Input.cs

namespace Lex
{
    /*
     * Class: CInput
     * Description: 
     */
    using System;
    using System.IO;

    public class Input
    {
        /*
         * Member Variables
         */
        private StreamReader instream; /* Lex specification file. */

        public bool eof_reached; /* Whether EOF has been encountered. */
        public bool pushback_line;

        public char[] line; /* Line buffer. */
        public int line_read; /* Number of bytes read into line buffer. */
        public int line_index; /* Current index into line buffer. */
        public int line_number; /* Current line number. */

        /***************************************************************
          Constants
          **************************************************************/
        private const int BUFFER_SIZE = 1024;
        const bool EOF = true;
        const bool NOT_EOF = false;

        /*
         * Function: Input
         */
        public Input(StreamReader ihandle)
        {
#if DEBUG
            Utility.assert(ihandle != null);
#endif

            /* Initialize input stream. */
            instream = ihandle;

            line = new char[BUFFER_SIZE];
            line_read = 0;
            line_index = 0;

            /* Initialize state variables. */
            eof_reached = false;
            line_number = 0;
            pushback_line = false;
        }

        /*
         * Function: GetLine
         * Description: Returns true on EOF, false otherwise.
         * Guarantees not to return a blank line, or a line
         * of zero length.
         */
        public bool GetLine()
        {
            int elem;

            /* Has EOF already been reached? */
            if (eof_reached)
                return true;

            /* pushback current line? */
            if (pushback_line)
            {
                pushback_line = false;

                /* check for empty line. */
                for (elem = 0; elem < line_read; ++elem)
                    if (!Utility.IsSpace(line[elem]))
                        break;

                /* nonempty? */
                if (elem < line_read)
                {
                    line_index = 0;
                    return false;
                }
            }

            while (true)
            {
                String lineStr = instream.ReadLine();
                if (lineStr == null)
                {
                    eof_reached = true;
                    line_index = 0;
                    return true;
                }
                line = (lineStr + "\n").ToCharArray();
                line_read = line.Length;
                line_number++;

                /* check for empty lines and discard them */
                elem = 0;
                while (Utility.IsSpace(line[elem]))
                {
                    elem++;
                    if (elem == line_read)
                        break;
                }
                if (elem < line_read)
                    break;
            }

            line_index = 0;
            return false;
        }
    }
}