use Lua 5.3's source for string packing

4 files changed, 1491 insertions, 9 deletions

diff --git a/compat53.lua b/compat53.lua
index 67a8c8f..4a78260 100644
--- a/compat53.lua
+++ b/compat53.lua
@@ -46,15 +46,24 @@ if lua_version < "5.3" then
    end
 
 
-   -- use Roberto's struct module for string packing/unpacking for now
-   -- maybe we'll later extract the functions from the 5.3 string
-   -- library for greater compatiblity, but it uses the 5.3 buffer API
-   -- which cannot easily be backported to Lua 5.1.
-   local struct_ok, struct = pcall(require, "struct")
-   if struct_ok then
-      string.pack = struct.pack
-      string.packsize = struct.size
-      string.unpack = struct.unpack
+   -- load string packing functions
+   local str_ok, strlib = pcall(require, "compat53.string")
+   if str_ok then
+      for k,v in pairs(strlib) do
+         string[k] = v
+      end
+   end
+
+
+   -- try Roberto's struct module for string packing/unpacking if
+   -- compat53.string is unavailable
+   if not str_ok then
+      local struct_ok, struct = pcall(require, "struct")
+      if struct_ok then
+         string.pack = struct.pack
+         string.packsize = struct.size
+         string.unpack = struct.unpack
+      end
    end
 
 
diff --git a/lprefix.h b/lprefix.h
index 79f0bd8..2ee5802 100644
--- a/lprefix.h
+++ b/lprefix.h
@@ -54,6 +54,9 @@
 
 #ifdef ltablib_c
 #  define luaopen_table luaopen_compat53_table
+/* lua_rawgeti in compat53.h is implemented as a macro, so the
+ * function signature doesn't match when you use a function pointer
+ */
 static int compat53_rawgeti (lua_State *L, int i, lua_Integer n) {
   return lua_rawgeti(L, i, n);
 }
@@ -64,11 +67,50 @@ static void compat53_rawseti (lua_State *L, int i, lua_Integer n) {
 }
 #  undef lua_rawseti
 #  define lua_rawseti compat53_rawseti
+/* we have lua_compare emulation for Lua 5.1, but it involves calling
+ * Lua code, and the only use in the table library is for '<', so ...
+ */
 #  if LUA_VERSION_NUM == 501
 #    undef lua_compare
 #    define lua_compare(L, a, b, op) lua_lessthan(L, a, b)
 #  endif
 #endif /* ltablib_c */
 
+#ifdef lstrlib_c
+/* move the string library open function out of the way (we only take
+ * the string packing functions)!
+ */
+#  define luaopen_string luaopen_string_XXX
+/* used in string.format implementation, which we don't use: */
+#  ifndef LUA_INTEGER_FRMLEN
+#    define LUA_INTEGER_FRMLEN ""
+#    define LUA_NUMBER_FRMLEN ""
+#  endif
+#  if LUA_VERSION_NUM < 503
+/* lstrlib assumes that lua_Integer and lua_Unsigned have the same
+ * size, so we use the unsigned equivalent of ptrdiff_t! */
+#  define lua_Unsigned size_t
+#  endif
+static int str_pack (lua_State *L);
+static int str_packsize (lua_State *L);
+static int str_unpack (lua_State *L);
+LUAMOD_API int luaopen_compat53_string (lua_State *L) {
+  luaL_Reg const funcs[] = {
+    { "pack", str_pack },
+    { "packsize", str_packsize },
+    { "unpack", str_unpack },
+    { NULL, NULL }
+  };
+  luaL_newlib(L, funcs);
+  return 1;
+}
+/* make luaopen_string(_XXX) static, so it (and all other referenced
+ * string functions) won't be included in the resulting dll
+ * (hopefully).
+ */
+#  undef LUAMOD_API
+#  define LUAMOD_API static
+#endif /* lstrlib.c */
+
 #endif
 
diff --git a/lstrlib.c b/lstrlib.c
new file mode 100644
index 0000000..a650b76
--- /dev/null
+++ b/lstrlib.c
@@ -0,0 +1,1430 @@
+/*
+** $Id: lstrlib.c,v 1.221 2014/12/11 14:03:07 roberto Exp $
+** Standard library for string operations and pattern-matching
+** See Copyright Notice in lua.h
+*/
+
+#define lstrlib_c
+#define LUA_LIB
+
+#include "lprefix.h"
+
+
+#include <ctype.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#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))
+
+
+/*
+** Some sizes are better limited to fit in 'int', but must also fit in
+** 'size_t'. (We assume that 'lua_Integer' cannot be smaller than 'int'.)
+*/
+#define MAXSIZE  \
+        (sizeof(size_t) < sizeof(int) ? (~(size_t)0) : (size_t)(INT_MAX))
+
+
+
+
+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 lua_Integer posrelat (lua_Integer pos, size_t len) {
+  if (pos >= 0) return pos;
+  else if (0u - (size_t)pos > len) return 0;
+  else return (lua_Integer)len + pos + 1;
+}
+
+
+static int str_sub (lua_State *L) {
+  size_t l;
+  const char *s = luaL_checklstring(L, 1, &l);
+  lua_Integer start = posrelat(luaL_checkinteger(L, 2), l);
+  lua_Integer end = posrelat(luaL_optinteger(L, 3, -1), l);
+  if (start < 1) start = 1;
+  if (end > (lua_Integer)l) end = l;
+  if (start <= end)
+    lua_pushlstring(L, s + start - 1, (size_t)(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;
+}
+
+
+static int str_rep (lua_State *L) {
+  size_t l, lsep;
+  const char *s = luaL_checklstring(L, 1, &l);
+  lua_Integer n = luaL_checkinteger(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 = (size_t)n * l + (size_t)(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) {  /* empty 'memcpy' is not that cheap */
+        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);
+  lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), l);
+  lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), l);
+  int n, i;
+  if (posi < 1) posi = 1;
+  if (pose > (lua_Integer)l) pose = l;
+  if (posi > pose) return 0;  /* empty interval; return no values */
+  n = (int)(pose -  posi + 1);
+  if (posi + n <= pose)  /* arithmetic 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++) {
+    lua_Integer c = luaL_checkinteger(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;
+  int strip = lua_toboolean(L, 2);
+  luaL_checktype(L, 1, LUA_TFUNCTION);
+  lua_settop(L, 1);
+  luaL_buffinit(L,&b);
+  if (lua_dump(L, writer, &b, strip) != 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 '%%')");
+      return p+1;
+    }
+    case '[': {
+      if (*p == '^') p++;
+      do {  /* look for a ']' */
+        if (p == ms->p_end)
+          luaL_error(ms->L, "malformed pattern (missing ']')");
+        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 '%%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 '[' after '%%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 %%%d", i + 1);
+  }
+  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);
+  lua_Integer init = posrelat(luaL_optinteger(L, 3, 1), ls);
+  if (init < 1) init = 1;
+  else if (init > (lua_Integer)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 - (size_t)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;
+  lua_State *L = ms->L;
+  const char *news = lua_tolstring(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(L, "invalid use of '%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_tolstring(L, -1, NULL);  /* if number, convert it to string */
+        lua_remove(L, -2);  /* remove original value */
+        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);
+  lua_Integer max_s = luaL_optinteger(L, 4, srcl + 1);
+  int anchor = (*p == '^');
+  lua_Integer 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
+** =======================================================
+*/
+
+/* 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")
+** (+2 for length modifiers; +10 accounts for %99.99x plus margin of error)
+*/
+#define MAX_FORMAT      (sizeof(FLAGS) + 2 + 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, (int)luaL_checkinteger(L, arg));
+          break;
+        }
+        case 'd': case 'i':
+        case 'o': case 'u': case 'x': case 'X': {
+          lua_Integer n = luaL_checkinteger(L, arg);
+          addlenmod(form, LUA_INTEGER_FRMLEN);
+          nb = sprintf(buff, form, n);
+          break;
+        }
+#if defined(LUA_USE_AFORMAT)
+        case 'a': case 'A':
+#endif
+        case 'e': case 'E': case 'f':
+        case 'g': case 'G': {
+          addlenmod(form, LUA_NUMBER_FRMLEN);
+          nb = sprintf(buff, form, 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 '%%%c' to 'format'",
+                               *(strfrmt - 1));
+        }
+      }
+      luaL_addsize(&b, nb);
+    }
+  }
+  luaL_pushresult(&b);
+  return 1;
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** PACK/UNPACK
+** =======================================================
+*/
+
+
+/* value used for padding */
+#if !defined(LUA_PACKPADBYTE)
+#define LUA_PACKPADBYTE         0x00
+#endif
+
+/* maximum size for the binary representation of an integer */
+#define MAXINTSIZE      16
+
+/* number of bits in a character */
+#define NB      CHAR_BIT
+
+/* mask for one character (NB 1's) */
+#define MC      ((1 << NB) - 1)
+
+/* size of a lua_Integer */
+#define SZINT   ((int)sizeof(lua_Integer))
+
+
+/* dummy union to get native endianness */
+static const union {
+  int dummy;
+  char little;  /* true iff machine is little endian */
+} nativeendian = {1};
+
+
+/* dummy structure to get native alignment requirements */
+struct cD {
+  char c;
+  union { double d; void *p; lua_Integer i; lua_Number n; } u;
+};
+
+#define MAXALIGN        (offsetof(struct cD, u))
+
+
+/*
+** Union for serializing floats
+*/
+typedef union Ftypes {
+  float f;
+  double d;
+  lua_Number n;
+  char buff[5 * sizeof(lua_Number)];  /* enough for any float type */
+} Ftypes;
+
+
+/*
+** information to pack/unpack stuff
+*/
+typedef struct Header {
+  lua_State *L;
+  int islittle;
+  int maxalign;
+} Header;
+
+
+/*
+** options for pack/unpack
+*/
+typedef enum KOption {
+  Kint,         /* signed integers */
+  Kuint,        /* unsigned integers */
+  Kfloat,       /* floating-point numbers */
+  Kchar,        /* fixed-length strings */
+  Kstring,      /* strings with prefixed length */
+  Kzstr,        /* zero-terminated strings */
+  Kpadding,     /* padding */
+  Kpaddalign,   /* padding for alignment */
+  Knop          /* no-op (configuration or spaces) */
+} KOption;
+
+
+/*
+** Read an integer numeral from string 'fmt' or return 'df' if
+** there is no numeral
+*/
+static int digit (int c) { return '0' <= c && c <= '9'; }
+
+static int getnum (const char **fmt, int df) {
+  if (!digit(**fmt))  /* no number? */
+    return df;  /* return default value */
+  else {
+    int a = 0;
+    do {
+      a = a*10 + (*((*fmt)++) - '0');
+    } while (digit(**fmt) && a <= ((int)MAXSIZE - 9)/10);
+    return a;
+  }
+}
+
+
+/*
+** Read an integer numeral and raises an error if it is larger
+** than the maximum size for integers.
+*/
+static int getnumlimit (Header *h, const char **fmt, int df) {
+  int sz = getnum(fmt, df);
+  if (sz > MAXINTSIZE || sz <= 0)
+    luaL_error(h->L, "integral size (%d) out of limits [1,%d]",
+                     sz, MAXINTSIZE);
+  return sz;
+}
+
+
+/*
+** Initialize Header
+*/
+static void initheader (lua_State *L, Header *h) {
+  h->L = L;
+  h->islittle = nativeendian.little;
+  h->maxalign = 1;
+}
+
+
+/*
+** Read and classify next option. 'size' is filled with option's size.
+*/
+static KOption getoption (Header *h, const char **fmt, int *size) {
+  int opt = *((*fmt)++);
+  *size = 0;  /* default */
+  switch (opt) {
+    case 'b': *size = sizeof(char); return Kint;
+    case 'B': *size = sizeof(char); return Kuint;
+    case 'h': *size = sizeof(short); return Kint;
+    case 'H': *size = sizeof(short); return Kuint;
+    case 'l': *size = sizeof(long); return Kint;
+    case 'L': *size = sizeof(long); return Kuint;
+    case 'j': *size = sizeof(lua_Integer); return Kint;
+    case 'J': *size = sizeof(lua_Integer); return Kuint;
+    case 'T': *size = sizeof(size_t); return Kuint;
+    case 'f': *size = sizeof(float); return Kfloat;
+    case 'd': *size = sizeof(double); return Kfloat;
+    case 'n': *size = sizeof(lua_Number); return Kfloat;
+    case 'i': *size = getnumlimit(h, fmt, sizeof(int)); return Kint;
+    case 'I': *size = getnumlimit(h, fmt, sizeof(int)); return Kuint;
+    case 's': *size = getnumlimit(h, fmt, sizeof(size_t)); return Kstring;
+    case 'c':
+      *size = getnum(fmt, -1);
+      if (*size == -1)
+        luaL_error(h->L, "missing size for format option 'c'");
+      return Kchar;
+    case 'z': return Kzstr;
+    case 'x': *size = 1; return Kpadding;
+    case 'X': return Kpaddalign;
+    case ' ': break;
+    case '<': h->islittle = 1; break;
+    case '>': h->islittle = 0; break;
+    case '=': h->islittle = nativeendian.little; break;
+    case '!': h->maxalign = getnumlimit(h, fmt, MAXALIGN); break;
+    default: luaL_error(h->L, "invalid format option '%c'", opt);
+  }
+  return Knop;
+}
+
+
+/*
+** Read, classify, and fill other details about the next option.
+** 'psize' is filled with option's size, 'notoalign' with its
+** alignment requirements.
+** Local variable 'size' gets the size to be aligned. (Kpadal option
+** always gets its full alignment, other options are limited by 
+** the maximum alignment ('maxalign'). Kchar option needs no alignment
+** despite its size.
+*/
+static KOption getdetails (Header *h, size_t totalsize,
+                           const char **fmt, int *psize, int *ntoalign) {
+  KOption opt = getoption(h, fmt, psize);
+  int align = *psize;  /* usually, alignment follows size */
+  if (opt == Kpaddalign) {  /* 'X' gets alignment from following option */
+    if (**fmt == '\0' || getoption(h, fmt, &align) == Kchar || align == 0)
+      luaL_argerror(h->L, 1, "invalid next option for option 'X'");
+  }
+  if (align <= 1 || opt == Kchar)  /* need no alignment? */
+    *ntoalign = 0;
+  else {
+    if (align > h->maxalign)  /* enforce maximum alignment */
+      align = h->maxalign;
+    if ((align & (align - 1)) != 0)  /* is 'align' not a power of 2? */
+      luaL_argerror(h->L, 1, "format asks for alignment not power of 2");
+    *ntoalign = (align - (int)(totalsize & (align - 1))) & (align - 1);
+  }
+  return opt;
+}
+
+
+/*
+** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
+** The final 'if' handles the case when 'size' is larger than
+** the size of a Lua integer, correcting the extra sign-extension
+** bytes if necessary (by default they would be zeros).
+*/
+static void packint (luaL_Buffer *b, lua_Unsigned n,
+                     int islittle, int size, int neg) {
+  char *buff = luaL_prepbuffsize(b, size);
+  int i;
+  buff[islittle ? 0 : size - 1] = (char)(n & MC);  /* first byte */
+  for (i = 1; i < size; i++) {
+    n >>= NB;
+    buff[islittle ? i : size - 1 - i] = (char)(n & MC);
+  }
+  if (neg && size > SZINT) {  /* negative number need sign extension? */
+    for (i = SZINT; i < size; i++)  /* correct extra bytes */
+      buff[islittle ? i : size - 1 - i] = (char)MC;
+  }
+  luaL_addsize(b, size);  /* add result to buffer */
+}
+
+
+/*
+** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
+** given 'islittle' is different from native endianness.
+*/
+static void copywithendian (volatile char *dest, volatile const char *src,
+                            int size, int islittle) {
+  if (islittle == nativeendian.little) {
+    while (size-- != 0)
+      *(dest++) = *(src++);
+  }
+  else {
+    dest += size - 1;
+    while (size-- != 0)
+      *(dest--) = *(src++);
+  }
+}
+
+
+static int str_pack (lua_State *L) {
+  luaL_Buffer b;
+  Header h;
+  const char *fmt = luaL_checkstring(L, 1);  /* format string */
+  int arg = 1;  /* current argument to pack */
+  size_t totalsize = 0;  /* accumulate total size of result */
+  initheader(L, &h);
+  lua_pushnil(L);  /* mark to separate arguments from string buffer */
+  luaL_buffinit(L, &b);
+  while (*fmt != '\0') {
+    int size, ntoalign;
+    KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
+    totalsize += ntoalign + size;
+    while (ntoalign-- > 0)
+     luaL_addchar(&b, LUA_PACKPADBYTE);  /* fill alignment */
+    arg++;
+    switch (opt) {
+      case Kint: {  /* signed integers */
+        lua_Integer n = luaL_checkinteger(L, arg);
+        if (size < SZINT) {  /* need overflow check? */
+          lua_Integer lim = (lua_Integer)1 << ((size * NB) - 1);
+          luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
+        }
+        packint(&b, (lua_Unsigned)n, h.islittle, size, (n < 0));
+        break;
+      }
+      case Kuint: {  /* unsigned integers */
+        lua_Integer n = luaL_checkinteger(L, arg);
+        if (size < SZINT)  /* need overflow check? */
+          luaL_argcheck(L, (lua_Unsigned)n < ((lua_Unsigned)1 << (size * NB)),
+                           arg, "unsigned overflow");
+        packint(&b, (lua_Unsigned)n, h.islittle, size, 0);
+        break;
+      }
+      case Kfloat: {  /* floating-point options */
+        volatile Ftypes u;
+        char *buff = luaL_prepbuffsize(&b, size);
+        lua_Number n = luaL_checknumber(L, arg);  /* get argument */
+        if (size == sizeof(u.f)) u.f = (float)n;  /* copy it into 'u' */
+        else if (size == sizeof(u.d)) u.d = (double)n;
+        else u.n = n;
+        /* move 'u' to final result, correcting endianness if needed */
+        copywithendian(buff, u.buff, size, h.islittle);
+        luaL_addsize(&b, size);
+        break;
+      }
+      case Kchar: {  /* fixed-size string */
+        size_t len;
+        const char *s = luaL_checklstring(L, arg, &len);
+        luaL_argcheck(L, len == (size_t)size, arg, "wrong length");
+        luaL_addlstring(&b, s, size);
+        break;
+      }
+      case Kstring: {  /* strings with length count */
+        size_t len;
+        const char *s = luaL_checklstring(L, arg, &len);
+        luaL_argcheck(L, size >= (int)sizeof(size_t) ||
+                         len < ((size_t)1 << (size * NB)),
+                         arg, "string length does not fit in given size");
+        packint(&b, (lua_Unsigned)len, h.islittle, size, 0);  /* pack length */
+        luaL_addlstring(&b, s, len);
+        totalsize += len;
+        break;
+      }
+      case Kzstr: {  /* zero-terminated string */
+        size_t len;
+        const char *s = luaL_checklstring(L, arg, &len);
+        luaL_argcheck(L, strlen(s) == len, arg, "string contains zeros");
+        luaL_addlstring(&b, s, len);
+        luaL_addchar(&b, '\0');  /* add zero at the end */
+        totalsize += len + 1;
+        break;
+      }
+      case Kpadding: luaL_addchar(&b, LUA_PACKPADBYTE);  /* go through */
+      case Kpaddalign: case Knop:
+        arg--;  /* undo increment */
+        break;
+    }
+  }
+  luaL_pushresult(&b);
+  return 1;
+}
+
+
+static int str_packsize (lua_State *L) {
+  Header h;
+  const char *fmt = luaL_checkstring(L, 1);  /* format string */
+  size_t totalsize = 0;  /* accumulate total size of result */
+  initheader(L, &h);
+  while (*fmt != '\0') {
+    int size, ntoalign;
+    KOption opt = getdetails(&h, totalsize, &fmt, &size, &ntoalign);
+    size += ntoalign;  /* total space used by option */
+    luaL_argcheck(L, totalsize <= MAXSIZE - size, 1,
+                     "format result too large");
+    totalsize += size;
+    switch (opt) {
+      case Kstring:  /* strings with length count */
+      case Kzstr:    /* zero-terminated string */
+        luaL_argerror(L, 1, "variable-length format");
+        break;
+      default:  break;
+    }
+  }
+  lua_pushinteger(L, (lua_Integer)totalsize);
+  return 1;
+}
+
+
+/*
+** Unpack an integer with 'size' bytes and 'islittle' endianness.
+** If size is smaller than the size of a Lua integer and integer
+** is signed, must do sign extension (propagating the sign to the
+** higher bits); if size is larger than the size of a Lua integer,
+** it must check the unread bytes to see whether they do not cause an
+** overflow.
+*/
+static lua_Integer unpackint (lua_State *L, const char *str,
+                              int islittle, int size, int issigned) {
+  lua_Unsigned res = 0;
+  int i;
+  int limit = (size  <= SZINT) ? size : SZINT;
+  for (i = limit - 1; i >= 0; i--) {
+    res <<= NB;
+    res |= (lua_Unsigned)(unsigned char)str[islittle ? i : size - 1 - i];
+  }
+  if (size < SZINT) {  /* real size smaller than lua_Integer? */
+    if (issigned) {  /* needs sign extension? */
+      lua_Unsigned mask = (lua_Unsigned)1 << (size*NB - 1);
+      res = ((res ^ mask) - mask);  /* do sign extension */
+    }
+  }
+  else if (size > SZINT) {  /* must check unread bytes */
+    int mask = (!issigned || (lua_Integer)res >= 0) ? 0 : MC;
+    for (i = limit; i < size; i++) {
+      if ((unsigned char)str[islittle ? i : size - 1 - i] != mask)
+        luaL_error(L, "%d-byte integer does not fit into Lua Integer", size);
+    }
+  }
+  return (lua_Integer)res;
+}
+
+
+static int str_unpack (lua_State *L) {
+  Header h;
+  const char *fmt = luaL_checkstring(L, 1);
+  size_t ld;
+  const char *data = luaL_checklstring(L, 2, &ld);
+  size_t pos = (size_t)posrelat(luaL_optinteger(L, 3, 1), ld) - 1;
+  int n = 0;  /* number of results */
+  luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
+  initheader(L, &h);
+  while (*fmt != '\0') {
+    int size, ntoalign;
+    KOption opt = getdetails(&h, pos, &fmt, &size, &ntoalign);
+    if ((size_t)ntoalign + size > ~pos || pos + ntoalign + size > ld)
+      luaL_argerror(L, 2, "data string too short");
+    pos += ntoalign;  /* skip alignment */
+    /* stack space for item + next position */
+    luaL_checkstack(L, 2, "too many results");
+    n++;
+    switch (opt) {
+      case Kint:
+      case Kuint: {
+        lua_Integer res = unpackint(L, data + pos, h.islittle, size,
+                                       (opt == Kint));
+        lua_pushinteger(L, res);
+        break;
+      }
+      case Kfloat: {
+        volatile Ftypes u;
+        lua_Number num;
+        copywithendian(u.buff, data + pos, size, h.islittle);
+        if (size == sizeof(u.f)) num = (lua_Number)u.f;
+        else if (size == sizeof(u.d)) num = (lua_Number)u.d;
+        else num = u.n;
+        lua_pushnumber(L, num);
+        break;
+      }
+      case Kchar: {
+        lua_pushlstring(L, data + pos, size);
+        break;
+      }
+      case Kstring: {
+        size_t len = (size_t)unpackint(L, data + pos, h.islittle, size, 0);
+        luaL_argcheck(L, pos + len + size <= ld, 2, "data string too short");
+        lua_pushlstring(L, data + pos + size, len);
+        pos += len;  /* skip string */
+        break;
+      }
+      case Kzstr: {
+        size_t len = (int)strlen(data + pos);
+        lua_pushlstring(L, data + pos, len);
+        pos += len + 1;  /* skip string plus final '\0' */
+        break;
+      }
+      case Kpaddalign: case Kpadding: case Knop:
+        n--;  /* undo increment */
+        break;
+    }
+    pos += size;
+  }
+  lua_pushinteger(L, pos + 1);  /* next position */
+  return n + 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},
+  {"pack", str_pack},
+  {"packsize", str_packsize},
+  {"unpack", str_unpack},
+  {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;
+}
+
diff --git a/rockspecs/compat53-scm-0.rockspec b/rockspecs/compat53-scm-0.rockspec
index ec56e51..2dd8cba 100644
--- a/rockspecs/compat53-scm-0.rockspec
+++ b/rockspecs/compat53-scm-0.rockspec
@@ -25,6 +25,7 @@ build = {
       ["compat53"] = "compat53.lua",
       ["compat53.utf8"] = "lutf8lib.c",
       ["compat53.table"] = "ltablib.c",
+      ["compat53.string"] = "lstrlib.c",
    }
 }