dlopen: switch to new pathfinder class

Instead of find_exec, without changing behaviour use new pathfinder
class with new allocator_interface around tmp_pathbuf and new vstrlist
class.
* pathfinder.h (pathfinder): New file.
* vstrlist.h (allocator_interface, allocated_type, vstrlist): New file.
* dlfcn.cc (dlopen): Avoid redundant GetModuleHandleExW with RTLD_NOLOAD
and RTLD_NODELETE.  Switch to new pathfinder class, using
(tmp_pathbuf_allocator): New class.
(get_full_path_of_dll): Drop.

winsup/cygwin/vstrlist.h

@@ -0,0 +1,373 @@
+/* vstrlist.h: class vstrlist
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+#ifdef __cplusplus
+
+struct allocator_interface
+{
+  virtual void * alloc (size_t) = 0;
+  virtual void free (void *) = 0;
+};
+
+
+/* The allocated_type makes sure to use the free () method of the
+   same allocator_interface than the alloc () method was used of.
+
+   Stores the allocator_interface address before the real object,
+   to hide it from (construction & destruction of) real object.  */
+class allocated_type
+{
+  union allocator_store
+  {
+    allocator_interface * allocator_;
+    char alignment_[8];
+
+    union pointer
+    {
+      void            * vptr;
+      allocator_store * real;
+    };
+  };
+
+public:
+  void * operator new (size_t class_size, allocator_interface & allocator)
+  {
+    allocator_store::pointer astore;
+    astore.vptr = allocator.alloc (sizeof (allocator_store) + class_size);
+    astore.real->allocator_ = &allocator;
+    ++ astore.real;
+    return astore.vptr;
+  }
+
+  void operator delete (void * p)
+  {
+    allocator_store::pointer astore;
+    astore.vptr = p;
+    -- astore.real;
+    astore.real->allocator_->free (astore.vptr);
+  }
+};
+
+
+/* Double linked list of char arrays, each being a string buffer,
+   which's final buffer size and initial string content is defined
+   by a NULL terminated variable argument list of STRING+LEN pairs,
+   where each STRING (up to LEN) is concatenated for the initial
+   string buffer content, and each LEN is added to the final size
+   of the allocated string buffer.
+   If LEN is -1, strlen(STRING) is used for LEN.
+
+   Needs:
+     An implementation of the allocator_interface.
+
+   Provides:
+     iterator:
+       short name for the string_iterator
+     string_iterator:
+       provides readonly access via member methods:
+	 string (): readonly string buffer
+	 stringlength (): length (readonly) of initial string
+     buffer_iterator:
+       extends string_iterator
+       provides writeable access via member methods:
+	 buffer (): writeable string buffer
+	 bufferlength (): length (readonly) of allocated buffer
+
+   Usage sample:
+     char * text = "snipe";
+     vstrlist l;
+     l.appendv (text, 4, text+3, 2, "", 2, NULL);
+     buffer_iterator it (l.begin ());
+     strcpy (it->buffer () + it->stringlength (), "ts");
+     printf ("Sample result is: '%s'", it->string ());
+   Sample result is: 'snippets' */
+class vstrlist
+{
+public:
+  class member
+    : public allocated_type
+  {
+    friend class vstrlist;
+    friend class string_iterator;
+
+    member * prev_;
+    member * next_;
+    size_t   bufferlength_;
+    size_t   stringlength_;
+    char     buffer_[1]; /* we always have space for the trailing zero */
+
+    /* no copy, just swap */
+    member (member const &);
+    member & operator = (member const &);
+
+    /* anchor */
+    void * operator new (size_t class_size, allocator_interface & allocator)
+    {
+      return allocated_type::operator new (class_size, allocator);
+    }
+
+    /* anchor */
+    member ()
+      : allocated_type ()
+      , prev_ (this)
+      , next_ (this)
+      , bufferlength_ (0)
+      , stringlength_ (0)
+      , buffer_ ()
+    {}
+
+    /* entry: determine memory size from args */
+    void * operator new (size_t class_size, allocator_interface & allocator,
+			 char const * part0, va_list parts)
+    {
+      char const * part = part0;
+      va_list partsdup;
+      va_copy (partsdup, parts);
+      while (part)
+	{
+	  int partlen = va_arg (partsdup, int);
+	  if (partlen < 0)
+	    partlen = strlen (part);
+	  class_size += partlen;
+	  part = va_arg (partsdup, char const *);
+	}
+      va_end (partsdup);
+
+      return allocated_type::operator new (class_size, allocator);
+    }
+
+    /* entry: instantly insert into list */
+    member (member * before, char const * part0, va_list parts)
+      : allocated_type ()
+      , prev_ (NULL)
+      , next_ (NULL)
+      , bufferlength_ (0)
+      , stringlength_ ()
+      , buffer_ ()
+    {
+      prev_ = before->prev_;
+      next_ = before;
+
+      prev_->next_ = this;
+      next_->prev_ = this;
+
+      char * dest = buffer_;
+      char const * part = part0;
+      va_list partsdup;
+      va_copy (partsdup, parts);
+      while (part)
+	{
+	  int partlen = va_arg (partsdup, int);
+	  if (partlen < 0)
+	    {
+	      char * old = dest;
+	      dest = stpcpy (old, part);
+	      partlen = dest - old;
+	    }
+	  else
+	    dest = stpncpy (dest, part, partlen);
+	  bufferlength_ += partlen;
+	  part = va_arg (partsdup, const char *);
+	}
+      va_end (partsdup);
+      *dest = (char)0;
+      stringlength_ = dest - buffer_;
+      if (bufferlength_ > stringlength_)
+	memset (++dest, 0, bufferlength_ - stringlength_);
+    }
+
+    /* remove entry from list */
+    ~member ()
+    {
+      member * next = next_;
+      member * prev = prev_;
+      if (next)
+	next->prev_ = prev;
+      if (prev)
+	prev->next_ = next;
+      prev_ = NULL;
+      next_ = NULL;
+    }
+
+  public:
+    member const * next () const { return next_; }
+    member       * next ()       { return next_; }
+    member const * prev () const { return next_; }
+    member       * prev ()       { return next_; }
+
+    /* readonly access */
+    char const * string () const { return buffer_; }
+    size_t stringlength () const { return stringlength_; }
+
+    /* writeable access */
+    char       * buffer ()       { return buffer_; }
+    size_t bufferlength ()       { return bufferlength_; }
+  };
+
+  /* readonly access */
+  class string_iterator
+  {
+    friend class vstrlist;
+    friend class buffer_iterator;
+
+    member * current_;
+
+    string_iterator ();
+
+    string_iterator (member * current)
+      : current_ (current)
+    {}
+
+  public:
+    string_iterator (string_iterator const & rhs)
+      : current_ (rhs.current_)
+    {}
+
+    string_iterator & operator = (string_iterator const & rhs)
+    {
+      current_ = rhs.current_;
+      return *this;
+    }
+
+    string_iterator & operator ++ ()
+    {
+      current_ = current_->next ();
+      return *this;
+    }
+
+    string_iterator operator ++ (int)
+    {
+      string_iterator ret (*this);
+      current_ = current_->next ();
+      return ret;
+    }
+
+    string_iterator & operator -- ()
+    {
+      current_ = current_->prev ();
+      return *this;
+    }
+
+    string_iterator operator -- (int)
+    {
+      string_iterator ret (*this);
+      current_ = current_->prev ();
+      return ret;
+    }
+
+    bool operator == (string_iterator const & rhs) const
+    {
+      return current_ == rhs.current_;
+    }
+
+    bool operator != (string_iterator const & rhs) const
+    {
+      return current_ != rhs.current_;
+    }
+
+    /* readonly member access */
+    member const & operator *  () const { return *current_; }
+    member const * operator -> () const { return  current_; }
+
+    void remove ()
+    {
+      member * old = current_;
+      ++ *this;
+      delete old;
+    }
+  };
+
+  /* writeable access */
+  class buffer_iterator
+    : public string_iterator
+  {
+  public:
+    explicit /* can be used with vstrlist.begin () */
+    buffer_iterator (string_iterator const & begin)
+      : string_iterator (begin)
+    {}
+
+    buffer_iterator (buffer_iterator const & rhs)
+      : string_iterator (rhs)
+    {}
+
+    buffer_iterator & operator = (buffer_iterator const & rhs)
+    {
+      string_iterator::operator = (rhs);
+      return *this;
+    }
+
+    /* writeable member access */
+    member & operator *  () const { return *current_; }
+    member * operator -> () const { return  current_; }
+  };
+
+private:
+  allocator_interface & allocator_;
+  member              * anchor_;
+
+  /* not without an allocator */
+  vstrlist ();
+
+  /* no copy, just swap () */
+  vstrlist (vstrlist const &);
+  vstrlist & operator = (vstrlist const &);
+
+public:
+  /* iterator is the string_iterator */
+  typedef class string_iterator iterator;
+
+  iterator  begin () { return iterator (anchor_->next ()); }
+  iterator  end   () { return iterator (anchor_         ); }
+  iterator rbegin () { return iterator (anchor_->prev ()); }
+  iterator rend   () { return iterator (anchor_         ); }
+
+  vstrlist (allocator_interface & a)
+    : allocator_ (a)
+    , anchor_ (NULL) /* exception safety */
+  {
+    anchor_ = new (allocator_) member ();
+  }
+
+  ~vstrlist ()
+  {
+    if (anchor_ != NULL)
+      {
+	for (iterator it = begin (); it != end (); it.remove ());
+	delete anchor_;
+      }
+  }
+
+  void swap (vstrlist & that)
+  {
+    allocator_interface & a = allocator_;
+    member              * m = anchor_;
+    allocator_ = that.allocator_;
+    anchor_    = that.anchor_;
+    that.allocator_ = a;
+    that.anchor_    = m;
+  }
+
+  string_iterator appendv (char const * part0, va_list parts)
+  {
+    member * ret = new (allocator_, part0, parts)
+		       member (anchor_, part0, parts);
+    return string_iterator (ret);
+  }
+
+  string_iterator appendv (char const * part0, ...)
+  {
+    va_list parts;
+    va_start (parts, part0);
+    string_iterator ret = appendv (part0, parts);
+    va_end (parts);
+    return ret;
+  }
+};
+
+#endif /* __cplusplus */