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/**
 * MODULE NOTES:
 * @update  gess 4/1/98
 * 
 * The scanner is a low-level service class that knows
 * how to consume characters out of an (internal) stream.
 * This class also offers a series of utility methods
 * that most tokenizers want, such as readUntil(), 
 * readWhile() and SkipWhitespace().
 */


#ifndef SCANNER
#define SCANNER

#include "nsString.h"
#include "nsIParser.h"
#include "prtypes.h"
#include "nsIUnicodeDecoder.h"
#include "nsFileStream.h"
#include "nsSlidingString.h"

class nsScannerString : public nsSlidingString {
  public: 
    nsScannerString(PRUnichar* aStorageStart, 
                    PRUnichar* aDataEnd, 
                    PRUnichar* aStorageEnd);

    virtual void UngetReadable(const nsAReadableString& aReadable, const nsReadingIterator<PRUnichar>& aCurrentPosition) { InsertReadable(aReadable,aCurrentPosition); }
    virtual void ReplaceCharacter(nsReadingIterator<PRUnichar>& aPosition,
                                  PRUnichar aChar);
};

class nsReadEndCondition {
public:
  const PRUnichar *mChars;
  PRUnichar mFilter;
  explicit nsReadEndCondition(const PRUnichar* aTerminateChars);
private:
  nsReadEndCondition(const nsReadEndCondition& aOther); // No copying
  void operator=(const nsReadEndCondition& aOther); // No assigning
};

class nsScanner {
  public:

      /**
       *  Use this constructor if you want i/o to be based on 
       *  a single string you hand in during construction.
       *  This short cut was added for Javascript.
       *
       *  @update  ftang 3/02/99
       *  @param   aCharset charset
       *  @param   aCharsetSource - where the charset info came from 
       *  @param   aMode represents the parser mode (nav, other)
       *  @return  
       */
      nsScanner(const nsAString& anHTMLString, const nsString& aCharset, PRInt32 aSource);

      /**
       *  Use this constructor if you want i/o to be based on 
       *  a file (therefore a stream) or just data you provide via Append().
       *
       *  @update  ftang 3/02/99
       *  @param   aCharset charset
       *  @param   aCharsetSource - where the charset info came from 
       *  @param   aMode represents the parser mode (nav, other)
       *  @return  
       */
      nsScanner(nsString& aFilename,PRBool aCreateStream, const nsString& aCharset, PRInt32 aSource);

      /**
       *  Use this constructor if you want i/o to be stream based.
       *
       *  @update  ftang 3/02/99
       *  @param   aCharset charset
       *  @param   aCharsetSource - where the charset info came from 
       *  @param   aMode represents the parser mode (nav, other)
       *  @return  
       */
      nsScanner(const nsAString& aFilename, nsInputStream& aStream, const nsString& aCharset, PRInt32 aSource);


      ~nsScanner();

      /**
       *  retrieve next char from internal input stream
       *  
       *  @update  gess 3/25/98
       *  @param   ch is the char to accept new value
       *  @return  error code reflecting read status
       */
      nsresult GetChar(PRUnichar& ch);

      /**
       *  peek ahead to consume next char from scanner's internal
       *  input buffer
       *  
       *  @update  gess 3/25/98
       *  @param   ch is the char to accept new value
       *  @return  error code reflecting read status
       */
      nsresult Peek(PRUnichar& ch, PRUint32 aOffset=0);

      nsresult Peek(nsAWritableString& aStr, PRInt32 aNumChars);

      /**
       *  Skip over chars as long as they're in aSkipSet
       *  
       *  @update  gess 3/25/98
       *  @param   set of chars to be skipped
       *  @return  error code
       */
      nsresult SkipOver(nsString& SkipChars);

      /**
       *  Skip over chars as long as they equal given char
       *  
       *  @update  gess 3/25/98
       *  @param   char to be skipped
       *  @return  error code
       */
      nsresult SkipOver(PRUnichar aSkipChar);

      /**
       *  Skip over chars until they're in aValidSet
       *  
       *  @update  gess 3/25/98
       *  @param   aValid set contains chars you're looking for
       *  @return  error code
       */
      nsresult SkipTo(nsString& aValidSet);

      /**
       *  Skip over chars as long as they're in aSequence
       *  
       *  @update  gess 3/25/98
       *  @param   contains sequence to be skipped
       *  @return  error code
       */
      nsresult SkipPast(nsString& aSequence);

      /**
       *  Skip whitespace on scanner input stream
       *  
       *  @update  gess 3/25/98
       *  @return  error status
       */
      nsresult SkipWhitespace(void);

      /**
       *  Determine if the scanner has reached EOF.
       *  This method can also cause the buffer to be filled
       *  if it happens to be empty
       *  
       *  @update  gess 3/25/98
       *  @return  PR_TRUE upon eof condition
       */
      nsresult Eof(void);

      /**
       *  Consume characters until you find the terminal char
       *  
       *  @update  gess 3/25/98
       *  @param   aString receives new data from stream
       *  @param   addTerminal tells us whether to append terminal to aString
       *  @return  error code
       */
      nsresult GetIdentifier(nsString& aString,PRBool allowPunct=PR_FALSE);
      nsresult ReadIdentifier(nsString& aString,PRBool allowPunct=PR_FALSE);
      nsresult ReadIdentifier(nsReadingIterator<PRUnichar>& aStart,
                              nsReadingIterator<PRUnichar>& aEnd,
                              PRBool allowPunct=PR_FALSE);
      nsresult ReadNumber(nsString& aString,PRInt32 aBase);
      nsresult ReadNumber(nsReadingIterator<PRUnichar>& aStart, 
                          nsReadingIterator<PRUnichar>& aEnd,
                          PRInt32 aBase);
      nsresult ReadWhitespace(nsString& aString);
      nsresult ReadWhitespace(nsReadingIterator<PRUnichar>& aStart, 
                              nsReadingIterator<PRUnichar>& aEnd);

      /**
       *  Consume characters until you find the terminal char
       *  
       *  @update  gess 3/25/98
       *  @param   aString receives new data from stream
       *  @param   aTerminal contains terminating char
       *  @param   addTerminal tells us whether to append terminal to aString
       *  @return  error code
       */
      nsresult ReadUntil(nsAWritableString& aString,
                         PRUnichar aTerminal,
                         PRBool addTerminal);

      /**
       *  Consume characters until you find one contained in given
       *  terminal set.
       *  
       *  @update  gess 3/25/98
       *  @param   aString receives new data from stream
       *  @param   aTermSet contains set of terminating chars
       *  @param   addTerminal tells us whether to append terminal to aString
       *  @return  error code
       */
      nsresult ReadUntil(nsAWritableString& aString,
                         const nsReadEndCondition& aEndCondition, 
                         PRBool addTerminal);

      nsresult ReadUntil(nsReadingIterator<PRUnichar>& aStart,
                         nsReadingIterator<PRUnichar>& aEnd,
                         const nsReadEndCondition& aEndCondition, 
                         PRBool addTerminal);


      /**
       *  Consume characters while they're members of anInputSet
       *  
       *  @update  gess 3/25/98
       *  @param   aString receives new data from stream
       *  @param   anInputSet contains valid chars
       *  @param   addTerminal tells us whether to append terminal to aString
       *  @return  error code
       */
      nsresult ReadWhile(nsString& aString,nsString& anInputSet,PRBool addTerminal);

      /**
       *  Records current offset position in input stream. This allows us
       *  to back up to this point if the need should arise, such as when
       *  tokenization gets interrupted.
       *  
       *  @update  gess 5/12/98
       *  @param   
       *  @return  
       */
      void Mark(void);

      /**
       *  Resets current offset position of input stream to marked position. 
       *  This allows us to back up to this point if the need should arise, 
       *  such as when tokenization gets interrupted.
       *  NOTE: IT IS REALLY BAD FORM TO CALL RELEASE WITHOUT CALLING MARK FIRST!
       *  
       *  @update  gess 5/12/98
       *  @param   
       *  @return  
       */
      void RewindToMark(void);


      /**
       *  
       *  
       *  @update  harishd 01/12/99
       *  @param   
       *  @return  
       */
      PRBool UngetReadable(const nsAReadableString& aBuffer);

      /**
       *  
       *  
       *  @update  gess 5/13/98
       *  @param   
       *  @return  
       */
      nsresult Append(const nsAReadableString& aBuffer);

      /**
       *  
       *  
       *  @update  gess 5/21/98
       *  @param   
       *  @return  
       */
      nsresult Append(const char* aBuffer, PRUint32 aLen);

      /**
       *  Call this to copy bytes out of the scanner that have not yet been consumed
       *  by the tokenization process.
       *  
       *  @update  gess 5/12/98
       *  @param   aCopyBuffer is where the scanner buffer will be copied to
       *  @return  nada
       */
      void CopyUnusedData(nsString& aCopyBuffer);

      /**
       *  Retrieve the name of the file that the scanner is reading from.
       *  In some cases, it's just a given name, because the scanner isn't
       *  really reading from a file.
       *  
       *  @update  gess 5/12/98
       *  @return  
       */
      nsString& GetFilename(void);

      static void SelfTest();

      /**
       *  Use this setter to change the scanner's unicode decoder
       *
       *  @update  ftang 3/02/99
       *  @param   aCharset a normalized (alias resolved) charset name
       *  @param   aCharsetSource- where the charset info came from
       *  @return  
       */
      nsresult SetDocumentCharset(const nsAString& aCharset, PRInt32 aSource);

      void BindSubstring(nsSlidingSubstring& aSubstring, const nsReadingIterator<PRUnichar>& aStart, const nsReadingIterator<PRUnichar>& aEnd);
      void CurrentPosition(nsReadingIterator<PRUnichar>& aPosition);
      void EndReading(nsReadingIterator<PRUnichar>& aPosition);
      void SetPosition(nsReadingIterator<PRUnichar>& aPosition,
                       PRBool aTruncate = PR_FALSE,
                       PRBool aReverse = PR_FALSE);
      void ReplaceCharacter(nsReadingIterator<PRUnichar>& aPosition,
                            PRUnichar aChar);

      /**
       * Internal method used to cause the internal buffer to
       * be filled with data. 
       *
       * @update  gess4/3/98
       */
      PRBool    IsIncremental(void) {return mIncremental;}
      void      SetIncremental(PRBool anIncrValue) {mIncremental=anIncrValue;}

      PRInt32   GetNewlinesSkipped(void) { return mNewlinesSkipped; }

  protected:


    enum {eBufferSizeThreshold=0x1000};  //4K

      /**
       * Internal method used to cause the internal buffer to
       * be filled with data. 
       *
       * @update  gess4/3/98
       */
      nsresult FillBuffer(void);

      void AppendToBuffer(PRUnichar* aStorageStart, 
                          PRUnichar* aDataEnd, 
                          PRUnichar* aStorageEnd);

      nsInputStream*  mInputStream;
      nsScannerString*             mSlidingBuffer;
      nsReadingIterator<PRUnichar> mCurrentPosition; // The position we will next read from in the scanner buffer
      nsReadingIterator<PRUnichar> mMarkPosition;    // The position last marked (we may rewind to here)
      nsReadingIterator<PRUnichar> mEndPosition;     // The current end of the scanner buffer
      nsString        mFilename;
      PRUint32        mCountRemaining; // The number of bytes still to be read
                                       // from the scanner buffer
      PRUint32        mTotalRead;
      PRBool          mOwnsStream;
      PRBool          mIncremental;
      PRInt32         mCharsetSource;
      nsString        mCharset;
      nsIUnicodeDecoder *mUnicodeDecoder;
      PRInt32         mNewlinesSkipped;
};

#endif


