/*
** $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))

static int str_len(lua_State *L)
{
    size_t l;
    luaL_checklstring(L, 1, &l);
    lua_pushinteger(L, l);
    return 1;
}

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;
}

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;
}

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;
}

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;
}

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;
}

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;
}

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;
}

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;
}

static 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 */
}

static int str_find_aux(lua_State *L, int find)
{
    size_t l1, l2;
    const char *s = luaL_checklstring(L, 1, &l1);
    const char *p = luaL_checklstring(L, 2, &l2);
    ptrdiff_t init = posrelat(luaL_optinteger(L, 3, 1), l1) - 1;
    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';
}

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;
}
