liquibase.io.EmptyLineAndCommentSkippingInputStream Maven / Gradle / Ivy
package liquibase.io;
import liquibase.util.StringUtils;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* Input stream that does not read (skips) lines starting with commentPattern and line endings.
* {@link #read()} method will not return either line endings or commented lines.
*/
public class EmptyLineAndCommentSkippingInputStream extends BufferedInputStream {
public static final int MAX_CHAR_SIZE_IN_BYTES = 4;
private String commentLineStartsWith;
private final boolean commentSkipEnabled;
private int lastRead = -1;
/**
* Creates Input stream that does not read (skips) lines starting with commentLineStartsWith
*
* @param in original input stream
* @param commentLineStartsWith comment line pattern (if empty or null, comments will not be enabled)
*/
public EmptyLineAndCommentSkippingInputStream(InputStream in, String commentLineStartsWith) {
super(in);
this.commentLineStartsWith = commentLineStartsWith;
this.commentSkipEnabled = StringUtils.isNotEmpty(commentLineStartsWith);
}
@Override
public synchronized int read() throws IOException {
return read(this.lastRead, false);
}
private int read(final int lastRead, final boolean lookAhead) throws IOException {
int read = super.read();
// skip comment
if (commentSkipEnabled && (read == this.commentLineStartsWith.toCharArray()[0])
&& (lastRead == '\n' || lastRead < 0)) {
while ((((read = super.read())) != '\n') && (read != '\r') && (read > 0)) {
;//keep looking
}
}
if (read < 0) {
return read;
}
if (read == '\r') {
return this.read();
}
if (read == '\n') {
if (lastRead == '\n') {
return this.read();
}
}
if (read == '\n') {
if (lastRead < 0) { //don't include beginning newlines
return this.read();
} else {//don't include last newline
mark(MAX_CHAR_SIZE_IN_BYTES);
if (this.read('\n', true) < 0) {
return -1;
} else {
reset();
}
}
}
if (!lookAhead) {
this.lastRead = read;
}
return read;
}
}