prototype implementation of JSR 308 in OW2 ASM

[Eric Bruneton]

Hi,

For your information, I added a prototype "implementation" of JSR 308 in 
the ASM_5_FUTURE branch of the OW2 ASM repository:

http://websvn.ow2.org/listing.php?repname=asm&path=%2Fbranches%2FASM_5_FUTURE%2F

Added code compared to HEAD:

http://websvn.ow2.org/comp.php?repname=asm&compare[]=%2Fbranches%2FASM_5_FUTURE@1642&compare[]=%2Fbranches%2FASM_5_FUTURE@1643

This prototype does not implement the exact specification in its current 
state. I used 3 modifications to make the implementation easier and more 
efficient. They are the following:

a) in Section 3, I assumed that the elements in the "annotations" array 
of the Runtime[In]VisibleTypeAnnotations_attribute are sorted by 
increasing order of bytecode offset (for target_type >= 0x86; the others 
can be in any order, and also interleaved with instruction annotations).
b) in Section 3.1, in the type_annotation structure, I put the 
target_type and target_info fields *before* the original fields from the 
"annotation" structure.
c) in sections 3.3.7 to 3.3.10, I replaced "A 
Runtime[In]visibleTypeAnnotations attribute containing a ***_target 
appears in the attributes table of a method_info structure." with "... 
in the attributes table of a Code attribute.". I also replaced, in 
Section 3, "A type annotation is stored in a 
Runtime[In]visibleTypeAnnotations attribute on the smallest enclosing 
class, field, or method." with "... class, field, method, or
Code structure.".

Changes a) and c) improve the performance of class parsing in 
ClassReader, by avoiding multiple parsing of the annotations structure, 
and also by avoiding sorting passes. Also change c) seems more natural, 
independently of any implementation consideration, since existing 
attributes that refer to bytecode are currently stored as attributes of 
the Code attribute (like  LineNumberTable, LocalVariableTable, 
LocalVariableTypeTable and StackMapTable).

Change b) improves the performance of class generation in ClassWriter. 
Indeed, with the proposed ASM 5 API, the target is known before the 
annotation, and so it is easier to store it first in the type_annotation 
structure. This change also improves the parsing performance in ClassReader.

Do you think it would be possible to make these changes in the 
specification? Especially change b), which is really critical to get 
good class generation performance with ASM?

Eric