/*
** $Id: lstrlib.c,v 1.178.1.1 2013/04/12 18:48:47 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"

/*
** maximum number of captures that a pattern can do during
** pattern-matching. This limit is arbitrary.
*/
#if !defined(LUA_MAXCAPTURES)
#define LUA_MAXCAPTURES 32
#endif

/* 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, (lua_Integer)l);
	return 1;
}

/* translate a relative string position: negative means back from end */
static size_t posrelat(ptrdiff_t pos, size_t len)
{
	if (pos >= 0)
		return (size_t)pos;
	else if (0u - (size_t)pos > len)
		return 0;
	else
		return len - ((size_t)-pos) + 1;
}

static int str_sub(lua_State *L)
{
	size_t l;
	const char *s = luaL_checklstring(L, 1, &l);
	size_t start = posrelat(luaL_checkinteger(L, 2), l);
	size_t end = posrelat(luaL_optinteger(L, 3, -1), l);
	if (start < 1) start = 1;
	if (end > l) end = 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, i;
	luaL_Buffer b;
	const char *s = luaL_checklstring(L, 1, &l);
	char *p = luaL_buffinitsize(L, &b, l);
	for (i = 0; i < l; i++)
		p[i] = s[l - i - 1];
	luaL_pushresultsize(&b, l);
	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);
	char *p = luaL_buffinitsize(L, &b, l);
	for (i = 0; i < l; i++)
		p[i] = tolower(uchar(s[i]));
	luaL_pushresultsize(&b, l);
	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);
	char *p = luaL_buffinitsize(L, &b, l);
	for (i = 0; i < l; i++)
		p[i] = toupper(uchar(s[i]));
	luaL_pushresultsize(&b, l);
	return 1;
}

/* reasonable limit to avoid arithmetic overflow */
#define MAXSIZE ((~(size_t)0) >> 1)

static int str_rep(lua_State *L)
{
	size_t l, lsep;
	const char *s = luaL_checklstring(L, 1, &l);
	int n = luaL_checkint(L, 2);
	const char *sep = luaL_optlstring(L, 3, "", &lsep);
	if (n <= 0)
		lua_pushliteral(L, "");
	else if (l + lsep < l || l + lsep >= MAXSIZE / n) /* may overflow? */
		return luaL_error(L, "resulting string too large");
	else
	{
		size_t totallen = n * l + (n - 1) * lsep;
		luaL_Buffer b;
		char *p = luaL_buffinitsize(L, &b, totallen);
		while (n-- > 1)
		{ /* first n-1 copies (followed by separator) */
			memcpy(p, s, l * sizeof(char));
			p += l;
			if (lsep > 0)
			{ /* avoid empty 'memcpy' (may be expensive) */
				memcpy(p, sep, lsep * sizeof(char));
				p += lsep;
			}
		}
		memcpy(p, s, l * sizeof(char)); /* last copy (not followed by separator) */
		luaL_pushresultsize(&b, totallen);
	}
	return 1;
}

static int str_byte(lua_State *L)
{
	size_t l;
	const char *s = luaL_checklstring(L, 1, &l);
	size_t posi = posrelat(luaL_optinteger(L, 2, 1), l);
	size_t pose = posrelat(luaL_optinteger(L, 3, posi), l);
	int n, i;
	if (posi < 1) posi = 1;
	if (pose > l) pose = l;
	if (posi > pose) return 0; /* empty interval; return no values */
	n = (int)(pose - posi + 1);
	if (posi + n <= pose) /* (size_t -> int) overflow? */
		return 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;
	char *p = luaL_buffinitsize(L, &b, n);
	for (i = 1; i <= n; i++)
	{
		int c = luaL_checkint(L, i);
		luaL_argcheck(L, uchar(c) == c, i, "value out of range");
		p[i - 1] = uchar(c);
	}
	luaL_pushresultsize(&b, n);
	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)
		return 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
{
	int matchdepth;       /* control for recursive depth (to avoid C stack overflow) */
	const char *src_init; /* init of source string */
	const char *src_end;  /* end ('\0') of source string */
	const char *p_end;    /* end ('\0') of pattern */
	lua_State *L;
	int level; /* total number of captures (finished or unfinished) */
	struct
	{
		const char *init;
		ptrdiff_t len;
	} capture[LUA_MAXCAPTURES];
} MatchState;

/* recursive function */
static const char *match(MatchState *ms, const char *s, const char *p);

/* maximum recursion depth for 'match' */
#if !defined(MAXCCALLS)
#define MAXCCALLS 200
#endif

#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 %%%d", l + 1);
	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 == ms->p_end)
				luaL_error(ms->L, "malformed pattern (ends with " LUA_QL("%%") ")");
			return p + 1;
		}
		case '[':
		{
			if (*p == '^') p++;
			do
			{ /* look for a `]' */
				if (p == ms->p_end)
					luaL_error(ms->L, "malformed pattern (missing " LUA_QL("]") ")");
				if (*(p++) == L_ESC && p < ms->p_end)
					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 'g':
			res = isgraph(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; /* deprecated option */
		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(MatchState *ms, const char *s, const char *p,
					   const char *ep)
{
	if (s >= ms->src_end)
		return 0;
	else
	{
		int c = uchar(*s);
		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 *matchbalance(MatchState *ms, const char *s,
								const char *p)
{
	if (p >= ms->p_end - 1)
		luaL_error(ms->L,
				   "malformed pattern "
				   "(missing arguments to " LUA_QL("%%b") ")");
	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 (singlematch(ms, 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 (singlematch(ms, 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)
{
	if (ms->matchdepth-- == 0)
		luaL_error(ms->L, "pattern too complex");
init: /* using goto's to optimize tail recursion */
	if (p != ms->p_end)
	{ /* end of pattern? */
		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 '$':
			{
				if ((p + 1) != ms->p_end)          /* is the `$' the last char in pattern? */
					goto dflt;                     /* no; go to default */
				s = (s == ms->src_end) ? s : NULL; /* check end of string */
				break;
			}
			case L_ESC:
			{ /* escaped sequences not in the format class[*+?-]? */
				switch (*(p + 1))
				{
					case 'b':
					{ /* balanced string? */
						s = matchbalance(ms, s, p + 2);
						if (s != NULL)
						{
							p += 4;
							goto init; /* return match(ms, s, p + 4); */
						}              /* else fail (s == NULL) */
						break;
					}
					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))
						{
							p = ep;
							goto init; /* return match(ms, s, ep); */
						}
						s = NULL; /* match failed */
						break;
					}
					case '0':
					case '1':
					case '2':
					case '3':
					case '4':
					case '5':
					case '6':
					case '7':
					case '8':
					case '9':
					{ /* capture results (%0-%9)? */
						s = match_capture(ms, s, uchar(*(p + 1)));
						if (s != NULL)
						{
							p += 2;
							goto init; /* return match(ms, s, p + 2) */
						}
						break;
					}
					default:
						goto dflt;
				}
				break;
			}
			default:
			dflt:
			{                                     /* pattern class plus optional suffix */
				const char *ep = classend(ms, p); /* points to optional suffix */
				/* does not match at least once? */
				if (!singlematch(ms, s, p, ep))
				{
					if (*ep == '*' || *ep == '?' || *ep == '-')
					{ /* accept empty? */
						p = ep + 1;
						goto init; /* return match(ms, s, ep + 1); */
					}
					else          /* '+' or no suffix */
						s = NULL; /* fail */
				}
				else
				{ /* matched once */
					switch (*ep)
					{ /* handle optional suffix */
						case '?':
						{ /* optional */
							const char *res;
							if ((res = match(ms, s + 1, ep + 1)) != NULL)
								s = res;
							else
							{
								p = ep + 1;
								goto init; /* else return match(ms, s, ep + 1); */
							}
							break;
						}
						case '+': /* 1 or more repetitions */
							s++;  /* 1 match already done */
								  /* go through */
						case '*': /* 0 or more repetitions */
							s = max_expand(ms, s, p, ep);
							break;
						case '-': /* 0 or more repetitions (minimum) */
							s = min_expand(ms, s, p, ep);
							break;
						default: /* no suffix */
							s++;
							p = ep;
							goto init; /* return match(ms, s + 1, ep); */
					}
				}
				break;
			}
		}
	}
	ms->matchdepth++;
	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 -= 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 */
}

/* check whether pattern has no special characters */
static int nospecials(const char *p, size_t l)
{
	size_t upto = 0;
	do
	{
		if (strpbrk(p + upto, SPECIALS))
			return 0;                 /* pattern has a special character */
		upto += strlen(p + upto) + 1; /* may have more after \0 */
	} while (upto <= l);
	return 1; /* no special chars found */
}

static int str_find_aux(lua_State *L, int find)
{
	size_t ls, lp;
	const char *s = luaL_checklstring(L, 1, &ls);
	const char *p = luaL_checklstring(L, 2, &lp);
	size_t init = posrelat(luaL_optinteger(L, 3, 1), ls);
	if (init < 1)
		init = 1;
	else if (init > ls + 1)
	{                   /* start after string's end? */
		lua_pushnil(L); /* cannot find anything */
		return 1;
	}
	/* explicit request or no special characters? */
	if (find && (lua_toboolean(L, 4) || nospecials(p, lp)))
	{
		/* do a plain search */
		const char *s2 = lmemfind(s + init - 1, ls - init + 1, p, lp);
		if (s2)
		{
			lua_pushinteger(L, s2 - s + 1);
			lua_pushinteger(L, s2 - s + lp);
			return 2;
		}
	}
	else
	{
		MatchState ms;
		const char *s1 = s + init - 1;
		int anchor = (*p == '^');
		if (anchor)
		{
			p++;
			lp--; /* skip anchor character */
		}
		ms.L = L;
		ms.matchdepth = MAXCCALLS;
		ms.src_init = s;
		ms.src_end = s + ls;
		ms.p_end = p + lp;
		do
		{
			const char *res;
			ms.level = 0;
			lua_assert(ms.matchdepth == MAXCCALLS);
			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, lp;
	const char *s = lua_tolstring(L, lua_upvalueindex(1), &ls);
	const char *p = lua_tolstring(L, lua_upvalueindex(2), &lp);
	const char *src;
	ms.L = L;
	ms.matchdepth = MAXCCALLS;
	ms.src_init = s;
	ms.src_end = s + ls;
	ms.p_end = p + lp;
	for (src = s + (size_t)lua_tointeger(L, lua_upvalueindex(3));
		 src <= ms.src_end;
		 src++)
	{
		const char *e;
		ms.level = 0;
		lua_assert(ms.matchdepth == MAXCCALLS);
		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 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])))
			{
				if (news[i] != L_ESC)
					luaL_error(ms->L, "invalid use of " LUA_QL("%c") " in replacement string", L_ESC);
				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, int tr)
{
	lua_State *L = ms->L;
	switch (tr)
	{
		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;
		}
		default:
		{ /* LUA_TNUMBER or LUA_TSTRING */
			add_s(ms, b, s, e);
			return;
		}
	}
	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, lp;
	const char *src = luaL_checklstring(L, 1, &srcl);
	const char *p = luaL_checklstring(L, 2, &lp);
	int tr = lua_type(L, 3);
	size_t max_s = luaL_optinteger(L, 4, srcl + 1);
	int anchor = (*p == '^');
	size_t 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);
	if (anchor)
	{
		p++;
		lp--; /* skip anchor character */
	}
	ms.L = L;
	ms.matchdepth = MAXCCALLS;
	ms.src_init = src;
	ms.src_end = src + srcl;
	ms.p_end = p + lp;
	while (n < max_s)
	{
		const char *e;
		ms.level = 0;
		lua_assert(ms.matchdepth == MAXCCALLS);
		e = match(&ms, src, p);
		if (e)
		{
			n++;
			add_value(&ms, &b, src, e, tr);
		}
		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;
}

/* }====================================================== */

/*
** {======================================================
** STRING FORMAT
** =======================================================
*/

/*
** LUA_INTFRMLEN is the length modifier for integer conversions in
** 'string.format'; LUA_INTFRM_T is the integer type corresponding to
** the previous length
*/
#if !defined(LUA_INTFRMLEN) /* { */
#if defined(LUA_USE_LONGLONG)

#define LUA_INTFRMLEN "ll"
#define LUA_INTFRM_T long long

#else

#define LUA_INTFRMLEN "l"
#define LUA_INTFRM_T long

#endif
#endif /* } */

/*
** LUA_FLTFRMLEN is the length modifier for float conversions in
** 'string.format'; LUA_FLTFRM_T is the float type corresponding to
** the previous length
*/
#if !defined(LUA_FLTFRMLEN)

#define LUA_FLTFRMLEN ""
#define LUA_FLTFRM_T double

#endif

/* 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--)
	{
		if (*s == '"' || *s == '\\' || *s == '\n')
		{
			luaL_addchar(b, '\\');
			luaL_addchar(b, *s);
		}
		else if (*s == '\0' || iscntrl(uchar(*s)))
		{
			char buff[10];
			if (!isdigit(uchar(*(s + 1))))
				sprintf(buff, "\\%d", (int)uchar(*s));
			else
				sprintf(buff, "\\%03d", (int)uchar(*s));
			luaL_addstring(b, buff);
		}
		else
			luaL_addchar(b, *s);
		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) / sizeof(char))
		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++) = '%';
	memcpy(form, strfrmt, (p - strfrmt + 1) * sizeof(char));
	form += p - strfrmt + 1;
	*form = '\0';
	return p;
}

/*
** add length modifier into formats
*/
static void addlenmod(char *form, const char *lenmod)
{
	size_t l = strlen(form);
	size_t lm = strlen(lenmod);
	char spec = form[l - 1];
	strcpy(form + l - 1, lenmod);
	form[l + lm - 1] = spec;
	form[l + lm] = '\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 = luaL_prepbuffsize(&b, MAX_ITEM); /* to put formatted item */
			int nb = 0;                                   /* number of bytes in added item */
			if (++arg > top)
				luaL_argerror(L, arg, "no value");
			strfrmt = scanformat(L, strfrmt, form);
			switch (*strfrmt++)
			{
				case 'c':
				{
					nb = sprintf(buff, form, luaL_checkint(L, arg));
					break;
				}
				case 'd':
				case 'i':
				{
					lua_Number n = luaL_checknumber(L, arg);
					LUA_INTFRM_T ni = (LUA_INTFRM_T)n;
					lua_Number diff = n - (lua_Number)ni;
					luaL_argcheck(L, -1 < diff && diff < 1, arg,
								  "not a number in proper range");
					addlenmod(form, LUA_INTFRMLEN);
					nb = sprintf(buff, form, ni);
					break;
				}
				case 'o':
				case 'u':
				case 'x':
				case 'X':
				{
					lua_Number n = luaL_checknumber(L, arg);
					unsigned LUA_INTFRM_T ni = (unsigned LUA_INTFRM_T)n;
					lua_Number diff = n - (lua_Number)ni;
					luaL_argcheck(L, -1 < diff && diff < 1, arg,
								  "not a non-negative number in proper range");
					addlenmod(form, LUA_INTFRMLEN);
					nb = sprintf(buff, form, ni);
					break;
				}
				case 'e':
				case 'E':
				case 'f':
#if defined(LUA_USE_AFORMAT)
				case 'a':
				case 'A':
#endif
				case 'g':
				case 'G':
				{
					addlenmod(form, LUA_FLTFRMLEN);
					nb = sprintf(buff, form, (LUA_FLTFRM_T)luaL_checknumber(L, arg));
					break;
				}
				case 'q':
				{
					addquoted(L, &b, arg);
					break;
				}
				case 's':
				{
					size_t l;
					const char *s = luaL_tolstring(L, arg, &l);
					if (!strchr(form, '.') && l >= 100)
					{
						/* no precision and string is too long to be formatted;
               keep original string */
						luaL_addvalue(&b);
						break;
					}
					else
					{
						nb = sprintf(buff, form, s);
						lua_pop(L, 1); /* remove result from 'luaL_tolstring' */
						break;
					}
				}
				default:
				{ /* also treat cases `pnLlh' */
					return luaL_error(L, "invalid option " LUA_QL("%%%c") " to " LUA_QL("format"), *(strfrmt - 1));
				}
			}
			luaL_addsize(&b, nb);
		}
	}
	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},
	{"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);       /* table to be metatable for strings */
	lua_pushliteral(L, "");         /* dummy string */
	lua_pushvalue(L, -2);           /* copy table */
	lua_setmetatable(L, -2);        /* set table as metatable for strings */
	lua_pop(L, 1);                  /* pop dummy string */
	lua_pushvalue(L, -2);           /* get string library */
	lua_setfield(L, -2, "__index"); /* metatable.__index = string */
	lua_pop(L, 1);                  /* pop metatable */
}

/*
** Open string library
*/
LUAMOD_API int luaopen_string(lua_State *L)
{
	luaL_newlib(L, strlib);
	createmetatable(L);
	return 1;
}
