/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "License"); you may not use this file except in
 * compliance with the License.  You may obtain a copy of the License at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is Mozilla Communicator client code.
 *
 * The Initial Developer of the Original Code is Netscape Communications
 * Corporation.  Portions created by Netscape are Copyright (C) 1998
 * Netscape Communications Corporation.  All Rights Reserved.
 */
#ifndef nsTextFragment_h___
#define nsTextFragment_h___

#include "nslayout.h"
class nsString;

// XXX should this normalize the code to keep a \u0000 at the end?

// XXX nsTextFragmentPool?

/**
 * A fragment of text. If mIs2b is 1 then the m2b pointer is valid
 * otherwise the m1b pointer is valid. If m1b is used then each byte
 * of data represents a single ucs2 character with the high byte being
 * zero.
 *
 * This class does not have a virtual destructor therefore it is not
 * meant to be subclassed.
 */
class NS_LAYOUT nsTextFragment {
public:
  /**
   * Default constructor. Initialize the fragment to be empty.
   */
  nsTextFragment() {
    m1b = nsnull;
    mInHeap = 0;
    mIs2b = 0;
    mLength = 0;
  }

  ~nsTextFragment();

  /**
   * Initialize the contents of this fragment to be a copy of
   * the argument fragment.
   */
  nsTextFragment(const nsTextFragment& aOther);

  /**
   * Initialize the contents of this fragment to be a copy of
   * the argument 7bit ascii string.
   */
  nsTextFragment(const char* aString);

  /**
   * Initialize the contents of this fragment to be a copy of
   * the argument ucs2 string.
   */
  nsTextFragment(const PRUnichar* aString);

  /**
   * Initialize the contents of this fragment to be a copy of
   * the argument string.
   */
  nsTextFragment(const nsString& aString);

  /**
   * Change the contents of this fragment to be a copy of the
   * the argument fragment.
   */
  nsTextFragment& operator=(const nsTextFragment& aOther);

  /**
   * Change the contents of this fragment to be a copy of the
   * the argument 7bit ascii string.
   */
  nsTextFragment& operator=(const char* aString);

  /**
   * Change the contents of this fragment to be a copy of the
   * the argument ucs2 string.
   */
  nsTextFragment& operator=(const PRUnichar* aString);

  /**
   * Change the contents of this fragment to be a copy of the
   * the argument string.
   */
  nsTextFragment& operator=(const nsString& aString);

  /**
   * Return PR_TRUE if this fragment is represented by PRUnichar data
   */
  PRBool Is2b() const {
    return mIs2b;
  }

  /**
   * Get a pointer to constant PRUnichar data.
   */
  const PRUnichar* Get2b() const {
    NS_ASSERTION(Is2b(), "not 2b text"); 
    return m2b;
  }

  /**
   * Get a pointer to constant char data.
   */
  const char* Get1b() const {
    NS_ASSERTION(!Is2b(), "not 1b text"); 
    return (const char*) m1b;
  }

  /**
   * Get the length of the fragment. The length is the number of logical
   * characters, not the number of bytes to store the characters.
   */
  PRInt32 GetLength() const {
    return PRInt32(mLength);
  }

  /**
   * Mutable version of Get2b. Only works for a non-const object.
   * Returns a pointer to the PRUnichar data.
   */
  PRUnichar* Get2b() {
    NS_ASSERTION(Is2b(), "not 2b text"); 
    return m2b;
  }

  /**
   * Mutable version of Get1b. Only works for a non-const object.
   * Returns a pointer to the char data.
   */
  char* Get1b() {
    NS_ASSERTION(!Is2b(), "not 1b text"); 
    return (char*) m1b;
  }

  /**
   * Change the contents of this fragment to be the given buffer and
   * length. The memory becomes owned by the fragment. In addition,
   * the memory for aBuffer must have been allocated using the "new[]"
   * because it will be released with "delete []".
   */
  void SetTo(PRUnichar* aBuffer, PRInt32 aLength, PRBool aRelease);

  /**
   * Change the contents of this fragment to be a copy of the given
   * buffer. Like operator= except a length is specified instead of
   * assuming 0 termination.
   */
  void SetTo(const PRUnichar* aBuffer, PRInt32 aLength);

  /**
   * Change the contents of this fragment to be a copy of the given
   * buffer. Like operator= except a length is specified instead of
   * assuming 0 termination.
   */
  void SetTo(const char* aBuffer, PRInt32 aLength);

  /**
   * Append the contents of this string fragment to aString
   */
  void AppendTo(nsString& aString) const;

  /**
   * Make a copy of the fragments contents starting at offset for
   * count characters. The offset and count will be adjusted to
   * lie within the fragments data. The fragments data is converted if
   * necessary.
   */
  void CopyTo(PRUnichar* aDest, PRInt32 aOffset, PRInt32 aCount);

  /**
   * Make a copy of the fragments contents starting at offset for
   * count characters. The offset and count will be adjusted to
   * lie within the fragments data. The fragments data is converted if
   * necessary.
   */
  void CopyTo(char* aDest, PRInt32 aOffset, PRInt32 aCount);

  /**
   * Return the character in the text-fragment at the given
   * index. This always returns a PRUnichar.
   */
  PRUnichar CharAt(PRInt32 aIndex) const {
    NS_ASSERTION(PRUint32(aIndex) < mLength, "bad index");
    return mIs2b ? m2b[aIndex] : PRUnichar(m1b[aIndex]);
  }

protected:
  union {
    PRUnichar* m2b;
    unsigned char* m1b;
  };
  PRUint32 mInHeap : 1;
  PRUint32 mIs2b : 1;
  PRUint32 mLength : 30;

  void ReleaseText();
};

#endif /* nsTextFragment_h___ */