package com.vividsolutions.jts.io;
import java.io.*;
import java.util.*;
import com.vividsolutions.jts.geom.*;
/**
* Reads a sequence of {@link Geometry}s in WKT format
* from a text file.
* The geometries in the file may be separated by any amount
* of whitespace and newlines.
*
* @author Martin Davis
*
*/
public class WKTFileReader
{
private File file = null;
private Reader reader;
// private Reader fileReader = new FileReader(file);
private WKTReader wktReader;
private int count = 0;
private int limit = -1;
private int offset = 0;
/**
* Creates a new <tt>WKTFileReader</tt> given the <tt>File</tt> to read from
* and a <tt>WKTReader</tt> to use to parse the geometries.
*
* @param file the <tt>File</tt> to read from
* @param wktReader the geometry reader to use
*/
public WKTFileReader(File file, WKTReader wktReader)
{
this.file = file;
this.wktReader = wktReader;
}
/**
* Creates a new <tt>WKTFileReader</tt>, given the name of the file to read from.
*
* @param filename the name of the file to read from
* @param wktReader the geometry reader to use
*/
public WKTFileReader(String filename, WKTReader wktReader)
{
this(new File(filename), wktReader);
}
/**
* Creates a new <tt>WKTFileReader</tt>, given a {@link Reader} to read from.
*
* @param reader the reader to read from
* @param wktReader the geometry reader to use
*/
public WKTFileReader(Reader reader, WKTReader wktReader)
{
this.reader = reader;
this.wktReader = wktReader;
}
/**
* Sets the maximum number of geometries to read.
*
* @param limit the maximum number of geometries to read
*/
public void setLimit(int limit)
{
this.limit = limit;
}
/**
* Sets the number of geometries to skip before storing.
*
* @param offset the number of geometries to skip
*/
public void setOffset(int offset)
{
this.offset = offset;
}
/**
* Reads a sequence of geometries.
* If an offset is specified, geometries read up to the offset count are skipped.
* If a limit is specified, no more than <tt>limit</tt> geometries are read.
*
* @return the list of geometries read
* @throws IOException if an I/O exception was encountered
* @throws ParseException if an error occured reading a geometry
*/
public List read()
throws IOException, ParseException
{
// do this here so that constructors don't throw exceptions
if (file != null)
reader = new FileReader(file);
count = 0;
try {
BufferedReader bufferedReader = new BufferedReader(reader);
try {
return read(bufferedReader);
} finally {
bufferedReader.close();
}
} finally {
reader.close();
}
}
private List read(BufferedReader bufferedReader) throws IOException,
ParseException {
List geoms = new ArrayList();
while (! isAtEndOfFile(bufferedReader) && ! isAtLimit(geoms)) {
Geometry g = wktReader.read(bufferedReader);
if (count >= offset)
geoms.add(g);
count++;
}
return geoms;
}
private boolean isAtLimit(List geoms)
{
if (limit < 0) return false;
if (geoms.size() < limit) return false;
return true;
}
private static final int MAX_LOOKAHEAD = 1000;
/**
* Tests if reader is at EOF.
*/
private boolean isAtEndOfFile(BufferedReader bufferedReader)
throws IOException
{
bufferedReader.mark(MAX_LOOKAHEAD);
StreamTokenizer tokenizer = new StreamTokenizer(bufferedReader);
int type = tokenizer.nextToken();
if (type == StreamTokenizer.TT_EOF) {
return true;
}
bufferedReader.reset();
return false;
}
}