Package org.mozilla.javascript

Class Decompiler

java.lang.Object

org.mozilla.javascript.Decompiler

public class Decompiler
extends 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

Fields

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

Constructor Summary

Constructors

Constructor	Description
Decompiler()

Method Summary

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

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

ONLY_BODY_FLAG

public static final int ONLY_BODY_FLAG

Flag to indicate that the decompilation should omit the function header and trailing brace.

See Also:

• Constant Field Values

TO_SOURCE_FLAG

public static final int TO_SOURCE_FLAG

Flag to indicate that the decompilation generates toSource result.

See Also:

• Constant Field Values

INITIAL_INDENT_PROP

public static final int INITIAL_INDENT_PROP

Decompilation property to specify initial ident value.

See Also:

• Constant Field Values

INDENT_GAP_PROP

public static final int INDENT_GAP_PROP

Decompilation property to specify default identation offset.

See Also:

• Constant Field Values

CASE_GAP_PROP

public static final int CASE_GAP_PROP

Decompilation property to specify identation offset for case labels.

See Also:

• Constant Field Values

Constructor Details

Decompiler

public Decompiler()

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