/*
* Copyright 2013 the original author or authors.
*
* Licensed 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.gradle.language.nativeplatform.internal.incremental.sourceparser;
import org.apache.tools.ant.filters.BaseFilterReader;
import java.io.IOException;
import java.io.Reader;
/**
* Replaces c-style comments with a single space, and removes line-continuation characters.
* This code is largely adopted from org.apache.tools.ant.filters.StripJavaComments.
*
* This avoids the synchronisation overhead of PushbackReader and is _not_ threadsafe.
*/
public class PreprocessingReader extends BaseFilterReader {
/**
* The read-ahead characters, used for reading ahead up to 2 characters and pushing back into stream.
* A value of -1 indicates that no character is in the buffer.
*/
private int[] readAheadChars = new int[2];
/**
* Whether or not the parser is currently in the middle of a string literal.
*/
private boolean inString;
/**
* Whether or not the last char has been a backslash.
*/
private boolean quoted;
public PreprocessingReader(Reader in) {
super(in);
readAheadChars[0] = -1;
readAheadChars[1] = -1;
}
/**
* Returns the next character in the filtered stream:
* <ul>
* <li>Comments will be replaced by a single space</li>
* <li>Line continuation (backslash-newline) will be removed</li>
* </ul>
*/
@Override
public int read() throws IOException {
int ch = next();
if (ch == '\\') {
if (discardNewLine()) {
return read();
}
}
if (ch == '"' && !quoted) {
inString = !inString;
quoted = false;
} else if (ch == '\\') {
quoted = !quoted;
} else {
quoted = false;
if (!inString) {
if (ch == '/') {
ch = next();
if (ch == '/') {
while (ch != '\n' && ch != -1 && ch != '\r') {
ch = next();
}
} else if (ch == '*') {
while (ch != -1) {
ch = next();
if (ch == '*') {
ch = next();
while (ch == '*') {
ch = next();
}
if (ch == '/') {
ch = ' ';
break;
}
}
}
} else {
pushBack(ch);
ch = '/';
}
}
}
}
return ch;
}
private boolean discardNewLine() throws IOException {
int nextChar = next();
if (nextChar == '\n') {
return true; // '\\\n' discarded from stream
} else if (nextChar == '\r') {
int followingChar = next();
if (followingChar == '\n') {
return true; // '\\\r\n' discarded from stream
}
pushBack(nextChar);
pushBack(followingChar);
return false;
} else {
pushBack(nextChar);
return false;
}
}
private int next() throws IOException {
if (readAheadChars[0] != -1) {
int ch = readAheadChars[0];
readAheadChars[0] = readAheadChars[1];
readAheadChars[1] = -1;
return ch;
}
return in.read();
}
private void pushBack(int ch) {
if (readAheadChars[1] != -1) {
throw new IllegalStateException();
}
if (readAheadChars[0] != -1) {
readAheadChars[1] = ch;
} else {
readAheadChars[0] = ch;
}
}
}