org.mozilla.javascript

Class Decompiler


public class Decompiler
extends java.lang.Object

The following class save decompilation information about the source. Source information is returned from the parser as a String associated with function nodes and with the toplevel script. When saved in the constant pool of a class, this string will be UTF-8 encoded, and token values will occupy a single byte. Source is saved (mostly) as token numbers. The tokens saved pretty much correspond to the token stream of a 'canonical' representation of the input program, as directed by the parser. (There were a few cases where tokens could have been left out where decompiler could easily reconstruct them, but I left them in for clarity). (I also looked adding source collection to TokenStream instead, where I could have limited the changes to a few lines in getToken... but this wouldn't have saved any space in the resulting source representation, and would have meant that I'd have to duplicate parser logic in the decompiler to disambiguate situations where newlines are important.) The function decompile expands the tokens back into their string representations, using simple lookahead to correct spacing and indentation. Assignments are saved as two-token pairs (Token.ASSIGN, op). Number tokens are stored inline, as a NUMBER token, a character representing the type, and either 1 or 4 characters representing the bit-encoding of the number. String types NAME, STRING and OBJECT are currently stored as a token type, followed by a character giving the length of the string (assumed to be less than 2^16), followed by the characters of the string inlined into the source string. Changing this to some reference to to the string in the compiled class' constant pool would probably save a lot of space... but would require some method of deriving the final constant pool entry from information available at parse time.

Field Summary

static int
CASE_GAP_PROP
Decompilation property to specify identation offset for case labels.
static int
INDENT_GAP_PROP
Decompilation property to specify default identation offset.
static int
INITIAL_INDENT_PROP
Decompilation property to specify initial ident value.
static int
ONLY_BODY_FLAG
Flag to indicate that the decompilation should omit the function header and trailing brace.
static int
TO_SOURCE_FLAG
Flag to indicate that the decompilation generates toSource result.

Method Summary

static String
decompile(String source, int flags, UintMap properties)
Decompile the source information associated with this js function/script back into a string.

Field Details

CASE_GAP_PROP

public static final int CASE_GAP_PROP
Decompilation property to specify identation offset for case labels.
Field Value:
3

INDENT_GAP_PROP

public static final int INDENT_GAP_PROP
Decompilation property to specify default identation offset.
Field Value:
2

INITIAL_INDENT_PROP

public static final int INITIAL_INDENT_PROP
Decompilation property to specify initial ident value.
Field Value:
1

ONLY_BODY_FLAG

public static final int ONLY_BODY_FLAG
Flag to indicate that the decompilation should omit the function header and trailing brace.
Field Value:
1

TO_SOURCE_FLAG

public static final int TO_SOURCE_FLAG
Flag to indicate that the decompilation generates toSource result.
Field Value:
2

Method Details

decompile

public static String decompile(String source,
                               int flags,
                               UintMap properties)
Decompile the source information associated with this js function/script back into a string. For the most part, this just means translating tokens back to their string representations; there's a little bit of lookahead logic to decide the proper spacing/indentation. Most of the work in mapping the original source to the prettyprinted decompiled version is done by the parser.
Parameters:
source - encoded source tree presentation
flags - flags to select output format
properties - indentation properties