Function match

other_src/lua/src/lpeg.cpp:440–636

#define condfailed(p)	{ int f = p->i.offset; if (f) p+=f; else goto fail; }

static const char *match (lua_State *L,
                          const char *o, const char *s, const char *e,
                          Instruction *op, Capture *capture, int ptop) {
  Stack stackbase[INITBACK];
  Stack *stacklimit = stackbase + INITBACK;
  Stack *stack = stackbase;  /* point to first empty slot in stack */
  int capsize = INITCAPSIZE;
  int captop = 0;  /* point to first empty slot in captures */
  const Instruction *p = op;
  stack->p = &giveup; stack->s = s; stack->caplevel = 0; stack++;
  lua_pushlightuserdata(L, stackbase);
  for (;;) {
#if defined(DEBUG)
      printf("s: |%s| stck: %d c: %d  ",
             s, (int)(stack - getstackbase(L, ptop)), captop);
      printinst(op, p);
#endif
    switch ((Opcode)p->i.code) {
      case IEnd: {
        assert(stack == getstackbase(L, ptop) + 1);
        capture[captop].kind = Cclose;
        capture[captop].s = NULL;
        return s;
      }
      case IGiveup: {
        assert(stack == getstackbase(L, ptop));
        return NULL;
      }
      case IRet: {
        assert(stack > getstackbase(L, ptop) && (stack - 1)->s == NULL);
        p = (--stack)->p;
        continue;
      }
      case IAny: {
        int n = p->i.aux;
        if (n <= e - s) { p++; s += n; }
        else condfailed(p);
        continue;
      }
      case IChar: {
        if ((byte)*s == p->i.aux && s < e) { p++; s++; }
        else condfailed(p);
        continue;
      }
      case ISet: {
        int c = (byte)*s;
        if (testchar((p+1)->buff, c) && s < e)
          { p += CHARSETINSTSIZE; s++; }
        else condfailed(p);
        continue;
      }
      case IBack: {
        int n = p->i.aux;
        if (n > s - o) goto fail;
        s -= n; p++;
        continue;
      }
      case ISpan: {