source: trunk/abcl/src/org/armedbear/lisp/jvm-class-file.lisp @ 13071

Last change on this file since 13071 was 13071, checked in by Mark Evenson, 11 years ago

Add support for writing Java interfaces via the classwriter.

One can create interfaces as follows:

(let* ((class-name (make-jvm-class-name "org/not/Foo"))

(class (make-class-file class-name +java-object+ '(:public :interface)))
(method (make-jvm-method "callback" :int '(:int) :flags

'(:public :abstract))))

(class-add-method class method)
(finalize-class-file class)
(with-open-file (s #p"Foo.class" :direction :output

:if-exists :supersede :element-type '(unsigned-byte 8))

(write-class-file class s)))

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 50.2 KB
Line 
1;;; jvm-class-file.lisp
2;;;
3;;; Copyright (C) 2010 Erik Huelsmann
4;;; $Id: jvm-class-file.lisp 13071 2010-11-30 19:58:15Z mevenson $
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 (jvm-class-name (:conc-name class-)
84         (:constructor %make-jvm-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-jvm-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-jvm-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-jvm-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-jvm-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-compiled-primitive+
171    "org.armedbear.lisp.CompiledPrimitive")
172(define-class-name +lisp-eql-hash-table+ "org.armedbear.lisp.EqlHashTable")
173(define-class-name +lisp-hash-table+ "org.armedbear.lisp.HashTable")
174(define-class-name +lisp-package+ "org.armedbear.lisp.Package")
175(define-class-name +lisp-readtable+ "org.armedbear.lisp.Readtable")
176(define-class-name +lisp-stream+ "org.armedbear.lisp.Stream")
177(define-class-name +lisp-closure+ "org.armedbear.lisp.Closure")
178(define-class-name +lisp-compiled-closure+ "org.armedbear.lisp.CompiledClosure")
179(define-class-name +lisp-closure-parameter+
180    "org.armedbear.lisp.Closure$Parameter")
181(defconstant +lisp-closure-parameter-array+
182  (class-array +lisp-closure-parameter+))
183
184#|
185
186Lisp-side descriptor representation:
187
188 - list: a list starting with a method return value, followed by
189     the argument types
190 - keyword: the primitive type associated with that keyword
191 - class-name structure instance: the class-ref value
192
193The latter two can be converted to a Java representation using
194the `internal-field-ref' function, the former is to be fed to
195`descriptor'.
196
197|#
198
199(defun internal-field-type (field-type)
200  "Returns a string containing the JVM-internal representation
201of `field-type', which should either be a symbol identifying a primitive
202type, or a `class-name' structure identifying a class or interface."
203  (if (symbolp field-type)
204      (map-primitive-type field-type)
205      (class-name-internal field-type)))
206
207(defun internal-field-ref (field-type)
208  "Returns a string containing the JVM-internal representation of a reference
209to `field-type', which should either be a symbol identifying a primitive
210type, or a `class-name' structure identifying a class or interface."
211  (if (symbolp field-type)
212      (map-primitive-type field-type)
213      (class-ref field-type)))
214
215(defun descriptor (return-type &rest argument-types)
216  "Returns a string describing the `return-type' and `argument-types'
217in JVM-internal representation."
218  (let* ((arg-strings (mapcar #'internal-field-ref argument-types))
219         (ret-string (internal-field-ref return-type))
220         (size (+ 2 (reduce #'+ arg-strings
221                            :key #'length
222                            :initial-value (length ret-string))))
223         (str (make-array size :fill-pointer 0 :element-type 'character)))
224    (with-output-to-string (s str)
225      (princ #\( s)
226      (dolist (arg-string arg-strings)
227        (princ arg-string s))
228      (princ #\) s)
229      (princ ret-string s))
230    str)
231;;  (format nil "(~{~A~})~A"
232;;          (internal-field-ref return-type))
233  )
234
235(defun descriptor-stack-effect (return-type &rest argument-types)
236  "Returns the effect on the stack position of the `argument-types' and
237`return-type' of a method call.
238
239If the method consumes an implicit `this' argument, this function does not
240take that effect into account."
241  (flet ((type-stack-effect (arg)
242           (case arg
243             ((:long :double) 2)
244             ((nil :void) 0)
245             (otherwise 1))))
246    (+ (reduce #'- argument-types
247               :key #'type-stack-effect
248               :initial-value 0)
249       (type-stack-effect return-type))))
250
251
252(defstruct pool
253  ;; `index' contains the index of the last allocated slot (0 == empty)
254  ;; "A constant pool entry is considered valid if it has
255  ;; an index greater than 0 (zero) and less than pool-count"
256  (index 0)
257  entries-list
258  ;; the entries hash stores raw values, except in case of string and
259  ;; utf8, because both are string values
260  (entries (make-hash-table :test #'equal :size 2048 :rehash-size 2.0)))
261
262
263(defstruct constant
264  "Structure to be included in all constant sub-types."
265  tag
266  index)
267
268(defparameter +constant-type-map+
269  '((:class          7 1)
270    (:field-ref      9 1)
271    (:method-ref    10 1)
272    ;; (:interface-method-ref 11)
273    (:string         8 1)
274    (:integer        3 1)
275    (:float          4 1)
276    (:long           5 2)
277    (:double         6 2)
278    (:name-and-type 12 1)
279    (:utf8           1 1)))
280
281(defstruct (constant-class (:constructor make-constant-class (index name-index))
282                           (:include constant
283                                     (tag 7)))
284  "Structure holding information on a 'class' type item in the constant pool."
285  name-index)
286
287(defstruct (constant-member-ref (:constructor
288                                 %make-constant-member-ref
289                                     (tag index class-index name/type-index))
290                                (:include constant))
291  "Structure holding information on a member reference type item
292(a field, method or interface method reference) in the constant pool."
293  class-index
294  name/type-index)
295
296(declaim (inline make-constant-field-ref make-constant-method-ref
297                 make-constant-interface-method-ref))
298(defun make-constant-field-ref (index class-index name/type-index)
299  "Creates a `constant-member-ref' instance containing a field reference."
300  (%make-constant-member-ref 9 index class-index name/type-index))
301
302(defun make-constant-method-ref (index class-index name/type-index)
303  "Creates a `constant-member-ref' instance containing a method reference."
304  (%make-constant-member-ref 10 index class-index name/type-index))
305
306(defun make-constant-interface-method-ref (index class-index name/type-index)
307  "Creates a `constant-member-ref' instance containing an
308interface-method reference."
309  (%make-constant-member-ref 11 index class-index name/type-index))
310
311(defstruct (constant-string (:constructor
312                             make-constant-string (index value-index))
313                            (:include constant
314                                      (tag 8)))
315  "Structure holding information on a 'string' type item in the constant pool."
316  value-index)
317
318(defstruct (constant-float/int (:constructor
319                                %make-constant-float/int (tag index value))
320                               (:include constant))
321  "Structure holding information on a 'float' or 'integer' type item
322in the constant pool."
323  value)
324
325(declaim (inline make-constant-float make-constant-int))
326(defun make-constant-float (index value)
327  "Creates a `constant-float/int' structure instance containing a float."
328  (%make-constant-float/int 4 index value))
329
330(defun make-constant-int (index value)
331  "Creates a `constant-float/int' structure instance containing an int."
332  (%make-constant-float/int 3 index value))
333
334(defstruct (constant-double/long (:constructor
335                                  %make-constant-double/long (tag index value))
336                                 (:include constant))
337  "Structure holding information on a 'double' or 'long' type item
338in the constant pool."
339  value)
340
341(declaim (inline make-constant-double make-constant-float))
342(defun make-constant-double (index value)
343  "Creates a `constant-double/long' structure instance containing a double."
344  (%make-constant-double/long 6 index value))
345
346(defun make-constant-long (index value)
347  "Creates a `constant-double/long' structure instance containing a long."
348  (%make-constant-double/long 5 index value))
349
350(defstruct (constant-name/type (:constructor
351                                make-constant-name/type (index
352                                                         name-index
353                                                         descriptor-index))
354                               (:include constant
355                                         (tag 12)))
356  "Structure holding information on a 'name-and-type' type item in the
357constant pool; this type of element is used by 'member-ref' type items."
358  name-index
359  descriptor-index)
360
361(defstruct (constant-utf8 (:constructor make-constant-utf8 (index value))
362                          (:include constant
363                                    (tag 1)))
364  "Structure holding information on a 'utf8' type item in the constant pool;
365
366This type of item is used for text representation of identifiers
367and string contents."
368  value)
369
370
371(defun pool-add-class (pool class)
372  "Returns the index of the constant-pool class item for `class'.
373
374`class' must be an instance of `class-name'."
375  (let ((entry (gethash class (pool-entries pool))))
376    (unless entry
377      (let ((utf8 (pool-add-utf8 pool (class-name-internal class))))
378        (setf entry
379              (make-constant-class (incf (pool-index pool)) utf8)
380              (gethash class (pool-entries pool)) entry))
381      (push entry (pool-entries-list pool)))
382    (constant-index entry)))
383
384(defun pool-add-field-ref (pool class name type)
385  "Returns the index of the constant-pool item which denotes a reference
386to the `name' field of the `class', being of `type'.
387
388`class' should be an instance of `class-name'.
389`name' is a string.
390`type' is a field-type (see `internal-field-type')"
391  (let ((entry (gethash (acons name type class) (pool-entries pool))))
392    (unless entry
393      (let ((c (pool-add-class pool class))
394            (n/t (pool-add-name/type pool name type)))
395        (setf entry (make-constant-field-ref (incf (pool-index pool)) c n/t)
396            (gethash (acons name type class) (pool-entries pool)) entry))
397      (push entry (pool-entries-list pool)))
398    (constant-index entry)))
399
400(defun pool-add-method-ref (pool class name type)
401  "Returns the index of the constant-pool item which denotes a reference
402to the method with `name' in `class', which is of `type'.
403
404Here, `type' is a method descriptor, which defines the argument types
405and return type. `class' is an instance of `class-name'."
406  (let ((entry (gethash (acons name type class) (pool-entries pool))))
407    (unless entry
408      (let ((c (pool-add-class pool class))
409            (n/t (pool-add-name/type pool name type)))
410        (setf entry (make-constant-method-ref (incf (pool-index pool)) c n/t)
411              (gethash (acons name type class) (pool-entries pool)) entry))
412      (push entry (pool-entries-list pool)))
413    (constant-index entry)))
414
415(defun pool-add-interface-method-ref (pool class name type)
416  "Returns the index of the constant-pool item which denotes a reference to
417the method `name' in the interface `class', which is of `type'.
418
419See `pool-add-method-ref' for remarks."
420  (let ((entry (gethash (acons name type class) (pool-entries pool))))
421    (unless entry
422      (let ((c (pool-add-class pool class))
423            (n/t (pool-add-name/type pool name type)))
424        (setf entry
425            (make-constant-interface-method-ref (incf (pool-index pool)) c n/t)
426            (gethash (acons name type class) (pool-entries pool)) entry))
427      (push entry (pool-entries-list pool)))
428    (constant-index entry)))
429
430(defun pool-add-string (pool string)
431  "Returns the index of the constant-pool item denoting the string."
432  (let ((entry (gethash (cons 8 string) ;; 8 == string-tag
433                        (pool-entries pool))))
434    (unless entry
435      (let ((utf8 (pool-add-utf8 pool string)))
436        (setf entry (make-constant-string (incf (pool-index pool)) utf8)
437              (gethash (cons 8 string) (pool-entries pool)) entry))
438      (push entry (pool-entries-list pool)))
439    (constant-index entry)))
440
441(defun pool-add-int (pool int)
442  "Returns the index of the constant-pool item denoting the int."
443  (let ((entry (gethash (cons 3 int) (pool-entries pool))))
444    (unless entry
445      (setf entry (make-constant-int (incf (pool-index pool)) int)
446            (gethash (cons 3 int) (pool-entries pool)) entry)
447      (push entry (pool-entries-list pool)))
448    (constant-index entry)))
449
450(defun pool-add-float (pool float)
451  "Returns the index of the constant-pool item denoting the float."
452  (let ((entry (gethash (cons 4 float) (pool-entries pool))))
453    (unless entry
454      (setf entry (make-constant-float (incf (pool-index pool))
455                                       (sys::%float-bits float))
456            (gethash (cons 4 float) (pool-entries pool)) entry)
457      (push entry (pool-entries-list pool)))
458    (constant-index entry)))
459
460(defun pool-add-long (pool long)
461  "Returns the index of the constant-pool item denoting the long."
462  (let ((entry (gethash (cons 5 long) (pool-entries pool))))
463    (unless entry
464      (setf entry (make-constant-long (incf (pool-index pool)) long)
465            (gethash (cons 5 long) (pool-entries pool)) entry)
466      (push entry (pool-entries-list pool))
467      (incf (pool-index pool))) ;; double index increase; long takes 2 slots
468    (constant-index entry)))
469
470(defun pool-add-double (pool double)
471  "Returns the index of the constant-pool item denoting the double."
472  (let ((entry (gethash (cons 6 double) (pool-entries pool))))
473    (unless entry
474      (setf entry (make-constant-double (incf (pool-index pool))
475                                        (sys::%float-bits double))
476            (gethash (cons 6 double) (pool-entries pool)) entry)
477      (push entry (pool-entries-list pool))
478      (incf (pool-index pool))) ;; double index increase; 'double' takes 2 slots
479    (constant-index entry)))
480
481(defun pool-add-name/type (pool name type)
482  "Returns the index of the constant-pool item denoting
483the name/type identifier."
484  (let ((entry (gethash (cons name type) (pool-entries pool)))
485        (internal-type (if (listp type)
486                           (apply #'descriptor type)
487                           (internal-field-ref type))))
488    (unless entry
489      (let ((n (pool-add-utf8 pool name))
490            (i-t (pool-add-utf8 pool internal-type)))
491        (setf entry (make-constant-name/type (incf (pool-index pool)) n i-t)
492              (gethash (cons name type) (pool-entries pool)) entry))
493      (push entry (pool-entries-list pool)))
494    (constant-index entry)))
495
496(defun pool-add-utf8 (pool utf8-as-string)
497  "Returns the index of the textual value that will be stored in the
498class file as UTF-8 encoded data."
499  (let ((entry (gethash (cons 11 utf8-as-string) ;; 11 == utf8
500                        (pool-entries pool))))
501    (unless entry
502      (setf entry (make-constant-utf8 (incf (pool-index pool)) utf8-as-string)
503            (gethash (cons 11 utf8-as-string) (pool-entries pool)) entry)
504      (push entry (pool-entries-list pool)))
505    (constant-index entry)))
506
507(defstruct (class-file (:constructor
508                        make-class-file (class superclass access-flags)))
509  "Holds the components of a class file."
510  (constants (make-pool))
511  access-flags
512  class
513  superclass
514  ;; support for implementing interfaces not yet available
515  ;; interfaces
516  fields
517  methods
518  attributes)
519
520(defun class-add-field (class field)
521  "Adds a `field' created by `make-field'."
522  (push field (class-file-fields class)))
523
524(defun class-field (class name)
525  "Finds a field by name." ;; ### strictly speaking, a field is uniquely
526  ;; identified by its name and type, not by the name alone.
527  (find name (class-file-fields class)
528        :test #'string= :key #'field-name))
529
530(defun class-add-method (class method)
531  "Adds a `method' to `class'; the method must have been created using
532`make-method'."
533  (push method (class-file-methods class)))
534
535(defun class-methods-by-name (class name)
536  "Returns all methods which have `name'."
537  (remove (map-method-name name) (class-file-methods class)
538          :test-not #'string= :key #'method-name))
539
540(defun class-method (class name return &rest args)
541  "Return the method which is (uniquely) identified by its name AND descriptor."
542  (let ((return-and-args (cons return args))
543        (name (map-method-name name)))
544    (find-if #'(lambda (c)
545                 (and (string= (method-name c) name)
546                      (equal (method-descriptor c) return-and-args)))
547             (class-file-methods class))))
548
549(defun class-add-attribute (class attribute)
550  "Adds `attribute' to the class; attributes must be instances of
551structure classes which include the `attribute' structure class."
552  (push attribute (class-file-attributes class)))
553
554(defun class-attribute (class name)
555  "Returns the attribute which is named `name'."
556  (find name (class-file-attributes class)
557        :test #'string= :key #'attribute-name))
558
559
560(defun finalize-class-file (class)
561  "Transforms the representation of the class-file from one
562which allows easy modification to one which works best for serialization.
563
564The class can't be modified after finalization."
565
566  ;; constant pool contains constants finalized on addition;
567  ;; no need for additional finalization
568
569  (setf (class-file-access-flags class)
570        (map-flags (class-file-access-flags class)))
571  (setf (class-file-superclass class)
572        (pool-add-class (class-file-constants class)
573                        (class-file-superclass class))
574        (class-file-class class)
575        (pool-add-class (class-file-constants class)
576                        (class-file-class class)))
577  ;;  (finalize-interfaces)
578  (dolist (field (class-file-fields class))
579    (finalize-field field class))
580  (dolist (method (class-file-methods class))
581    (finalize-method method class))
582  ;; top-level attributes (no parent attributes to refer to)
583  (finalize-attributes (class-file-attributes class) nil class))
584
585
586(declaim (inline write-u1 write-u2 write-u4 write-s4))
587(defun write-u1 (n stream)
588  (declare (optimize speed))
589  (declare (type (unsigned-byte 8) n))
590  (declare (type stream stream))
591  (write-8-bits n stream))
592
593(defknown write-u2 (t t) t)
594(defun write-u2 (n stream)
595  (declare (optimize speed))
596  (declare (type (unsigned-byte 16) n))
597  (declare (type stream stream))
598  (write-8-bits (logand (ash n -8) #xFF) stream)
599  (write-8-bits (logand n #xFF) stream))
600
601(defknown write-u4 (integer stream) t)
602(defun write-u4 (n stream)
603  (declare (optimize speed))
604  (declare (type (unsigned-byte 32) n))
605  (write-u2 (logand (ash n -16) #xFFFF) stream)
606  (write-u2 (logand n #xFFFF) stream))
607
608(declaim (ftype (function (t t) t) write-s4))
609(defun write-s4 (n stream)
610  (declare (optimize speed))
611  (cond ((minusp n)
612         (write-u4 (1+ (logxor (- n) #xFFFFFFFF)) stream))
613        (t
614         (write-u4 n stream))))
615
616(declaim (ftype (function (t t t) t) write-ascii))
617(defun write-ascii (string length stream)
618  (declare (type string string))
619  (declare (type (unsigned-byte 16) length))
620  (declare (type stream stream))
621  (write-u2 length stream)
622  (dotimes (i length)
623    (declare (type (unsigned-byte 16) i))
624    (write-8-bits (char-code (char string i)) stream)))
625
626
627(declaim (ftype (function (t t) t) write-utf8))
628(defun write-utf8 (string stream)
629  (declare (optimize speed))
630  (declare (type string string))
631  (declare (type stream stream))
632  (let ((length (length string))
633        (must-convert nil))
634    (declare (type fixnum length))
635    (dotimes (i length)
636      (declare (type fixnum i))
637      (unless (< 0 (char-code (char string i)) #x80)
638        (setf must-convert t)
639        (return)))
640    (if must-convert
641        (let ((octets (make-array (* length 2)
642                                  :element-type '(unsigned-byte 8)
643                                  :adjustable t
644                                  :fill-pointer 0)))
645          (declare (type (vector (unsigned-byte 8)) octets))
646          (dotimes (i length)
647            (declare (type fixnum i))
648            (let* ((c (char string i))
649                   (n (char-code c)))
650              (cond ((zerop n)
651                     (vector-push-extend #xC0 octets)
652                     (vector-push-extend #x80 octets))
653                    ((< 0 n #x80)
654                     (vector-push-extend n octets))
655                    (t
656                     (let ((char-octets (char-to-utf8 c)))
657                       (dotimes (j (length char-octets))
658                         (declare (type fixnum j))
659                         (vector-push-extend (svref char-octets j) octets)))))))
660          (write-u2 (length octets) stream)
661          (dotimes (i (length octets))
662            (declare (type fixnum i))
663            (write-8-bits (aref octets i) stream)))
664        (write-ascii string length stream))))
665
666
667(defun write-class-file (class stream)
668  "Serializes `class' to `stream', after it has been finalized."
669
670  ;; header
671  (write-u4 #xCAFEBABE stream)
672  (write-u2 3 stream)
673  (write-u2 45 stream)
674
675   ;; constants pool
676  (write-constants (class-file-constants class) stream)
677  ;; flags
678  (write-u2  (class-file-access-flags class) stream)
679
680  ;; class name
681  (write-u2 (class-file-class class) stream)
682
683  ;; superclass
684  (write-u2 (class-file-superclass class) stream)
685
686  ;; interfaces
687  (write-u2 0 stream)
688
689  ;; fields
690  (write-u2 (length (class-file-fields class)) stream)
691  (dolist (field (class-file-fields class))
692    (write-field field stream))
693
694  ;; methods
695  (write-u2 (length (class-file-methods class)) stream)
696  (dolist (method (class-file-methods class))
697    (write-method method stream))
698
699  ;; attributes
700  (write-attributes (class-file-attributes class) stream))
701
702
703(defvar *jvm-class-debug-pool* nil
704  "When bound to a non-NIL value, enables output to *standard-output*
705to allow debugging output of the constant section of the class file.")
706
707(defun write-constants (constants stream)
708  "Writes the constant section given in `constants' to the class file `stream'."
709  (let ((pool-index 0))
710    (write-u2 (1+ (pool-index constants)) stream)
711    (when *jvm-class-debug-pool*
712      (sys::%format t "pool count ~A~%" (pool-index constants)))
713    (dolist (entry (reverse (pool-entries-list constants)))
714      (incf pool-index)
715      (let ((tag (constant-tag entry)))
716        (when *jvm-class-debug-pool*
717          (print-constant entry t))
718        (write-u1 tag stream)
719        (case tag
720          (1                            ; UTF8
721           (write-utf8 (constant-utf8-value entry) stream))
722          ((3 4)                        ; float int
723           (write-u4 (constant-float/int-value entry) stream))
724          ((5 6)                        ; long double
725           (write-u4 (logand (ash (constant-double/long-value entry) -32)
726                             #xFFFFffff) stream)
727           (write-u4 (logand (constant-double/long-value entry) #xFFFFffff)
728                     stream))
729          ((9 10 11)           ; fieldref methodref InterfaceMethodref
730           (write-u2 (constant-member-ref-class-index entry) stream)
731           (write-u2 (constant-member-ref-name/type-index entry) stream))
732          (12                           ; nameAndType
733           (write-u2 (constant-name/type-name-index entry) stream)
734           (write-u2 (constant-name/type-descriptor-index entry) stream))
735          (7                            ; class
736           (write-u2 (constant-class-name-index entry) stream))
737          (8                            ; string
738           (write-u2 (constant-string-value-index entry) stream))
739          (t
740           (error "write-constant-pool-entry unhandled tag ~D~%" tag)))))))
741
742
743(defun print-constant (entry stream)
744  "Debugging helper to print the content of a constant-pool entry."
745  (let ((tag (constant-tag entry))
746        (index (constant-index entry)))
747    (sys::%format stream "pool element ~a, tag ~a, " index tag)
748    (case tag
749      (1     (sys::%format t "utf8: ~a~%" (constant-utf8-value entry)))
750      ((3 4) (sys::%format t "f/i: ~a~%" (constant-float/int-value entry)))
751      ((5 6) (sys::%format t "d/l: ~a~%" (constant-double/long-value entry)))
752      ((9 10 11) (sys::%format t "ref: ~a,~a~%"
753                               (constant-member-ref-class-index entry)
754                               (constant-member-ref-name/type-index entry)))
755      (12 (sys::%format t "n/t: ~a,~a~%"
756                        (constant-name/type-name-index entry)
757                        (constant-name/type-descriptor-index entry)))
758      (7 (sys::%format t "cls: ~a~%" (constant-class-name-index entry)))
759      (8 (sys::%format t "str: ~a~%" (constant-string-value-index entry))))))
760
761
762#|
763
764ABCL doesn't use interfaces, so don't implement it here at this time
765
766(defstruct interface)
767
768|#
769
770
771(defparameter +access-flags-map+
772  '((:public       #x0001)
773    (:private      #x0002)
774    (:protected    #x0004)
775    (:static       #x0008)
776    (:final        #x0010)
777    (:volatile     #x0040)
778    (:synchronized #x0020)
779    (:transient    #x0080)
780    (:native       #x0100)
781    (:interface    #x0200)
782    (:abstract     #x0400)
783    (:strict       #x0800))
784  "List of keyword symbols used for human readable representation of (access)
785flags and their binary values.")
786
787(defun map-flags (flags)
788  "Calculates the bitmap of the flags from a list of symbols."
789  (reduce #'(lambda (y x)
790              (logior (or (when (member (car x) flags)
791                            (second x))
792                          0) y))
793          +access-flags-map+
794          :initial-value 0))
795
796(defstruct (field (:constructor %make-field))
797  "Holds information on the properties of fields in the class(-file)."
798  access-flags
799  name
800  descriptor
801  attributes)
802
803(defun make-field (name type &key (flags '(:public)))
804  "Creates a field for addition to a class file."
805  (%make-field :access-flags flags
806               :name name
807               :descriptor type))
808
809(defun field-add-attribute (field attribute)
810  "Adds an attribute to a field."
811  (push attribute (field-attributes field)))
812
813(defun field-attribute (field name)
814  "Retrieves an attribute named `name' of `field'.
815
816Returns NIL if the attribute isn't found."
817  (find name (field-attributes field)
818        :test #'string= :key #'attribute-name))
819
820(defun finalize-field (field class)
821  "Prepares `field' for serialization."
822  (let ((pool (class-file-constants class)))
823    (setf (field-access-flags field)
824          (map-flags (field-access-flags field))
825          (field-descriptor field)
826          (pool-add-utf8 pool (internal-field-ref (field-descriptor field)))
827          (field-name field)
828          (pool-add-utf8 pool (field-name field))))
829  (finalize-attributes (field-attributes field) nil class))
830
831(defun write-field (field stream)
832  "Writes classfile representation of `field' to `stream'."
833  (write-u2 (field-access-flags field) stream)
834  (write-u2 (field-name field) stream)
835  (write-u2 (field-descriptor field) stream)
836  (write-attributes (field-attributes field) stream))
837
838
839(defstruct (jvm-method (:constructor %make-jvm-method)
840           (:conc-name method-))
841  "Holds information on the properties of methods in the class(-file)."
842  access-flags
843  name
844  descriptor
845  attributes)
846
847
848(defun map-method-name (name)
849  "Methods should be identified by strings containing their names, or,
850be one of two keyword identifiers to identify special methods:
851
852 * :static-initializer
853 * :constructor
854"
855  (cond
856    ((eq name :static-initializer)
857     "<clinit>")
858    ((eq name :constructor)
859     "<init>")
860    (t name)))
861
862(defun make-jvm-method (name return args &key (flags '(:public)))
863  "Creates a method for addition to a class file."
864  (%make-jvm-method :descriptor (cons return args)
865        :access-flags flags
866        :name (map-method-name name)))
867
868(defun method-add-attribute (method attribute)
869  "Add `attribute' to the list of attributes of `method',
870returning `attribute'."
871  (push attribute (method-attributes method))
872  attribute)
873
874(defun method-add-code (method)
875  "Creates an (empty) 'Code' attribute for the method,
876returning the created attribute."
877  (method-add-attribute
878   method
879   (make-code-attribute (+ (length (cdr (method-descriptor method)))
880                           (if (member :static (method-access-flags method))
881                               0 1))))) ;; 1 == implicit 'this'
882
883(defun method-ensure-code (method)
884  "Ensures the existence of a 'Code' attribute for the method,
885returning the attribute."
886  (let ((code (method-attribute method "Code")))
887    (if (null code)
888        (method-add-code method)
889        code)))
890
891(defun method-attribute (method name)
892  "Returns the first attribute of `method' with `name'."
893  (find name (method-attributes method)
894        :test #'string= :key #'attribute-name))
895
896
897(defun finalize-method (method class)
898  "Prepares `method' for serialization."
899  (let ((pool (class-file-constants class)))
900    (setf (method-access-flags method)
901          (map-flags (method-access-flags method))
902          (method-descriptor method)
903          (pool-add-utf8 pool (apply #'descriptor (method-descriptor method)))
904          (method-name method)
905          (pool-add-utf8 pool (method-name method))))
906  (finalize-attributes (method-attributes method) nil class))
907
908
909(defun write-method (method stream)
910  "Write class file representation of `method' to `stream'."
911  (write-u2 (method-access-flags method) stream)
912  (write-u2 (method-name method) stream)
913  ;;(sys::%format t "method-name: ~a~%" (method-name method))
914  (write-u2 (method-descriptor method) stream)
915  (write-attributes (method-attributes method) stream))
916
917(defstruct attribute
918  "Parent attribute structure to be included into other attributes, mainly
919to define common fields.
920
921Having common fields allows common driver code for
922finalizing and serializing attributes."
923  name
924
925  ;; not in the class file:
926  finalizer  ;; function of 3 arguments: the attribute, parent and class-file
927  writer     ;; function of 2 arguments: the attribute and the output stream
928  )
929
930(defun finalize-attributes (attributes att class)
931  "Prepare `attributes' (a list) of attribute `att' list for serialization."
932  (dolist (attribute attributes)
933    ;; assure header: make sure 'name' is in the pool
934    (setf (attribute-name attribute)
935          (pool-add-utf8 (class-file-constants class)
936                         (attribute-name attribute)))
937    ;; we're saving "root" attributes: attributes which have no parent
938    (funcall (attribute-finalizer attribute) attribute att class)))
939
940(defun write-attributes (attributes stream)
941  "Writes the `attributes' to `stream'."
942  (write-u2 (length attributes) stream)
943  (dolist (attribute attributes)
944    (write-u2 (attribute-name attribute) stream)
945    ;; set up a bulk catcher for (UNSIGNED-BYTE 8)
946    ;; since we need to know the attribute length (excluding the header)
947    (let ((local-stream (sys::%make-byte-array-output-stream)))
948      (funcall (attribute-writer attribute) attribute local-stream)
949      (let ((array (sys::%get-output-stream-array local-stream)))
950        (write-u4 (length array) stream)
951        (write-sequence array stream)))))
952
953
954
955(defstruct (code-attribute (:conc-name code-)
956                           (:include attribute
957                                     (name "Code")
958                                     (finalizer #'finalize-code-attribute)
959                                     (writer #'write-code-attribute))
960                           (:constructor %make-code-attribute))
961  "The attribute containing the actual JVM byte code;
962an attribute of a method."
963  max-stack
964  max-locals
965  code
966  exception-handlers
967  attributes
968
969  ;; fields not in the class file start here
970
971  ;; labels contains offsets into the code array after it's finalized
972  labels ;; an alist
973
974  (current-local 0)) ;; used for handling nested WITH-CODE-TO-METHOD blocks
975
976
977
978(defun code-label-offset (code label)
979  "Retrieves the `label' offset within a `code' attribute after the
980attribute has been finalized."
981  (cdr (assoc label (code-labels code))))
982
983(defun (setf code-label-offset) (offset code label)
984  "Sets the `label' offset within a `code' attribute after the attribute
985has been finalized."
986  (setf (code-labels code)
987        (acons label offset (code-labels code))))
988
989(defun finalize-code-attribute (code parent class)
990  "Prepares the `code' attribute for serialization, within method `parent'."
991  (declare (ignore parent))
992  (let* ((handlers (code-exception-handlers code))
993         (c (finalize-code
994                     (code-code code)
995                     (nconc (mapcar #'exception-start-pc handlers)
996                            (mapcar #'exception-end-pc handlers)
997                            (mapcar #'exception-handler-pc handlers))
998                     t)))
999    (unless (code-max-stack code)
1000      (setf (code-max-stack code)
1001            (analyze-stack c (mapcar #'exception-handler-pc handlers))))
1002    (unless (code-max-locals code)
1003      (setf (code-max-locals code)
1004            (analyze-locals code)))
1005    (multiple-value-bind
1006          (c labels)
1007        (code-bytes c)
1008      (setf (code-code code) c
1009            (code-labels code) labels)))
1010
1011  (setf (code-exception-handlers code)
1012        (remove-if #'(lambda (h)
1013                       (eql (code-label-offset code (exception-start-pc h))
1014                            (code-label-offset code (exception-end-pc h))))
1015                   (code-exception-handlers code)))
1016
1017  (dolist (exception (code-exception-handlers code))
1018    (setf (exception-start-pc exception)
1019          (code-label-offset code (exception-start-pc exception))
1020          (exception-end-pc exception)
1021          (code-label-offset code (exception-end-pc exception))
1022          (exception-handler-pc exception)
1023          (code-label-offset code (exception-handler-pc exception))
1024          (exception-catch-type exception)
1025          (if (null (exception-catch-type exception))
1026              0  ;; generic 'catch all' class index number
1027              (pool-add-class (class-file-constants class)
1028                              (exception-catch-type exception)))))
1029
1030  (finalize-attributes (code-attributes code) code class))
1031
1032(defun write-code-attribute (code stream)
1033  "Writes the attribute `code' to `stream'."
1034  ;;(sys::%format t "max-stack: ~a~%" (code-max-stack code))
1035  (write-u2 (code-max-stack code) stream)
1036  ;;(sys::%format t "max-locals: ~a~%" (code-max-locals code))
1037  (write-u2 (code-max-locals code) stream)
1038  (let ((code-array (code-code code)))
1039    ;;(sys::%format t "length: ~a~%" (length code-array))
1040    (write-u4 (length code-array) stream)
1041    (dotimes (i (length code-array))
1042      (write-u1 (svref code-array i) stream)))
1043
1044  (write-u2 (length (code-exception-handlers code)) stream)
1045  (dolist (exception (reverse (code-exception-handlers code)))
1046    ;;(sys::%format t "start-pc: ~a~%" (exception-start-pc exception))
1047    (write-u2 (exception-start-pc exception) stream)
1048    ;;(sys::%format t "end-pc: ~a~%" (exception-end-pc exception))
1049    (write-u2 (exception-end-pc exception) stream)
1050    ;;(sys::%format t "handler-pc: ~a~%" (exception-handler-pc exception))
1051    (write-u2 (exception-handler-pc exception) stream)
1052    (write-u2 (exception-catch-type exception) stream))
1053
1054  (write-attributes (code-attributes code) stream))
1055
1056(defun make-code-attribute (arg-count)
1057  "Creates an empty 'Code' attribute for a method which takes
1058`arg-count` parameters, including the implicit `this` parameter."
1059  (%make-code-attribute :max-locals arg-count))
1060
1061(defun code-add-attribute (code attribute)
1062  "Adds `attribute' to `code', returning `attribute'."
1063  (push attribute (code-attributes code))
1064  attribute)
1065
1066(defun code-attribute (code name)
1067  "Returns an attribute of `code' identified by `name'."
1068  (find name (code-attributes code)
1069        :test #'string= :key #'attribute-name))
1070
1071
1072(defun code-add-exception-handler (code start end handler type)
1073  "Adds an exception handler to `code' protecting the region from
1074labels `start' to `end' (inclusive) from exception `type' - where
1075a value of NIL indicates all types. Upon an exception of the given
1076type, control is transferred to label `handler'."
1077  (push (make-exception :start-pc start
1078                        :end-pc end
1079                        :handler-pc handler
1080                        :catch-type type)
1081        (code-exception-handlers code)))
1082
1083(defstruct exception
1084  "Exception handler information.
1085
1086After finalization, the fields contain offsets instead of labels."
1087  start-pc    ;; label target
1088  end-pc      ;; label target
1089  handler-pc  ;; label target
1090  catch-type  ;; a string for a specific type, or NIL for all
1091  )
1092
1093
1094(defstruct (constant-value-attribute (:conc-name constant-value-)
1095                                     (:include attribute
1096                                               (name "ConstantValue")
1097                                               ;; finalizer
1098                                               ;; writer
1099                                               ))
1100  "An attribute of a field of primitive type.
1101
1102"
1103  ;;; ### TODO
1104  )
1105
1106
1107(defstruct (checked-exceptions-attribute
1108             (:conc-name checked-)
1109             (:include attribute
1110                       (name "Exceptions")
1111                       (finalizer #'finalize-checked-exceptions)
1112                       (writer #'write-checked-exceptions)))
1113  "An attribute of `code-attribute', "
1114  table ;; a list of checked classes corresponding to Java's 'throws'
1115)
1116
1117(defun finalize-checked-exceptions (checked-exceptions code class)
1118  (declare (ignorable code class))
1119
1120  "Prepare `checked-exceptions' for serialization."
1121  (setf (checked-table checked-exceptions)
1122        (mapcar #'(lambda (exception)
1123                    (pool-add-class (class-file-constants class)
1124                                    exception))
1125                (checked-table checked-exceptions))))
1126
1127(defun write-checked-exceptions (checked-exceptions stream)
1128  "Write `checked-exceptions' to `stream' in class file representation."
1129  (write-u2 (length (checked-table checked-exceptions)) stream)
1130  (dolist (exception (reverse (checked-table checked-exceptions)))
1131    (write-u2 exception stream)))
1132
1133;; Can't be used yet: serialization missing
1134(defstruct (deprecated-attribute (:include attribute
1135                                           (name "Deprecated")
1136                                           (finalizer (constantly nil))
1137                                           (writer (constantly nil))))
1138  ;; finalizer and writer need to do nothing: Deprecated attributes are empty
1139  "An attribute of a class file, field or method, indicating the element
1140to which it has been attached has been superseded.")
1141
1142(defvar *current-code-attribute* nil)
1143(defvar *method*)
1144
1145(defun save-code-specials (code)
1146  (setf (code-code code) *code*
1147        (code-max-locals code) *registers-allocated*
1148        (code-current-local code) *register*))
1149
1150(defun restore-code-specials (code)
1151  (setf *code* (code-code code)
1152        *registers-allocated* (code-max-locals code)
1153        *register* (code-current-local code)))
1154
1155(defmacro with-code-to-method ((class-file method)
1156                               &body body)
1157  (let ((m (gensym))
1158        (c (gensym)))
1159    `(progn
1160       (when *current-code-attribute*
1161         (save-code-specials *current-code-attribute*))
1162       (let* ((,m ,method)
1163              (*method* ,m)
1164              (,c (method-ensure-code ,method))
1165              (*pool* (class-file-constants ,class-file))
1166              (*code* (code-code ,c))
1167              (*registers-allocated* (code-max-locals ,c))
1168              (*register* (code-current-local ,c))
1169              (*current-code-attribute* ,c))
1170         ,@body
1171         (setf (code-code ,c) *code*
1172               (code-current-local ,c) *register*
1173               (code-max-locals ,c) *registers-allocated*))
1174       (when *current-code-attribute*
1175         (restore-code-specials *current-code-attribute*)))))
1176
1177
1178(defstruct (source-file-attribute (:conc-name source-)
1179                                  (:include attribute
1180                                            (name "SourceFile")
1181                                            (finalizer #'finalize-source-file)
1182                                            (writer #'write-source-file)))
1183  "An attribute of the class file indicating which source file
1184it was compiled from."
1185  filename)
1186
1187(defun finalize-source-file (source-file code class)
1188  (declare (ignorable code class))
1189  (setf (source-filename source-file)
1190        (pool-add-utf8 (class-file-constants class)
1191                       (source-filename source-file))))
1192
1193(defun write-source-file (source-file stream)
1194  (write-u2 (source-filename source-file) stream))
1195
1196
1197(defstruct (synthetic-attribute (:include attribute
1198                                          (name "Synthetic")
1199                                          (finalizer (constantly nil))
1200                                          (writer (constantly nil))))
1201  ;; finalizer and writer need to do nothing: Synthetic attributes are empty
1202  "An attribute of a class file, field or method to mark that it wasn't
1203included in the sources - but was generated artificially.")
1204
1205
1206(defstruct (line-numbers-attribute
1207             (:conc-name line-numbers-)
1208             (:include attribute
1209                       (name "LineNumberTable")
1210                       (finalizer #'finalize-line-numbers)
1211                       (writer #'write-line-numbers)))
1212  "An attribute of `code-attribute', containing a mapping of offsets
1213within the code section to the line numbers in the source file."
1214  table ;; a list of line-number structures, in reverse order
1215  )
1216
1217(defstruct line-number
1218  start-pc  ;; a label, before finalization, or 0 for "start of function"
1219  line)
1220
1221(defun finalize-line-numbers (line-numbers code class)
1222  (declare (ignorable code class))
1223  (dolist (line-number (line-numbers-table line-numbers))
1224    (unless (zerop (line-number-start-pc line-number))
1225      (setf (line-number-start-pc line-number)
1226            (code-label-offset code (line-number-start-pc line-number))))))
1227
1228(defun write-line-numbers (line-numbers stream)
1229  (write-u2 (length (line-numbers-table line-numbers)) stream)
1230  (dolist (line-number (reverse (line-numbers-table line-numbers)))
1231    (write-u2 (line-number-start-pc line-number) stream)
1232    (write-u2 (line-number-line line-number) stream)))
1233
1234(defun line-numbers-add-line (line-numbers start-pc line)
1235  (push (make-line-number :start-pc start-pc :line line)
1236        (line-numbers-table line-numbers)))
1237
1238(defstruct (local-variables-attribute
1239             (:conc-name local-var-)
1240             (:include attribute
1241                       (name "LocalVariableTable")
1242                       (finalizer #'finalize-local-variables)
1243                       (writer #'write-local-variables)))
1244  "An attribute of the `code-attribute', containing a table of local variable
1245names, their type and their scope of validity."
1246  table ;; a list of local-variable structures, in reverse order
1247  )
1248
1249(defstruct (local-variable (:conc-name local-))
1250  start-pc  ;; a label, before finalization
1251  length    ;; a label (at the ending position) before finalization
1252  name
1253  descriptor
1254  index ;; The index of the variable inside the block of locals
1255  )
1256
1257(defun finalize-local-variables (local-variables code class)
1258  (dolist (local-variable (local-var-table local-variables))
1259    (setf (local-start-pc local-variable)
1260          (code-label-offset code (local-start-pc local-variable))
1261          (local-length local-variable)
1262          ;; calculate 'length' from the distance between 2 labels
1263          (- (code-label-offset code (local-length local-variable))
1264             (local-start-pc local-variable))
1265          (local-name local-variable)
1266          (pool-add-utf8 (class-file-constants class)
1267                         (local-name local-variable))
1268          (local-descriptor local-variable)
1269          (pool-add-utf8 (class-file-constants class)
1270                         (local-descriptor local-variable)))))
1271
1272(defun write-local-variables (local-variables stream)
1273  (write-u2 (length (local-var-table local-variables)) stream)
1274  (dolist (local-variable (reverse (local-var-table local-variables)))
1275    (write-u2 (local-start-pc local-variable) stream)
1276    (write-u2 (local-length local-variable) stream)
1277    (write-u2 (local-name local-variable) stream)
1278    (write-u2 (local-descriptor local-variable) stream)
1279    (write-u2 (local-index local-variable) stream)))
1280
1281#|
1282
1283;; this is the minimal sequence we need to support:
1284
1285;;  create a class file structure
1286;;  add methods
1287;;  add code to the methods, switching from one method to the other
1288;;  finalize the methods, one by one
1289;;  write the class file
1290
1291to support the sequence above, we probably need to
1292be able to
1293
1294- find methods by signature
1295- find the method's code attribute
1296- add code to the code attribute
1297- finalize the code attribute contents (blocking it for further addition)
1298-
1299
1300
1301|#
1302
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