/*
** String library.
** Copyright (C) 2005-2014 Mike Pall. See Copyright Notice in luajit.h
**
** Major portions taken verbatim or adapted from the Lua interpreter.
** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
*/

#include <stdio.h>

#define lib_string_c
#define LUA_LIB

#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"

#include "lj_obj.h"
#include "lj_gc.h"
#include "lj_err.h"
#include "lj_str.h"
#include "lj_tab.h"
#include "lj_meta.h"
#include "lj_state.h"
#include "lj_ff.h"
#include "lj_bcdump.h"
#include "lj_char.h"
#include "lj_lib.h"

/* ------------------------------------------------------------------------ */

#define LJLIB_MODULE_string

LJLIB_ASM(string_len) LJLIB_REC(.)
{
    lj_lib_checkstr(L, 1);
    return FFH_RETRY;
}

LJLIB_ASM(string_byte) LJLIB_REC(string_range 0)
{
    GCstr *s = lj_lib_checkstr(L, 1);
    int32_t len = (int32_t)s->len;
    int32_t start = lj_lib_optint(L, 2, 1);
    int32_t stop = lj_lib_optint(L, 3, start);
    int32_t n, i;
    const unsigned char *p;
    if (stop < 0)
        stop += len + 1;
    if (start < 0)
        start += len + 1;
    if (start <= 0)
        start = 1;
    if (stop > len)
        stop = len;
    if (start > stop)
        return FFH_RES(0); /* Empty interval: return no results. */
    start--;
    n = stop - start;
    if ((uint32_t)n > LUAI_MAXCSTACK)
        lj_err_caller(L, LJ_ERR_STRSLC);
    lj_state_checkstack(L, (MSize)n);
    p = (const unsigned char *)strdata(s) + start;
    for (i = 0; i < n; i++)
        setintV(L->base + i - 1, p[i]);
    return FFH_RES(n);
}

LJLIB_ASM(string_char)
{
    int i, nargs = (int)(L->top - L->base);
    char *buf = lj_str_needbuf(L, &G(L)->tmpbuf, (MSize)nargs);
    for (i = 1; i <= nargs; i++) {
        int32_t k = lj_lib_checkint(L, i);
        if (!checku8(k))
            lj_err_arg(L, i, LJ_ERR_BADVAL);
        buf[i - 1] = (char)k;
    }
    setstrV(L, L->base - 1, lj_str_new(L, buf, (size_t)nargs));
    return FFH_RES(1);
}

LJLIB_ASM(string_sub) LJLIB_REC(string_range 1)
{
    lj_lib_checkstr(L, 1);
    lj_lib_checkint(L, 2);
    setintV(L->base + 2, lj_lib_optint(L, 3, -1));
    return FFH_RETRY;
}

LJLIB_ASM(string_rep)
{
    GCstr *s = lj_lib_checkstr(L, 1);
    int32_t k = lj_lib_checkint(L, 2);
    GCstr *sep = lj_lib_optstr(L, 3);
    int32_t len = (int32_t)s->len;
    global_State *g = G(L);
    int64_t tlen;
    const char *src;
    char *buf;
    if (k <= 0) {
    empty:
        setstrV(L, L->base - 1, &g->strempty);
        return FFH_RES(1);
    }
    if (sep) {
        tlen = (int64_t)len + sep->len;
        if (tlen > LJ_MAX_STR)
            lj_err_caller(L, LJ_ERR_STROV);
        tlen *= k;
        if (tlen > LJ_MAX_STR)
            lj_err_caller(L, LJ_ERR_STROV);
    }
    else {
        tlen = (int64_t)k * len;
        if (tlen > LJ_MAX_STR)
            lj_err_caller(L, LJ_ERR_STROV);
    }
    if (tlen == 0)
        goto empty;
    buf = lj_str_needbuf(L, &g->tmpbuf, (MSize)tlen);
    src = strdata(s);
    if (sep) {
        tlen -= sep->len; /* Ignore trailing separator. */
        if (k > 1) {      /* Paste one string and one separator. */
            int32_t i;
            i = 0;
            while (i < len)
                *buf++ = src[i++];
            src = strdata(sep);
            len = sep->len;
            i = 0;
            while (i < len)
                *buf++ = src[i++];
            src = g->tmpbuf.buf;
            len += s->len;
            k--; /* Now copy that k-1 times. */
        }
    }
    do {
        int32_t i = 0;
        do {
            *buf++ = src[i++];
        } while (i < len);
    } while (--k > 0);
    setstrV(L, L->base - 1, lj_str_new(L, g->tmpbuf.buf, (size_t)tlen));
    return FFH_RES(1);
}

LJLIB_ASM(string_reverse)
{
    GCstr *s = lj_lib_checkstr(L, 1);
    lj_str_needbuf(L, &G(L)->tmpbuf, s->len);
    return FFH_RETRY;
}
LJLIB_ASM_(string_lower)
LJLIB_ASM_(string_upper)

/* ------------------------------------------------------------------------ */

static int writer_buf(lua_State *L, const void *p, size_t size, void *b)
{
    luaL_addlstring((luaL_Buffer *)b, (const char *)p, size);
    UNUSED(L);
    return 0;
}

LJLIB_CF(string_dump)
{
    GCfunc *fn = lj_lib_checkfunc(L, 1);
    int strip = L->base + 1 < L->top && tvistruecond(L->base + 1);
    luaL_Buffer b;
    L->top = L->base + 1;
    luaL_buffinit(L, &b);
    if (!isluafunc(fn) || lj_bcwrite(L, funcproto(fn), writer_buf, &b, strip))
        lj_err_caller(L, LJ_ERR_STRDUMP);
    luaL_pushresult(&b);
    return 1;
}

/* ------------------------------------------------------------------------ */

/* macro to `unsign' a character */
#define uchar(c) ((unsigned char)(c))

#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) */
    int depth;
    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)
        lj_err_caller(ms->L, LJ_ERR_STRCAPI);
    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;
    lj_err_caller(ms->L, LJ_ERR_STRPATC);
    return 0; /* unreachable */
}

static const char *classend(MatchState *ms, const char *p)
{
    switch (*p++) {
    case L_ESC:
        if (*p == '\0')
            lj_err_caller(ms->L, LJ_ERR_STRPATE);
        return p + 1;
    case '[':
        if (*p == '^')
            p++;
        do { /* look for a `]' */
            if (*p == '\0')
                lj_err_caller(ms->L, LJ_ERR_STRPATM);
            if (*(p++) == L_ESC && *p != '\0')
                p++; /* skip escapes (e.g. `%]') */
        } while (*p != ']');
        return p + 1;
    default:
        return p;
    }
}

static const unsigned char match_class_map[32] = {0,
                                                  LJ_CHAR_ALPHA,
                                                  0,
                                                  LJ_CHAR_CNTRL,
                                                  LJ_CHAR_DIGIT,
                                                  0,
                                                  0,
                                                  LJ_CHAR_GRAPH,
                                                  0,
                                                  0,
                                                  0,
                                                  0,
                                                  LJ_CHAR_LOWER,
                                                  0,
                                                  0,
                                                  0,
                                                  LJ_CHAR_PUNCT,
                                                  0,
                                                  0,
                                                  LJ_CHAR_SPACE,
                                                  0,
                                                  LJ_CHAR_UPPER,
                                                  0,
                                                  LJ_CHAR_ALNUM,
                                                  LJ_CHAR_XDIGIT,
                                                  0,
                                                  0,
                                                  0,
                                                  0,
                                                  0,
                                                  0,
                                                  0};

static int match_class(int c, int cl)
{
    if ((cl & 0xc0) == 0x40) {
        int t = match_class_map[(cl & 0x1f)];
        if (t) {
            t = lj_char_isa(c, t);
            return (cl & 0x20) ? t : !t;
        }
        if (cl == 'z')
            return c == 0;
        if (cl == 'Z')
            return c != 0;
    }
    return (cl == c);
}

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)
        lj_err_caller(ms->L, LJ_ERR_STRPATU);
    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)
        lj_err_caller(ms->L, LJ_ERR_STRCAPN);
    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 = (size_t)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)
{
    if (++ms->depth > LJ_MAX_XLEVEL)
        lj_err_caller(ms->L, LJ_ERR_STRPATX);
init: /* using goto's to optimize tail recursion */
    switch (*p) {
    case '(':                /* start capture */
        if (*(p + 1) == ')') /* position capture? */
            s = start_capture(ms, s, p + 2, CAP_POSITION);
        else
            s = start_capture(ms, s, p + 1, CAP_UNFINISHED);
        break;
    case ')': /* end capture */
        s = end_capture(ms, s, p + 1);
        break;
    case L_ESC:
        switch (*(p + 1)) {
        case 'b': /* balanced string? */
            s = matchbalance(ms, s, p + 2);
            if (s == NULL)
                break;
            p += 4;
            goto init; /* else s = match(ms, s, p+4); */
        case 'f': {    /* frontier? */
            const char *ep;
            char previous;
            p += 2;
            if (*p != '[')
                lj_err_caller(ms->L, LJ_ERR_STRPATB);
            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)) {
                s = NULL;
                break;
            }
            p = ep;
            goto init; /* else s = match(ms, s, ep); */
        }
        default:
            if (lj_char_isdigit(
                    uchar(*(p + 1)))) { /* capture results (%0-%9)? */
                s = match_capture(ms, s, uchar(*(p + 1)));
                if (s == NULL)
                    break;
                p += 2;
                goto init; /* else s = match(ms, s, p+2) */
            }
            goto dflt; /* case default */
        }
        break;
    case '\0': /* end of pattern */
        break; /* match succeeded */
    case '$':
        /* is the `$' the last char in pattern? */
        if (*(p + 1) != '\0')
            goto dflt;
        if (s != ms->src_end)
            s = NULL; /* check end of string */
        break;
    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)) {
                s = res;
                break;
            }
            p = ep + 1;
            goto init; /* else s = match(ms, s, ep+1); */
        }
        case '*': /* 0 or more repetitions */
            s = max_expand(ms, s, p, ep);
            break;
        case '+': /* 1 or more repetitions */
            s = (m ? max_expand(ms, s + 1, p, ep) : NULL);
            break;
        case '-': /* 0 or more repetitions (minimum) */
            s = min_expand(ms, s, p, ep);
            break;
        default:
            if (m) {
                s++;
                p = ep;
                goto init;
            } /* else s = match(ms, s+1, ep); */
            s = NULL;
            break;
        }
        break;
    }
    }
    ms->depth--;
    return s;
}

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 -= (size_t)(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, (size_t)(e - s)); /* add whole match */
        else
            lj_err_caller(ms->L, LJ_ERR_STRCAPI);
    }
    else {
        ptrdiff_t l = ms->capture[i].len;
        if (l == CAP_UNFINISHED)
            lj_err_caller(ms->L, LJ_ERR_STRCAPU);
        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, (size_t)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 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_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) {
#if LJ_52
        setnilV(L->top - 1);
        return 1;
#else
        init = (ptrdiff_t)l1;
#endif
    }
    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 - (size_t)init, p, l2);
        if (s2) {
            lua_pushinteger(L, s2 - s + 1);
            lua_pushinteger(L, s2 - s + (ptrdiff_t)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 = ms.depth = 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;
}

LJLIB_CF(string_find) { return str_find_aux(L, 1); }

LJLIB_CF(string_match) { return str_find_aux(L, 0); }

LJLIB_NOREG LJLIB_CF(string_gmatch_aux)
{
    const char *p = strVdata(lj_lib_upvalue(L, 2));
    GCstr *str = strV(lj_lib_upvalue(L, 1));
    const char *s = strdata(str);
    TValue *tvpos = lj_lib_upvalue(L, 3);
    const char *src = s + tvpos->u32.lo;
    MatchState ms;
    ms.L = L;
    ms.src_init = s;
    ms.src_end = s + str->len;
    for (; src <= ms.src_end; src++) {
        const char *e;
        ms.level = ms.depth = 0;
        if ((e = match(&ms, src, p)) != NULL) {
            int32_t pos = (int32_t)(e - s);
            if (e == src)
                pos++; /* Ensure progress for empty match. */
            tvpos->u32.lo = (uint32_t)pos;
            return push_captures(&ms, src, e);
        }
    }
    return 0; /* not found */
}

LJLIB_CF(string_gmatch)
{
    lj_lib_checkstr(L, 1);
    lj_lib_checkstr(L, 2);
    L->top = L->base + 3;
    (L->top - 1)->u64 = 0;
    lj_lib_pushcc(L, lj_cf_string_gmatch_aux, FF_string_gmatch_aux, 3);
    return 1;
}

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 (!lj_char_isdigit(uchar(news[i]))) {
                luaL_addchar(b, news[i]);
            }
            else if (news[i] == '0') {
                luaL_addlstring(b, s, (size_t)(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, (size_t)(e - s)); /* keep original text */
    }
    else if (!lua_isstring(L, -1)) {
        lj_err_callerv(L, LJ_ERR_STRGSRV, luaL_typename(L, -1));
    }
    luaL_addvalue(b); /* add result to accumulator */
}

LJLIB_CF(string_gsub)
{
    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, (int)(srcl + 1));
    int anchor = (*p == '^') ? (p++, 1) : 0;
    int n = 0;
    MatchState ms;
    luaL_Buffer b;
    if (!(tr == LUA_TNUMBER || tr == LUA_TSTRING || tr == LUA_TFUNCTION ||
          tr == LUA_TTABLE))
        lj_err_arg(L, 3, LJ_ERR_NOSFT);
    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 = ms.depth = 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, (size_t)(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_FMTITEM 512
/* valid flags in a format specification */
#define FMT_FLAGS "-+ #0"
/*
** maximum size of each format specification (such as '%-099.99d')
** (+10 accounts for %99.99x plus margin of error)
*/
#define MAX_FMTSPEC (sizeof(FMT_FLAGS) + sizeof(LUA_INTFRMLEN) + 10)

static void addquoted(lua_State *L, luaL_Buffer *b, int arg)
{
    GCstr *str = lj_lib_checkstr(L, arg);
    int32_t len = (int32_t)str->len;
    const char *s = strdata(str);
    luaL_addchar(b, '"');
    while (len--) {
        uint32_t c = uchar(*s);
        if (c == '"' || c == '\\' || c == '\n') {
            luaL_addchar(b, '\\');
        }
        else if (lj_char_iscntrl(c)) { /* This can only be 0-31 or 127. */
            uint32_t d;
            luaL_addchar(b, '\\');
            if (c >= 100 || lj_char_isdigit(uchar(s[1]))) {
                luaL_addchar(b, '0' + (c >= 100));
                if (c >= 100)
                    c -= 100;
                goto tens;
            }
            else if (c >= 10) {
            tens:
                d = (c * 205) >> 11;
                c -= d * 10;
                luaL_addchar(b, '0' + d);
            }
            c += '0';
        }
        luaL_addchar(b, c);
        s++;
    }
    luaL_addchar(b, '"');
}

static const char *scanformat(lua_State *L, const char *strfrmt, char *form)
{
    const char *p = strfrmt;
    while (*p != '\0' && strchr(FMT_FLAGS, *p) != NULL)
        p++; /* skip flags */
    if ((size_t)(p - strfrmt) >= sizeof(FMT_FLAGS))
        lj_err_caller(L, LJ_ERR_STRFMTR);
    if (lj_char_isdigit(uchar(*p)))
        p++; /* skip width */
    if (lj_char_isdigit(uchar(*p)))
        p++; /* (2 digits at most) */
    if (*p == '.') {
        p++;
        if (lj_char_isdigit(uchar(*p)))
            p++; /* skip precision */
        if (lj_char_isdigit(uchar(*p)))
            p++; /* (2 digits at most) */
    }
    if (lj_char_isdigit(uchar(*p)))
        lj_err_caller(L, LJ_ERR_STRFMTW);
    *(form++) = '%';
    strncpy(form, strfrmt, (size_t)(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 unsigned LUA_INTFRM_T num2intfrm(lua_State *L, int arg)
{
    if (sizeof(LUA_INTFRM_T) == 4) {
        return (LUA_INTFRM_T)lj_lib_checkbit(L, arg);
    }
    else {
        cTValue *o;
        lj_lib_checknumber(L, arg);
        o = L->base + arg - 1;
        if (tvisint(o))
            return (LUA_INTFRM_T)intV(o);
        else
            return (LUA_INTFRM_T)numV(o);
    }
}

static unsigned LUA_INTFRM_T num2uintfrm(lua_State *L, int arg)
{
    if (sizeof(LUA_INTFRM_T) == 4) {
        return (unsigned LUA_INTFRM_T)lj_lib_checkbit(L, arg);
    }
    else {
        cTValue *o;
        lj_lib_checknumber(L, arg);
        o = L->base + arg - 1;
        if (tvisint(o))
            return (unsigned LUA_INTFRM_T)intV(o);
        else if ((int32_t)o->u32.hi < 0)
            return (unsigned LUA_INTFRM_T)(LUA_INTFRM_T)numV(o);
        else
            return (unsigned LUA_INTFRM_T)numV(o);
    }
}

static GCstr *meta_tostring(lua_State *L, int arg)
{
    TValue *o = L->base + arg - 1;
    cTValue *mo;
    lua_assert(o < L->top); /* Caller already checks for existence. */
    if (LJ_LIKELY(tvisstr(o)))
        return strV(o);
    if (!tvisnil(mo = lj_meta_lookup(L, o, MM_tostring))) {
        copyTV(L, L->top++, mo);
        copyTV(L, L->top++, o);
        lua_call(L, 1, 1);
        L->top--;
        if (tvisstr(L->top))
            return strV(L->top);
        o = L->base + arg - 1;
        copyTV(L, o, L->top);
    }
    if (tvisnumber(o)) {
        return lj_str_fromnumber(L, o);
    }
    else if (tvisnil(o)) {
        return lj_str_newlit(L, "nil");
    }
    else if (tvisfalse(o)) {
        return lj_str_newlit(L, "false");
    }
    else if (tvistrue(o)) {
        return lj_str_newlit(L, "true");
    }
    else {
        if (tvisfunc(o) && isffunc(funcV(o)))
            lj_str_pushf(L, "function: builtin#%d", funcV(o)->c.ffid);
        else
            lj_str_pushf(L, "%s: %p", lj_typename(o), lua_topointer(L, arg));
        L->top--;
        return strV(L->top);
    }
}

LJLIB_CF(string_format)
{
    int arg = 1, top = (int)(L->top - L->base);
    GCstr *fmt = lj_lib_checkstr(L, arg);
    const char *strfrmt = strdata(fmt);
    const char *strfrmt_end = strfrmt + fmt->len;
    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_FMTSPEC]; /* to store the format (`%...') */
            char buff[MAX_FMTITEM]; /* to store the formatted item */
            if (++arg > top)
                luaL_argerror(L, arg, lj_obj_typename[0]);
            strfrmt = scanformat(L, strfrmt, form);
            switch (*strfrmt++) {
            case 'c':
                sprintf(buff, form, lj_lib_checkint(L, arg));
                break;
            case 'd':
            case 'i':
                addintlen(form);
                sprintf(buff, form, num2intfrm(L, arg));
                break;
            case 'o':
            case 'u':
            case 'x':
            case 'X':
                addintlen(form);
                sprintf(buff, form, num2uintfrm(L, arg));
                break;
            case 'e':
            case 'E':
            case 'f':
            case 'g':
            case 'G':
            case 'a':
            case 'A': {
                TValue tv;
                tv.n = lj_lib_checknum(L, arg);
                if (LJ_UNLIKELY((tv.u32.hi << 1) >= 0xffe00000)) {
                    /* Canonicalize output of non-finite values. */
                    char *p, nbuf[LJ_STR_NUMBUF];
                    size_t len = lj_str_bufnum(nbuf, &tv);
                    if (strfrmt[-1] < 'a') {
                        nbuf[len - 3] = nbuf[len - 3] - 0x20;
                        nbuf[len - 2] = nbuf[len - 2] - 0x20;
                        nbuf[len - 1] = nbuf[len - 1] - 0x20;
                    }
                    nbuf[len] = '\0';
                    for (p = form; *p < 'A' && *p != '.'; p++)
                        ;
                    *p++ = 's';
                    *p = '\0';
                    sprintf(buff, form, nbuf);
                    break;
                }
                sprintf(buff, form, (double)tv.n);
                break;
            }
            case 'q':
                addquoted(L, &b, arg);
                continue;
            case 'p':
                lj_str_pushf(L, "%p", lua_topointer(L, arg));
                luaL_addvalue(&b);
                continue;
            case 's': {
                GCstr *str = meta_tostring(L, arg);
                if (!strchr(form, '.') && str->len >= 100) {
                    /* no precision and string is too long to be formatted;
	     keep original string */
                    setstrV(L, L->top++, str);
                    luaL_addvalue(&b);
                    continue;
                }
                sprintf(buff, form, strdata(str));
                break;
            }
            default:
                lj_err_callerv(L, LJ_ERR_STRFMTO, *(strfrmt - 1));
                break;
            }
            luaL_addlstring(&b, buff, strlen(buff));
        }
    }
    luaL_pushresult(&b);
    return 1;
}

/* ------------------------------------------------------------------------ */

#include "lj_libdef.h"

LUALIB_API int luaopen_string(lua_State *L)
{
    GCtab *mt;
    global_State *g;
    LJ_LIB_REG(L, LUA_STRLIBNAME, string);
#if defined(LUA_COMPAT_GFIND) && !LJ_52
    lua_getfield(L, -1, "gmatch");
    lua_setfield(L, -2, "gfind");
#endif
    mt = lj_tab_new(L, 0, 1);
    /* NOBARRIER: basemt is a GC root. */
    g = G(L);
    setgcref(basemt_it(g, LJ_TSTR), obj2gco(mt));
    settabV(L, lj_tab_setstr(L, mt, mmname_str(g, MM_index)), tabV(L->top - 1));
    mt->nomm = (uint8_t)(~(1u << MM_index));
    return 1;
}
