| 1. About the decompiler |
| |
| Fernflower is the first actually working analytical decompiler for Java and |
| probably for a high-level programming language in general. Naturally it is still |
| under development, please send your bug reports and improvement suggestions at |
| [email protected] |
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| 2. License |
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| http://www.apache.org/licenses/LICENSE-2.0 |
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| 3. Running from the command line |
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| java -jar fernflower.jar [-<option>=<value>]* [<source>]+ <destination> |
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| * means 0 or more times |
| + means 1 or more times |
| |
| <source>: file or directory with files to be decompiled. Directories are recursively scanned. Allowed file extensions are class, zip and jar. |
| Sources prefixed with -e= mean "library" files that won't be decompiled, but taken into account when analysing relationships between |
| classes or methods. Especially renaming of identifiers (s. option 'ren') can benefit from information about external classes. |
| <destination>: destination directory |
| <option>,<value>: command line option with the corresponding value, see 4. |
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| Examples: |
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| java -jar fernflower.jar -hes=0 -hdc=0 c:\Temp\binary\ -e=c:\Java\rt.jar c:\Temp\source\ |
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| java -jar fernflower.jar -dgs=1 c:\Temp\binary\library.jar c:\Temp\binary\Boot.class c:\Temp\source\ |
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| 4. Command line options |
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| With the exception of mpm and urc the value of 1 means the option is activated, 0 - deactivated. Default |
| value, if any, is given between parentheses. |
| |
| Typically, the following options will be changed by user, if any: hes, hdc, dgs, mpm, ren, urc |
| The rest of options can be left as they are: they are aimed at professional reverse engineers. |
| |
| rbr (1): hide bridge methods |
| rsy (0): hide synthetic class members |
| din (1): decompile inner classes |
| dc4 (1): collapse 1.4 class references |
| das (1): decompile assertions |
| hes (1): hide empty super invocation |
| hdc (1): hide empty default constructor |
| dgs (0): decompile generic signatures |
| ner (1): assume return not throwing exceptions |
| den (1): decompile enumerations |
| rgn (1): remove getClass() invocation, when it is part of a qualified new statement |
| lit (0): output numeric literals "as-is" |
| asc (0): encode non-ASCII characters in string and character literals as Unicode escapes |
| bto (1): interpret int 1 as boolean true (workaround to a compiler bug) |
| nns (1): allow for not set synthetic attribute (workaround to a compiler bug) |
| uto (1): consider nameless types as java.lang.Object (workaround to a compiler architecture flaw) |
| udv (1): reconstruct variable names from debug information, if present |
| rer (1): remove empty exception ranges |
| fdi (1): de-inline finally structures |
| mpm (0): maximum allowed processing time per decompiled method, in seconds. 0 means no upper limit |
| ren (0): rename ambiguous (resp. obfuscated) classes and class elements |
| urc : full name of user-supplied class implementing IIdentifierRenamer. It is used to determine which class identifiers |
| should be renamed and provides new identifier names. For more information see section 5 |
| inn (1): check for IntelliJ IDEA-specific @NotNull annotation and remove inserted code if found |
| lac (0): decompile lambda expressions to anonymous classes |
| nls (0): define new line character to be used for output. 0 - '\r\n' (Windows), 1 - '\n' (Linux), default is OS-dependent |
| ind : indentation string (default is " " (3 spaces)) |
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| The default logging level is INFO. This value can be overwritten by setting the option 'log' as follows: |
| log (INFO): possible values TRACE, INFO, WARN, ERROR |
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| 5. Renaming identifiers |
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| Some obfuscators give classes and their member elements short, meaningless and above all ambiguous names. Recompiling of such |
| code leads to a great number of conflicts. Therefore it is advisable to let the decompiler rename elements in its turn, |
| ensuring uniqueness of each identifier. |
| |
| Option 'ren' (i.e. -ren=1) activates renaming functionality. Default renaming strategy goes as follows: |
| - rename an element if its name is a reserved word or is shorter than 3 characters |
| - new names are built according to a simple pattern: (class|method|field)_<consecutive unique number> |
| You can overwrite this rules by providing your own implementation of the 4 key methods invoked by the decompiler while renaming. Simply |
| pass a class that implements org.jetbrains.java.decompiler.main.extern.IIdentifierRenamer in the option 'urc' |
| (e.g. -urc=com.mypackage.MyRenamer) to Fernflower. The class must be available on the application classpath. |
| |
| The meaning of each method should be clear from naming: toBeRenamed determine whether the element will be renamed, while the other three |
| provide new names for classes, methods and fields respectively. |
