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<!-- Generated by javadoc on Mon Jun 17 10:56:34 EDT 2002 -->
<title>W3C Flute version 1.3 - Java API: Interface
CharStream</title>
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<h2>org.w3c.flute.parser<br />
Interface CharStream</h2>
<dl>
<dt><b>All Known Implementing Classes:</b></dt>
<dd><a href=
"../../../../org/w3c/flute/parser/Generic_CharStream.html">Generic_CharStream</a></dd>
</dl>
<hr />
<dl>
<dt>public interface <b>CharStream</b></dt>
</dl>
<p>This interface describes a character stream that maintains line
and column number positions of the characters. It also has the
capability to backup the stream to some extent. An implementation
of this interface is used in the TokenManager implementation
generated by JavaCCParser. All the methods except backup can be
implemented in any fashion. backup needs to be implemented
correctly for the correct operation of the lexer. Rest of the
methods are all used to get information like line number, column
number and the String that constitutes a token and are not used by
the lexer. Hence their implementation won't affect the generated
lexer's operation.</p>
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<td colspan="2"><b>Method Summary</b></td>
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<td align="right" valign="top" width="1%">
<code> void</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#backup_int_">backup</a></b>(int amount)</code>
<br />
Backs
up the input stream by amount steps.</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> char</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#BeginToken__">BeginToken</a></b>()</code>
<br />
Returns
the next character that marks the beginning of the next token.</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> void</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#Done__">Done</a></b>()</code>
<br />
The
lexer calls this function to indicate that it is done with the
stream and hence implementations can free any resources held by
this class.</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> int</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#getBeginColumn__">
getBeginColumn</a></b>()</code> <br />
Returns
the column number of the first character for current token (being
matched after the last call to BeginTOken).</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> int</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#getBeginLine__">getBeginLine</a></b>()</code>
<br />
Returns
the line number of the first character for current token (being
matched after the last call to BeginTOken).</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> int</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#getEndColumn__">getEndColumn</a></b>()</code>
<br />
Returns
the column number of the last character for current token (being
matched after the last call to BeginTOken).</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> int</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#getEndLine__">getEndLine</a></b>()</code>
<br />
Returns
the line number of the last character for current token (being
matched after the last call to BeginTOken).</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> java.lang.String</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#GetImage__">GetImage</a></b>()</code>
<br />
Returns
a string made up of characters from the marked token beginning to
the current buffer position.</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> char[]</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#GetSuffix_int_">GetSuffix</a></b>(int len)</code>
<br />
Returns
an array of characters that make up the suffix of length 'len' for
the currently matched token.</td>
</tr>
<tr bgcolor="white" class="TableRowColor">
<td align="right" valign="top" width="1%">
<code> char</code></td>
<td><code><b><a href=
"../../../../org/w3c/flute/parser/CharStream.html#readChar__">readChar</a></b>()</code>
<br />
Returns
the next character from the selected input.</td>
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<a id="backup_int_" name="backup_int_"><!-- --></a>
<h3>backup</h3>
<pre>
public void <b>backup</b>(int amount)
</pre>
<dl>
<dd>Backs up the input stream by amount steps. Lexer calls this
method if it had already read some characters, but could not use
them to match a (longer) token. So, they will be used again as the
prefix of the next token and it is the implemetation's
responsibility to do this right.</dd>
</dl>
<hr />
<a id="BeginToken__" name="BeginToken__"><!-- --></a>
<h3>BeginToken</h3>
<pre>
public char <b>BeginToken</b>()
throws java.io.IOException
</pre>
<dl>
<dd>Returns the next character that marks the beginning of the next
token. All characters must remain in the buffer between two
successive calls to this method to implement backup correctly.</dd>
</dl>
<hr />
<a id="Done__" name="Done__"><!-- --></a>
<h3>Done</h3>
<pre>
public void <b>Done</b>()
</pre>
<dl>
<dd>The lexer calls this function to indicate that it is done with
the stream and hence implementations can free any resources held by
this class. Again, the body of this function can be just empty and
it will not affect the lexer's operation.</dd>
</dl>
<hr />
<a id="getBeginColumn__" name="getBeginColumn__"><!-- --></a>
<h3>getBeginColumn</h3>
<pre>
public int <b>getBeginColumn</b>()
</pre>
<dl>
<dd>Returns the column number of the first character for current
token (being matched after the last call to BeginTOken).</dd>
</dl>
<hr />
<a id="getBeginLine__" name="getBeginLine__"><!-- --></a>
<h3>getBeginLine</h3>
<pre>
public int <b>getBeginLine</b>()
</pre>
<dl>
<dd>Returns the line number of the first character for current
token (being matched after the last call to BeginTOken).</dd>
</dl>
<hr />
<a id="getEndColumn__" name="getEndColumn__"><!-- --></a>
<h3>getEndColumn</h3>
<pre>
public int <b>getEndColumn</b>()
</pre>
<dl>
<dd>Returns the column number of the last character for current
token (being matched after the last call to BeginTOken).</dd>
</dl>
<hr />
<a id="getEndLine__" name="getEndLine__"><!-- --></a>
<h3>getEndLine</h3>
<pre>
public int <b>getEndLine</b>()
</pre>
<dl>
<dd>Returns the line number of the last character for current token
(being matched after the last call to BeginTOken).</dd>
</dl>
<hr />
<a id="GetImage__" name="GetImage__"><!-- --></a>
<h3>GetImage</h3>
<pre>
public java.lang.String <b>GetImage</b>()
</pre>
<dl>
<dd>Returns a string made up of characters from the marked token
beginning to the current buffer position. Implementations have the
choice of returning anything that they want to. For example, for
efficiency, one might decide to just return null, which is a valid
implementation.</dd>
</dl>
<hr />
<a id="GetSuffix_int_" name="GetSuffix_int_"><!-- --></a>
<h3>GetSuffix</h3>
<pre>
public char[] <b>GetSuffix</b>(int len)
</pre>
<dl>
<dd>Returns an array of characters that make up the suffix of
length 'len' for the currently matched token. This is used to build
up the matched string for use in actions in the case of MORE. A
simple and inefficient implementation of this is as follows : {
String t = GetImage(); return t.substring(t.length() - len,
t.length()).toCharArray(); }</dd>
</dl>
<hr />
<a id="readChar__" name="readChar__"><!-- --></a>
<h3>readChar</h3>
<pre>
public char <b>readChar</b>()
throws java.io.IOException
</pre>
<dl>
<dd>Returns the next character from the selected input. The method
of selecting the input is the responsibility of the class
implementing this interface. Can throw any
java.io.IOException.</dd>
</dl>
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