/**
* Copyright 2005-2014 Restlet
*
* The contents of this file are subject to the terms of one of the following
* open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
* select the license that you prefer but you may not use this file except in
* compliance with one of these Licenses.
*
* You can obtain a copy of the Apache 2.0 license at
* http://www.opensource.org/licenses/apache-2.0
*
* You can obtain a copy of the EPL 1.0 license at
* http://www.opensource.org/licenses/eclipse-1.0
*
* See the Licenses for the specific language governing permissions and
* limitations under the Licenses.
*
* Alternatively, you can obtain a royalty free commercial license with less
* limitations, transferable or non-transferable, directly at
* http://restlet.com/products/restlet-framework
*
* Restlet is a registered trademark of Restlet S.A.S.
*/
package org.restlet.ext.rdf.internal.ntriples;
import java.io.BufferedReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.restlet.data.Reference;
import org.restlet.engine.io.IoUtils;
import org.restlet.ext.rdf.GraphHandler;
import org.restlet.ext.rdf.Link;
import org.restlet.ext.rdf.Literal;
import org.restlet.ext.rdf.internal.RdfReader;
import org.restlet.representation.Representation;
/**
* Handler of RDF content according to the N-Triples notation.
*
* @author Thierry Boileau
*/
public class RdfNTriplesReader extends RdfReader {
/** Internal buffered reader. */
private BufferedReader br;
/** The reading buffer. */
private final char[] buffer;
/** Size of the reading buffer. */
private final int BUFFER_SIZE = 4096;
/** End of reading buffer marker. */
public final int EOF = 0;
/**
* Index that discovers the end of the current token and the beginning of
* the futur one.
*/
private int scoutIndex;
/** Start index of current lexical unit. */
private int startTokenIndex;
/**
* Constructor.
*
* @param rdfRepresentation
* The representation to read.
* @param graphHandler
* The graph handler invoked during the parsing.
* @throws IOException
*/
public RdfNTriplesReader(Representation rdfRepresentation,
GraphHandler graphHandler) throws IOException {
super(rdfRepresentation, graphHandler);
// Initialize the buffer in two parts
this.buffer = new char[(BUFFER_SIZE + 1) * 2];
// Mark the upper index of each part.
this.buffer[BUFFER_SIZE] = this.buffer[2 * BUFFER_SIZE + 1] = EOF;
this.scoutIndex = 2 * BUFFER_SIZE;
this.startTokenIndex = 0;
this.br = new BufferedReader(getRdfRepresentation().getReader(),
IoUtils.BUFFER_SIZE);
}
/**
* Discard all read characters until the end of the statement is reached
* (marked by a '.').
*
* @throws IOException
*/
protected void consumeStatement() throws IOException {
int c = getChar();
while (!isEndOfFile(c) && c != '.') {
c = step();
}
if (getChar() == '.') {
// A further step at the right of the statement.
step();
}
discard();
}
/**
* Discard all read characters. A call to {@link getCurrentToken} will
* return a single character.
*
* @throws IOException
*/
protected void consumeWhiteSpaces() throws IOException {
while (isWhiteSpace(getChar())) {
step();
}
discard();
}
/**
* Discard all read characters. A call to {@link getCurrentToken} will
* return a single character.
*/
protected void discard() {
startTokenIndex = scoutIndex;
}
/**
* Returns the current parsed character.
*
* @return The current parsed character.
*/
protected char getChar() {
return buffer[scoutIndex];
}
/**
* Returns the current token.
*
* @return The current token.
*/
protected String getCurrentToken() {
StringBuilder builder = new StringBuilder();
if (startTokenIndex <= scoutIndex) {
if (scoutIndex <= BUFFER_SIZE) {
for (int i = startTokenIndex; i < scoutIndex; i++) {
builder.append(buffer[i]);
}
} else {
for (int i = startTokenIndex; i < BUFFER_SIZE; i++) {
builder.append(buffer[i]);
}
for (int i = BUFFER_SIZE + 1; i < scoutIndex; i++) {
builder.append(buffer[i]);
}
}
} else {
if (startTokenIndex <= BUFFER_SIZE) {
for (int i = startTokenIndex; i < BUFFER_SIZE; i++) {
builder.append(buffer[i]);
}
for (int i = BUFFER_SIZE + 1; i < (2 * BUFFER_SIZE + 1); i++) {
builder.append(buffer[i]);
}
for (int i = 0; i < scoutIndex; i++) {
builder.append(buffer[i]);
}
} else {
for (int i = startTokenIndex; i < (2 * BUFFER_SIZE + 1); i++) {
builder.append(buffer[i]);
}
for (int i = 0; i < scoutIndex; i++) {
builder.append(buffer[i]);
}
}
}
// the current token is consumed.
startTokenIndex = scoutIndex;
return builder.toString();
}
/**
* Returns a message describing the current state of the parsing process.
*
* @return A message describing the current state of the parsing process.
*/
public String getParsingMessage() {
return getParsingMessage(buffer, startTokenIndex, scoutIndex);
}
/**
* Returns a message describing the current state of the parsing process.
*
* @param buffer
* The current buffer.
* @param startTokenIndex
* The start index of parsing.
* @param scoutIndex
* The index of the probable future token.
* @return
*/
protected String getParsingMessage(char[] buffer, int startTokenIndex,
int scoutIndex) {
StringBuilder sb = new StringBuilder("Parsing data [");
sb.append(startTokenIndex);
sb.append(",");
sb.append(scoutIndex);
sb.append("] near ");
if (startTokenIndex < 25) {
sb.append(buffer, buffer.length - 30, 28);
sb.append(buffer, 0, 25);
} else if (startTokenIndex > (buffer.length - 25)) {
sb.append(buffer, buffer.length - 30, 28);
sb.append(buffer, 0, 20);
} else {
sb.append(buffer, startTokenIndex - 25, 50);
}
return sb.toString();
}
/**
* Returns true if the given character is alphanumeric.
*
* @param c
* The given character to check.
* @return true if the given character is alphanumeric.
*/
protected boolean isAlphaNum(int c) {
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
|| (c >= '0' && c <= '9');
}
/**
* Returns true if the given character is a delimiter.
*
* @param c
* The given character to check.
* @return true if the given character is a delimiter.
*/
protected boolean isDelimiter(int c) {
return isWhiteSpace(c) || c == '"' || c == '.';
}
protected boolean isEndOfFile(int c) {
return c == EOF;
}
/**
* Returns true if the given character is a whitespace.
*
* @param c
* The given character to check.
* @return true if the given character is a whitespace.
*/
protected boolean isWhiteSpace(int c) {
return c == ' ' || c == '\n' || c == '\r' || c == '\t';
}
/**
* Parses the current representation.
*
* @throws IOException
*/
@Override
public void parse() throws IOException {
// Init the reading.
step();
do {
consumeWhiteSpaces();
switch (getChar()) {
case '#':
parseComment();
break;
case '.':
step();
break;
default:
parseStatement();
break;
}
} while (!isEndOfFile(getChar()));
}
/**
* Parses a comment.
*
* @throws IOException
*/
protected void parseComment() throws IOException {
int c;
do {
c = step();
} while (!isEndOfFile(getChar()) && c != '\n' && c != '\r');
discard();
}
/**
* Reads the current statement until its end, and parses it.
*
* @param context
* The current context.
* @throws IOException
*/
protected void parseStatement() throws IOException {
List<Reference> lexicalUnits = new ArrayList<Reference>();
String object = null;
do {
consumeWhiteSpaces();
switch (getChar()) {
case '<':
lexicalUnits.add(new Reference(parseUri()));
break;
case '_':
lexicalUnits.add(Link.createBlankRef(parseToken()));
break;
case '"':
int c = step();
discard();
while (!isEndOfFile(c) && (c != '"')) {
c = step();
}
object = getCurrentToken();
step();
discard();
break;
case '.':
break;
case '#':
parseComment();
break;
case EOF:
break;
default:
throw new IOException(
"This document does not seem to follow the N-Triples syntax. "
+ getParsingMessage());
}
} while (!isEndOfFile(getChar()) && getChar() != '.'
&& getChar() != '}');
// Generate the links
if (!lexicalUnits.isEmpty()) {
if (object != null) {
getGraphHandler().link(lexicalUnits.get(0),
lexicalUnits.get(1), new Literal(object));
} else {
getGraphHandler().link(lexicalUnits.get(0),
lexicalUnits.get(1), lexicalUnits.get(2));
}
}
}
/**
* Returns the value of the current token.
*
* @return The value of the current token.
* @throws IOException
*/
protected String parseToken() throws IOException {
int c;
do {
c = step();
} while (!isEndOfFile(c) && !isDelimiter(c));
String result = getCurrentToken();
return result;
}
/**
* Returns the value of the current URI.
*
* @return The value of the current URI.
* @throws IOException
*/
protected String parseUri() throws IOException {
StringBuilder builder = new StringBuilder();
// Suppose the current character is "<".
int c = step();
while (c != EOF && c != '>') {
if (!isWhiteSpace(c)) {
// Discard white spaces.
builder.append((char) c);
}
c = step();
}
if (c == '>') {
// Set the cursor at the right of the uri.
step();
}
discard();
return builder.toString();
}
/**
* Read a new character.
*
* @return The new read character.
* @throws IOException
*/
protected int step() throws IOException {
scoutIndex++;
if (buffer[scoutIndex] == EOF) {
if (scoutIndex == BUFFER_SIZE) {
// Reached the end of the first part of the buffer, read into
// the second one.
scoutIndex++;
int len = this.br.read(buffer, 0, BUFFER_SIZE);
if (len == -1) {
// End of the stream reached
buffer[scoutIndex] = EOF;
} else {
buffer[BUFFER_SIZE + len + 1] = EOF;
}
} else if (scoutIndex == (2 * BUFFER_SIZE + 1)) {
scoutIndex = 0;
// Reached the end of the second part of the buffer, read into
// the first one.
int len = this.br.read(buffer, 0, BUFFER_SIZE);
if (len == -1) {
// End of the stream reached
buffer[scoutIndex] = EOF;
} else {
buffer[len] = EOF;
}
} else {
// Reached the end of the stream.
}
}
return buffer[scoutIndex];
}
/**
* Steps forward.
*
* @param n
* The number of steps to go forward.
* @throws IOException
*/
protected void step(int n) throws IOException {
for (int i = 0; i < n; i++) {
step();
}
}
/**
* Steps back of one step.
*
*/
protected void stepBack() {
stepBack(1);
}
/**
* Steps back.
*
* @param n
* The number of steps to go back.
*/
protected void stepBack(int n) {
scoutIndex -= n;
if (scoutIndex < 0) {
scoutIndex = BUFFER_SIZE * 2 + 1 - scoutIndex;
}
}
}