Package org.htmlunit.corejs.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

      Fields 
      Modifier and Type Field Description
      static int CASE_GAP_PROP
      Decompilation property to specify identation offset for case labels.
      private static int FUNCTION_END  
      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.
      private static boolean printSource  
      private char[] sourceBuffer  
      private int sourceTop  
      static int TO_SOURCE_FLAG
      Flag to indicate that the decompilation generates toSource result.

    • Constructor Summary

      Constructors 
      Constructor Description
      Decompiler()  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      (package private) void addBigInt​(java.math.BigInteger n)  
      (package private) void addEOL​(int token)  
      (package private) void addName​(java.lang.String str)  
      (package private) void addNumber​(double n)  
      (package private) void addRegexp​(java.lang.String regexp, java.lang.String flags)  
      (package private) void addString​(java.lang.String str)  
      (package private) void addTemplateLiteral​(java.lang.String str)  
      (package private) void addToken​(int token)  
      private void append​(char c)  
      private void appendString​(java.lang.String str)  
      static java.lang.String decompile​(java.lang.String source, int flags, UintMap properties)
      Decompile the source information associated with this js function/script back into a string.
      (package private) int getCurrentOffset()  
      (package private) java.lang.String getEncodedSource()  
      private static int getNext​(java.lang.String source, int length, int i)  
      private static int getSourceStringEnd​(java.lang.String source, int offset)  
      private void increaseSourceCapacity​(int minimalCapacity)  
      (package private) int markFunctionEnd​(int functionStart)  
      (package private) int markFunctionStart​(int functionType)
      Deprecated.
      use markFunctionStart(int, boolean) instead
      (package private) int markFunctionStart​(int functionType, boolean isGenerator)  
      private static int printSourceBigInt​(java.lang.String source, int offset, java.lang.StringBuilder sb)  
      private static int printSourceNumber​(java.lang.String source, int offset, java.lang.StringBuilder sb)  
      private static int printSourceString​(java.lang.String source, int offset, boolean asQuotedString, java.lang.StringBuilder sb)  
      private java.lang.String sourceToString​(int offset)  

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • 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

      • sourceBuffer

        private char[] sourceBuffer

      • sourceTop

        private int sourceTop

    • Constructor Detail

      • Decompiler

        public Decompiler()

    • Method Detail

      • getEncodedSource

        java.lang.String getEncodedSource()

      • getCurrentOffset

        int getCurrentOffset()

      • markFunctionStart

        int markFunctionStart​(int functionType,
                      boolean isGenerator)

      • markFunctionEnd

        int markFunctionEnd​(int functionStart)

      • addToken

        void addToken​(int token)

      • addEOL

        void addEOL​(int token)

      • addName

        void addName​(java.lang.String str)

      • addString

        void addString​(java.lang.String str)

      • addTemplateLiteral

        void addTemplateLiteral​(java.lang.String str)

      • addRegexp

        void addRegexp​(java.lang.String regexp,
               java.lang.String flags)

      • addNumber

        void addNumber​(double n)

      • addBigInt

        void addBigInt​(java.math.BigInteger n)

      • appendString

        private void appendString​(java.lang.String str)

      • append

        private void append​(char c)

      • increaseSourceCapacity

        private void increaseSourceCapacity​(int minimalCapacity)

      • sourceToString

        private java.lang.String sourceToString​(int offset)

      • decompile

        public static java.lang.String decompile​(java.lang.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​(java.lang.String source,
                           int length,
                           int i)

      • getSourceStringEnd

        private static int getSourceStringEnd​(java.lang.String source,
                                      int offset)

      • printSourceString

        private static int printSourceString​(java.lang.String source,
                                     int offset,
                                     boolean asQuotedString,
                                     java.lang.StringBuilder sb)

      • printSourceNumber

        private static int printSourceNumber​(java.lang.String source,
                                     int offset,
                                     java.lang.StringBuilder sb)