1 files changed, 1282 insertions, 0 deletions

diff --git a/lptree.c b/lptree.c
new file mode 100644
index 0000000..5d2933d
--- /dev/null
+++ b/lptree.c
@@ -0,0 +1,1282 @@
+/*
+** $Id: lptree.c,v 1.10 2013/04/12 16:30:33 roberto Exp $
+** Copyright 2013, Lua.org & PUC-Rio  (see 'lpeg.html' for license)
+*/
+
+#include <ctype.h>
+#include <limits.h>
+#include <string.h>
+
+
+#include "lua.h"
+#include "lauxlib.h"
+
+#include "lptypes.h"
+#include "lpcap.h"
+#include "lpcode.h"
+#include "lpprint.h"
+#include "lptree.h"
+
+
+/* number of siblings for each tree */
+const byte numsiblings[] = {
+  0, 0, 0,      /* char, set, any */
+  0, 0,         /* true, false */       
+  1,            /* rep */
+  2, 2,         /* seq, choice */
+  1, 1,         /* not, and */
+  0, 0, 2, 1,  /* call, opencall, rule, grammar */
+  1,  /* behind */
+  1, 1,  /* capture, runtime capture */
+  0, 2  /* labeled failure throw, labeled choice */
+};
+
+
+static TTree *newgrammar (lua_State *L, int arg);
+
+
+/*
+** returns a reasonable name for value at index 'idx' on the stack
+*/
+static const char *val2str (lua_State *L, int idx) {
+  const char *k = lua_tostring(L, idx);
+  if (k != NULL)
+    return lua_pushfstring(L, "%s", k);
+  else
+    return lua_pushfstring(L, "(a %s)", luaL_typename(L, idx));
+}
+
+
+/*
+** Fix a TOpenCall into a TCall node, using table 'postable' to
+** translate a key to its rule address in the tree. Raises an
+** error if key does not exist.
+*/
+static void fixonecall (lua_State *L, int postable, TTree *g, TTree *t) {
+  int n;
+  lua_rawgeti(L, -1, t->key);  /* get rule's name */
+  lua_gettable(L, postable);  /* query name in position table */
+  n = lua_tonumber(L, -1);  /* get (absolute) position */
+  lua_pop(L, 1);  /* remove position */
+  if (n == 0) {  /* no position? */
+    lua_rawgeti(L, -1, t->key);  /* get rule's name again */
+    luaL_error(L, "rule '%s' undefined in given grammar", val2str(L, -1));
+  }
+  t->tag = TCall;
+  t->u.ps = n - (t - g);  /* position relative to node */
+  assert(sib2(t)->tag == TRule);
+  sib2(t)->key = t->key;
+}
+
+
+/*
+** Transform left associative constructions into right
+** associative ones, for sequence and choice; that is:
+** (t11 + t12) + t2  =>  t11 + (t12 + t2)
+** (t11 * t12) * t2  =>  t11 * (t12 * t2)
+** (that is, Op (Op t11 t12) t2 => Op t11 (Op t12 t2))
+*/
+static void correctassociativity (TTree *tree) {
+  TTree *t1 = sib1(tree);
+  assert(tree->tag == TChoice || tree->tag == TSeq);
+  while (t1->tag == tree->tag) {
+    int n1size = tree->u.ps - 1;  /* t1 == Op t11 t12 */
+    int n11size = t1->u.ps - 1;
+    int n12size = n1size - n11size - 1;
+    memmove(sib1(tree), sib1(t1), n11size * sizeof(TTree)); /* move t11 */
+    tree->u.ps = n11size + 1;
+    sib2(tree)->tag = tree->tag;
+    sib2(tree)->u.ps = n12size + 1;
+  }
+}
+
+
+/*
+** Make final adjustments in a tree. Fix open calls in tree 't',
+** making them refer to their respective rules or raising appropriate
+** errors (if not inside a grammar). Correct associativity of associative
+** constructions (making them right associative). Assume that tree's
+** ktable is at the top of the stack (for error messages).
+*/
+static void finalfix (lua_State *L, int postable, TTree *g, TTree *t) {
+ tailcall:
+  switch (t->tag) {
+    case TGrammar:  /* subgrammars were already fixed */
+      return;
+    case TOpenCall: {
+      if (g != NULL)  /* inside a grammar? */
+        fixonecall(L, postable, g, t);
+      else {  /* open call outside grammar */
+        lua_rawgeti(L, -1, t->key);
+        luaL_error(L, "rule '%s' used outside a grammar", val2str(L, -1));
+      }
+      break;
+    }
+    case TSeq: case TChoice:
+      correctassociativity(t);
+      break;
+  }
+  switch (numsiblings[t->tag]) {
+    case 1: /* finalfix(L, postable, g, sib1(t)); */
+      t = sib1(t); goto tailcall;
+    case 2:
+      finalfix(L, postable, g, sib1(t));
+      t = sib2(t); goto tailcall;  /* finalfix(L, postable, g, sib2(t)); */
+    default: assert(numsiblings[t->tag] == 0); break;
+  }
+}
+
+
+/*
+** {======================================================
+** Tree generation
+** =======================================================
+*/
+
+/*
+** In 5.2, could use 'luaL_testudata'...
+*/
+static int testpattern (lua_State *L, int idx) {
+  if (lua_touserdata(L, idx)) {  /* value is a userdata? */
+    if (lua_getmetatable(L, idx)) {  /* does it have a metatable? */
+      luaL_getmetatable(L, PATTERN_T);
+      if (lua_rawequal(L, -1, -2)) {  /* does it have the correct mt? */
+        lua_pop(L, 2);  /* remove both metatables */
+        return 1;
+      }
+    }
+  }
+  return 0;
+}
+
+
+static Pattern *getpattern (lua_State *L, int idx) {
+  return (Pattern *)luaL_checkudata(L, idx, PATTERN_T);
+}
+
+
+static int getsize (lua_State *L, int idx) {
+  return (lua_objlen(L, idx) - sizeof(Pattern)) / sizeof(TTree) + 1;
+}
+
+
+static TTree *gettree (lua_State *L, int idx, int *len) {
+  Pattern *p = getpattern(L, idx);
+  if (len)
+    *len = getsize(L, idx);
+  return p->tree;
+}
+
+
+/*
+** create a pattern
+*/
+static TTree *newtree (lua_State *L, int len) {
+  size_t size = (len - 1) * sizeof(TTree) + sizeof(Pattern);
+  Pattern *p = (Pattern *)lua_newuserdata(L, size);
+  luaL_getmetatable(L, PATTERN_T);
+  lua_setmetatable(L, -2);
+  p->code = NULL;  p->codesize = 0;
+  return p->tree;
+}
+
+
+static TTree *newleaf (lua_State *L, int tag) {
+  TTree *tree = newtree(L, 1);
+  tree->tag = tag;
+  return tree;
+}
+
+
+/* labeled failure begin */
+static TTree *newlabelleaf (lua_State *L, Labelset ls) {
+  TTree *tree = newtree(L, 1);
+  tree->tag = TThrow;
+        tree->labels = ls;
+  return tree;
+}
+/* labeled failure end */
+
+
+static TTree *newcharset (lua_State *L) {
+  TTree *tree = newtree(L, bytes2slots(CHARSETSIZE) + 1);
+  tree->tag = TSet;
+  loopset(i, treebuffer(tree)[i] = 0);
+  return tree;
+}
+
+
+/*
+** add to tree a sequence where first sibling is 'sib' (with size
+** 'sibsize'); returns position for second sibling
+*/
+static TTree *seqaux (TTree *tree, TTree *sib, int sibsize) {
+  tree->tag = TSeq; tree->u.ps = sibsize + 1;
+  memcpy(sib1(tree), sib, sibsize * sizeof(TTree));
+  return sib2(tree);
+}
+
+
+/*
+** Add element 'idx' to 'ktable' of pattern at the top of the stack;
+** create new 'ktable' if necessary. Return index of new element.
+*/
+static int addtoktable (lua_State *L, int idx) {
+  if (idx == 0 || lua_isnil(L, idx))  /* no actual value to insert? */
+    return 0;
+  else {
+    int n;
+    lua_getfenv(L, -1);  /* get ktable from pattern */
+    n = lua_objlen(L, -1);
+    if (n == 0) {  /* is it empty/non-existent? */
+      lua_pop(L, 1);  /* remove it */
+      lua_createtable(L, 1, 0);  /* create a fresh table */
+    }
+    lua_pushvalue(L, idx);  /* element to be added */
+    lua_rawseti(L, -2, n + 1);
+    lua_setfenv(L, -2);  /* set it as ktable for pattern */
+    return n + 1;
+  }
+}
+
+
+/*
+** Build a sequence of 'n' nodes, each with tag 'tag' and 'u.n' got
+** from the array 's' (or 0 if array is NULL). (TSeq is binary, so it
+** must build a sequence of sequence of sequence...)
+*/
+static void fillseq (TTree *tree, int tag, int n, const char *s) {
+  int i;
+  for (i = 0; i < n - 1; i++) {  /* initial n-1 copies of Seq tag; Seq ... */
+    tree->tag = TSeq; tree->u.ps = 2;
+    sib1(tree)->tag = tag;
+    sib1(tree)->u.n = s ? (byte)s[i] : 0;
+    tree = sib2(tree);
+  }
+  tree->tag = tag;  /* last one does not need TSeq */
+  tree->u.n = s ? (byte)s[i] : 0;
+}
+
+
+/*
+** Numbers as patterns:
+** 0 == true (always match); n == TAny repeated 'n' times;
+** -n == not (TAny repeated 'n' times)
+*/
+static TTree *numtree (lua_State *L, int n) {
+  if (n == 0)
+    return newleaf(L, TTrue);
+  else {
+    TTree *tree, *nd;
+    if (n > 0)
+      tree = nd = newtree(L, 2 * n - 1);
+    else {  /* negative: code it as !(-n) */
+      n = -n;
+      tree = newtree(L, 2 * n);
+      tree->tag = TNot;
+      nd = sib1(tree);
+    }
+    fillseq(nd, TAny, n, NULL);  /* sequence of 'n' any's */
+    return tree;
+  }
+}
+
+
+/*
+** Convert value at index 'idx' to a pattern
+*/
+static TTree *getpatt (lua_State *L, int idx, int *len) {
+  TTree *tree;
+  switch (lua_type(L, idx)) {
+    case LUA_TSTRING: {
+      size_t slen;
+      const char *s = lua_tolstring(L, idx, &slen);  /* get string */
+      if (slen == 0)  /* empty? */
+        tree = newleaf(L, TTrue);  /* always match */
+      else {
+        tree = newtree(L, 2 * (slen - 1) + 1);
+        fillseq(tree, TChar, slen, s);  /* sequence of 'slen' chars */
+      }
+      break;
+    }
+    case LUA_TNUMBER: {
+      int n = lua_tointeger(L, idx);
+      tree = numtree(L, n);
+      break;
+    }
+    case LUA_TBOOLEAN: {
+      tree = (lua_toboolean(L, idx) ? newleaf(L, TTrue) : newleaf(L, TFalse));
+      break;
+    }
+    case LUA_TTABLE: {
+      tree = newgrammar(L, idx);
+      break;
+    }
+    case LUA_TFUNCTION: {
+      tree = newtree(L, 2);
+      tree->tag = TRunTime;
+      tree->key = addtoktable(L, idx);
+      sib1(tree)->tag = TTrue;
+      break;
+    }
+    default: {
+      return gettree(L, idx, len);
+    }
+  }
+  lua_replace(L, idx);  /* put new tree into 'idx' slot */
+  if (len)
+    *len = getsize(L, idx);
+  return tree;
+}
+
+
+/*
+** Return the number of elements in the ktable of pattern at 'idx'.
+** In Lua 5.2, default "environment" for patterns is nil, not
+** a table. Treat it as an empty table. In Lua 5.1, assumes that
+** the environment has no numeric indices (len == 0)
+*/
+static int ktablelen (lua_State *L, int idx) {
+  if (!lua_istable(L, idx)) return 0;
+  else return lua_objlen(L, idx);
+}
+
+
+/*
+** Concatentate the contents of table 'idx1' into table 'idx2'.
+** (Assume that both indices are negative.)
+** Return the original length of table 'idx2'
+*/
+static int concattable (lua_State *L, int idx1, int idx2) {
+  int i;
+  int n1 = ktablelen(L, idx1);
+  int n2 = ktablelen(L, idx2);
+  if (n1 == 0) return 0;  /* nothing to correct */
+  for (i = 1; i <= n1; i++) {
+    lua_rawgeti(L, idx1, i);
+    lua_rawseti(L, idx2 - 1, n2 + i);  /* correct 'idx2' */
+  }
+  return n2;
+}
+
+
+/*
+** Make a merge of ktables from p1 and p2 the ktable for the new
+** pattern at the top of the stack.
+*/
+static int joinktables (lua_State *L, int p1, int p2) {
+  int n1, n2;
+  lua_getfenv(L, p1);  /* get ktables */
+  lua_getfenv(L, p2);
+  n1 = ktablelen(L, -2);
+  n2 = ktablelen(L, -1);
+  if (n1 == 0 && n2 == 0) {  /* are both tables empty? */
+    lua_pop(L, 2);  /* nothing to be done; pop tables */
+    return 0;  /* nothing to correct */
+  }
+  if (n2 == 0 || lua_equal(L, -2, -1)) {  /* second table is empty or equal? */
+    lua_pop(L, 1);  /* pop 2nd table */
+    lua_setfenv(L, -2);  /* set 1st ktable into new pattern */
+    return 0;  /* nothing to correct */
+  }
+  if (n1 == 0) {  /* first table is empty? */
+    lua_setfenv(L, -3);  /* set 2nd table into new pattern */
+    lua_pop(L, 1);  /* pop 1st table */
+    return 0;  /* nothing to correct */
+  }
+  else {
+    lua_createtable(L, n1 + n2, 0);  /* create ktable for new pattern */
+    /* stack: new p; ktable p1; ktable p2; new ktable */
+    concattable(L, -3, -1);  /* from p1 into new ktable */
+    concattable(L, -2, -1);  /* from p2 into new ktable */
+    lua_setfenv(L, -4);  /* new ktable becomes p env */
+    lua_pop(L, 2);  /* pop other ktables */
+    return n1;  /* correction for indices from p2 */
+  }
+}
+
+
+static void correctkeys (TTree *tree, int n) {
+  if (n == 0) return;  /* no correction? */
+ tailcall:
+  switch (tree->tag) {
+    case TOpenCall: case TCall: case TRunTime: case TRule: {
+      if (tree->key > 0)
+        tree->key += n;
+      break;
+    }
+    case TCapture: {
+      if (tree->key > 0 && tree->cap != Carg && tree->cap != Cnum)
+        tree->key += n;
+      break;
+    }
+    default: break;
+  }
+  switch (numsiblings[tree->tag]) {
+    case 1:  /* correctkeys(sib1(tree), n); */
+      tree = sib1(tree); goto tailcall;
+    case 2:
+      correctkeys(sib1(tree), n);
+      tree = sib2(tree); goto tailcall;  /* correctkeys(sib2(tree), n); */
+    default: assert(numsiblings[tree->tag] == 0); break;
+  }
+}
+
+
+/*
+** copy 'ktable' of element 'idx' to new tree (on top of stack)
+*/
+static void copyktable (lua_State *L, int idx) {
+  lua_getfenv(L, idx);
+  lua_setfenv(L, -2);
+}
+
+
+/*
+** merge 'ktable' from rule at stack index 'idx' into 'ktable'
+** from tree at the top of the stack, and correct corresponding
+** tree.
+*/
+static void mergektable (lua_State *L, int idx, TTree *rule) {
+  int n;
+  lua_getfenv(L, -1);  /* get ktables */
+  lua_getfenv(L, idx);
+  n = concattable(L, -1, -2);
+  lua_pop(L, 2);  /* remove both ktables */
+  correctkeys(rule, n);
+}
+
+
+/*
+** create a new tree, whith a new root and one sibling.
+** Sibling must be on the Lua stack, at index 1.
+*/
+static TTree *newroot1sib (lua_State *L, int tag) {
+  int s1;
+  TTree *tree1 = getpatt(L, 1, &s1);
+  TTree *tree = newtree(L, 1 + s1);  /* create new tree */
+  tree->tag = tag;
+  memcpy(sib1(tree), tree1, s1 * sizeof(TTree));
+  copyktable(L, 1);
+  return tree;
+}
+
+
+/*
+** create a new tree, whith a new root and 2 siblings.
+** Siblings must be on the Lua stack, first one at index 1.
+*/
+static TTree *newroot2sib (lua_State *L, int tag) {
+  int s1, s2;
+  TTree *tree1 = getpatt(L, 1, &s1);
+  TTree *tree2 = getpatt(L, 2, &s2);
+  TTree *tree = newtree(L, 1 + s1 + s2);  /* create new tree */
+  tree->tag = tag;
+  tree->u.ps =  1 + s1;
+  memcpy(sib1(tree), tree1, s1 * sizeof(TTree));
+  memcpy(sib2(tree), tree2, s2 * sizeof(TTree));
+  correctkeys(sib2(tree), joinktables(L, 1, 2));
+  return tree;
+}
+
+
+static int lp_P (lua_State *L) {
+  luaL_checkany(L, 1);
+  getpatt(L, 1, NULL);
+  lua_settop(L, 1);
+  return 1;
+}
+
+
+/*
+** sequence operator; optimizations:
+** false x => false, x true => x, true x => x
+** (cannot do x . false => false because x may have runtime captures)
+*/
+static int lp_seq (lua_State *L) {
+  TTree *tree1 = getpatt(L, 1, NULL);
+  TTree *tree2 = getpatt(L, 2, NULL);
+  if (tree1->tag == TFalse || tree2->tag == TTrue)
+    lua_pushvalue(L, 1);  /* false . x == false, x . true = x */
+  else if (tree1->tag == TTrue)
+    lua_pushvalue(L, 2);  /* true . x = x */
+  else
+    newroot2sib(L, TSeq);
+  return 1;
+}
+
+
+/*
+** choice operator; optimizations:
+** charset / charset => charset
+** true / x => true, x / false => x, false / x => x
+** (x / true is not equivalent to true)
+*/
+static int lp_choice (lua_State *L) {
+  Charset st1, st2;
+  TTree *t1 = getpatt(L, 1, NULL);
+  TTree *t2 = getpatt(L, 2, NULL);
+  if (tocharset(t1, &st1) && tocharset(t2, &st2)) {
+    TTree *t = newcharset(L);
+    loopset(i, treebuffer(t)[i] = st1.cs[i] | st2.cs[i]);
+  }
+  else if (nofail(t1) || t2->tag == TFalse)
+    lua_pushvalue(L, 1);  /* true / x => true, x / false => x */
+  else if (t1->tag == TFalse)
+    lua_pushvalue(L, 2);  /* false / x => x */
+  else
+    newroot2sib(L, TChoice);
+  return 1;
+}
+
+
+/*
+** p^n
+*/
+static int lp_star (lua_State *L) {
+  int size1;
+  int n = luaL_checkint(L, 2);
+  TTree *tree1 = gettree(L, 1, &size1);
+  if (n >= 0) {  /* seq tree1 (seq tree1 ... (seq tree1 (rep tree1))) */
+    TTree *tree = newtree(L, (n + 1) * (size1 + 1));
+    if (nullable(tree1))
+      luaL_error(L, "loop body may accept empty string");
+    while (n--)  /* repeat 'n' times */
+      tree = seqaux(tree, tree1, size1);
+    tree->tag = TRep;
+    memcpy(sib1(tree), tree1, size1 * sizeof(TTree));
+  }
+  else {  /* choice (seq tree1 ... choice tree1 true ...) true */
+    TTree *tree;
+    n = -n;
+    /* size = (choice + seq + tree1 + true) * n, but the last has no seq */
+    tree = newtree(L, n * (size1 + 3) - 1);
+    for (; n > 1; n--) {  /* repeat (n - 1) times */
+      tree->tag = TChoice; tree->u.ps = n * (size1 + 3) - 2;
+      sib2(tree)->tag = TTrue;
+      tree = sib1(tree);
+      tree = seqaux(tree, tree1, size1);
+    }
+    tree->tag = TChoice; tree->u.ps = size1 + 1;
+    sib2(tree)->tag = TTrue;
+    memcpy(sib1(tree), tree1, size1 * sizeof(TTree));
+  }
+  copyktable(L, 1);
+  return 1;
+}
+
+
+/*
+** #p == &p
+*/
+static int lp_and (lua_State *L) {
+  newroot1sib(L, TAnd);
+  return 1;
+}
+
+
+/*
+** -p == !p
+*/
+static int lp_not (lua_State *L) {
+  newroot1sib(L, TNot);
+  return 1;
+}
+
+
+/*
+** [t1 - t2] == Seq (Not t2) t1
+** If t1 and t2 are charsets, make their difference.
+*/
+static int lp_sub (lua_State *L) {
+  Charset st1, st2;
+  int s1, s2;
+  TTree *t1 = getpatt(L, 1, &s1);
+  TTree *t2 = getpatt(L, 2, &s2);
+  if (tocharset(t1, &st1) && tocharset(t2, &st2)) {
+    TTree *t = newcharset(L);
+    loopset(i, treebuffer(t)[i] = st1.cs[i] & ~st2.cs[i]);
+  }
+  else {
+    TTree *tree = newtree(L, 2 + s1 + s2);
+    tree->tag = TSeq;  /* sequence of... */
+    tree->u.ps =  2 + s2;
+    sib1(tree)->tag = TNot;  /* ...not... */
+    memcpy(sib1(sib1(tree)), t2, s2 * sizeof(TTree));  /* ...t2 */
+    memcpy(sib2(tree), t1, s1 * sizeof(TTree));  /* ... and t1 */
+    correctkeys(sib1(tree), joinktables(L, 1, 2));
+  }
+  return 1;
+}
+
+
+static int lp_set (lua_State *L) {
+  size_t l;
+  const char *s = luaL_checklstring(L, 1, &l);
+  TTree *tree = newcharset(L);
+  while (l--) {
+    setchar(treebuffer(tree), (byte)(*s));
+    s++;
+  }
+  return 1;
+}
+
+
+static int lp_range (lua_State *L) {
+  int arg;
+  int top = lua_gettop(L);
+  TTree *tree = newcharset(L);
+  for (arg = 1; arg <= top; arg++) {
+    int c;
+    size_t l;
+    const char *r = luaL_checklstring(L, arg, &l);
+    luaL_argcheck(L, l == 2, arg, "range must have two characters");
+    for (c = (byte)r[0]; c <= (byte)r[1]; c++)
+      setchar(treebuffer(tree), c);
+  }
+  return 1;
+}
+
+
+/*
+** Look-behind predicate
+*/
+static int lp_behind (lua_State *L) {
+  TTree *tree;
+  TTree *tree1 = getpatt(L, 1, NULL);
+  int n = fixedlen(tree1);
+  luaL_argcheck(L, !hascaptures(tree1), 1, "pattern have captures");
+  luaL_argcheck(L, n > 0, 1, "pattern may not have fixed length");
+  luaL_argcheck(L, n <= MAXBEHIND, 1, "pattern too long to look behind");
+  tree = newroot1sib(L, TBehind);
+  tree->u.n = n;
+  return 1;
+}
+
+
+/* labeled failure begin */
+/*
+** Throws a label or a set of labels  
+*/
+static int lp_throw (lua_State *L) {
+        int n = lua_gettop(L);
+        Labelset ls = 0;
+        int i;
+        for (i = 1; i <= n; i++) {
+                int d = luaL_checkint(L, i);
+                luaL_argcheck(L, d >= 0 && d < (int)MAXLABELS, i, "invalid label index");
+                setlabel(ls, d);
+        }
+        newlabelleaf(L, ls);
+        return 1;
+}
+
+/*
+** labeled choice function
+*/
+static int lp_labchoice (lua_State *L) {
+        TTree *tree;
+        int n = lua_gettop(L);
+        int i;
+        Labelset ls = 0;
+        for (i = 3; i <= n; i++) {
+                int d = luaL_checkint(L, i);
+                luaL_argcheck(L, d >= 0 && d < (int)MAXLABELS, i, "invalid label index");
+                setlabel(ls, d);
+        }
+  tree = newroot2sib(L, TLabChoice);
+        tree->labels = ls;
+  return 1;
+}
+/* labeled failure end */
+
+
+/*
+** Create a non-terminal
+*/
+static int lp_V (lua_State *L) {
+  TTree *tree = newleaf(L, TOpenCall);
+  luaL_argcheck(L, !lua_isnoneornil(L, 1), 1, "non-nil value expected");
+  tree->key = addtoktable(L, 1);
+  return 1;
+}
+
+
+/*
+** Create a tree for a non-empty capture, with a body and
+** optionally with an associated Lua value (at index 'labelidx' in the
+** stack)
+*/
+static int capture_aux (lua_State *L, int cap, int labelidx) {
+  TTree *tree = newroot1sib(L, TCapture);
+  tree->cap = cap;
+  tree->key = addtoktable(L, labelidx);
+  return 1;
+}
+
+
+/*
+** Fill a tree with an empty capture, using an empty (TTrue) sibling.
+*/
+static TTree *auxemptycap (lua_State *L, TTree *tree, int cap, int idx) {
+  tree->tag = TCapture;
+  tree->cap = cap;
+  tree->key = addtoktable(L, idx);
+  sib1(tree)->tag = TTrue;
+  return tree;
+}
+
+
+/*
+** Create a tree for an empty capture
+*/
+static TTree *newemptycap (lua_State *L, int cap, int idx) {
+  return auxemptycap(L, newtree(L, 2), cap, idx);
+}
+
+
+/*
+** Captures with syntax p / v
+** (function capture, query capture, string capture, or number capture)
+*/
+static int lp_divcapture (lua_State *L) {
+  switch (lua_type(L, 2)) {
+    case LUA_TFUNCTION: return capture_aux(L, Cfunction, 2);
+    case LUA_TTABLE: return capture_aux(L, Cquery, 2);
+    case LUA_TSTRING: return capture_aux(L, Cstring, 2);
+    case LUA_TNUMBER: {
+      int n = lua_tointeger(L, 2);
+      TTree *tree = newroot1sib(L, TCapture);
+      luaL_argcheck(L, 0 <= n && n <= SHRT_MAX, 1, "invalid number");
+      tree->cap = Cnum;
+      tree->key = n;
+      return 1;
+    }
+    default: return luaL_argerror(L, 2, "invalid replacement value");
+  }
+}
+
+
+static int lp_substcapture (lua_State *L) {
+  return capture_aux(L, Csubst, 0);
+}
+
+
+static int lp_tablecapture (lua_State *L) {
+  return capture_aux(L, Ctable, 0);
+}
+
+
+static int lp_groupcapture (lua_State *L) {
+  if (lua_isnoneornil(L, 2))
+    return capture_aux(L, Cgroup, 0);
+  else {
+    luaL_checkstring(L, 2);
+    return capture_aux(L, Cgroup, 2);
+  }
+}
+
+
+static int lp_foldcapture (lua_State *L) {
+  luaL_checktype(L, 2, LUA_TFUNCTION);
+  return capture_aux(L, Cfold, 2);
+}
+
+
+static int lp_simplecapture (lua_State *L) {
+  return capture_aux(L, Csimple, 0);
+}
+
+
+static int lp_poscapture (lua_State *L) {
+  newemptycap(L, Cposition, 0);
+  return 1;
+}
+
+
+static int lp_argcapture (lua_State *L) {
+  int n = luaL_checkint(L, 1);
+  TTree *tree = newemptycap(L, Carg, 0);
+  tree->key = n;
+  luaL_argcheck(L, 0 < n && n <= SHRT_MAX, 1, "invalid argument index");
+  return 1;
+}
+
+
+static int lp_backref (lua_State *L) {
+  luaL_checkstring(L, 1);
+  newemptycap(L, Cbackref, 1);
+  return 1;
+}
+
+
+/*
+** Constant capture
+*/
+static int lp_constcapture (lua_State *L) {
+  int i;
+  int n = lua_gettop(L);  /* number of values */
+  if (n == 0)  /* no values? */
+    newleaf(L, TTrue);  /* no capture */
+  else if (n == 1)
+    newemptycap(L, Cconst, 1);  /* single constant capture */
+  else {  /* create a group capture with all values */
+    TTree *tree = newtree(L, 1 + 3 * (n - 1) + 2);
+    tree->tag = TCapture;
+    tree->cap = Cgroup;
+    tree->key = 0;
+    tree = sib1(tree);
+    for (i = 1; i <= n - 1; i++) {
+      tree->tag = TSeq;
+      tree->u.ps = 3;  /* skip TCapture and its sibling */
+      auxemptycap(L, sib1(tree), Cconst, i);
+      tree = sib2(tree);
+    }
+    auxemptycap(L, tree, Cconst, i);
+  }
+  return 1;
+}
+
+
+static int lp_matchtime (lua_State *L) {
+  TTree *tree;
+  luaL_checktype(L, 2, LUA_TFUNCTION);
+  tree = newroot1sib(L, TRunTime);
+  tree->key = addtoktable(L, 2);
+  return 1;
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** Grammar - Tree generation
+** =======================================================
+*/
+
+/*
+** push on the stack the index and the pattern for the
+** initial rule of grammar at index 'arg' in the stack;
+** also add that index into position table.
+*/
+static void getfirstrule (lua_State *L, int arg, int postab) {
+  lua_rawgeti(L, arg, 1);  /* access first element */
+  if (lua_isstring(L, -1)) {  /* is it the name of initial rule? */
+    lua_pushvalue(L, -1);  /* duplicate it to use as key */
+    lua_gettable(L, arg);  /* get associated rule */
+  }
+  else {
+    lua_pushinteger(L, 1);  /* key for initial rule */
+    lua_insert(L, -2);  /* put it before rule */
+  }
+  if (!testpattern(L, -1)) {  /* initial rule not a pattern? */
+    if (lua_isnil(L, -1))
+      luaL_error(L, "grammar has no initial rule");
+    else
+      luaL_error(L, "initial rule '%s' is not a pattern", lua_tostring(L, -2));
+  }
+  lua_pushvalue(L, -2);  /* push key */
+  lua_pushinteger(L, 1);  /* push rule position (after TGrammar) */
+  lua_settable(L, postab);  /* insert pair at position table */
+}
+
+/*
+** traverse grammar at index 'arg', pushing all its keys and patterns
+** into the stack. Create a new table (before all pairs key-pattern) to
+** collect all keys and their associated positions in the final tree
+** (the "position table").
+** Return the number of rules and (in 'totalsize') the total size
+** for the new tree.
+*/
+static int collectrules (lua_State *L, int arg, int *totalsize) {
+  int n = 1;  /* to count number of rules */
+  int postab = lua_gettop(L) + 1;  /* index of position table */
+  int size;  /* accumulator for total size */
+  lua_newtable(L);  /* create position table */
+  getfirstrule(L, arg, postab);
+  size = 2 + getsize(L, postab + 2);  /* TGrammar + TRule + rule */
+  lua_pushnil(L);  /* prepare to traverse grammar table */
+  while (lua_next(L, arg) != 0) {
+    if (lua_tonumber(L, -2) == 1 ||
+        lua_equal(L, -2, postab + 1)) {  /* initial rule? */
+      lua_pop(L, 1);  /* remove value (keep key for lua_next) */
+      continue;
+    }
+    if (!testpattern(L, -1))  /* value is not a pattern? */
+      luaL_error(L, "rule '%s' is not a pattern", val2str(L, -2));
+    luaL_checkstack(L, LUA_MINSTACK, "grammar has too many rules");
+    lua_pushvalue(L, -2);  /* push key (to insert into position table) */
+    lua_pushinteger(L, size);
+    lua_settable(L, postab);
+    size += 1 + getsize(L, -1);  /* update size */
+    lua_pushvalue(L, -2);  /* push key (for next lua_next) */
+    n++;
+  }
+  *totalsize = size + 1;  /* TTrue to finish list of rules */
+  return n;
+}
+
+
+static void buildgrammar (lua_State *L, TTree *grammar, int frule, int n) {
+  int i;
+  TTree *nd = sib1(grammar);  /* auxiliary pointer to traverse the tree */
+  for (i = 0; i < n; i++) {  /* add each rule into new tree */
+    int ridx = frule + 2*i + 1;  /* index of i-th rule */
+    int rulesize;
+    TTree *rn = gettree(L, ridx, &rulesize);
+    nd->tag = TRule;
+    nd->key = 0;
+    nd->cap = i;  /* rule number */
+    nd->u.ps = rulesize + 1;  /* point to next rule */
+    memcpy(sib1(nd), rn, rulesize * sizeof(TTree));  /* copy rule */
+    mergektable(L, ridx, sib1(nd));  /* merge its ktable into new one */
+    nd = sib2(nd);  /* move to next rule */
+  }
+  nd->tag = TTrue;  /* finish list of rules */
+}
+
+
+/*
+** Check whether a tree has potential infinite loops
+*/
+static int checkloops (TTree *tree) {
+ tailcall:
+  if (tree->tag == TRep && nullable(sib1(tree)))
+    return 1;
+  else if (tree->tag == TGrammar)
+    return 0;  /* sub-grammars already checked */
+  else {
+    switch (numsiblings[tree->tag]) {
+      case 1:  /* return checkloops(sib1(tree)); */
+        tree = sib1(tree); goto tailcall;
+      case 2:
+        if (checkloops(sib1(tree))) return 1;
+        /* else return checkloops(sib2(tree)); */
+        tree = sib2(tree); goto tailcall;
+      default: assert(numsiblings[tree->tag] == 0); return 0;
+    }
+  }
+}
+
+
+static int verifyerror (lua_State *L, int *passed, int npassed) {
+  int i, j;
+  for (i = npassed - 1; i >= 0; i--) {  /* search for a repetition */
+    for (j = i - 1; j >= 0; j--) {
+      if (passed[i] == passed[j]) {
+        lua_rawgeti(L, -1, passed[i]);  /* get rule's key */
+        return luaL_error(L, "rule '%s' may be left recursive", val2str(L, -1));
+      }
+    }
+  }
+  return luaL_error(L, "too many left calls in grammar");
+}
+
+
+/*
+** Check whether a rule can be left recursive; raise an error in that
+** case; otherwise return 1 iff pattern is nullable. Assume ktable at
+** the top of the stack.
+*/
+static int verifyrule (lua_State *L, TTree *tree, int *passed, int npassed,
+                       int nullable) {
+ tailcall:
+  switch (tree->tag) {
+    case TChar: case TSet: case TAny:
+    case TFalse: case TThrow: /* labeled failure */
+      return nullable;  /* cannot pass from here */
+    case TTrue:
+    case TBehind:  /* look-behind cannot have calls */
+      return 1;
+    case TNot: case TAnd: case TRep:
+      /* return verifyrule(L, sib1(tree), passed, npassed, 1); */
+      tree = sib1(tree); nullable = 1; goto tailcall;
+    case TCapture: case TRunTime:
+      /* return verifyrule(L, sib1(tree), passed, npassed); */
+      tree = sib1(tree); goto tailcall;
+    case TCall:
+      /* return verifyrule(L, sib2(tree), passed, npassed); */
+      tree = sib2(tree); goto tailcall;
+    case TSeq:  /* only check 2nd child if first is nullable */
+      if (!verifyrule(L, sib1(tree), passed, npassed, 0))
+        return nullable;
+      /* else return verifyrule(L, sib2(tree), passed, npassed); */
+      tree = sib2(tree); goto tailcall;
+    case TChoice: case TLabChoice:  /* must check both children */  /* labeled failure */
+      nullable = verifyrule(L, sib1(tree), passed, npassed, nullable);
+      /* return verifyrule(L, sib2(tree), passed, npassed, nullable); */
+      tree = sib2(tree); goto tailcall;
+    case TRule:
+      if (npassed >= MAXRULES)
+        return verifyerror(L, passed, npassed);
+      else {
+        passed[npassed++] = tree->key;
+        /* return verifyrule(L, sib1(tree), passed, npassed); */
+        tree = sib1(tree); goto tailcall;
+      }
+    case TGrammar:
+      return nullable(tree);  /* sub-grammar cannot be left recursive */
+    default: assert(0); return 0;
+  }
+}
+
+
+static void verifygrammar (lua_State *L, TTree *grammar) {
+  int passed[MAXRULES];
+  TTree *rule;
+  /* check left-recursive rules */
+  for (rule = sib1(grammar); rule->tag == TRule; rule = sib2(rule)) {
+    if (rule->key == 0) continue;  /* unused rule */
+    verifyrule(L, sib1(rule), passed, 0, 0);
+  }
+  assert(rule->tag == TTrue);
+  /* check infinite loops inside rules */
+  for (rule = sib1(grammar); rule->tag == TRule; rule = sib2(rule)) {
+    if (rule->key == 0) continue;  /* unused rule */
+    if (checkloops(sib1(rule))) {
+      lua_rawgeti(L, -1, rule->key);  /* get rule's key */
+      luaL_error(L, "empty loop in rule '%s'", val2str(L, -1));
+    }
+  }
+  assert(rule->tag == TTrue);
+}
+
+
+/*
+** Give a name for the initial rule if it is not referenced
+*/
+static void initialrulename (lua_State *L, TTree *grammar, int frule) {
+  if (sib1(grammar)->key == 0) {  /* initial rule is not referenced? */
+    int n = lua_objlen(L, -1) + 1;  /* index for name */
+    lua_pushvalue(L, frule);  /* rule's name */
+    lua_rawseti(L, -2, n);  /* ktable was on the top of the stack */
+    sib1(grammar)->key = n;
+  }
+}
+
+
+static TTree *newgrammar (lua_State *L, int arg) {
+  int treesize;
+  int frule = lua_gettop(L) + 2;  /* position of first rule's key */
+  int n = collectrules(L, arg, &treesize);
+  TTree *g = newtree(L, treesize);
+  luaL_argcheck(L, n <= MAXRULES, arg, "grammar has too many rules");
+  g->tag = TGrammar;  g->u.n = n;
+  lua_newtable(L);  /* create 'ktable' */
+  lua_setfenv(L, -2);
+  buildgrammar(L, g, frule, n);
+  lua_getfenv(L, -1);  /* get 'ktable' for new tree */
+  finalfix(L, frule - 1, g, sib1(g));
+  initialrulename(L, g, frule);
+  verifygrammar(L, g);
+  lua_pop(L, 1);  /* remove 'ktable' */
+  lua_insert(L, -(n * 2 + 2));  /* move new table to proper position */
+  lua_pop(L, n * 2 + 1);  /* remove position table + rule pairs */
+  return g;  /* new table at the top of the stack */
+}
+
+/* }====================================================== */
+
+
+static Instruction *prepcompile (lua_State *L, Pattern *p, int idx) {
+  lua_getfenv(L, idx);  /* push 'ktable' (may be used by 'finalfix') */
+  finalfix(L, 0, NULL, p->tree);
+  lua_pop(L, 1);  /* remove 'ktable' */
+  return compile(L, p);
+}
+
+
+static int lp_printtree (lua_State *L) {
+  TTree *tree = getpatt(L, 1, NULL);
+  int c = lua_toboolean(L, 2);
+  if (c) {
+    lua_getfenv(L, 1);  /* push 'ktable' (may be used by 'finalfix') */
+    finalfix(L, 0, NULL, tree);
+    lua_pop(L, 1);  /* remove 'ktable' */
+  }
+  printktable(L, 1);
+  printtree(tree, 0);
+  return 0;
+}
+
+
+static int lp_printcode (lua_State *L) {
+  Pattern *p = getpattern(L, 1);
+  printktable(L, 1);
+  if (p->code == NULL)  /* not compiled yet? */
+    prepcompile(L, p, 1);
+  printpatt(p->code, p->codesize);
+  return 0;
+}
+
+
+/*
+** Get the initial position for the match, interpreting negative
+** values from the end of the subject
+*/
+static size_t initposition (lua_State *L, size_t len) {
+  lua_Integer ii = luaL_optinteger(L, 3, 1);
+  if (ii > 0) {  /* positive index? */
+    if ((size_t)ii <= len)  /* inside the string? */
+      return (size_t)ii - 1;  /* return it (corrected to 0-base) */
+    else return len;  /* crop at the end */
+  }
+  else {  /* negative index */
+    if ((size_t)(-ii) <= len)  /* inside the string? */
+      return len - ((size_t)(-ii));  /* return position from the end */
+    else return 0;  /* crop at the beginning */
+  }
+}
+
+
+/*
+** Main match function
+*/
+static int lp_match (lua_State *L) {
+  Capture capture[INITCAPSIZE];
+  const char *r;
+  size_t l;
+  Pattern *p = (getpatt(L, 1, NULL), getpattern(L, 1));
+  Instruction *code = (p->code != NULL) ? p->code : prepcompile(L, p, 1);
+  const char *s = luaL_checklstring(L, SUBJIDX, &l);
+  size_t i = initposition(L, l);
+  int ptop = lua_gettop(L);
+  lua_pushnil(L);  /* initialize subscache */
+  lua_pushlightuserdata(L, capture);  /* initialize caplistidx */
+  lua_getfenv(L, 1);  /* initialize penvidx */
+  r = match(L, s, s + i, s + l, code, capture, ptop);
+  if (r == NULL) {
+    lua_pushnil(L);
+    return 1;
+  }
+  return getcaptures(L, s, r, ptop);
+}
+
+
+
+/*
+** {======================================================
+** Library creation and functions not related to matching
+** =======================================================
+*/
+
+static int lp_setmax (lua_State *L) {
+  luaL_optinteger(L, 1, -1);
+  lua_settop(L, 1);
+  lua_setfield(L, LUA_REGISTRYINDEX, MAXSTACKIDX);
+  return 0;
+}
+
+
+static int lp_version (lua_State *L) {
+  lua_pushstring(L, VERSION);
+  return 1;
+}
+
+
+static int lp_type (lua_State *L) {
+  if (testpattern(L, 1))
+    lua_pushliteral(L, "pattern");
+  else
+    lua_pushnil(L);
+  return 1;
+}
+
+
+int lp_gc (lua_State *L) {
+  Pattern *p = getpattern(L, 1);
+  if (p->codesize > 0)
+    reallocprog(L, p, 0);
+  return 0;
+}
+
+
+static void createcat (lua_State *L, const char *catname, int (catf) (int)) {
+  TTree *t = newcharset(L);
+  int i;
+  for (i = 0; i <= UCHAR_MAX; i++)
+    if (catf(i)) setchar(treebuffer(t), i);
+  lua_setfield(L, -2, catname);
+}
+
+
+static int lp_locale (lua_State *L) {
+  if (lua_isnoneornil(L, 1)) {
+    lua_settop(L, 0);
+    lua_createtable(L, 0, 12);
+  }
+  else {
+    luaL_checktype(L, 1, LUA_TTABLE);
+    lua_settop(L, 1);
+  }
+  createcat(L, "alnum", isalnum);
+  createcat(L, "alpha", isalpha);
+  createcat(L, "cntrl", iscntrl);
+  createcat(L, "digit", isdigit);
+  createcat(L, "graph", isgraph);
+  createcat(L, "lower", islower);
+  createcat(L, "print", isprint);
+  createcat(L, "punct", ispunct);
+  createcat(L, "space", isspace);
+  createcat(L, "upper", isupper);
+  createcat(L, "xdigit", isxdigit);
+  return 1;
+}
+
+
+static struct luaL_Reg pattreg[] = {
+  {"ptree", lp_printtree},
+  {"pcode", lp_printcode},
+  {"match", lp_match},
+  {"B", lp_behind},
+  {"V", lp_V},
+  {"C", lp_simplecapture},
+  {"Cc", lp_constcapture},
+  {"Cmt", lp_matchtime},
+  {"Cb", lp_backref},
+  {"Carg", lp_argcapture},
+  {"Cp", lp_poscapture},
+  {"Cs", lp_substcapture},
+  {"Ct", lp_tablecapture},
+  {"Cf", lp_foldcapture},
+  {"Cg", lp_groupcapture},
+  {"P", lp_P},
+  {"S", lp_set},
+  {"R", lp_range},
+  {"locale", lp_locale},
+  {"version", lp_version},
+  {"setmaxstack", lp_setmax},
+  {"type", lp_type},
+        {"T", lp_throw}, /* labeled failure throw */
+        {"Lc", lp_labchoice}, /* labeled failure choice */
+  {NULL, NULL}
+};
+
+
+static struct luaL_Reg metareg[] = {
+  {"__mul", lp_seq},
+  {"__add", lp_choice},
+  {"__pow", lp_star},
+  {"__gc", lp_gc},
+  {"__len", lp_and},
+  {"__div", lp_divcapture},
+  {"__unm", lp_not},
+  {"__sub", lp_sub},
+  {NULL, NULL}
+};
+
+
+int luaopen_lpeglabel (lua_State *L);
+int luaopen_lpeglabel (lua_State *L) {
+  luaL_newmetatable(L, PATTERN_T);
+  lua_pushnumber(L, MAXBACK);  /* initialize maximum backtracking */
+  lua_setfield(L, LUA_REGISTRYINDEX, MAXSTACKIDX);
+  luaL_register(L, NULL, metareg);
+  luaL_register(L, "lpeglabel", pattreg);
+  lua_pushvalue(L, -1);
+  lua_setfield(L, -3, "__index");
+  return 1;
+}
+
+/* }====================================================== */