rdblue commented on code in PR #3202: URL: https://github.com/apache/parquet-java/pull/3202#discussion_r2072162025
########## parquet-variant/src/main/java/org/apache/parquet/variant/VariantBuilder.java: ########## @@ -0,0 +1,658 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.parquet.variant; + +import java.math.BigDecimal; +import java.math.BigInteger; +import java.nio.ByteBuffer; +import java.nio.ByteOrder; +import java.nio.charset.StandardCharsets; +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collections; +import java.util.HashMap; + +/** + * Builder for creating Variant value and metadata. + */ +public class VariantBuilder { + /** The buffer for building the Variant value. The first `writePos` bytes have been written. */ + protected byte[] writeBuffer = new byte[1024]; + + protected int writePos = 0; + /** The dictionary for mapping keys to monotonically increasing ids. */ + private final HashMap<String, Integer> dictionary = new HashMap<>(); + /** The keys in the dictionary, in id order. */ + private final ArrayList<byte[]> dictionaryKeys = new ArrayList<>(); + + /** + * These are used to build nested objects and arrays, via startObject() and startArray(). + * Only one of these can be non-null at a time. If one of these is non-null, then no append() + * methods can be called on this builder, until endObject() or endArray() is called. + */ + protected VariantObjectBuilder objectBuilder = null; + + protected VariantArrayBuilder arrayBuilder = null; + + /** + * Creates a VariantBuilder. + */ + public VariantBuilder() {} + + /** + * @return the Variant value + */ + public Variant build() { + if (objectBuilder != null) { + throw new IllegalStateException( + "Cannot call build() while an object is being built. Must call endObject() first."); + } + if (arrayBuilder != null) { + throw new IllegalStateException( + "Cannot call build() while an array is being built. Must call endArray() first."); + } + int numKeys = dictionaryKeys.size(); + // Use long to avoid overflow in accumulating lengths. + long dictionaryTotalDataSize = 0; + for (byte[] key : dictionaryKeys) { + dictionaryTotalDataSize += key.length; + } + // Determine the number of bytes required per offset entry. + // The largest offset is the one-past-the-end value, which is total data size. It's very + // unlikely that the number of keys could be larger, but incorporate that into the calculation + // in case of pathological data. + long maxSize = Math.max(dictionaryTotalDataSize, numKeys); + int offsetSize = getMinIntegerSize((int) maxSize); + + int offsetListOffset = 1 + offsetSize; + int dataOffset = offsetListOffset + (numKeys + 1) * offsetSize; + long metadataSize = dataOffset + dictionaryTotalDataSize; + + byte[] metadata = new byte[(int) metadataSize]; + // Only unsorted dictionary keys are supported. + // TODO: Support sorted dictionary keys. + int headerByte = VariantUtil.VERSION | ((offsetSize - 1) << 6); + VariantUtil.writeLong(metadata, 0, headerByte, 1); + VariantUtil.writeLong(metadata, 1, numKeys, offsetSize); + int currentOffset = 0; + for (int i = 0; i < numKeys; ++i) { + VariantUtil.writeLong(metadata, offsetListOffset + i * offsetSize, currentOffset, offsetSize); + byte[] key = dictionaryKeys.get(i); + System.arraycopy(key, 0, metadata, dataOffset + currentOffset, key.length); + currentOffset += key.length; + } + VariantUtil.writeLong(metadata, offsetListOffset + numKeys * offsetSize, currentOffset, offsetSize); + // Copying the data to a new buffer, to retain only the required data length, not the capacity. + return new Variant(Arrays.copyOfRange(writeBuffer, 0, writePos), metadata); + } + + /** + * Appends a string value to the Variant builder. + * @param str the string value to append + */ + public void appendString(String str) { + onAppend(); + byte[] data = str.getBytes(StandardCharsets.UTF_8); + boolean longStr = data.length > VariantUtil.MAX_SHORT_STR_SIZE; + checkCapacity((longStr ? 1 + VariantUtil.U32_SIZE : 1) + data.length); + if (longStr) { + writeBuffer[writePos] = VariantUtil.HEADER_LONG_STRING; + writePos += 1; + VariantUtil.writeLong(writeBuffer, writePos, data.length, VariantUtil.U32_SIZE); + writePos += VariantUtil.U32_SIZE; + } else { + writeBuffer[writePos] = VariantUtil.shortStrHeader(data.length); + writePos += 1; + } + System.arraycopy(data, 0, writeBuffer, writePos, data.length); + writePos += data.length; + incrementNumValues(); Review Comment: As noted above, if we can do this in `onAppend` then we probably should. -- This is an automated message from the Apache Git Service. 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