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// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.tensor.serialization;
import com.yahoo.slime.ArrayTraverser;
import com.yahoo.slime.Cursor;
import com.yahoo.slime.Inspector;
import com.yahoo.slime.JsonDecoder;
import com.yahoo.slime.ObjectTraverser;
import com.yahoo.slime.Slime;
import com.yahoo.slime.Type;
import com.yahoo.tensor.Tensor;
import com.yahoo.tensor.TensorAddress;
import com.yahoo.tensor.TensorType;
import java.util.Iterator;
/**
* Writes tensors on the JSON format used in Vespa tensor document fields:
* A JSON map containing a 'cells' array.
* See http://docs.vespa.ai/documentation/reference/document-json-put-format.html#tensor
*/
// TODO: We should probably move reading of this format from the document module to here
public class JsonFormat {
/** Serializes the given tensor into JSON format */
public static byte[] encode(Tensor tensor) {
Slime slime = new Slime();
Cursor root = slime.setObject();
Cursor cellsArray = root.setArray("cells");
for (Iterator<Tensor.Cell> i = tensor.cellIterator(); i.hasNext(); ) {
Tensor.Cell cell = i.next();
Cursor cellObject = cellsArray.addObject();
encodeAddress(tensor.type(), cell.getKey(), cellObject.setObject("address"));
cellObject.setDouble("value", cell.getValue());
}
return com.yahoo.slime.JsonFormat.toJsonBytes(slime);
}
private static void encodeAddress(TensorType type, TensorAddress address, Cursor addressObject) {
for (int i = 0; i < address.size(); i++)
addressObject.setString(type.dimensions().get(i).name(), address.label(i));
}
/** Deserializes the given tensor from JSON format */
public static Tensor decode(TensorType type, byte[] jsonTensorValue) {
Tensor.Builder tensorBuilder = Tensor.Builder.of(type);
Inspector root = new JsonDecoder().decode(new Slime(), jsonTensorValue).get();
Inspector cells = root.field("cells");
if ( cells.type() != Type.ARRAY)
throw new IllegalArgumentException("Excepted an array item named 'cells' at the top level");
cells.traverse((ArrayTraverser) (__, cell) -> decodeCell(cell, tensorBuilder.cell()));
return tensorBuilder.build();
}
private static void decodeCell(Inspector cell, Tensor.Builder.CellBuilder cellBuilder) {
Inspector address = cell.field("address");
if ( address.type() != Type.OBJECT)
throw new IllegalArgumentException("Excepted a cell to contain an object called 'address'");
address.traverse((ObjectTraverser) (dimension, label) -> cellBuilder.label(dimension, label.asString()));
Inspector value = cell.field("value");
if (value.type() != Type.LONG && value.type() != Type.DOUBLE)
throw new IllegalArgumentException("Excepted a cell to contain a numeric value called 'value'");
cellBuilder.value(value.asDouble());
}
}
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