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A CBOR-based serialization for Linked Data
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package com.apicatalog.cborld.encoder;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.util.Collection;
import com.apicatalog.cborld.CborLd;
import com.apicatalog.cborld.context.ContextError;
import com.apicatalog.cborld.encoder.EncoderError.Code;
import com.apicatalog.cborld.encoder.value.ValueEncoder;
import com.apicatalog.cborld.mapping.Mapping;
import com.apicatalog.cborld.mapping.TypeMap;
import com.apicatalog.cursor.ArrayCursor;
import com.apicatalog.cursor.ArrayItemCursor;
import com.apicatalog.cursor.MapCursor;
import com.apicatalog.cursor.MapEntryCursor;
import com.apicatalog.cursor.ValueCursor;
import com.apicatalog.cursor.jakarta.JakartaJsonCursor;
import com.apicatalog.jsonld.JsonLdError;
import co.nstant.in.cbor.CborBuilder;
import co.nstant.in.cbor.CborEncoder;
import co.nstant.in.cbor.CborException;
import co.nstant.in.cbor.builder.ArrayBuilder;
import co.nstant.in.cbor.builder.MapBuilder;
import co.nstant.in.cbor.model.DataItem;
import co.nstant.in.cbor.model.DoublePrecisionFloat;
import co.nstant.in.cbor.model.NegativeInteger;
import co.nstant.in.cbor.model.SimpleValue;
import co.nstant.in.cbor.model.UnicodeString;
import co.nstant.in.cbor.model.UnsignedInteger;
import jakarta.json.JsonObject;
public class Encoder {
protected final EncoderConfig config;
protected Encoder(EncoderConfig config) {
this.config = config;
}
/**
* Encodes JSON-LD document as CBOR-LD document.
*
* @param document JSON-LD document to encode
* @return a byte array representing the encoded CBOR-LD document.
*
* @throws EncoderError
* @throws ContextError
*/
public final byte[] encode(JsonObject document) throws EncoderError, ContextError {
if (document == null) {
throw new IllegalArgumentException("The 'document' parameter must not be null.");
}
return encode(JakartaJsonCursor.from(document));
}
/**
* Encode JSON-LD document as CBOR-LD document.
*
* @return a byte array representing the encoded CBOR-LD document.
*
* @throws EncoderError
* @throws ContextError
*/
byte[] encode(MapCursor document) throws EncoderError, ContextError {
try {
final Collection contexts = EncoderContext.get(document);
if (contexts.isEmpty()) { // is not JSON-LD document
throw new EncoderError(Code.InvalidDocument, "Not a valid JSON-LD document in a compacted form.");
}
return compress(document, contexts);
// non compressable context
} catch (IllegalArgumentException e) {
/* ignored, expected in a case of non compress-able documents */
}
throw new EncoderError(Code.InvalidDocument, "Non compress-able document.");
}
/**
* Compress the given JSON-LD document into CBOR-LD byte array.
*
* @param document the document to compress
* @param contextUrls a set of URLs of @context referenced by the
* document
* @return the compressed document as byte array
*
* @throws IOException
* @throws ContextError
* @throws EncoderError
*/
final byte[] compress(final MapCursor document, Collection contextUrls) throws ContextError, EncoderError {
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
final Mapping mapping = config.encoderMapping().getEncoderMapping(document, config);
final CborBuilder builder = (CborBuilder) encode(document, new CborBuilder().addMap(), mapping.typeMap(), mapping).end();
// 2.CBOR Tag - 0xD9, CBOR-LD - version, Compressed - CBOR-LD compression
// algorithm
baos.write(CborLd.LEADING_BYTE);
baos.write(config.version());
baos.write(config.dictionary().code());
new CborEncoder(baos).encode(builder.build());
return baos.toByteArray();
} catch (CborException e) {
throw new EncoderError(Code.InvalidDocument, e);
} catch (JsonLdError e) {
throw new EncoderError(Code.Internal, e);
}
}
final MapBuilder encode(final MapCursor object, final MapBuilder builder, TypeMap typeMapping, Mapping mapping) throws EncoderError, JsonLdError {
if (object.isEmpty()) {
return builder;
}
MapBuilder flow = builder;
for (final MapEntryCursor entry : object) {
final String property = entry.mapKey();
final Integer encodedProperty = mapping.terms().getCode(property);
if (entry.isArray()) {
final DataItem key = encodedProperty != null
? new UnsignedInteger(encodedProperty + 1)
: new UnicodeString(property);
if (config.isCompactArrays() && object.asArray().size() == 1) {
object.asArray().item(0);
if (object.isMap()) {
final TypeMap propertyTypeMapping = typeMapping.getMapping(property);
flow = (MapBuilder) encode(object.asMap(), flow.putMap(key), propertyTypeMapping, mapping).end();
} else if (object.isArray()) {
flow = (MapBuilder) encode(
object.asArray(),
flow.putArray(key),
property,
typeMapping,
mapping).end();
} else {
final DataItem value = encode(object, property, typeMapping, mapping);
flow = flow.put(key, value);
}
object.parent();
} else {
flow = (MapBuilder) encode(object.asArray(), flow.putArray(key),
property,
typeMapping, mapping).end();
}
continue;
}
final DataItem key = encodedProperty != null
? new UnsignedInteger(encodedProperty)
: new UnicodeString(property);
if (entry.isMap()) {
final TypeMap propertyTypeMapping = typeMapping.getMapping(property);
flow = (MapBuilder) encode(entry.asMap(), flow.putMap(key),
propertyTypeMapping, mapping).end();
continue;
}
final DataItem value = encode(entry, property, typeMapping, mapping);
flow = flow.put(key, value);
}
object.parent();
return flow;
}
final DataItem encode(final ValueCursor value, final String term, TypeMap typeMapping, Mapping mapping) throws EncoderError {
if (value.isBoolean()) {
return value.booleanValue() ? SimpleValue.TRUE : SimpleValue.FALSE;
}
if (value.isString()) {
if (typeMapping != null) {
final Collection types = typeMapping.getType(term);
for (final ValueEncoder valueEncoder : config.valueEncoders()) {
final DataItem dataItem = valueEncoder.encode(mapping, value, term, types);
if (dataItem != null) {
return dataItem;
}
}
}
return new UnicodeString(value.stringValue());
}
if (value.isInteger()) {
BigInteger integer = value.integerValue();
switch (integer.signum()) {
case -1:
return new NegativeInteger(integer);
case 0:
return new UnsignedInteger(BigInteger.ZERO);
case 1:
return new UnsignedInteger(integer);
}
}
if (value.isDecimal()) {
return new DoublePrecisionFloat(value.decimalValue().doubleValue());
}
if (value.isNull()) {
return SimpleValue.NULL;
}
throw new IllegalStateException();
}
final ArrayBuilder encode(final ArrayCursor object, final ArrayBuilder builder, String property, TypeMap typeMapping, Mapping mapping) throws EncoderError, JsonLdError {
if (object.isEmpty()) {
return builder;
}
ArrayBuilder flow = builder;
for (final ArrayItemCursor item : object) {
if (item.isMap()) {
flow = (ArrayBuilder) encode(item.asMap(), flow.startMap(), typeMapping, mapping).end();
continue;
}
if (item.isArray()) {
flow = (ArrayBuilder) encode(item.asArray(), flow.startArray(), property, typeMapping, mapping).end();
continue;
}
final DataItem value = encode(item, property, typeMapping, mapping);
flow = flow.add(value);
}
object.parent();
return flow;
}
}