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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.tensor.serialization;
import com.google.common.annotations.Beta;
import com.google.common.collect.Sets;
import com.yahoo.io.GrowableByteBuffer;
import com.yahoo.tensor.MapTensorBuilder;
import com.yahoo.tensor.Tensor;
import com.yahoo.tensor.TensorAddress;
import com.yahoo.text.Utf8;
import java.util.*;
/**
* Implementation of a compact binary format for a tensor on the form:
*
* Sorted dimensions = num_dimensions [dimension_str_len dimension_str_bytes]*
* Cells = num_cells [label_1_str_len label_1_str_bytes ... label_N_str_len label_N_str_bytes cell_value]*
*
* Note that the dimensions are sorted and the tensor address labels are given in the same sorted order.
* Unspecified labels are encoded as the empty string "".
*
* @author <a href="mailto:geirst@yahoo-inc.com">Geir Storli</a>
*/
@Beta
class CompactBinaryFormat implements BinaryFormat {
@Override
public void encode(GrowableByteBuffer buffer, Tensor tensor) {
List<String> sortedDimensions = new ArrayList<>(tensor.dimensions());
Collections.sort(sortedDimensions);
encodeDimensions(buffer, sortedDimensions);
encodeCells(buffer, tensor.cells(), sortedDimensions);
}
private static void encodeDimensions(GrowableByteBuffer buffer, List<String> sortedDimensions) {
buffer.putInt1_4Bytes(sortedDimensions.size());
for (String dimension : sortedDimensions) {
encodeString(buffer, dimension);
}
}
private static void encodeCells(GrowableByteBuffer buffer, Map<TensorAddress, Double> cells,
List<String> sortedDimensions) {
buffer.putInt1_4Bytes(cells.size());
for (Map.Entry<TensorAddress, Double> cellEntry : cells.entrySet()) {
encodeAddress(buffer, cellEntry.getKey(), sortedDimensions);
buffer.putDouble(cellEntry.getValue().doubleValue());
}
}
private static void encodeAddress(GrowableByteBuffer buffer, TensorAddress address, List<String> sortedDimensions) {
for (String dimension : sortedDimensions) {
Optional<TensorAddress.Element> element =
address.elements().stream().filter(elem -> elem.dimension().equals(dimension)).findFirst();
String label = (element.isPresent() ? element.get().label() : "");
encodeString(buffer, label);
}
}
private static void encodeString(GrowableByteBuffer buffer, String value) {
byte[] stringBytes = Utf8.toBytes(value);
buffer.putInt1_4Bytes(stringBytes.length);
buffer.put(stringBytes);
}
@Override
public Tensor decode(GrowableByteBuffer buffer) {
List<String> sortedDimensions = decodeDimensions(buffer);
MapTensorBuilder builder = new MapTensorBuilder();
for (String dimension : sortedDimensions) {
builder.dimension(dimension);
}
decodeCells(buffer, builder, sortedDimensions);
return builder.build();
}
private static List<String> decodeDimensions(GrowableByteBuffer buffer) {
int numDimensions = buffer.getInt1_4Bytes();
List<String> sortedDimensions = new ArrayList<>();
for (int i = 0; i < numDimensions; ++i) {
sortedDimensions.add(decodeString(buffer));
}
return sortedDimensions;
}
private static void decodeCells(GrowableByteBuffer buffer, MapTensorBuilder builder,
List<String> sortedDimensions) {
int numCells = buffer.getInt1_4Bytes();
for (int i = 0; i < numCells; ++i) {
MapTensorBuilder.CellBuilder cellBuilder = builder.cell();
decodeAddress(buffer, cellBuilder, sortedDimensions);
cellBuilder.value(buffer.getDouble());
}
}
private static void decodeAddress(GrowableByteBuffer buffer, MapTensorBuilder.CellBuilder builder,
List<String> sortedDimensions) {
for (String dimension : sortedDimensions) {
String label = decodeString(buffer);
if (!label.isEmpty()) {
builder.label(dimension, label);
}
}
}
private static String decodeString(GrowableByteBuffer buffer) {
int stringLength = buffer.getInt1_4Bytes();
byte[] stringBytes = new byte[stringLength];
buffer.get(stringBytes);
return Utf8.toString(stringBytes);
}
}
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