path: root/Lisp/method-invocation.lisp

;;;; Objective-CL, an Objective-C bridge for Common Lisp.
;;;; Copyright (C) 2007  Matthias Andreas Benkard.
;;;;
;;;; This program is free software: you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public License
;;;; as published by the Free Software Foundation, either version 3 of
;;;; the License, or (at your option) any later version.
;;;;
;;;; This program is distributed in the hope that it will be useful, but
;;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this program.  If not, see
;;;; <http://www.gnu.org/licenses/>.

(in-package #:mulk.objective-cl)


;;; (@* "Method invocation")
(defun invoke (receiver message-start &rest message-components)
  "Send a message to an Objective-C instance.

## Arguments and Values:

*receiver* --- an Objective-C wrapper object.

*message-start* --- a **symbol**.

*message-components* --- an alternating **list** of **object**s and
**symbol**s.

Returns: *result* --- the return value of the method invocation.


## Description:

All even-numbered *message components* are collected in order and the
resulting **list** used as if as additional **argument**s to
__invoke-by-name__.

All uneven-numbered *message components*, which must be **symbol**s, are
first split into parts separated by hyphens and each part converted into
a **string** according to the following rules:

<ol>
 <li>
 <ol>
  <li>If the keywords' **symbol name**s do contain
  **lowercase** **character**s, their case is left intact.</li>

  <li>If the keywords' **symbol name**s do not contain any **lowercase**
  **character**s, the following steps are taken in order to adjust their
  case.

  <ol>
   <li>The first part is fully converted to **lowercase**.</li>

   <li>Any additional parts are also fully converted to **lowercase**
   except for their first letters, which are left intact.</li>
  </ol>
  </li>
 </ol>
 </li>

 <li>If the symbol is a **keyword**, the resulting **string** is suffixed
 by a **colon** (`:').</li>
</ol>

After that, all parts are concatenated in order to form a
single *message name component*.  The *message name components* are in
turn concatenated in order to form the *message name* which is used as
if as the second **argument** to __invoke-by-name__.


## Examples:

    (invoke (find-objc-class 'ns-string)
            :string-with-u-t-f-8-string \"Mulk.\")
      ;=> #<GSCBufferString `Mulk.' {5B36087}>

    (invoke (find-objc-class 'ns-string)
            '|:stringWithUTF8String| \"Mulk.\")
      ;=> #<GSCBufferString `Mulk.' {5B36087}>

    (invoke (find-objc-class 'ns-object)
            'self)                           
      ;=> #<NSObject `NSObject' {16ECF598}>

    (invoke (find-objc-class 'ns-object)
            'name)                           
      ;=> \"NSObject\"

    (invoke (find-objc-class 'ns-string)
            :string-with-c-string \"Mulk.\"
            :encoding 4)
      ;=> #<GSCBufferString `Mulk.' {5B36087}>

    #.(setq \\*readtable\\* (copy-readtable)) 
    #.(setf (readtable-case \\*readtable\\*) :invert)
    (invoke (find-objc-class 'ns-string)
            :stringWithCString \"Mulk.\"
            :encoding 4)
      ;=> #<GSCBufferString `Mulk.' {5B36087}>


## Note:

Setting the **readtable case** of the **current readtable** to `:INVERT`
is a good way of making the Lisp system behave as traditionally as
possible while making Objective-C method names case-sensitive.

On the other hand, writing all method names in lower case while
separating parts by hyphens works nicely in all of the `:INVERT`,
`:UPCASE`, `:DOWNCASE`, and `:PRESERVE` modes as well as Allegro CL's
*modern mode*.


## Note 2:

Instead of using __invoke__, which is neither macro-friendly nor very
useful for method selection at run-time, you may **funcall** selectors
directly.  Naturally, __apply__ works as well.

The following calls are all equivalent (though the last one needs the
syntax enhancement provided by __enable-method-syntax__ enabled and the
selector registered by way of __collect-methods__):

    (invoke-by-name class \"stringWithCString:encoding:\" \"Mulk.\" 4)
    (invoke class :string-with-c-string \"Mulk.\" :encoding 4)
    (funcall (selector \"stringWithCString:encoding:\") class \"Mulk.\" 4)
    (apply (selector \"stringWithCString:encoding:\") (list class \"Mulk.\" 4))
    (#/stringWithCString:encoding: class \"Mulk.\" 4)

## See also:

  __invoke-by-name__"

  (multiple-value-bind (message arglist)
      (split-method-call message-start message-components)
    (apply #'invoke-by-name receiver message arglist)))


(defun invoke-by-name (receiver method-name &rest args)
  "Send a message to an Objective-C object by the name of the method.

## Arguments and Values:

*receiver* --- an Objective-C wrapper object.

*method-name* --- a *selector designator*.

*args* --- a list of **object**s.

Returns: *result* --- the return value of the method invocation.


## Description:

__invoke-by-name__ is like __invoke__ except in its syntax.  It sends
the message whose selector is designated by *method-name*, which must be
either a *string*, a *symbol*, a list of message name components as in a
call to __invoke__, or an object of *type* __selector__, to *receiver*.


## Examples:

    (invoke-by-name (find-objc-class 'ns-string)
                    '(:string-with-u-t-f-8-string) \"Mulk.\")
      ;=> #<GSCBufferString `Mulk.' {5B36087}>

    (invoke-by-name (find-objc-class 'ns-object)
                    \"self\")
      ;=> #<NSObject `NSObject' {16ECF598}>

    (invoke-by-name (find-objc-class 'ns-string)
                    \"stringWithCString:encoding:\"
                    \"Mulk.\"
                    4)
      ;=> #<GSCBufferString `Mulk.' {5B36087}>


## Note:

__selector__ objects are funcallable.  Therefore, the following calls
are all equivalent:

    (invoke-by-name instance \"stringWithCString:encoding:\" \"Mulk.\" 4)
    (invoke instance :string-with-c-string \"Mulk.\" :encoding 4)
    (funcall (selector \"stringWithCString:encoding:\") instance \"Mulk.\" 4)

In fact, using __invoke-by-name__ is discouraged in favour of the latter
form.


## Rationale:

Whereas __invoke__ tries to make writing as well as reading method
invocations easy by interspersing method name components with arguments
as Objective-C does, __invoke-by-name__ is better suited for method
selection at run time as well as code generation.  It is also slightly
easier to use with __apply__.


## See also:

  __invoke__"

  (invoke-by-name-super-v (typecase receiver
                            (symbol (find-objc-class receiver))
                            ((or id objective-c-class) receiver)
                            (t (pointer receiver)))
                          method-name
                          nil
                          args))


(defun invoke-by-name-super-v (receiver method-name superclass-for-send-super
                               args)
  ;; TODO: Support varargs.
  (let* ((selector (if (typep method-name 'selector)
                       method-name
                       (find-selector method-name))))
    (multiple-value-bind (argc
                          method-return-typestring
                          method-return-type
                          method-arg-typestrings
                          method-arg-types)
        (retrieve-method-signature-info receiver selector)
      (assert (= argc (+ 2 (length args)))
              (args)
              "Wrong number of arguments (expected ~A, got ~A)."
              argc (+ 2 (length args)))
      (low-level-invoke receiver
                        selector
                        (if (and superclass-for-send-super
                                 (not (and (pointerp superclass-for-send-super)
                                           (null-pointer-p superclass-for-send-super))))
                            (pointer-to superclass-for-send-super)
                            (null-pointer))
                        method-return-typestring
                        method-return-type
                        method-arg-typestrings
                        method-arg-types
                        argc
                        args))))


(defun split-method-call (message-start message-components)
  (do* ((components-left (cons message-start message-components)
                         (cddr components-left))
        (message-list    (list message-start)
                         (cons (first components-left) message-list))
        (arglist         (if (null (rest components-left))
                             nil
                             (list (second components-left)))
                         (if (null (rest components-left))
                             arglist
                             (cons (second components-left) arglist))))
       ((null (cddr components-left))
        (values (nreverse message-list)
                (nreverse arglist)))))


(defun primitive-invoke (receiver method-name return-type &rest args)
  (flet ((ad-hoc-value->typespec (arg)
           (typespec
            (etypecase arg
              ;; According to Allegro CL, strings
              ;; are POINTERP (and thus elements of
              ;; the C-POINTER type), so they have
              ;; to come first in this TYPECASE
              ;; form.  Weird.
              ;;
              ;; By the way, pointers are
              ;; represented as integers in Allegro
              ;; CL, so all integers are POINTERP,
              ;; too.
              (string '(:string ()))
              (selector '(selector ()))
              (c-pointer-wrapper '(id ()))
              (c-pointer '(:pointer ()))
              (integer '(:int ()))))))
    (let ((return-typespec (typespec `(,return-type ())))
          (arg-typespecs (list* (typespec '(id ()))
                                (typespec '(selector ()))
                                (mapcar #'ad-hoc-value->typespec args))))
      (low-level-invoke receiver
                        (selector method-name)
                        (null-pointer)
                        (print-typespec-to-string return-typespec)
                        return-typespec
                        (mapcar #'print-typespec-to-string arg-typespecs)
                        arg-typespecs
                        (+ 2 (length args))
                        args))))


(define-cached-function retrieve-method-signature-info
    (receiver selector
     &aux (class-ptr (%objcl-object-get-class (pointer receiver))))
    (cons (cffi:pointer-address class-ptr)
          (cffi:pointer-address (pointer-to selector)))
  (let* ((signature
          (objc-or (if (object-is-class-p receiver)
                       (primitive-invoke receiver
                                         "methodSignatureForSelector:"
                                         'id
                                         selector)
                       (primitive-invoke (object-get-class receiver)
                                         "instanceMethodSignatureForSelector:"
                                         'id
                                         selector))
                   (error (make-condition 'message-not-understood
                                          :class (object-get-class receiver)
                                          :selector selector))))
         (argc (primitive-invoke signature "numberOfArguments" :unsigned-int))
         (method-return-typestring (primitive-invoke signature
                                                     "methodReturnType"
                                                     :string))
         (method-return-type (parse-typespec method-return-typestring t))
         (method-arg-typestrings (loop for x from 0 below argc
                                       collect (primitive-invoke
                                                         signature
                                                         "getArgumentTypeAtIndex:"
                                                         :string
                                                         x)))
         (method-arg-types (mapcar #'parse-typespec method-arg-typestrings)))
    (values argc
            method-return-typestring
            method-return-type
            method-arg-typestrings
            method-arg-types)))


(defun typespec->c-type (typespec)
  (case (typespec-primary-type typespec)
    ((:pointer pointer struct union id objective-c-class exception array
      selector :id :class :exception :selector)
     :pointer)
    ((:string) :string)
    (otherwise (typespec-primary-type typespec))))


(defun low-level-invoke (receiver selector superclass-pointer-for-send-super
                         return-typestring return-type
                         arg-typestrings arg-types argc args)
  (when (object-is-class-p receiver)
    (foreign-class-ensure-registered receiver))
  (let ((return-c-type (typespec->c-type return-type))
        (arg-c-types (mapcar #'typespec->c-type arg-types)))
    (with-foreign-string-pool (register-temporary-string
                               allocate-string-and-register)
      (cffi:with-foreign-objects ((objc-arg-typestrings :string
                                                        (- argc 2))
                                  (objc-arg-ptrs :pointer argc)
                                  (objc-return-value-cell
                                   ;; Note that this cell is not used if
                                   ;; the method returns a struct, array
                                   ;; or union.  For these, see
                                   ;; OBJC-STRUCT-RETURN-VALUE-CELL
                                   ;; below.
                                   (if (eq return-c-type :void)
                                       :int
                                       return-c-type))
                                  (objc-arg-buffer +pessimistic-allocation-type+
                                                   argc))
        ;; Prepare the argument pointer vector.
        (loop for i from 0 below argc
              do (setf (cffi:mem-aref objc-arg-ptrs :pointer i)
                       (cffi:inc-pointer objc-arg-buffer
                                         (* i +pessimistic-allocation-size+))))
        ;; Prepare the argument typestring vector.  Note that we don't
        ;; pass the first two strings, as they are always the same.
        (loop for i from 0
              for arg-typestring in (cddr arg-typestrings)
              do (setf (mem-aref objc-arg-typestrings :string i)
                       (allocate-string-and-register arg-typestring)))
        (macrolet ((argref (type num)
                     `(cffi:mem-ref objc-arg-buffer ,type
                                    (* ,num +pessimistic-allocation-size+))))
          ;; Prepare the arguments.
          (setf (argref :pointer 0) (if (pointerp receiver)
                                        receiver
                                        (pointer-to receiver)))
          (setf (argref :pointer 1) (if (pointerp selector)
                                        selector
                                        (pointer-to selector)))
          (loop for i from 2
                for arg in args
                for arg-type in (cddr arg-types) ;skip the first two arguments
                for arg-c-type in (cddr arg-c-types) ;likewise
                do (case (typespec-primary-type arg-type)
                     ((:pointer)
                      (setf (argref :pointer i) arg))
                     ((objective-c-class exception)
                      (setf (argref :pointer i) (pointer-to arg)))
                     ((selector)
                      (setf (argref :pointer i) (pointer-to (selector arg))))
                     ((:string)
                      (setf (argref :string i)
                            (allocate-string-and-register arg)))
                     ((struct union)
                      ;; This is not very sophisticated, but, at
                      ;; present, we don't care about the internals of
                      ;; structs and unions much.  Functions returning
                      ;; structs actually just give us pointers to them,
                      ;; so we just put those pointers back into the
                      ;; functions as arguments.
                      ;;
                      ;; Note that the target type is a struct/union,
                      ;; not a pointer.  This means that we actually
                      ;; have to pass a struct/union as an argument.  We
                      ;; therefore ignore the memory space reserved for
                      ;; argument cells in the argument buffer and
                      ;; simply set the argument pointer directly.
                      (setf (cffi:mem-aref objc-arg-ptrs :pointer i)
                            arg))
                     ((array)
                      (error "Method ~A of object ~A tried to accept an array ~
                              as argument #~D.  It must be mistaken."
                             selector receiver i))
                     ((id)
                      ;; This case is actually interesting.  We can do a
                      ;; lot of automatic conversion between different
                      ;; kinds of stuff.  The conversion rules are
                      ;; somewhat arbitrary, but in the absence of more
                      ;; detailed method signature type information,
                      ;; it's the best we can do.
                      (setf (argref arg-c-type i)
                            (pointer-to (coerce-object arg :id))))
                     (t (setf (argref arg-c-type i)
                              (case arg
                                ;; Do the right thing for booleans.
                                ;;
                                ;; Note that Objective-C method
                                ;; invocations do not understand
                                ;; generalised booleans.  Among other
                                ;; things, this means that passing 0 for
                                ;; a boolean is the same as passing NIL,
                                ;; not the same as passing T.
                                ((nil) 0)
                                ((t) 1)
                                (otherwise arg)))))))
        (let* ((objc-struct-return-value-cell
                (if (member (typespec-primary-type return-type)
                            '(struct union array))
                    ;; Note that sizeof(char) is defined to be 1.  That
                    ;; is, sizeof returns a size in units of chars, not
                    ;; in units of bytes.
                    (foreign-alloc :char :count (%objcl-sizeof-type
                                                 return-typestring))
                    nil))
               (error-cell
                (%objcl-invoke-with-types (- argc 2)
                                          superclass-pointer-for-send-super
                                          return-typestring
                                          objc-arg-typestrings
                                          (or objc-struct-return-value-cell
                                              objc-return-value-cell)
                                          objc-arg-ptrs)))
          (unless (cffi:null-pointer-p error-cell)
            (error (make-condition 'exception :pointer error-cell)
                   #+(or) (intern-pointer-wrapper 'exception :pointer error-cell)))
          (when (eq (typespec-primary-type return-type) 'array)
            (error "Method ~A of object ~A tried to return an array.  ~
                    It must be mistaken."
                   selector receiver))
          (convert-from-foreign-value (or objc-struct-return-value-cell
                                          objc-return-value-cell)
                                      return-type
                                      (or *skip-retaining*
                                          (constructor-name-p
                                           (selector-name selector)))
                                      (returned-char-is-bool-p receiver
                                                               selector)))))))


;;; (@* "Helper functions")
(defun constructor-name-p (method-name)
  (flet ((method-name-starts-with (prefix)
           (let ((mismatch (mismatch method-name prefix)))
             (or (not mismatch)
                 (>= mismatch (length prefix))))))
    (or (method-name-starts-with "alloc")
        (method-name-starts-with "new"))))