s < ms->src_end) {      if (*s == e) {        if (--cont == 0) return s+1;      }      else if (*s == b) cont++;    }  }  return NULL;  /* string ends out of balance */}static const char *max_expand (MatchState *ms, const char *s,                                 const char *p, const char *ep) {  ptrdiff_t i = 0;  /* counts maximum expand for item */  while ((s+i)<ms->src_end && singlematch(uchar(*(s+i)), p, ep))    i++;  /* keeps trying to match with the maximum repetitions */  while (i>=0) {    const char *res = match(ms, (s+i), ep+1);    if (res) return res;    i--;  /* else didn't match; reduce 1 repetition to try again */  }  return NULL;}static const char *min_expand (MatchState *ms, const char *s,                                 const char *p, const char *ep) {  for (;;) {    const char *res = match(ms, s, ep+1);    if (res != NULL)      return res;    else if (s<ms->src_end && singlematch(uchar(*s), p, ep))      s++;  /* try with one more repetition */    else return NULL;  }}static const char *start_capture (MatchState *ms, const char *s,                                    const char *p, int what) {  const char *res;  int level = ms->level;  if (level >= LUA_MAXCAPTURES) luaL_error(ms->L, "too many captures");  ms->capture[level].init = s;  ms->capture[level].len = what;  ms->level = level+1;  if ((res=match(ms, s, p)) == NULL)  /* match failed? */    ms->level--;  /* undo capture */  return res;}static const char *end_capture (MatchState *ms, const char *s,                                  const char *p) {  int l = capture_to_close(ms);  const char *res;  ms->capture[l].len = s - ms->capture[l].init;  /* close capture */  if ((res = match(ms, s, p)) == NULL)  /* match failed? */    ms->capture[l].len = CAP_UNFINISHED;  /* undo capture */  return res;}static const char *match_capture (MatchState *ms, const char *s, int l) {  size_t len;  l = check_capture(ms, l);  len = ms->capture[l].len;  if ((size_t)(ms->src_end-s) >= len &&      memcmp(ms->capture[l].init, s, len) == 0)    return s+len;  else return NULL;}static const char *match (MatchState *ms, const char *s, const char *p) {  init: /* using goto's to optimize tail recursion */  switch (*p) {    case '(': {  /* start capture */      if (*(p+1) == ')')  /* position capture? */        return start_capture(ms, s, p+2, CAP_POSITION);      else        return start_capture(ms, s, p+1, CAP_UNFINISHED);    }    case ')': {  /* end capture */      return end_capture(ms, s, p+1);    }    case L_ESC: {      switch (*(p+1)) {        case 'b': {  /* balanced string? */          s = matchbalance(ms, s, p+2);          if (s == NULL) return NULL;          p+=4; goto init;  /* else return match(ms, s, p+4); */        }        case 'f': {  /* frontier? */          const char *ep; char PRevious;          p += 2;          if (*p != '[')            luaL_error(ms->L, "missing " LUA_QL("[") " after "                               LUA_QL("%%f") " in pattern");          ep = classend(ms, p);  /* points to what is next */          previous = (s == ms->src_init) ? '/0' : *(s-1);          if (matchbracketclass(uchar(previous), p, ep-1) ||             !matchbracketclass(uchar(*s), p, ep-1)) return NULL;          p=ep; goto init;  /* else return match(ms, s, ep); */        }        default: {          if (isdigit(uchar(*(p+1)))) {  /* capture results (%0-%9)? */            s = match_capture(ms, s, uchar(*(p+1)));            if (s == NULL) return NULL;            p+=2; goto init;  /* else return match(ms, s, p+2) */          }          goto dflt;  /* case default */        }      }    }    case '/0': {  /* end of pattern */      return s;  /* match succeeded */    }    case '$': {      if (*(p+1) == '/0')  /* is the `$' the last char in pattern? */        return (s == ms->src_end) ? s : NULL;  /* check end of string */      else goto dflt;    }    default: dflt: {  /* it is a pattern item */      const char *ep = classend(ms, p);  /* points to what is next */      int m = s<ms->src_end && singlematch(uchar(*s), p, ep);      switch (*ep) {        case '?': {  /* optional */          const char *res;          if (m && ((res=match(ms, s+1, ep+1)) != NULL))            return res;          p=ep+1; goto init;  /* else return match(ms, s, ep+1); */        }        case '*': {  /* 0 or more repetitions */          return max_expand(ms, s, p, ep);        }        case '+': {  /* 1 or more repetitions */          return (m ? max_expand(ms, s+1, p, ep) : NULL);        }        case '-': {  /* 0 or more repetitions (minimum) */          return min_expand(ms, s, p, ep);        }        default: {          if (!m) return NULL;          s++; p=ep; goto init;  /* else return match(ms, s+1, ep); */        }      }    }  }}static const char *lmemfind (const char *s1, size_t l1,                               const char *s2, size_t l2) {  if (l2 == 0) return s1;  /* empty strings are everywhere */  else if (l2 > l1) return NULL;  /* avoids a negative `l1' */  else {    const char *init;  /* to search for a `*s2' inside `s1' */    l2--;  /* 1st char will be checked by `memchr' */    l1 = l1-l2;  /* `s2' cannot be found after that */    while (l1 > 0 && (init = (const char *)memchr(s1, *s2, l1)) != NULL) {      init++;   /* 1st char is already checked */      if (memcmp(init, s2+1, l2) == 0)        return init-1;      else {  /* correct `l1' and `s1' to try again */        l1 -= init-s1;        s1 = init;      }    }    return NULL;  /* not found */  }}static void push_onecapture (MatchState *ms, int i, const char *s,                                                    const char *e) {  if (i >= ms->level) {    if (i == 0)  /* ms->level == 0, too */      lua_pushlstring(ms->L, s, e - s);  /* add whole match */    else      luaL_error(ms->L, "invalid capture index");  }  else {    ptrdiff_t l = ms->capture[i].len;    if (l == CAP_UNFINISHED) luaL_error(ms->L, "unfinished capture");    if (l == CAP_POSITION)      lua_pushinteger(ms->L, ms->capture[i].init - ms->src_init + 1);    else      lua_pushlstring(ms->L, ms->capture[i].init, l);  }}static int push_captures (MatchState *ms, const char *s, const char *e) {  int i;  int nlevels = (ms->level == 0 && s) ? 1 : ms->level;  luaL_checkstack(ms->L, nlevels, "too many captures");  for (i = 0; i < nlevels; i++)    push_onecapture(ms, i, s, e);  return nlevels;  /* number of strings pushed */} //若調用的是string.find()并且第四個參數為true，表明忽略模式中的特殊字符，只做簡單的原始匹配 //或者模式中，不存在特殊字符，也是做簡單的原始匹配，這些特殊字符，包括"^$*+?.([%-"，它是用 //宏SPECIALS來定義的，利用內部接口nospecials來判斷模式中是否有特殊字符static int str_find_aux (lua_State *L, int find) {  size_t l1, l2;  const char *s = luaL_checklstring(L, 1, &l1);////獲取原始數據字符串  const char *p = luaL_checklstring(L, 2, &l2);////獲取模式字符串  ptrdiff_t init = posrelat(luaL_optinteger(L, 3, 1), l1) - 1;//獲取開始匹配的位置  if (init < 0) init = 0;  else if ((size_t)(init) > l1) init = (ptrdiff_t)l1;  if (find && (lua_toboolean(L, 4) ||  /* explicit request? */      strpbrk(p, SPECIALS) == NULL)) {  /* or no special characters? */    /* do a plain search */    const char *s2 = lmemfind(s+init, l1-init, p, l2);    if (s2) {      lua_pushinteger(L, s2-s+1);      lua_pushinteger(L, s2-s+l2);      return 2;    }  }  else {    MatchState ms;    int anchor = (*p == '^') ? (p++, 1) : 0;    const char *s1=s+init;    ms.L = L;    ms.src_init = s;    ms.src_end = s+l1;    do {      const char *res;      ms.level = 0;      if ((res=match(&ms, s1, p)) != NULL) {        if (find) {          lua_pushinteger(L, s1-s+1);  /* start */          lua_pushinteger(L, res-s);   /* end */          return push_captures(&ms, NULL, 0) + 2;        }        else          return push_captures(&ms, s1, res);      }    } while (s1++ < ms.src_end && !anchor);  }  lua_pushnil(L);  /* not found */  return 1;}static int str_find (lua_State *L) {  return str_find_aux(L, 1);}static int str_match (lua_State *L) {  return str_find_aux(L, 0);}static int gmatch_aux (lua_State *L) {  MatchState ms;  size_t ls;  const char *s = lua_tolstring(L, lua_upvalueindex(1), &ls);  const char *p = lua_tostring(L, lua_upvalueindex(2));  const char *src;  ms.L = L;  ms.src_init = s;  ms.src_end = s+ls;  for (src = s + (size_t)lua_tointeger(L, lua_upvalueindex(3));       src <= ms.src_end;       src++) {    const char *e;    ms.level = 0;    if ((e = match(&ms, src, p)) != NULL) {      lua_Integer newstart = e-s;      if (e == src) newstart++;  /* empty match? go at least one position */      lua_pushinteger(L, newstart);      lua_replace(L, lua_upvalueindex(3));      return push_captures(&ms, src, e);    }  }  return 0;  /* not found */}static int gmatch (lua_State *L) {  luaL_checkstring(L, 1);  luaL_checkstring(L, 2);  lua_settop(L, 2);  lua_pushinteger(L, 0);  lua_pushcclosure(L, gmatch_aux, 3);  return 1;}static int gfind_nodef (lua_State *L) {  return luaL_error(L, LUA_QL("string.gfind") " was renamed to "                       LUA_QL("string.gmatch"));}static void add_s (MatchState *ms, luaL_Buffer *b, const char *s,                                                   const char *e) {  size_t l, i;  const char *news = lua_tolstring(ms->L, 3, &l);  for (i = 0; i < l; i++) {    if (news[i] != L_ESC)      luaL_addchar(b, news[i]);    else {      i++;  /* skip ESC */      if (!isdigit(uchar(news[i])))        luaL_addchar(b, news[i]);      else if (news[i] == '0')          luaL_addlstring(b, s, e - s);      else {        push_onecapture(ms, news[i] - '1', s, e);        luaL_addvalue(b);  /* add capture to accumulated result */      }    }  }}static void add_value (MatchState *ms, luaL_Buffer *b, const char *s,                                                       const char *e) {  lua_State *L = ms->L;  switch (lua_type(L, 3)) {    case LUA_TNUMBER:    case LUA_TSTRING: {      add_s(ms, b, s, e);      return;    }    case LUA_TFUNCTION: {      int n;      lua_pushvalue(L, 3);      n = push_captures(ms, s, e);      lua_call(L, n, 1);      break;    }    case LUA_TTABLE: {      push_onecapture(ms, 0, s, e);      lua_gettable(L, 3);      break;    }  }  if (!lua_toboolean(L, -1)) {  /* nil or false? */    lua_pop(L, 1);    lua_pushlstring(L, s, e - s);  /* keep original text */  }  else if (!lua_isstring(L, -1))    luaL_error(L, "invalid replacement value (a %s)", luaL_typename(L, -1));   luaL_addvalue(b);  /* add result to accumulator */}static int str_gsub (lua_State *L) {  size_t srcl;  const char *src = luaL_checklstring(L, 1, &srcl);  const char *p = luaL_checkstring(L, 2);  int  tr = lua_type(L, 3);  int max_s = luaL_optint(L, 4, srcl+1);  int anchor = (*p == '^') ? (p++, 1) : 0;  int n = 0;  MatchState ms;  luaL_Buffer b;  luaL_argcheck(L, tr == LUA_TNUMBER || tr == LUA_TSTRING ||                   tr == LUA_TFUNCTION || tr == LUA_TTABLE, 3,                      "string/function/table expected");  luaL_buffinit(L, &b);  ms.L = L;  ms.src_init = src;  ms.src_end = src+srcl;  while (n < max_s) {    const char *e;    ms.level = 0;    e = match(&ms, src, p);    if (e) {      n++;      add_value(&ms, &b, src, e);    }    if (e && e>src) /* non empty match? */      src = e;  /* skip it */    else if (src < ms.src_end)      luaL_addchar(&b, *src++);    else break;    if (anchor) break;  }  luaL_addlstring(&b, src, ms.src_end-src);  luaL_pushresult(&b);  lua_pushinteger(L, n);  /* number of substitutions */  return 2;}/* }====================================================== *//* maximum size of each formatted item (> len(format('%99.99f', -1e308))) */#define MAX_ITEM	512/* valid flags in a format specification */#define FLAGS	"-+ #0"/*** maximum size of each format specification (such as '%-099.99d')** (+10 accounts for %99.99x plus margin of error)*/#define MAX_FORMAT	(sizeof(FLAGS) + sizeof(LUA_INTFRMLEN) + 10)static void addquoted (lua_State *L, luaL_Buffer *b, int arg) {  size_t l;  const char *s = luaL_checklstring(L, arg, &l);  luaL_addchar(b, '"');  while (l--) {    switch (*s) {      case '"': case '//': case '/n': {        luaL_addchar(b, '//');        luaL_addchar(b, *s);        break;      }      case '/r': {        luaL_addlstring(b, "//r", 2);        break;      }      case '/0': {        luaL_addlstring(b, "//000", 4);        break;      }      default: {        luaL_addchar(b, *s);        break;      }    }    s++;  }  luaL_addchar(b, '"');}static const char *scanformat (lua_State *L, const char *strfrmt, char *form) {  const char *p = strfrmt;  while (*p != '/0' && strchr(FLAGS, *p) != NULL) p++;  /* skip flags */  if ((size_t)(p - strfrmt) >= sizeof(FLAGS))    luaL_error(L, "invalid format (repeated flags)");  if (isdigit(uchar(*p))) p++;  /* skip width */  if (isdigit(uchar(*p))) p++;  /* (2 digits at most) */  if (*p == '.') {    p++;    if (isdigit(uchar(*p))) p++;  /* skip precision */    if (isdigit(uchar(*p))) p++;  /* (2 digits at most) */  }  if (isdigit(uchar(*p)))    luaL_error(L, "invalid format (width or precision too long)");  *(form++) = '%';  strncpy(form, strfrmt, p - strfrmt + 1);  form += p - strfrmt + 1;  *form = '/0';  return p;}static void addintlen (char *form) {  size_t l = strlen(form);  char spec = form[l - 1];  strcpy(form + l - 1, LUA_INTFRMLEN);  form[l + sizeof(LUA_INTFRMLEN) - 2] = spec;  form[l + sizeof(LUA_INTFRMLEN) - 1] = '/0';}// 控制字符串的輸出格式static int str_format (lua_State *L) {  int top = lua_gettop(L);  int arg = 1;  size_t sfl;  const char *strfrmt = luaL_checklstring(L, arg, &sfl);  const char *strfrmt_end = strfrmt+sfl;  luaL_Buffer b;  luaL_buffinit(L, &b);  while (strfrmt < strfrmt_end) {    if (*strfrmt != L_ESC)      luaL_addchar(&b, *strfrmt++);    else if (*++strfrmt == L_ESC)      luaL_addchar(&b, *strfrmt++);  /* %% */    else { /* format item */      char form[MAX_FORMAT];  /* to store the format (`%...') */      char buff[MAX_ITEM];  /* to store the formatted item */      if (++arg > top)        luaL_argerror(L, arg, "no value");      strfrmt = scanformat(L, strfrmt, form);      switch (*strfrmt++) {        case 'c': {          sprintf(buff, form, (int)luaL_checknumber(L, arg));          break;        }        case 'd':  case 'i': {          addintlen(form);          sprintf(buff, form, (LUA_INTFRM_T)luaL_checknumber(L, arg));          break;        }        case 'o':  case 'u':  case 'x':  case 'X': {          addintlen(form);          sprintf(buff, form, (unsigned LUA_INTFRM_T)luaL_checknumber(L, arg));          break;        }        case 'e':  case 'E': case 'f':        case 'g': case 'G': {          sprintf(buff, form, (double)luaL_checknumber(L, arg));          break;        }        case 'q': {          addquoted(L, &b, arg);          continue;  /* skip the 'addsize' at the end */        }        case 's': {          size_t l;          const char *s = luaL_checklstring(L, arg, &l);          if (!strchr(form, '.') && l >= 100) {            /* no precision and string is too long to be formatted;               keep original string */            lua_pushvalue(L, arg);            luaL_addvalue(&b);            continue;  /* skip the `addsize' at the end */          }          else {            sprintf(buff, form, s);            break;          }        }        default: {  /* also treat cases `pnLlh' */          return luaL_error(L, "invalid option " LUA_QL("%%%c") " to "                               LUA_QL("format"), *(strfrmt - 1));        }      }      luaL_addlstring(&b, buff, strlen(buff));    }  }  luaL_pushresult(&b);  return 1;}static const luaL_Reg strlib[] = {  {"byte", str_byte},  {"char", str_char},  {"dump", str_dump},  {"find", str_find},  {"format", str_format},  {"gfind", gfind_nodef},  {"gmatch", gmatch},  {"gsub", str_gsub},  {"len", str_len},  {"lower", str_lower},  {"match", str_match},  {"rep", str_rep},  {"reverse", str_reverse},  {"sub", str_sub},  {"upper", str_upper},  {NULL, NULL}};static void createmetatable (lua_State *L) {  lua_createtable(L, 0, 1);  /* create metatable for strings */  lua_pushliteral(L, "");  /* dummy string */  lua_pushvalue(L, -2);  lua_setmetatable(L, -2);  /* set string metatable */  lua_pop(L, 1);  /* pop dummy string */  lua_pushvalue(L, -2);  /* string library... */  lua_setfield(L, -2, "__index");  /* ...is the __index metamethod */  lua_pop(L, 1);  /* pop metatable */}/*** Open string library*/LUALIB_API int luaopen_string (lua_State *L) {  luaL_register(L, LUA_STRLIBNAME, strlib);#if defined(LUA_COMPAT_GFIND)  lua_getfield(L, -1, "gmatch");  lua_setfield(L, -2, "gfind");#endif  createmetatable(L);  return 1;}