/// <summary>
 /// Initializes a new instance of the <see cref="LexSpan"/> class with parameters specifying the start and end location and the <see cref="ScanBuff"/>
 /// that represents the currently active file.
 /// </summary>
 /// <param name="sl">The line number where the token starts.</param>
 /// <param name="sc">The column number of the line where the token starts.</param>
 /// <param name="el">The line number where the token ends.</param>
 /// <param name="ec">The column number of the line where the token ends.</param>
 /// <param name="sp">The index of the active file where the token starts.</param>
 /// <param name="ep">The index of the active file where the token ends.</param>
 /// <param name="bf">The <see cref="ScanBuff"/> that represents the active file.</param>
 public LexSpan(int sl, int sc, int el, int ec, int sp, int ep, ScanBuff bf)
 {
     Contract.Requires (sl >= 0);
     Contract.Requires (sc >= 0);
     Contract.Requires (el >= 0);
     Contract.Requires (ec >= 0);
     Contract.Requires (sp >= 0);
     Contract.Requires (ep >= 0);
     Contract.Requires (bf != null);
     startLine = sl;
     startColumn = sc;
     endLine = el;
     endColumn = ec;
     startIndex = sp;
     endIndex = ep;
     buffer = bf;
 }

 public void SetSource(System.IO.Stream source)
 {
     this.buffer = new BuildBuffer(source);
     code = buffer.Read();
 }

        void RestoreBuffCtx(BufferContext value)
		{
			this.buffer = value.buffSv;
			this.code = value.chrSv;
			this.cCol = value.cColSv;
			this.lNum = value.lNumSv;
        }