source: branches/generic-class-file/abcl/src/org/armedbear/lisp/jvm-class-file.lisp @ 12895

Last change on this file since 12895 was 12895, checked in by ehuelsmann, 13 years ago

Remove exclamation marks which were in place to avoid naming
conflicts; the conflicting names have been deleted from pass2 now.

  • Property svn:eol-style set to native
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1;;; jvm-class-file.lisp
2;;;
3;;; Copyright (C) 2010 Erik Huelsmann
4;;; $Id: jvm-class-file.lisp 12895 2010-08-13 21:10:39Z ehuelsmann $
5;;;
6;;; This program is free software; you can redistribute it and/or
7;;; modify it under the terms of the GNU General Public License
8;;; as published by the Free Software Foundation; either version 2
9;;; of the License, or (at your option) any later version.
10;;;
11;;; This program is distributed in the hope that it will be useful,
12;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14;;; GNU General Public License for more details.
15;;;
16;;; You should have received a copy of the GNU General Public License
17;;; along with this program; if not, write to the Free Software
18;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
19;;;
20;;; As a special exception, the copyright holders of this library give you
21;;; permission to link this library with independent modules to produce an
22;;; executable, regardless of the license terms of these independent
23;;; modules, and to copy and distribute the resulting executable under
24;;; terms of your choice, provided that you also meet, for each linked
25;;; independent module, the terms and conditions of the license of that
26;;; module.  An independent module is a module which is not derived from
27;;; or based on this library.  If you modify this library, you may extend
28;;; this exception to your version of the library, but you are not
29;;; obligated to do so.  If you do not wish to do so, delete this
30;;; exception statement from your version.
31
32(in-package "JVM")
33
34#|
35
36The general design of the class-file writer is to have generic
37- human readable - representations of the class being generated
38during the construction and manipulation phases.
39
40After completing the creation/manipulation of the class, all its
41components will be finalized. This process translates readable
42(e.g. string) representations to indices to be stored on disc.
43
44The only thing to be done after finalization is sending the
45output to a stream ("writing").
46
47
48Finalization happens highest-level first. As an example, take a
49method with exception handlers. The exception handlers are stored
50as attributes in the class file structure. They are children of the
51method's Code attribute. In this example, the body of the Code
52attribute (the higher level) gets finalized before the attributes.
53The reason to do so is that the exceptions need to refer to labels
54(offsets) in the Code segment.
55
56
57|#
58
59
60(defun map-primitive-type (type)
61  "Maps a symbolic primitive type name to its Java string representation."
62  (case type
63    (:int        "I")
64    (:long       "J")
65    (:float      "F")
66    (:double     "D")
67    (:boolean    "Z")
68    (:char       "C")
69    (:byte       "B")
70    (:short      "S")
71    ((nil :void) "V")))
72
73
74#|
75
76The `class-name' facility helps to abstract from "this instruction takes
77a reference" and "this instruction takes a class name". We simply pass
78the class name around and the instructions themselves know which
79representation to use.
80
81|#
82
83(defstruct (class-name (:conc-name class-)
84                       (:constructor %make-class-name))
85  "Used for class identification.
86
87The caller should instantiate only one `class-name' per class, as they are
88used as class identifiers and compared using EQ.
89
90Some instructions need a class argument, others need a reference identifier.
91This class is used to abstract from the difference."
92  name-internal
93  ref
94  array-class ;; cached array class reference
95  ;; keeping a reference to the associated array class allows class
96  ;; name comparisons to be EQ: all classes should exist only once,
97  )
98
99(defun make-class-name (name)
100  "Creates a `class-name' structure for the class or interface `name'.
101
102`name' should be specified using Java representation, which is converted
103to 'internal' (JVM) representation by this function."
104  (setf name (substitute #\/ #\. name))
105  (%make-class-name :name-internal name
106                    :ref (concatenate 'string "L" name ";")))
107
108(defun class-array (class-name)
109  "Returns a class-name representing an array of `class-name'.
110For multi-dimensional arrays, call this function multiple times, using
111its own result.
112
113This function can be called multiple times on the same `class-name' without
114violating the 'only one instance' requirement: the returned value is cached
115and used on successive calls."
116  (unless (class-array-class class-name)
117    ;; Alessio Stalla found by dumping a class file that the JVM uses
118    ;; the same representation (ie '[L<class-name>;') in CHECKCAST as
119    ;; it does in field references, meaning the class name and class ref
120    ;; are identified by the same string
121    (let ((name-and-ref (concatenate 'string "[" (class-ref class-name))))
122      (setf (class-array-class class-name)
123            (%make-class-name :name-internal name-and-ref
124                              :ref name-and-ref))))
125  (class-array-class class-name))
126
127(defmacro define-class-name (symbol java-dotted-name &optional documentation)
128  "Convenience macro to define constants for `class-name' structures,
129initialized from the `java-dotted-name'."
130  `(defconstant ,symbol (make-class-name ,java-dotted-name)
131     ,documentation))
132
133(define-class-name +java-object+ "java.lang.Object")
134(define-class-name +java-string+ "java.lang.String")
135(define-class-name +java-system+ "java.lang.System")
136(define-class-name +lisp-object+ "org.armedbear.lisp.LispObject")
137(defconstant +lisp-object-array+ (class-array +lisp-object+))
138(define-class-name +lisp-simple-string+ "org.armedbear.lisp.SimpleString")
139(define-class-name +lisp+ "org.armedbear.lisp.Lisp")
140(define-class-name +lisp-nil+ "org.armedbear.lisp.Nil")
141(define-class-name +lisp-class+ "org.armedbear.lisp.LispClass")
142(define-class-name +lisp-symbol+ "org.armedbear.lisp.Symbol")
143(define-class-name +lisp-thread+ "org.armedbear.lisp.LispThread")
144(define-class-name +lisp-closure-binding+ "org.armedbear.lisp.ClosureBinding")
145(defconstant +closure-binding-array+ (class-array +lisp-closure-binding+))
146(define-class-name +lisp-integer+ "org.armedbear.lisp.LispInteger")
147(define-class-name +lisp-fixnum+ "org.armedbear.lisp.Fixnum")
148(defconstant +lisp-fixnum-array+ (class-array +lisp-fixnum+))
149(define-class-name +lisp-bignum+ "org.armedbear.lisp.Bignum")
150(define-class-name +lisp-single-float+ "org.armedbear.lisp.SingleFloat")
151(define-class-name +lisp-double-float+ "org.armedbear.lisp.DoubleFloat")
152(define-class-name +lisp-cons+ "org.armedbear.lisp.Cons")
153(define-class-name +lisp-load+ "org.armedbear.lisp.Load")
154(define-class-name +lisp-character+ "org.armedbear.lisp.LispCharacter")
155(defconstant +lisp-character-array+ (class-array +lisp-character+))
156(define-class-name +lisp-structure-object+ "org.armedbear.lisp.StructureObject")
157(define-class-name +lisp-simple-vector+ "org.armedbear.lisp.SimpleVector")
158(define-class-name +lisp-abstract-string+ "org.armedbear.lisp.AbstractString")
159(define-class-name +lisp-abstract-vector+ "org.armedbear.lisp.AbstractVector")
160(define-class-name +lisp-abstract-bit-vector+
161    "org.armedbear.lisp.AbstractBitVector")
162(define-class-name +lisp-environment+ "org.armedbear.lisp.Environment")
163(define-class-name +lisp-special-binding+ "org.armedbear.lisp.SpecialBinding")
164(define-class-name +lisp-special-bindings-mark+
165    "org.armedbear.lisp.SpecialBindingsMark")
166(define-class-name +lisp-throw+ "org.armedbear.lisp.Throw")
167(define-class-name +lisp-return+ "org.armedbear.lisp.Return")
168(define-class-name +lisp-go+ "org.armedbear.lisp.Go")
169(define-class-name +lisp-primitive+ "org.armedbear.lisp.Primitive")
170(define-class-name +lisp-eql-hash-table+ "org.armedbear.lisp.EqlHashTable")
171(define-class-name +lisp-hash-table+ "org.armedbear.lisp.HashTable")
172(define-class-name +lisp-package+ "org.armedbear.lisp.Package")
173(define-class-name +lisp-readtable+ "org.armedbear.lisp.Readtable")
174(define-class-name +lisp-stream+ "org.armedbear.lisp.Stream")
175(define-class-name +lisp-closure+ "org.armedbear.lisp.Closure")
176(define-class-name +lisp-compiled-closure+ "org.armedbear.lisp.CompiledClosure")
177(define-class-name +lisp-closure-parameter+
178    "org.armedbear.lisp.Closure$Parameter")
179(defconstant +lisp-closure-parameter-array+
180  (class-array +lisp-closure-parameter+))
181
182#|
183
184Lisp-side descriptor representation:
185
186 - list: a list starting with a method return value, followed by
187     the argument types
188 - keyword: the primitive type associated with that keyword
189 - class-name structure instance: the class-ref value
190
191The latter two can be converted to a Java representation using
192the `internal-field-ref' function, the former is to be fed to
193`descriptor'.
194
195|#
196
197(defun internal-field-type (field-type)
198  "Returns a string containing the JVM-internal representation
199of `field-type', which should either be a symbol identifying a primitive
200type, or a `class-name' structure identifying a class or interface."
201  (if (symbolp field-type)
202      (map-primitive-type field-type)
203      (class-name-internal field-type)))
204
205(defun internal-field-ref (field-type)
206  "Returns a string containing the JVM-internal representation of a reference
207to `field-type', which should either be a symbol identifying a primitive
208type, or a `class-name' structure identifying a class or interface."
209  (if (symbolp field-type)
210      (map-primitive-type field-type)
211      (class-ref field-type)))
212
213(defun descriptor (return-type &rest argument-types)
214  "Returns a string describing the `return-type' and `argument-types'
215in JVM-internal representation."
216  (let* ((arg-strings (mapcar #'internal-field-ref argument-types))
217         (ret-string (internal-field-ref return-type))
218         (size (+ 2 (reduce #'+ arg-strings
219                            :key #'length
220                            :initial-value (length ret-string))))
221         (str (make-array size :fill-pointer 0 :element-type 'character)))
222    (with-output-to-string (s str)
223      (princ #\( s)
224      (dolist (arg-string arg-strings)
225        (princ arg-string s))
226      (princ #\) s)
227      (princ ret-string s))
228    str)
229;;  (format nil "(~{~A~})~A"
230;;          (internal-field-ref return-type))
231  )
232
233(defun descriptor-stack-effect (return-type &rest argument-types)
234  "Returns the effect on the stack position of the `argument-types' and
235`return-type' of a method call.
236
237If the method consumes an implicit `this' argument, this function does not
238take that effect into account."
239  (flet ((type-stack-effect (arg)
240           (case arg
241             ((:long :double) 2)
242             ((nil :void) 0)
243             (otherwise 1))))
244    (+ (reduce #'- argument-types
245               :key #'type-stack-effect
246               :initial-value 0)
247       (type-stack-effect return-type))))
248
249
250(defstruct pool
251  ;; `index' contains the index of the last allocated slot (0 == empty)
252  ;; "A constant pool entry is considered valid if it has
253  ;; an index greater than 0 (zero) and less than pool-count"
254  (index 0)
255  entries-list
256  ;; the entries hash stores raw values, except in case of string and
257  ;; utf8, because both are string values
258  (entries (make-hash-table :test #'equal :size 2048 :rehash-size 2.0)))
259
260
261(defstruct constant
262  "Structure to be included in all constant sub-types."
263  tag
264  index)
265
266(defparameter +constant-type-map+
267  '((:class          7 1)
268    (:field-ref      9 1)
269    (:method-ref    10 1)
270    ;; (:interface-method-ref 11)
271    (:string         8 1)
272    (:integer        3 1)
273    (:float          4 1)
274    (:long           5 2)
275    (:double         6 2)
276    (:name-and-type 12 1)
277    (:utf8           1 1)))
278
279(defstruct (constant-class (:constructor make-constant-class (index name-index))
280                           (:include constant
281                                     (tag 7)))
282  "Structure holding information on a 'class' type item in the constant pool."
283  name-index)
284
285(defstruct (constant-member-ref (:constructor
286                                 %make-constant-member-ref
287                                     (tag index class-index name/type-index))
288                                (:include constant))
289  "Structure holding information on a member reference type item
290(a field, method or interface method reference) in the constant pool."
291  class-index
292  name/type-index)
293
294(declaim (inline make-constant-field-ref make-constant-method-ref
295                 make-constant-interface-method-ref))
296(defun make-constant-field-ref (index class-index name/type-index)
297  "Creates a `constant-member-ref' instance containing a field reference."
298  (%make-constant-member-ref 9 index class-index name/type-index))
299
300(defun make-constant-method-ref (index class-index name/type-index)
301  "Creates a `constant-member-ref' instance containing a method reference."
302  (%make-constant-member-ref 10 index class-index name/type-index))
303
304(defun make-constant-interface-method-ref (index class-index name/type-index)
305  "Creates a `constant-member-ref' instance containing an
306interface-method reference."
307  (%make-constant-member-ref 11 index class-index name/type-index))
308
309(defstruct (constant-string (:constructor
310                             make-constant-string (index value-index))
311                            (:include constant
312                                      (tag 8)))
313  "Structure holding information on a 'string' type item in the constant pool."
314  value-index)
315
316(defstruct (constant-float/int (:constructor
317                                %make-constant-float/int (tag index value))
318                               (:include constant))
319  "Structure holding information on a 'float' or 'integer' type item
320in the constant pool."
321  value)
322
323(declaim (inline make-constant-float make-constant-int))
324(defun make-constant-float (index value)
325  "Creates a `constant-float/int' structure instance containing a float."
326  (%make-constant-float/int 4 index value))
327
328(defun make-constant-int (index value)
329  "Creates a `constant-float/int' structure instance containing an int."
330  (%make-constant-float/int 3 index value))
331
332(defstruct (constant-double/long (:constructor
333                                  %make-constant-double/long (tag index value))
334                                 (:include constant))
335  "Structure holding information on a 'double' or 'long' type item
336in the constant pool."
337  value)
338
339(declaim (inline make-constant-double make-constant-float))
340(defun make-constant-double (index value)
341  "Creates a `constant-double/long' structure instance containing a double."
342  (%make-constant-double/long 6 index value))
343
344(defun make-constant-long (index value)
345  "Creates a `constant-double/long' structure instance containing a long."
346  (%make-constant-double/long 5 index value))
347
348(defstruct (constant-name/type (:constructor
349                                make-constant-name/type (index
350                                                         name-index
351                                                         descriptor-index))
352                               (:include constant
353                                         (tag 12)))
354  "Structure holding information on a 'name-and-type' type item in the
355constant pool; this type of element is used by 'member-ref' type items."
356  name-index
357  descriptor-index)
358
359(defstruct (constant-utf8 (:constructor make-constant-utf8 (index value))
360                          (:include constant
361                                    (tag 1)))
362  "Structure holding information on a 'utf8' type item in the constant pool;
363
364This type of item is used for text representation of identifiers
365and string contents."
366  value)
367
368
369(defun pool-add-class (pool class)
370  "Returns the index of the constant-pool class item for `class'.
371
372`class' must be an instance of `class-name'."
373  (let ((entry (gethash class (pool-entries pool))))
374    (unless entry
375      (let ((utf8 (pool-add-utf8 pool (class-name-internal class))))
376        (setf entry
377              (make-constant-class (incf (pool-index pool)) utf8)
378              (gethash class (pool-entries pool)) entry))
379      (push entry (pool-entries-list pool)))
380    (constant-index entry)))
381
382(defun pool-add-field-ref (pool class name type)
383  "Returns the index of the constant-pool item which denotes a reference
384to the `name' field of the `class', being of `type'.
385
386`class' should be an instance of `class-name'.
387`name' is a string.
388`type' is a field-type (see `internal-field-type')"
389  (let ((entry (gethash (acons name type class) (pool-entries pool))))
390    (unless entry
391      (let ((c (pool-add-class pool class))
392            (n/t (pool-add-name/type pool name type)))
393        (setf entry (make-constant-field-ref (incf (pool-index pool)) c n/t)
394            (gethash (acons name type class) (pool-entries pool)) entry))
395      (push entry (pool-entries-list pool)))
396    (constant-index entry)))
397
398(defun pool-add-method-ref (pool class name type)
399  "Returns the index of the constant-pool item which denotes a reference
400to the method with `name' in `class', which is of `type'.
401
402Here, `type' is a method descriptor, which defines the argument types
403and return type. `class' is an instance of `class-name'."
404  (let ((entry (gethash (acons name type class) (pool-entries pool))))
405    (unless entry
406      (let ((c (pool-add-class pool class))
407            (n/t (pool-add-name/type pool name type)))
408        (setf entry (make-constant-method-ref (incf (pool-index pool)) c n/t)
409              (gethash (acons name type class) (pool-entries pool)) entry))
410      (push entry (pool-entries-list pool)))
411    (constant-index entry)))
412
413(defun pool-add-interface-method-ref (pool class name type)
414  "Returns the index of the constant-pool item which denotes a reference to
415the method `name' in the interface `class', which is of `type'.
416
417See `pool-add-method-ref' for remarks."
418  (let ((entry (gethash (acons name type class) (pool-entries pool))))
419    (unless entry
420      (let ((c (pool-add-class pool class))
421            (n/t (pool-add-name/type pool name type)))
422        (setf entry
423            (make-constant-interface-method-ref (incf (pool-index pool)) c n/t)
424            (gethash (acons name type class) (pool-entries pool)) entry))
425      (push entry (pool-entries-list pool)))
426    (constant-index entry)))
427
428(defun pool-add-string (pool string)
429  "Returns the index of the constant-pool item denoting the string."
430  (let ((entry (gethash (cons 8 string) ;; 8 == string-tag
431                        (pool-entries pool))))
432    (unless entry
433      (let ((utf8 (pool-add-utf8 pool string)))
434        (setf entry (make-constant-string (incf (pool-index pool)) utf8)
435              (gethash (cons 8 string) (pool-entries pool)) entry))
436      (push entry (pool-entries-list pool)))
437    (constant-index entry)))
438
439(defun pool-add-int (pool int)
440  "Returns the index of the constant-pool item denoting the int."
441  (let ((entry (gethash (cons 3 int) (pool-entries pool))))
442    (unless entry
443      (setf entry (make-constant-int (incf (pool-index pool)) int)
444            (gethash (cons 3 int) (pool-entries pool)) entry)
445      (push entry (pool-entries-list pool)))
446    (constant-index entry)))
447
448(defun pool-add-float (pool float)
449  "Returns the index of the constant-pool item denoting the float."
450  (let ((entry (gethash (cons 4 float) (pool-entries pool))))
451    (unless entry
452      (setf entry (make-constant-float (incf (pool-index pool))
453                                       (sys::%float-bits float))
454            (gethash (cons 4 float) (pool-entries pool)) entry)
455      (push entry (pool-entries-list pool)))
456    (constant-index entry)))
457
458(defun pool-add-long (pool long)
459  "Returns the index of the constant-pool item denoting the long."
460  (let ((entry (gethash (cons 5 long) (pool-entries pool))))
461    (unless entry
462      (setf entry (make-constant-long (incf (pool-index pool)) long)
463            (gethash (cons 5 long) (pool-entries pool)) entry)
464      (push entry (pool-entries-list pool))
465      (incf (pool-index pool))) ;; double index increase; long takes 2 slots
466    (constant-index entry)))
467
468(defun pool-add-double (pool double)
469  "Returns the index of the constant-pool item denoting the double."
470  (let ((entry (gethash (cons 6 double) (pool-entries pool))))
471    (unless entry
472      (setf entry (make-constant-double (incf (pool-index pool))
473                                        (sys::%float-bits double))
474            (gethash (cons 6 double) (pool-entries pool)) entry)
475      (push entry (pool-entries-list pool))
476      (incf (pool-index pool))) ;; double index increase; 'double' takes 2 slots
477    (constant-index entry)))
478
479(defun pool-add-name/type (pool name type)
480  "Returns the index of the constant-pool item denoting
481the name/type identifier."
482  (let ((entry (gethash (cons name type) (pool-entries pool)))
483        (internal-type (if (listp type)
484                           (apply #'descriptor type)
485                           (internal-field-ref type))))
486    (unless entry
487      (let ((n (pool-add-utf8 pool name))
488            (i-t (pool-add-utf8 pool internal-type)))
489        (setf entry (make-constant-name/type (incf (pool-index pool)) n i-t)
490              (gethash (cons name type) (pool-entries pool)) entry))
491      (push entry (pool-entries-list pool)))
492    (constant-index entry)))
493
494(defun pool-add-utf8 (pool utf8-as-string)
495  "Returns the index of the textual value that will be stored in the
496class file as UTF-8 encoded data."
497  (let ((entry (gethash (cons 11 utf8-as-string) ;; 11 == utf8
498                        (pool-entries pool))))
499    (unless entry
500      (setf entry (make-constant-utf8 (incf (pool-index pool)) utf8-as-string)
501            (gethash (cons 11 utf8-as-string) (pool-entries pool)) entry)
502      (push entry (pool-entries-list pool)))
503    (constant-index entry)))
504
505(defstruct (class-file (:constructor
506                        make-class-file (class superclass access-flags)))
507  "Holds the components of a class file."
508  (constants (make-pool))
509  access-flags
510  class
511  superclass
512  ;; support for implementing interfaces not yet available
513  ;; interfaces
514  fields
515  methods
516  attributes)
517
518(defun class-add-field (class field)
519  "Adds a `field' created by `make-field'."
520  (push field (class-file-fields class)))
521
522(defun class-field (class name)
523  "Finds a field by name." ;; ### strictly speaking, a field is uniquely
524  ;; identified by its name and type, not by the name alone.
525  (find name (class-file-fields class)
526        :test #'string= :key #'field-name))
527
528(defun class-add-method (class method)
529  "Adds a `method' to `class'; the method must have been created using
530`make-method'."
531  (push method (class-file-methods class)))
532
533(defun class-methods-by-name (class name)
534  "Returns all methods which have `name'."
535  (remove name (class-file-methods class)
536          :test-not #'string= :key #'method-name))
537
538(defun class-method (class name return &rest args)
539  "Return the method which is (uniquely) identified by its name AND descriptor."
540  (let ((return-and-args (cons return args)))
541    (find-if #'(lambda (c)
542                 (and (string= (method-name c) name)
543                      (equal (method-descriptor c) return-and-args)))
544             (class-file-methods class))))
545
546(defun class-add-attribute (class attribute)
547  "Adds `attribute' to the class; attributes must be instances of
548structure classes which include the `attribute' structure class."
549  (push attribute (class-file-attributes class)))
550
551(defun class-attribute (class name)
552  "Returns the attribute which is named `name'."
553  (find name (class-file-attributes class)
554        :test #'string= :key #'attribute-name))
555
556
557(defun finalize-class-file (class)
558  "Transforms the representation of the class-file from one
559which allows easy modification to one which works best for serialization.
560
561The class can't be modified after finalization."
562
563  ;; constant pool contains constants finalized on addition;
564  ;; no need for additional finalization
565
566  (setf (class-file-access-flags class)
567        (map-flags (class-file-access-flags class)))
568  (setf (class-file-superclass class)
569        (pool-add-class (class-file-constants class)
570                        (class-file-superclass class))
571        (class-file-class class)
572        (pool-add-class (class-file-constants class)
573                        (class-file-class class)))
574  ;;  (finalize-interfaces)
575  (dolist (field (class-file-fields class))
576    (finalize-field field class))
577  (dolist (method (class-file-methods class))
578    (finalize-method method class))
579  ;; top-level attributes (no parent attributes to refer to)
580  (finalize-attributes (class-file-attributes class) nil class))
581
582
583(declaim (inline write-u1 write-u2 write-u4 write-s4))
584(defun write-u1 (n stream)
585  (declare (optimize speed))
586  (declare (type (unsigned-byte 8) n))
587  (declare (type stream stream))
588  (write-8-bits n stream))
589
590(defknown write-u2 (t t) t)
591(defun write-u2 (n stream)
592  (declare (optimize speed))
593  (declare (type (unsigned-byte 16) n))
594  (declare (type stream stream))
595  (write-8-bits (logand (ash n -8) #xFF) stream)
596  (write-8-bits (logand n #xFF) stream))
597
598(defknown write-u4 (integer stream) t)
599(defun write-u4 (n stream)
600  (declare (optimize speed))
601  (declare (type (unsigned-byte 32) n))
602  (write-u2 (logand (ash n -16) #xFFFF) stream)
603  (write-u2 (logand n #xFFFF) stream))
604
605(declaim (ftype (function (t t) t) write-s4))
606(defun write-s4 (n stream)
607  (declare (optimize speed))
608  (cond ((minusp n)
609         (write-u4 (1+ (logxor (- n) #xFFFFFFFF)) stream))
610        (t
611         (write-u4 n stream))))
612
613(declaim (ftype (function (t t t) t) write-ascii))
614(defun write-ascii (string length stream)
615  (declare (type string string))
616  (declare (type (unsigned-byte 16) length))
617  (declare (type stream stream))
618  (write-u2 length stream)
619  (dotimes (i length)
620    (declare (type (unsigned-byte 16) i))
621    (write-8-bits (char-code (char string i)) stream)))
622
623
624(declaim (ftype (function (t t) t) write-utf8))
625(defun write-utf8 (string stream)
626  (declare (optimize speed))
627  (declare (type string string))
628  (declare (type stream stream))
629  (let ((length (length string))
630        (must-convert nil))
631    (declare (type fixnum length))
632    (dotimes (i length)
633      (declare (type fixnum i))
634      (unless (< 0 (char-code (char string i)) #x80)
635        (setf must-convert t)
636        (return)))
637    (if must-convert
638        (let ((octets (make-array (* length 2)
639                                  :element-type '(unsigned-byte 8)
640                                  :adjustable t
641                                  :fill-pointer 0)))
642          (declare (type (vector (unsigned-byte 8)) octets))
643          (dotimes (i length)
644            (declare (type fixnum i))
645            (let* ((c (char string i))
646                   (n (char-code c)))
647              (cond ((zerop n)
648                     (vector-push-extend #xC0 octets)
649                     (vector-push-extend #x80 octets))
650                    ((< 0 n #x80)
651                     (vector-push-extend n octets))
652                    (t
653                     (let ((char-octets (char-to-utf8 c)))
654                       (dotimes (j (length char-octets))
655                         (declare (type fixnum j))
656                         (vector-push-extend (svref char-octets j) octets)))))))
657          (write-u2 (length octets) stream)
658          (dotimes (i (length octets))
659            (declare (type fixnum i))
660            (write-8-bits (aref octets i) stream)))
661        (write-ascii string length stream))))
662
663
664(defun !write-class-file (class stream)
665  "Serializes `class' to `stream', after it has been finalized."
666
667  ;; header
668  (write-u4 #xCAFEBABE stream)
669  (write-u2 3 stream)
670  (write-u2 45 stream)
671
672   ;; constants pool
673  (write-constants (class-file-constants class) stream)
674  ;; flags
675  (write-u2  (class-file-access-flags class) stream)
676
677  ;; class name
678  (write-u2 (class-file-class class) stream)
679
680  ;; superclass
681  (write-u2 (class-file-superclass class) stream)
682
683  ;; interfaces
684  (write-u2 0 stream)
685
686  ;; fields
687  (write-u2 (length (class-file-fields class)) stream)
688  (dolist (field (class-file-fields class))
689    (write-field field stream))
690
691  ;; methods
692  (write-u2 (length (class-file-methods class)) stream)
693  (dolist (method (class-file-methods class))
694    (write-method method stream))
695
696  ;; attributes
697  (write-attributes (class-file-attributes class) stream))
698
699
700(defvar *jvm-class-debug-pool* nil
701  "When bound to a non-NIL value, enables output to *standard-output*
702to allow debugging output of the constant section of the class file.")
703
704(defun write-constants (constants stream)
705  "Writes the constant section given in `constants' to the class file `stream'."
706  (let ((pool-index 0))
707    (write-u2 (1+ (pool-index constants)) stream)
708    (when *jvm-class-debug-pool*
709      (sys::%format t "pool count ~A~%" (pool-index constants)))
710    (dolist (entry (reverse (pool-entries-list constants)))
711      (incf pool-index)
712      (let ((tag (constant-tag entry)))
713        (when *jvm-class-debug-pool*
714          (print-constant entry t))
715        (write-u1 tag stream)
716        (case tag
717          (1                            ; UTF8
718           (write-utf8 (constant-utf8-value entry) stream))
719          ((3 4)                        ; float int
720           (write-u4 (constant-float/int-value entry) stream))
721          ((5 6)                        ; long double
722           (write-u4 (logand (ash (constant-double/long-value entry) -32)
723                             #xFFFFffff) stream)
724           (write-u4 (logand (constant-double/long-value entry) #xFFFFffff)
725                     stream))
726          ((9 10 11)           ; fieldref methodref InterfaceMethodref
727           (write-u2 (constant-member-ref-class-index entry) stream)
728           (write-u2 (constant-member-ref-name/type-index entry) stream))
729          (12                           ; nameAndType
730           (write-u2 (constant-name/type-name-index entry) stream)
731           (write-u2 (constant-name/type-descriptor-index entry) stream))
732          (7                            ; class
733           (write-u2 (constant-class-name-index entry) stream))
734          (8                            ; string
735           (write-u2 (constant-string-value-index entry) stream))
736          (t
737           (error "write-constant-pool-entry unhandled tag ~D~%" tag)))))))
738
739
740(defun print-constant (entry stream)
741  "Debugging helper to print the content of a constant-pool entry."
742  (let ((tag (constant-tag entry))
743        (index (constant-index entry)))
744    (sys::%format stream "pool element ~a, tag ~a, " index tag)
745    (case tag
746      (1     (sys::%format t "utf8: ~a~%" (constant-utf8-value entry)))
747      ((3 4) (sys::%format t "f/i: ~a~%" (constant-float/int-value entry)))
748      ((5 6) (sys::%format t "d/l: ~a~%" (constant-double/long-value entry)))
749      ((9 10 11) (sys::%format t "ref: ~a,~a~%"
750                               (constant-member-ref-class-index entry)
751                               (constant-member-ref-name/type-index entry)))
752      (12 (sys::%format t "n/t: ~a,~a~%"
753                        (constant-name/type-name-index entry)
754                        (constant-name/type-descriptor-index entry)))
755      (7 (sys::%format t "cls: ~a~%" (constant-class-name-index entry)))
756      (8 (sys::%format t "str: ~a~%" (constant-string-value-index entry))))))
757
758
759#|
760
761ABCL doesn't use interfaces, so don't implement it here at this time
762
763(defstruct interface)
764
765|#
766
767
768(defparameter +access-flags-map+
769  '((:public       #x0001)
770    (:private      #x0002)
771    (:protected    #x0004)
772    (:static       #x0008)
773    (:final        #x0010)
774    (:volatile     #x0040)
775    (:synchronized #x0020)
776    (:transient    #x0080)
777    (:native       #x0100)
778    (:abstract     #x0400)
779    (:strict       #x0800))
780  "List of keyword symbols used for human readable representation of (access)
781flags and their binary values.")
782
783(defun map-flags (flags)
784  "Calculates the bitmap of the flags from a list of symbols."
785  (reduce #'(lambda (y x)
786              (logior (or (when (member (car x) flags)
787                            (second x))
788                          0) y))
789          +access-flags-map+
790          :initial-value 0))
791
792(defstruct (field (:constructor %make-field))
793  "Holds information on the properties of fields in the class(-file)."
794  access-flags
795  name
796  descriptor
797  attributes)
798
799(defun make-field (name type &key (flags '(:public)))
800  "Creates a field for addition to a class file."
801  (%make-field :access-flags flags
802               :name name
803               :descriptor type))
804
805(defun field-add-attribute (field attribute)
806  "Adds an attribute to a field."
807  (push attribute (field-attributes field)))
808
809(defun field-attribute (field name)
810  "Retrieves an attribute named `name' of `field'.
811
812Returns NIL if the attribute isn't found."
813  (find name (field-attributes field)
814        :test #'string= :key #'attribute-name))
815
816(defun finalize-field (field class)
817  "Prepares `field' for serialization."
818  (let ((pool (class-file-constants class)))
819    (setf (field-access-flags field)
820          (map-flags (field-access-flags field))
821          (field-descriptor field)
822          (pool-add-utf8 pool (internal-field-ref (field-descriptor field)))
823          (field-name field)
824          (pool-add-utf8 pool (field-name field))))
825  (finalize-attributes (field-attributes field) nil class))
826
827(defun write-field (field stream)
828  "Writes classfile representation of `field' to `stream'."
829  (write-u2 (field-access-flags field) stream)
830  (write-u2 (field-name field) stream)
831  (write-u2 (field-descriptor field) stream)
832  (write-attributes (field-attributes field) stream))
833
834
835(defstruct (method (:constructor %make-method)
836                   (:conc-name method-))
837  "Holds information on the properties of methods in the class(-file)."
838  access-flags
839  name
840  descriptor
841  attributes)
842
843
844(defun map-method-name (name)
845  "Methods should be identified by strings containing their names, or,
846be one of two keyword identifiers to identify special methods:
847
848 * :class-constructor
849 * :constructor
850"
851  (cond
852    ((eq name :class-constructor)
853     "<clinit>")
854    ((eq name :constructor)
855     "<init>")
856    (t name)))
857
858(defun make-method (name return args &key (flags '(:public)))
859  "Creates a method for addition to a class file."
860  (%make-method :descriptor (cons return args)
861                :access-flags flags
862                :name name))
863
864(defun method-add-attribute (method attribute)
865  "Add `attribute' to the list of attributes of `method',
866returning `attribute'."
867  (push attribute (method-attributes method))
868  attribute)
869
870(defun method-add-code (method)
871  "Creates an (empty) 'Code' attribute for the method,
872returning the created attribute."
873  (method-add-attribute
874   method
875   (make-code-attribute (+ (length (cdr (method-descriptor method)))
876                           (if (member :static (method-access-flags method))
877                               0 1))))) ;; 1 == implicit 'this'
878
879(defun method-ensure-code (method)
880  "Ensures the existence of a 'Code' attribute for the method,
881returning the attribute."
882  (let ((code (method-attribute method "Code")))
883    (if (null code)
884        (method-add-code method)
885        code)))
886
887(defun method-attribute (method name)
888  "Returns the first attribute of `method' with `name'."
889  (find name (method-attributes method)
890        :test #'string= :key #'attribute-name))
891
892
893(defun finalize-method (method class)
894  "Prepares `method' for serialization."
895  (let ((pool (class-file-constants class)))
896    (setf (method-access-flags method)
897          (map-flags (method-access-flags method))
898          (method-descriptor method)
899          (pool-add-utf8 pool (apply #'descriptor (method-descriptor method)))
900          (method-name method)
901          (pool-add-utf8 pool (map-method-name (method-name method)))))
902  (finalize-attributes (method-attributes method) nil class))
903
904
905(defun write-method (method stream)
906  "Write class file representation of `method' to `stream'."
907  (write-u2 (method-access-flags method) stream)
908  (write-u2 (method-name method) stream)
909  ;;(sys::%format t "method-name: ~a~%" (method-name method))
910  (write-u2 (method-descriptor method) stream)
911  (write-attributes (method-attributes method) stream))
912
913(defstruct attribute
914  "Parent attribute structure to be included into other attributes, mainly
915to define common fields.
916
917Having common fields allows common driver code for
918finalizing and serializing attributes."
919  name
920
921  ;; not in the class file:
922  finalizer  ;; function of 3 arguments: the attribute, parent and class-file
923  writer     ;; function of 2 arguments: the attribute and the output stream
924  )
925
926(defun finalize-attributes (attributes att class)
927  "Prepare `attributes' (a list) of attribute `att' list for serialization."
928  (dolist (attribute attributes)
929    ;; assure header: make sure 'name' is in the pool
930    (setf (attribute-name attribute)
931          (pool-add-utf8 (class-file-constants class)
932                         (attribute-name attribute)))
933    ;; we're saving "root" attributes: attributes which have no parent
934    (funcall (attribute-finalizer attribute) attribute att class)))
935
936(defun write-attributes (attributes stream)
937  "Writes the `attributes' to `stream'."
938  (write-u2 (length attributes) stream)
939  (dolist (attribute attributes)
940    (write-u2 (attribute-name attribute) stream)
941    ;; set up a bulk catcher for (UNSIGNED-BYTE 8)
942    ;; since we need to know the attribute length (excluding the header)
943    (let ((local-stream (sys::%make-byte-array-output-stream)))
944      (funcall (attribute-writer attribute) attribute local-stream)
945      (let ((array (sys::%get-output-stream-array local-stream)))
946        (write-u4 (length array) stream)
947        (write-sequence array stream)))))
948
949
950
951(defstruct (code-attribute (:conc-name code-)
952                           (:include attribute
953                                     (name "Code")
954                                     (finalizer #'finalize-code-attribute)
955                                     (writer #'write-code-attribute))
956                           (:constructor %make-code-attribute))
957  "The attribute containing the actual JVM byte code;
958an attribute of a method."
959  max-stack
960  max-locals
961  code
962  exception-handlers
963  attributes
964
965  ;; fields not in the class file start here
966
967  ;; labels contains offsets into the code array after it's finalized
968  labels ;; an alist
969
970  (current-local 0)) ;; used for handling nested WITH-CODE-TO-METHOD blocks
971
972
973
974(defun code-label-offset (code label)
975  "Retrieves the `label' offset within a `code' attribute after the
976attribute has been finalized."
977  (cdr (assoc label (code-labels code))))
978
979(defun (setf code-label-offset) (offset code label)
980  "Sets the `label' offset within a `code' attribute after the attribute
981has been finalized."
982  (setf (code-labels code)
983        (acons label offset (code-labels code))))
984
985(defun finalize-code-attribute (code parent class)
986  "Prepares the `code' attribute for serialization, within method `parent'."
987  (declare (ignore parent))
988  (let* ((handlers (code-exception-handlers code))
989         (c (finalize-code
990                     (code-code code)
991                     (nconc (mapcar #'exception-start-pc handlers)
992                            (mapcar #'exception-end-pc handlers)
993                            (mapcar #'exception-handler-pc handlers))
994                     t)))
995    (setf (code-max-stack code)
996          (analyze-stack c (mapcar #'exception-handler-pc handlers)))
997    (multiple-value-bind
998          (c labels)
999        (code-bytes c)
1000      (setf (code-code code) c
1001            (code-labels code) labels)))
1002
1003  (setf (code-exception-handlers code)
1004        (remove-if #'(lambda (h)
1005                       (eql (code-label-offset code (exception-start-pc h))
1006                            (code-label-offset code (exception-end-pc h))))
1007                   (code-exception-handlers code)))
1008
1009  (dolist (exception (code-exception-handlers code))
1010    (setf (exception-start-pc exception)
1011          (code-label-offset code (exception-start-pc exception))
1012          (exception-end-pc exception)
1013          (code-label-offset code (exception-end-pc exception))
1014          (exception-handler-pc exception)
1015          (code-label-offset code (exception-handler-pc exception))
1016          (exception-catch-type exception)
1017          (if (null (exception-catch-type exception))
1018              0  ;; generic 'catch all' class index number
1019              (pool-add-class (class-file-constants class)
1020                              (exception-catch-type exception)))))
1021
1022  (finalize-attributes (code-attributes code) code class))
1023
1024(defun write-code-attribute (code stream)
1025  "Writes the attribute `code' to `stream'."
1026  ;;(sys::%format t "max-stack: ~a~%" (code-max-stack code))
1027  (write-u2 (code-max-stack code) stream)
1028  ;;(sys::%format t "max-locals: ~a~%" (code-max-locals code))
1029  (write-u2 (code-max-locals code) stream)
1030  (let ((code-array (code-code code)))
1031    ;;(sys::%format t "length: ~a~%" (length code-array))
1032    (write-u4 (length code-array) stream)
1033    (dotimes (i (length code-array))
1034      (write-u1 (svref code-array i) stream)))
1035
1036  (write-u2 (length (code-exception-handlers code)) stream)
1037  (dolist (exception (reverse (code-exception-handlers code)))
1038    ;;(sys::%format t "start-pc: ~a~%" (exception-start-pc exception))
1039    (write-u2 (exception-start-pc exception) stream)
1040    ;;(sys::%format t "end-pc: ~a~%" (exception-end-pc exception))
1041    (write-u2 (exception-end-pc exception) stream)
1042    ;;(sys::%format t "handler-pc: ~a~%" (exception-handler-pc exception))
1043    (write-u2 (exception-handler-pc exception) stream)
1044    (write-u2 (exception-catch-type exception) stream))
1045
1046  (write-attributes (code-attributes code) stream))
1047
1048(defun make-code-attribute (arg-count)
1049  "Creates an empty 'Code' attribute for a method which takes
1050`arg-count` parameters, including the implicit `this` parameter."
1051  (%make-code-attribute :max-locals arg-count))
1052
1053(defun code-add-attribute (code attribute)
1054  "Adds `attribute' to `code', returning `attribute'."
1055  (push attribute (code-attributes code))
1056  attribute)
1057
1058(defun code-attribute (code name)
1059  "Returns an attribute of `code' identified by `name'."
1060  (find name (code-attributes code)
1061        :test #'string= :key #'attribute-name))
1062
1063
1064(defun code-add-exception-handler (code start end handler type)
1065  "Adds an exception handler to `code' protecting the region from
1066labels `start' to `end' (inclusive) from exception `type' - where
1067a value of NIL indicates all types. Upon an exception of the given
1068type, control is transferred to label `handler'."
1069  (push (make-exception :start-pc start
1070                        :end-pc end
1071                        :handler-pc handler
1072                        :catch-type type)
1073        (code-exception-handlers code)))
1074
1075(defstruct exception
1076  "Exception handler information.
1077
1078After finalization, the fields contain offsets instead of labels."
1079  start-pc    ;; label target
1080  end-pc      ;; label target
1081  handler-pc  ;; label target
1082  catch-type  ;; a string for a specific type, or NIL for all
1083  )
1084
1085
1086(defstruct (constant-value-attribute (:conc-name constant-value-)
1087                                     (:include attribute
1088                                               (name "ConstantValue")
1089                                               ;; finalizer
1090                                               ;; writer
1091                                               ))
1092  "An attribute of a field of primitive type.
1093
1094"
1095  ;;; ### TODO
1096  )
1097
1098
1099(defstruct (checked-exceptions-attribute
1100             (:conc-name checked-)
1101             (:include attribute
1102                       (name "Exceptions")
1103                       (finalizer #'finalize-checked-exceptions)
1104                       (writer #'write-checked-exceptions)))
1105  "An attribute of `code-attribute', "
1106  table ;; a list of checked classes corresponding to Java's 'throws'
1107)
1108
1109(defun finalize-checked-exceptions (checked-exceptions code class)
1110  (declare (ignorable code class))
1111
1112  "Prepare `checked-exceptions' for serialization."
1113  (setf (checked-table checked-exceptions)
1114        (mapcar #'(lambda (exception)
1115                    (pool-add-class (class-file-constants class)
1116                                    exception))
1117                (checked-table checked-exceptions))))
1118
1119(defun write-checked-exceptions (checked-exceptions stream)
1120  "Write `checked-exceptions' to `stream' in class file representation."
1121  (write-u2 (length (checked-table checked-exceptions)) stream)
1122  (dolist (exception (reverse (checked-table checked-exceptions)))
1123    (write-u2 exception stream)))
1124
1125;; Can't be used yet: serialization missing
1126(defstruct (deprecated-attribute (:include attribute
1127                                           (name "Deprecated")
1128                                           (finalizer (constantly nil))
1129                                           (writer (constantly nil))))
1130  ;; finalizer and writer need to do nothing: Deprecated attributes are empty
1131  "An attribute of a class file, field or method, indicating the element
1132to which it has been attached has been superseded.")
1133
1134(defvar *current-code-attribute* nil)
1135
1136(defun save-code-specials (code)
1137  (setf (code-code code) *code*
1138        (code-max-locals code) *registers-allocated*
1139        (code-current-local code) *register*))
1140
1141(defun restore-code-specials (code)
1142  (setf *code* (code-code code)
1143        *registers-allocated* (code-max-locals code)
1144        *register* (code-current-local code)))
1145
1146(defmacro with-code-to-method ((class-file method &key (safe-nesting t))
1147             &body body)
1148  (let ((m (gensym))
1149        (c (gensym)))
1150    `(progn
1151       ,@(when safe-nesting
1152           `((when *current-code-attribute*
1153               (save-code-specials *current-code-attribute*))))
1154       (let* ((,m ,method)
1155              (,c (method-ensure-code ,method))
1156              (*pool* (class-file-constants ,class-file))
1157              (*code* (code-code ,c))
1158              (*registers-allocated* (code-max-locals ,c))
1159              (*register* (code-current-local ,c))
1160              (*current-code-attribute* ,c))
1161         ,@body
1162         (setf (code-code ,c) *code*
1163         (code-current-local ,c) *register*
1164;;               (code-exception-handlers ,c) *handlers*
1165               (code-max-locals ,c) *registers-allocated*))
1166       ,@(when safe-nesting
1167           `((when *current-code-attribute*
1168               (restore-code-specials *current-code-attribute*)))))))
1169
1170
1171(defstruct (source-file-attribute (:conc-name source-)
1172                                  (:include attribute
1173                                            (name "SourceFile")
1174                                            (finalizer #'finalize-source-file)
1175                                            (writer #'write-source-file)))
1176  "An attribute of the class file indicating which source file
1177it was compiled from."
1178  filename)
1179
1180(defun finalize-source-file (source-file code class)
1181  (declare (ignorable code class))
1182  (setf (source-filename source-file)
1183        (pool-add-utf8 (class-file-constants class)
1184                       (source-filename source-file))))
1185
1186(defun write-source-file (source-file stream)
1187  (write-u2 (source-filename source-file) stream))
1188
1189
1190(defstruct (synthetic-attribute (:include attribute
1191                                          (name "Synthetic")
1192                                          (finalizer (constantly nil))
1193                                          (writer (constantly nil))))
1194  ;; finalizer and writer need to do nothing: Synthetic attributes are empty
1195  "An attribute of a class file, field or method to mark that it wasn't
1196included in the sources - but was generated artificially.")
1197
1198
1199(defstruct (line-numbers-attribute
1200             (:conc-name line-numbers-)
1201             (:include attribute
1202                       (name "LineNumberTable")
1203                       (finalizer #'finalize-line-numbers)
1204                       (writer #'write-line-numbers)))
1205  "An attribute of `code-attribute', containing a mapping of offsets
1206within the code section to the line numbers in the source file."
1207  table ;; a list of line-number structures, in reverse order
1208  )
1209
1210(defstruct line-number
1211  start-pc  ;; a label, before finalization
1212  line)
1213
1214(defun finalize-line-numbers (line-numbers code class)
1215  (declare (ignorable code class))
1216  (dolist (line-number (line-numbers-table line-numbers))
1217    (setf (line-number-start-pc line-number)
1218          (code-label-offset code (line-number-start-pc line-number)))))
1219
1220(defun write-line-numbers (line-numbers stream)
1221  (write-u2 (length (line-numbers-table line-numbers)) stream)
1222  (dolist (line-number (reverse (line-numbers-table line-numbers)))
1223    (write-u2 (line-number-start-pc line-number) stream)
1224    (write-u2 (line-number-line line-number) stream)))
1225
1226
1227
1228(defstruct (local-variables-attribute
1229             (:conc-name local-var-)
1230             (:include attribute
1231                       (name "LocalVariableTable")
1232                       (finalizer #'finalize-local-variables)
1233                       (writer #'write-local-variables)))
1234  "An attribute of the `code-attribute', containing a table of local variable
1235names, their type and their scope of validity."
1236  table ;; a list of local-variable structures, in reverse order
1237  )
1238
1239(defstruct (local-variable (:conc-name local-))
1240  start-pc  ;; a label, before finalization
1241  length    ;; a label (at the ending position) before finalization
1242  name
1243  descriptor
1244  index ;; The index of the variable inside the block of locals
1245  )
1246
1247(defun finalize-local-variables (local-variables code class)
1248  (dolist (local-variable (local-var-table local-variables))
1249    (setf (local-start-pc local-variable)
1250          (code-label-offset code (local-start-pc local-variable))
1251          (local-length local-variable)
1252          ;; calculate 'length' from the distance between 2 labels
1253          (- (code-label-offset code (local-length local-variable))
1254             (local-start-pc local-variable))
1255          (local-name local-variable)
1256          (pool-add-utf8 (class-file-constants class)
1257                         (local-name local-variable))
1258          (local-descriptor local-variable)
1259          (pool-add-utf8 (class-file-constants class)
1260                         (local-descriptor local-variable)))))
1261
1262(defun write-local-variables (local-variables stream)
1263  (write-u2 (length (local-var-table local-variables)) stream)
1264  (dolist (local-variable (reverse (local-var-table local-variables)))
1265    (write-u2 (local-start-pc local-variable) stream)
1266    (write-u2 (local-length local-variable) stream)
1267    (write-u2 (local-name local-variable) stream)
1268    (write-u2 (local-descriptor local-variable) stream)
1269    (write-u2 (local-index local-variable) stream)))
1270
1271#|
1272
1273;; this is the minimal sequence we need to support:
1274
1275;;  create a class file structure
1276;;  add methods
1277;;  add code to the methods, switching from one method to the other
1278;;  finalize the methods, one by one
1279;;  write the class file
1280
1281to support the sequence above, we probably need to
1282be able to
1283
1284- find methods by signature
1285- find the method's code attribute
1286- add code to the code attribute
1287- finalize the code attribute contents (blocking it for further addition)
1288-
1289
1290
1291|#
1292
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