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 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.
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    • TO_SOURCE_FLAG

      public static final int TO_SOURCE_FLAG
      Flag to indicate that the decompilation generates toSource result.
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    • INITIAL_INDENT_PROP

      public static final int INITIAL_INDENT_PROP
      Decompilation property to specify initial ident value.
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    • INDENT_GAP_PROP

      public static final int INDENT_GAP_PROP
      Decompilation property to specify default identation offset.
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    • CASE_GAP_PROP

      public static final int CASE_GAP_PROP
      Decompilation property to specify identation offset for case labels.
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    • FUNCTION_END

      private static final int FUNCTION_END
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    • sourceBuffer

      private char[] sourceBuffer

    • sourceTop

      private int sourceTop

    • printSource

      private static final boolean printSource
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  • Constructor Details

    • Decompiler

      public Decompiler()

  • Method Details

    • getEncodedSource

      String getEncodedSource()

    • getCurrentOffset

      int getCurrentOffset()

    • markFunctionStart

      int markFunctionStart(int functionType)

    • markFunctionEnd

      int markFunctionEnd(int functionStart)

    • addToken

      void addToken(int token)

    • addEOL

      void addEOL(int token)

    • addName

      void addName(String str)

    • addString

      void addString(String str)

    • addTemplateLiteral

      void addTemplateLiteral(String str)

    • addRegexp

      void addRegexp(String regexp, String flags)

    • addNumber

      void addNumber(double n)

    • addBigInt

      void addBigInt(BigInteger n)

    • appendString

      private void appendString(String str)

    • append

      private void append(char c)

    • increaseSourceCapacity

      private void increaseSourceCapacity(int minimalCapacity)

    • sourceToString

      private String sourceToString(int offset)

    • 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

    • getNext

      private static int getNext(String source, int length, int i)

    • getSourceStringEnd

      private static int getSourceStringEnd(String source, int offset)

    • printSourceString

      private static int printSourceString(String source, int offset, boolean asQuotedString, StringBuilder sb)

    • printSourceNumber

      private static int printSourceNumber(String source, int offset, StringBuilder sb)

    • printSourceBigInt

      private static int printSourceBigInt(String source, int offset, StringBuilder sb)
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