Some clarificaation…. a while back you helped me write a testing framework…here is the code:get_all_tests(Tests) :- setof(Line-Name, get_one_test(Name, Line), Tests).
get_one_test(Name, Line) :- current_predicate(Name/0), atom_concat('test_', _, Name), predicate_property(Name, prolog_line(Line)).
It uses ‘pairs’ as I understand them, using the ‘-‘ to combine the key and value, so in your response, what is ‘=‘ doing in this context in the list of flags????
Just when I thouthgh I was beginning to understand! LMAO
Thanks once again,
Sean.
Hello Sean,
you can do this with your own loop or use findall like this:
flag(public, 0x0001).
flag(final, 0x0010).
flag(super, 0x0020).
flag(interface, 0x0200).
flag(abstract, 0x0400).
flag(synthetic, 0x1000).
flag(annotation, 0x2000).
flag(enum, 0x4000).
get_java_flags(Value, Flags) :-
findall(Name, has_flag(Value, Name), Flags).
has_flag(Value, Name) :-
flag(Name, Mask),
Value /\ Mask =\= 0.
then call it with:
| ?- get_java_flags(0x421, Flags).
Flags = [public,super,abstract]
I have detailed a bit to be more comprehensive: the has_flag/2
predicate could be inlined inside the findall surrounding with ().
If you prefer to have the flags as a parameter pass them as a list
and use member to handle backtracking (done by get_flags/3 here):
get_java_flags(Value, Flags) :-
FlagNames = [public = 0x0001,
final = 0x0010,
super = 0x0020,
interface = 0x0200,
abstract = 0x0400,
synthetic = 0x1000,
annotation = 0x2000,
enum = 0x4000],
get_flags(FlagNames, Value, Flags).
get_flags(FlagNames, Value, Flags) :-
findall(Name, has_flag(FlagNames, Value, Name),
Flags).
has_flag(NameFlags, Value, Name) :-
member(Name=Mask, NameFlags),
Value /\ Mask =\= 0.
Daniel
Le 09/04/2014 01:02, Sean Charles a écrit :
Hello list,
I have almost completed a predicate called ‘jread’ which
parses a Java .class file into a term that will allow me to
create a database of all of the methods, fields, superclass and
interfaces for that class and ultimately create a database for a
complete “android.jar” file of any required API level.
I am, for educational purposes and my own learning, trying
to build a system like Hoogle/Hayoo for Android. I do a lot of
Android and I wanted to create a sytem I can wire into
Emacs/IntelliJ or anything for that matter, a simple HTTP
server that can supply a list of methods that have a certain
type signature using a si mple query language. Searching by
types it very very useful when using Haskell and I wanted to
improve my Prolog so I figured why not do something like that
in GNU Prolog? I have already started a simple HTTP library in
pure GNU Prolog as well but this comes first now.
Progress so far is good…if I run it like this from a folder
containing the unpacked android.jar file...
| ?-
jread('javax/net/SocketFactory.class',X).
X =
javaclass(super('java/lang/Object'),class('javax/net/SocketFactory'),implements([]),
methods([method(access_flags(4),name('<init>'),returns('()V'),[attr(9,
[0,3,0,1,0,0,0,14,42,183,0,1,187,0,2,89,18,3,183,0,4,191,0,0,0,2,0,10,0,0,0,6,0,1,0,0,0
,4,0,11,0,0,0,12,0,1,0,0,0,14,0,12,0,13,0,0])]),method(access_flags(41),name(getDefault)
,returns('()Ljavax/net/SocketFactory;'),attr(9,0,3,0,0,0,0,0,10,187,0,2,89,18,3,183,0,4,
191,0,0,0,1,0,10,0,0,0,6,0,1,0,0,0,5])]),method(access_flags(1),name(createSocket),
returns('()Ljava/net/Socket;'),[attr(9,0,3,0,1,0,0,0,10,187,0,2,89,18,3,183,0,4,191,
0,0,0,2,0,10,0,0,0,6,0,1,0,0,0,6,0,11,0,0,0,12,0,1,0,0,0,10,0,12,0,13,0,0]),
attr(18,0,1,0,19])]),method(access_flags(1025),name(createSocket),
returns('(Ljava/lang/String;I)Ljava/net/Socket;'),[attr(18,[0,2,0,19,0,21])]),
method(access_flags(1025),name(createSocket),
returns('(Ljava/lang/String;ILjava/net/InetAddress;I)Ljava/net/Socket;’),
[attr(18,[0,2,0,19,0,21])]),method(access_flags(1025),name(createSocket),
returns('(Ljava/net/InetAddress;I)Ljava/net/Socket;’),[attr(18[0,1,0,19])]),method(access_flags(1025),name(createSocket),
returns('(Ljava/net/InetAddress;ILjava/net/InetAddress;I)Ljava/net/Socket;'),[attr(18,[0,1,0,19])])]))
?
The place I am at now is decoding the bit flags for the
class (and eventually the methods etc) into a term.
A typical value would be “1057” decimal, 0x421, this
contains the flags:
ACC_PUBLIC |
0x0001 |
Declared public; may
be accessed from outside its package. |
ACC_FINAL |
0x0010 |
Declared final; no
subclasses allowed. |
ACC_SUPER |
0x0020 |
Treat superclass methods specially when invoked by
the invokespecial
instruction. |
ACC_INTERFACE |
0x0200 |
Is an interface, not a class. |
ACC_ABSTRACT |
0x0400 |
Declared abstract;
must not be instantiated. |
ACC_SYNTHETIC |
0x1000 |
Declared synthetic; not present in the source code.
|
ACC_ANNOTATION |
0x2000 |
Declared as an annotation type. |
ACC_ENUM |
0x4000 |
Declared as an enum
type. |
So you can see that 0x421 means “ACC_PUBLIC, ACC_SUPER and
ACC_ABSTRACT”. I would like to produce a term something like
this:
access_flags(public,super,abstract)
It’s not that I don’t know how to do it or that I can’t do
it but I am not sure what is the *most elegant* way to do it
in Prolog! Heaven knows I have written bit shifting loops to
test for flags in a dozen languages but not in Prolog.
So, there’s the challenge, what is the most elegant way to
turn a list of bits into a list of atom terms. Ideally I would
make the list of atoms a parameter so that I can reuse it for
the other flag based values.
Consider the gauntlet thrown! In the meantime I am
continuing to research the possibilities for myself. I will of
course put it all on GitHub along with my Redis client. I may
even create a Redis database with the information!
:)
Sean.
--
Ce message a été vérifié par
MailScanner
pour des virus ou des polluriels et rien de
suspect n'a été trouvé.
|