StackWriter.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.calcite.util;
import java.io.FilterWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.ArrayDeque;
import java.util.Deque;
/**
* A helper class for generating formatted text. StackWriter keeps track of
* nested formatting state like indentation level and quote escaping. Typically,
* it is inserted between a PrintWriter and the real Writer; directives are
* passed straight through the PrintWriter via the write method, as in the
* following example:
*
* <blockquote><pre><code>
* StringWriter sw = new StringWriter();
* StackWriter stackw = new StackWriter(sw, StackWriter.INDENT_SPACE4);
* PrintWriter pw = new PrintWriter(stackw);
* pw.write(StackWriter.INDENT);
* pw.print("execute remote(link_name,");
* pw.write(StackWriter.OPEN_SQL_STRING_LITERAL);
* pw.println();
* pw.write(StackWriter.INDENT);
* pw.println("select * from t where c > 'alabama'");
* pw.write(StackWriter.OUTDENT);
* pw.write(StackWriter.CLOSE_SQL_STRING_LITERAL);
* pw.println(");");
* pw.write(StackWriter.OUTDENT);
* pw.close();
* System.out.println(sw.toString());
* </code></pre></blockquote>
*
* <p>which produces the following output:
*
* <blockquote><pre><code>
* execute remote(link_name,'
* select * from t where c > ''alabama''
* ');
* </code></pre></blockquote>
*/
public class StackWriter extends FilterWriter {
//~ Static fields/initializers ---------------------------------------------
/**
* Directive for increasing the indentation level.
*/
public static final int INDENT = 0xF0000001;
/**
* Directive for decreasing the indentation level.
*/
public static final int OUTDENT = 0xF0000002;
/**
* Directive for beginning an SQL string literal.
*/
public static final int OPEN_SQL_STRING_LITERAL = 0xF0000003;
/**
* Directive for ending an SQL string literal.
*/
public static final int CLOSE_SQL_STRING_LITERAL = 0xF0000004;
/**
* Directive for beginning an SQL identifier.
*/
public static final int OPEN_SQL_IDENTIFIER = 0xF0000005;
/**
* Directive for ending an SQL identifier.
*/
public static final int CLOSE_SQL_IDENTIFIER = 0xF0000006;
/**
* Tab indentation.
*/
public static final String INDENT_TAB = "\t";
/**
* Four-space indentation.
*/
public static final String INDENT_SPACE4 = " ";
private static final Character SINGLE_QUOTE = '\'';
private static final Character DOUBLE_QUOTE = '"';
//~ Instance fields --------------------------------------------------------
private int indentationDepth;
private final String indentation;
private boolean needIndent;
private final Deque<Character> quoteStack = new ArrayDeque<>();
//~ Constructors -----------------------------------------------------------
/**
* Creates a new StackWriter on top of an existing Writer, with the
* specified string to be used for each level of indentation.
*
* @param writer underlying writer
* @param indentation indentation unit such as {@link #INDENT_TAB} or
* {@link #INDENT_SPACE4}
*/
public StackWriter(Writer writer, String indentation) {
super(writer);
this.indentation = indentation;
}
//~ Methods ----------------------------------------------------------------
private void indentIfNeeded() throws IOException {
if (needIndent) {
for (int i = 0; i < indentationDepth; i++) {
out.write(indentation);
}
needIndent = false;
}
}
private void writeQuote(Character quoteChar) throws IOException {
indentIfNeeded();
int n = 1;
for (Character quote : quoteStack) {
if (quote.equals(quoteChar)) {
n *= 2;
}
}
for (int i = 0; i < n; i++) {
out.write(quoteChar);
}
}
private void pushQuote(Character quoteChar) throws IOException {
writeQuote(quoteChar);
quoteStack.push(quoteChar);
}
private void popQuote(Character quoteChar) throws IOException {
final Character pop = quoteStack.pop();
assert pop.equals(quoteChar);
writeQuote(quoteChar);
}
// implement Writer
@Override public void write(int c) throws IOException {
switch (c) {
case INDENT:
indentationDepth++;
break;
case OUTDENT:
indentationDepth--;
break;
case OPEN_SQL_STRING_LITERAL:
pushQuote(SINGLE_QUOTE);
break;
case CLOSE_SQL_STRING_LITERAL:
popQuote(SINGLE_QUOTE);
break;
case OPEN_SQL_IDENTIFIER:
pushQuote(DOUBLE_QUOTE);
break;
case CLOSE_SQL_IDENTIFIER:
popQuote(DOUBLE_QUOTE);
break;
case '\n':
out.write(c);
needIndent = true;
break;
case '\r':
// NOTE jvs 3-Jan-2006: suppress indentIfNeeded() in this case
// so that we don't get spurious diffs on Windows vs. Linux
out.write(c);
break;
case '\'':
writeQuote(SINGLE_QUOTE);
break;
case '"':
writeQuote(DOUBLE_QUOTE);
break;
default:
indentIfNeeded();
out.write(c);
break;
}
}
// implement Writer
@Override public void write(char[] cbuf, int off, int len) throws IOException {
// TODO: something more efficient using searches for
// special characters
for (int i = off; i < (off + len); i++) {
write(cbuf[i]);
}
}
// implement Writer
@Override public void write(String str, int off, int len) throws IOException {
// TODO: something more efficient using searches for
// special characters
for (int i = off; i < (off + len); i++) {
write(str.charAt(i));
}
}
/**
* Writes an SQL string literal.
*
* @param pw PrintWriter on which to write
* @param s text of literal
*/
public static void printSqlStringLiteral(PrintWriter pw, String s) {
pw.write(OPEN_SQL_STRING_LITERAL);
pw.print(s);
pw.write(CLOSE_SQL_STRING_LITERAL);
}
/**
* Writes an SQL identifier.
*
* @param pw PrintWriter on which to write
* @param s identifier
*/
public static void printSqlIdentifier(PrintWriter pw, String s) {
pw.write(OPEN_SQL_IDENTIFIER);
pw.print(s);
pw.write(CLOSE_SQL_IDENTIFIER);
}
}