findepi commented on code in PR #4537: URL: https://github.com/apache/iceberg/pull/4537#discussion_r877828034
########## core/src/main/java/org/apache/iceberg/stats/StatsReader.java: ########## @@ -0,0 +1,188 @@ +/* + * 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.iceberg.stats; + +import java.io.Closeable; +import java.io.IOException; +import java.io.UncheckedIOException; +import java.nio.ByteBuffer; +import java.nio.charset.StandardCharsets; +import java.util.Arrays; +import java.util.Comparator; +import java.util.EnumSet; +import java.util.List; +import java.util.Set; +import javax.annotation.Nullable; +import org.apache.iceberg.io.InputFile; +import org.apache.iceberg.io.RangeReadable; +import org.apache.iceberg.io.SeekableInputStream; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList; +import org.apache.iceberg.relocated.com.google.common.io.ByteStreams; +import org.apache.iceberg.stats.StatsFormat.Flag; +import org.apache.iceberg.util.Pair; + +public class StatsReader implements Closeable { + // Must not be modified + private static final byte[] MAGIC = StatsFormat.getMagic(); + + private final long fileSize; + private final SeekableInputStream input; + private Integer knownFooterSize; + private FileMetadata knownFileMetadata; + + public StatsReader(InputFile inputFile, @Nullable Long fileSize, @Nullable Long footerSize) { + Preconditions.checkNotNull(inputFile, "inputFile is null"); + this.fileSize = fileSize == null ? inputFile.getLength() : fileSize; + this.input = inputFile.newStream(); + if (footerSize != null) { + Preconditions.checkArgument(0 < footerSize && footerSize <= this.fileSize - MAGIC.length, + "Invalid footer size: %s", footerSize); + this.knownFooterSize = Math.toIntExact(footerSize); + } + } + + public FileMetadata fileMetadata() throws IOException { + if (knownFileMetadata == null) { + int footerSize = footerSize(); + byte[] footer = readInput(fileSize - footerSize, footerSize); + + checkMagic(footer, StatsFormat.FOOTER_MAGIC_OFFSET); + int footerStructOffset = footerSize - StatsFormat.FOOTER_STRUCT_LENGTH; + checkMagic(footer, footerStructOffset + StatsFormat.FOOTER_STRUCT_MAGIC_OFFSET); + + StatsCompressionCodec footerCompression = StatsCompressionCodec.NONE; + for (Flag flag : decodeFlags(footer, footerStructOffset)) { + switch (flag) { + case FOOTER_PAYLOAD_COMPRESSED: + footerCompression = StatsFormat.FOOTER_COMPRESSION_CODEC; + break; + default: + throw new IllegalStateException("Unsupported flag: " + flag); + } + } + + int footerPayloadSize = StatsFormat.readIntegerLittleEndian( + footer, + footerStructOffset + StatsFormat.FOOTER_STRUCT_PAYLOAD_SIZE_OFFSET); + Preconditions.checkState(footerSize == footerPayloadSize + StatsFormat.FOOTER_STRUCT_LENGTH + 4 /* magic */, + "Unexpected footer payload size value %s for footer size %s", footerPayloadSize, footerSize); + + ByteBuffer footerPayload = ByteBuffer.wrap(footer, 4, footerPayloadSize); + ByteBuffer footerJson = StatsFormat.decompress(footerCompression, footerPayload); + this.knownFileMetadata = parseFileMetadata(footerJson); + } + return knownFileMetadata; + } + + private Set<Flag> decodeFlags(byte[] footer, int footerStructOffset) { + EnumSet<Flag> flags = EnumSet.noneOf(Flag.class); + for (int byteNumber = 0; byteNumber < StatsFormat.FOOTER_STRUCT_FLAGS_LENGTH; byteNumber++) { + int flagByte = + Byte.toUnsignedInt(footer[footerStructOffset + StatsFormat.FOOTER_STRUCT_FLAGS_OFFSET + byteNumber]); + int bitNumber = 0; + while (flagByte != 0) { + if ((flagByte & 0x1) != 0) { + Flag flag = Flag.fromBit(byteNumber, bitNumber); + Preconditions.checkState(flag != null, "Unknown flag byte %s and bit %s set", byteNumber, bitNumber); + flags.add(flag); + } + flagByte = flagByte >> 1; + bitNumber++; + } + } + return flags; + } + + public Iterable<Pair<BlobMetadata, ByteBuffer>> readAll(List<BlobMetadata> blobs) { + if (blobs.isEmpty()) { + return ImmutableList.of(); + } + + // TODO inspect blob offsets and coalesce read regions close to each other + + return () -> blobs.stream() + .sorted(Comparator.comparingLong(BlobMetadata::offset)) + .map((BlobMetadata blobMetadata) -> { + try { + input.seek(blobMetadata.offset()); + byte[] bytes = new byte[Math.toIntExact(blobMetadata.length())]; + ByteStreams.readFully(input, bytes); + ByteBuffer rawData = ByteBuffer.wrap(bytes); + StatsCompressionCodec codec = StatsCompressionCodec.forName(blobMetadata.compressionCodec()); + ByteBuffer data = StatsFormat.decompress(codec, rawData); + return Pair.of(blobMetadata, data); + } catch (IOException e) { + throw new UncheckedIOException(e); + } + }) + .iterator(); + } + + private static void checkMagic(byte[] data, int offset) { + byte[] read = Arrays.copyOfRange(data, offset, offset + MAGIC.length); + if (!Arrays.equals(read, MAGIC)) { + throw new IllegalStateException(String.format( + "Invalid file: expected magic at offset %s: %s, but got %s", + offset, Arrays.toString(MAGIC), Arrays.toString(read))); + } + } + + private int footerSize() throws IOException { + if (knownFooterSize == null) { + if (fileSize < StatsFormat.FOOTER_STRUCT_LENGTH) { Review Comment: done -- This is an automated message from the Apache Git Service. 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