freemarker.template.utility.StandardCompress Maven / Gradle / Ivy
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/*
* 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 freemarker.template.utility;
import java.io.IOException;
import java.io.Writer;
import java.util.Map;
import freemarker.template.TemplateBooleanModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateNumberModel;
import freemarker.template.TemplateTransformModel;
/**
* A filter that compresses each sequence of consecutive whitespace
* to a single line break (if the sequence contains a line break) or a
* single space. In addition, leading and trailing whitespace is
* completely removed.
*
* Specify the transform parameter single_line = true
* to always compress to a single space instead of a line break.
*
* The default buffer size can be overridden by specifying a
* buffer_size transform parameter (in bytes).
*
* Note: The compress tag is implemented using this filter
*
* Usage:
* From java:
*
* SimpleHash root = new SimpleHash();
*
* root.put( "standardCompress", new freemarker.template.utility.StandardCompress() );
*
* ...
*
*
* From your FreeMarker template:
*
* <transform standardCompress>
* <p>This paragraph will have
* extraneous
*
* whitespace removed.</p>
* </transform>
*
*
* Output:
*
* <p>This paragraph will have
* extraneous
* whitespace removed.</p>
*
*/
public class StandardCompress implements TemplateTransformModel {
private static final String BUFFER_SIZE_KEY = "buffer_size";
private static final String SINGLE_LINE_KEY = "single_line";
private int defaultBufferSize;
public static final StandardCompress INSTANCE = new StandardCompress();
public StandardCompress() {
this(2048);
}
/**
* @param defaultBufferSize the default amount of characters to buffer
*/
public StandardCompress(int defaultBufferSize) {
this.defaultBufferSize = defaultBufferSize;
}
@Override
public Writer getWriter(final Writer out, Map args)
throws TemplateModelException {
int bufferSize = defaultBufferSize;
boolean singleLine = false;
if (args != null) {
try {
TemplateNumberModel num = (TemplateNumberModel) args.get(BUFFER_SIZE_KEY);
if (num != null)
bufferSize = num.getAsNumber().intValue();
} catch (ClassCastException e) {
throw new TemplateModelException("Expecting numerical argument to " + BUFFER_SIZE_KEY);
}
try {
TemplateBooleanModel flag = (TemplateBooleanModel) args.get(SINGLE_LINE_KEY);
if (flag != null)
singleLine = flag.getAsBoolean();
} catch (ClassCastException e) {
throw new TemplateModelException("Expecting boolean argument to " + SINGLE_LINE_KEY);
}
}
return new StandardCompressWriter(out, bufferSize, singleLine);
}
private static class StandardCompressWriter extends Writer {
private static final int MAX_EOL_LENGTH = 2; // CRLF is two bytes
private static final int AT_BEGINNING = 0;
private static final int SINGLE_LINE = 1;
private static final int INIT = 2;
private static final int SAW_CR = 3;
private static final int LINEBREAK_CR = 4;
private static final int LINEBREAK_CRLF = 5;
private static final int LINEBREAK_LF = 6;
private final Writer out;
private final char[] buf;
private final boolean singleLine;
private int pos = 0;
private boolean inWhitespace = true;
private int lineBreakState = AT_BEGINNING;
public StandardCompressWriter(Writer out, int bufSize, boolean singleLine) {
this.out = out;
this.singleLine = singleLine;
buf = new char[bufSize];
}
@Override
public void write(char[] cbuf, int off, int len) throws IOException {
for (; ; ) {
// Need to reserve space for the EOL potentially left in the state machine
int room = buf.length - pos - MAX_EOL_LENGTH;
if (room >= len) {
writeHelper(cbuf, off, len);
break;
} else if (room <= 0) {
flushInternal();
} else {
writeHelper(cbuf, off, room);
flushInternal();
off += room;
len -= room;
}
}
}
private void writeHelper(char[] cbuf, int off, int len) {
for (int i = off, end = off + len; i < end; i++) {
char c = cbuf[i];
if (Character.isWhitespace(c)) {
inWhitespace = true;
updateLineBreakState(c);
} else if (inWhitespace) {
inWhitespace = false;
writeLineBreakOrSpace();
buf[pos++] = c;
} else {
buf[pos++] = c;
}
}
}
/*
\r\n => CRLF
\r[^\n] => CR
\r$ => CR
[^\r]\n => LF
^\n => LF
*/
private void updateLineBreakState(char c) {
switch (lineBreakState) {
case INIT:
if (c == '\r') {
lineBreakState = SAW_CR;
} else if (c == '\n') {
lineBreakState = LINEBREAK_LF;
}
break;
case SAW_CR:
if (c == '\n') {
lineBreakState = LINEBREAK_CRLF;
} else {
lineBreakState = LINEBREAK_CR;
}
}
}
private void writeLineBreakOrSpace() {
switch (lineBreakState) {
case SAW_CR:
// whitespace ended with CR, fall through
case LINEBREAK_CR:
buf[pos++] = '\r';
break;
case LINEBREAK_CRLF:
buf[pos++] = '\r';
// fall through
case LINEBREAK_LF:
buf[pos++] = '\n';
break;
case AT_BEGINNING:
// ignore leading whitespace
break;
case INIT:
case SINGLE_LINE:
buf[pos++] = ' ';
}
lineBreakState = (singleLine) ? SINGLE_LINE : INIT;
}
private void flushInternal() throws IOException {
out.write(buf, 0, pos);
pos = 0;
}
@Override
public void flush() throws IOException {
flushInternal();
out.flush();
}
@Override
public void close() throws IOException {
flushInternal();
}
}
}