https://github.com/japrozs/rum
a full-spec compliant parser for the Java Class File Format
https://github.com/japrozs/rum
Last synced: 4 months ago
JSON representation
a full-spec compliant parser for the Java Class File Format
- Host: GitHub
- URL: https://github.com/japrozs/rum
- Owner: japrozs
- License: mit
- Created: 2023-06-07T09:25:12.000Z (about 2 years ago)
- Default Branch: master
- Last Pushed: 2023-08-27T20:00:38.000Z (almost 2 years ago)
- Last Synced: 2025-01-09T01:03:41.270Z (5 months ago)
- Language: C
- Homepage:
- Size: 138 KB
- Stars: 2
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
- Codeowners: .github/CODEOWNERS
Awesome Lists containing this project
README
# Rum
Rum is a fully-spec compliant parser for the Java Class File Format that is capable of parsing a Java Class file generate by a simple hello world program.
> `PLEASE DON'T READ THE CODE IF YOU VALUE YOUR MENTAL HEALTH. THE CODE IS EXTREMELY EXTREMELY BAD, ALTHOUGH FUNCTIONAL ;)`
## Usage
To build `rum`, run the following commands:
```bash
git clone https://github.com/japrozs/rum.git
cd rum
./make.sh
./out/rum
```
to run test, on the [sample files](./samples), run the following commands:
```bash
./make.sh
./test.sh
```
running `rum` on a [hello-world program](./samples/Main.java) yields the following results
```sh
magic : cafebabe
minor : 0
major : 61
constant_pool_count : 29
attribute_count : 1
access_flags : 33
this_class : 21
super_class : 2
interfaces_count : 0
fields_count : 0
methods_count : 2
interfaces -> []
constant_pool ->
tag : CONSTANT_Methodref
class_index : 2
name_and_type_index : 3
-------------------------
tag : CONSTANT_Class
name_index : 4
-------------------------
tag : CONSTANT_NameAndType
name_index : 5
descriptor_index : 6
-------------------------
tag : CONSTANT_Utf8
length : 16
bytes : "java/lang/Object"
-------------------------
tag : CONSTANT_Utf8
length : 6
bytes : ""
-------------------------
tag : CONSTANT_Utf8
length : 3
bytes : "()V"
-------------------------
tag : CONSTANT_Fieldref
class_index : 8
name_and_type_index : 9
-------------------------
tag : CONSTANT_Class
name_index : 10
-------------------------
tag : CONSTANT_NameAndType
name_index : 11
descriptor_index : 12
-------------------------
tag : CONSTANT_Utf8
length : 16
bytes : "java/lang/Systemout"
-------------------------
tag : CONSTANT_Utf8
length : 3
bytes : "out"
-------------------------
tag : CONSTANT_Utf8
length : 21
bytes : "Ljava/io/PrintStream;"
-------------------------
tag : CONSTANT_String
string_index : 14
-------------------------
tag : CONSTANT_Utf8
length : 16
bytes : "hello, universe!java/io/PrintStream"
-------------------------
tag : CONSTANT_Methodref
class_index : 16
name_and_type_index : 17
-------------------------
tag : CONSTANT_Class
name_index : 18
-------------------------
tag : CONSTANT_NameAndType
name_index : 19
descriptor_index : 20
-------------------------
tag : CONSTANT_Utf8
length : 19
bytes : "java/io/PrintStream"
-------------------------
tag : CONSTANT_Utf8
length : 7
bytes : "println"
-------------------------
tag : CONSTANT_Utf8
length : 21
bytes : "(Ljava/lang/String;)V"
-------------------------
tag : CONSTANT_Class
name_index : 22
-------------------------
tag : CONSTANT_Utf8
length : 4
bytes : "Main"
-------------------------
tag : CONSTANT_Utf8
length : 4
bytes : "Code"
-------------------------
tag : CONSTANT_Utf8
length : 15
bytes : "LineNumberTable"
-------------------------
tag : CONSTANT_Utf8
length : 4
bytes : "main"
-------------------------
tag : CONSTANT_Utf8
length : 22
bytes : "([Ljava/lang/String;)V"
-------------------------
tag : CONSTANT_Utf8
length : 10
bytes : "SourceFile"
-------------------------
tag : CONSTANT_Utf8
length : 9
bytes : "Main.java"
-------------------------
fields -> []
methods ->
access_flags : ACC_PUBLIC
name_index : 5
descriptor_index : 6
attributes_count : 1
attributes ->
attribute_name_index : 23
attribute_length : 29
info : ""
----------------------------
access_flags : ACC_PUBLIC, ACC_STATIC
name_index : 25
descriptor_index : 26
attributes_count : 1
attributes ->
attribute_name_index : 23
attribute_length : 37
info : ""
----------------------------
attributes ->
attribute_name_index : 27
attribute_length : 2
info : ""
----------------------------
```
## Credits
All the sample Java files for testing purposes have been copied directly from [William Fiset's DSA repository](https://github.com/williamfiset/DEPRECATED-data-structures)
## Reference
[`Java Class File Format`](https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html)