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    1   /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 4.0 */
    2   package net.sourceforge.pmd.ast;
    3
    4   /***
    5    * This interface describes a character stream that maintains line and
    6    * column number positions of the characters.  It also has the capability
    7    * to backup the stream to some extent.  An implementation of this
    8    * interface is used in the TokenManager implementation generated by
    9    * JavaCCParser.
    10   * <p/>
    11   * All the methods except backup can be implemented in any fashion. backup
    12   * needs to be implemented correctly for the correct operation of the lexer.
    13   * Rest of the methods are all used to get information like line number,
    14   * column number and the String that constitutes a token and are not used
    15   * by the lexer. Hence their implementation won't affect the generated lexer's
    16   * operation.
    17   */
    18
    19  public interface CharStream {
    20
    21      /***
    22       * Returns the next character from the selected input.  The method
    23       * of selecting the input is the responsibility of the class
    24       * implementing this interface.  Can throw any java.io.IOException.
    25       */
    26      char readChar() throws java.io.IOException;
    27
    28      /***
    29       * Returns the column position of the character last read.
    30       *
    31       * @see #getEndColumn
    32       * @deprecated
    33       */
    34      int getColumn();
    35
    36      /***
    37       * Returns the line number of the character last read.
    38       *
    39       * @see #getEndLine
    40       * @deprecated
    41       */
    42      int getLine();
    43
    44      /***
    45       * Returns the column number of the last character for current token (being
    46       * matched after the last call to BeginTOken).
    47       */
    48      int getEndColumn();
    49
    50      /***
    51       * Returns the line number of the last character for current token (being
    52       * matched after the last call to BeginTOken).
    53       */
    54      int getEndLine();
    55
    56      /***
    57       * Returns the column number of the first character for current token (being
    58       * matched after the last call to BeginTOken).
    59       */
    60      int getBeginColumn();
    61
    62      /***
    63       * Returns the line number of the first character for current token (being
    64       * matched after the last call to BeginTOken).
    65       */
    66      int getBeginLine();
    67
    68      /***
    69       * Backs up the input stream by amount steps. Lexer calls this method if it
    70       * had already read some characters, but could not use them to match a
    71       * (longer) token. So, they will be used again as the prefix of the next
    72       * token and it is the implemetation's responsibility to do this right.
    73       */
    74      void backup(int amount);
    75
    76      /***
    77       * Returns the next character that marks the beginning of the next token.
    78       * All characters must remain in the buffer between two successive calls
    79       * to this method to implement backup correctly.
    80       */
    81      char BeginToken() throws java.io.IOException;
    82
    83      /***
    84       * Returns a string made up of characters from the marked token beginning
    85       * to the current buffer position. Implementations have the choice of returning
    86       * anything that they want to. For example, for efficiency, one might decide
    87       * to just return null, which is a valid implementation.
    88       */
    89      String GetImage();
    90
    91      /***
    92       * Returns an array of characters that make up the suffix of length 'len' for
    93       * the currently matched token. This is used to build up the matched string
    94       * for use in actions in the case of MORE. A simple and inefficient
    95       * implementation of this is as follows :
    96       * <p/>
    97       * {
    98       * String t = GetImage();
    99       * return t.substring(t.length() - len, t.length()).toCharArray();
    100      * }
    101      */
    102     char[] GetSuffix(int len);
    103
    104     /***
    105      * The lexer calls this function to indicate that it is done with the stream
    106      * and hence implementations can free any resources held by this class.
    107      * Again, the body of this function can be just empty and it will not
    108      * affect the lexer's operation.
    109      */
    110     void Done();
    111
    112 }