RE: [Ikvm-developers] (no subject)

[Jonathan P. <jp...@ny...>]

Jeroen,

>the calling code expects an interface CharSequence. I can't just
>substitute a string for that because the same code might also want work
>with other classes that implement CharSequence.

I finally understand now, thanks for explaining it so well.
 
>BTW, it would be possible for me to implement String.subSequence, by
>returning an instance of my own helper class that implements
>CharSequence, but since this is only a partial (and probably useless)
>solution, I chose not to do that.

Here's some code that I wrote that you may want to use seems to work for me
that implements CharSequence as an interface. It works as you suggest,
returning a concrete implementation of the CharSequence interface.

-Jonathan

In StringHelper.cs:

public static object subSequence(string s, int offset, int count)
	{
		// throw new NotImplementedException();
		return (new StringWrapper (s, offset, count));
	}

New File: CharSequence.cs added to IK.VM.NET

using System;

interface CharSequence 

{

	/**
	 * Returns the length of this character sequence.  The length is the
number
	 * of 16-bit Unicode characters in the sequence. </p>
	 *
	 * @return  the number of characters in this sequence
	 */
	int length();

    /**
     * Returns the character at the specified index.  An index ranges from
zero
     * to <tt>length() - 1</tt>.  The first character of the sequence is at
     * index zero, the next at index one, and so on, as for array
     * indexing. </p>
     *
     * @param   index   the index of the character to be returned
     *
     * @return  the specified character
     *
     * @throws  IndexOutOfBoundsException
     *          if the <tt>index</tt> argument is negative or not less than
     *          <tt>length()</tt>
     */
	char charAt(int index);

    /**
     * Returns a new character sequence that is a subsequence of this
sequence.
     * The subsequence starts with the character at the specified index and
     * ends with the character at index <tt>end - 1</tt>.  The length of the
     * returned sequence is <tt>end - start</tt>, so if <tt>start ==
end</tt>
     * then an empty sequence is returned. </p>
     * 
     * @param   start   the start index, inclusive
     * @param   end     the end index, exclusive
     *
     * @return  the specified subsequence
     *
     * @throws  IndexOutOfBoundsException
     *          if <tt>start</tt> or <tt>end</tt> are negative,
     *          if <tt>end</tt> is greater than <tt>length()</tt>,
     *          or if <tt>start</tt> is greater than <tt>end</tt>
     */
    CharSequence subSequence(int start, int end);

    /**
     * Returns a string containing the characters in this sequence in the
same
     * order as this sequence.  The length of the string will be the length
of
     * this sequence. </p>
     *
     * @return  a string consisting of exactly this sequence of characters
     */
    string toString();

}

New File: StringWrapper.cs

using System;

public class StringWrapper : CharSequence

{

	private String		fData = "";
	private int				fOffset = 0;
	private int				fLength = 0;

	// length of sequence
	public int length ()
	
	{
		return fLength;
	}

	// character at a given index
	public char charAt (int index)
	
	{
		if (index < 0 || index >= fLength)
		{
			throw new System.Exception
("IndexOutOfBoundsException invalid index");
		}
		return (fData [index + fOffset]);
	}
		   
	// subsequence from start (inclusive) to end (exclusive)
	CharSequence CharSequence.subSequence (int start, int end)

	{
		return (this.subSequence (start, end));
	}

	public StringWrapper subSequence (int start, int end)
	
	{
		if (start < 0 || end < 0 || end > fLength ||  start > end) 
		{
			throw new System.Exception ("
IndexOutOfBoundsException invalid start/end");
		}
		return new StringWrapper (fData, start + fOffset, end -
start);
	}

	// convert to string
	public String toString ()
	
	{
		return (this.fData);
	}

	// construct an StringWrapper from a portion of a String
	public StringWrapper (String theString, int itsOffset, int
itsLength) 
	
	{
		if (theString == null) 
		{
			throw new System.Exception ("NullPointerException
null String");
		}
		if ( (fOffset < 0) || (fLength < 0) || (fOffset >
(theString.Length - fLength)))
		{
			throw new System.Exception
("IllegalArgumentException bad Offset / Length");
		}
		this.fData = theString;
		this.fOffset = itsOffset;
		this.fLength = itsLength;
	}

	// construct a StringWrapper from a char array
	public StringWrapper (String itsString)
		: this (itsString, 0, itsString.Length)
	
	{
	}
}