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/**
* 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.hadoop.io.file.tfile;
import java.io.ByteArrayInputStream;
import java.io.Closeable;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Comparator;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.io.BoundedByteArrayOutputStream;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.io.file.tfile.BCFile.Reader.BlockReader;
import org.apache.hadoop.io.file.tfile.BCFile.Writer.BlockAppender;
import org.apache.hadoop.io.file.tfile.Chunk.ChunkDecoder;
import org.apache.hadoop.io.file.tfile.Chunk.ChunkEncoder;
import org.apache.hadoop.io.file.tfile.CompareUtils.BytesComparator;
import org.apache.hadoop.io.file.tfile.CompareUtils.MemcmpRawComparator;
import org.apache.hadoop.io.file.tfile.Utils.Version;
import org.apache.hadoop.io.serializer.JavaSerializationComparator;
import io.prestosql.hadoop.$internal.org.slf4j.Logger;
import io.prestosql.hadoop.$internal.org.slf4j.LoggerFactory;
/**
* A TFile is a container of key-value pairs. Both keys and values are type-less
* bytes. Keys are restricted to 64KB, value length is not restricted
* (practically limited to the available disk storage). TFile further provides
* the following features:
*
* - Block Compression.
*
- Named meta data blocks.
*
- Sorted or unsorted keys.
*
- Seek by key or by file offset.
*
* The memory footprint of a TFile includes the following:
*
* - Some constant overhead of reading or writing a compressed block.
*
* - Each compressed block requires one compression/decompression codec for
* I/O.
*
- Temporary space to buffer the key.
*
- Temporary space to buffer the value (for TFile.Writer only). Values are
* chunk encoded, so that we buffer at most one chunk of user data. By default,
* the chunk buffer is 1MB. Reading chunked value does not require additional
* memory.
*
* - TFile index, which is proportional to the total number of Data Blocks.
* The total amount of memory needed to hold the index can be estimated as
* (56+AvgKeySize)*NumBlocks.
*
- MetaBlock index, which is proportional to the total number of Meta
* Blocks.The total amount of memory needed to hold the index for Meta Blocks
* can be estimated as (40+AvgMetaBlockName)*NumMetaBlock.
*
*
* The behavior of TFile can be customized by the following variables through
* Configuration:
*
* - tfile.io.chunk.size: Value chunk size. Integer (in bytes). Default
* to 1MB. Values of the length less than the chunk size is guaranteed to have
* known value length in read time (See
* {@link TFile.Reader.Scanner.Entry#isValueLengthKnown()}).
*
- tfile.fs.output.buffer.size: Buffer size used for
* FSDataOutputStream. Integer (in bytes). Default to 256KB.
*
- tfile.fs.input.buffer.size: Buffer size used for
* FSDataInputStream. Integer (in bytes). Default to 256KB.
*
*
* Suggestions on performance optimization.
*
* - Minimum block size. We recommend a setting of minimum block size between
* 256KB to 1MB for general usage. Larger block size is preferred if files are
* primarily for sequential access. However, it would lead to inefficient random
* access (because there are more data to decompress). Smaller blocks are good
* for random access, but require more memory to hold the block index, and may
* be slower to create (because we must flush the compressor stream at the
* conclusion of each data block, which leads to an FS I/O flush). Further, due
* to the internal caching in Compression codec, the smallest possible block
* size would be around 20KB-30KB.
*
- The current implementation does not offer true multi-threading for
* reading. The implementation uses FSDataInputStream seek()+read(), which is
* shown to be much faster than positioned-read call in single thread mode.
* However, it also means that if multiple threads attempt to access the same
* TFile (using multiple scanners) simultaneously, the actual I/O is carried out
* sequentially even if they access different DFS blocks.
*
- Compression codec. Use "none" if the data is not very compressable (by
* compressable, I mean a compression ratio at least 2:1). Generally, use "lzo"
* as the starting point for experimenting. "gz" overs slightly better
* compression ratio over "lzo" but requires 4x CPU to compress and 2x CPU to
* decompress, comparing to "lzo".
*
- File system buffering, if the underlying FSDataInputStream and
* FSDataOutputStream is already adequately buffered; or if applications
* reads/writes keys and values in large buffers, we can reduce the sizes of
* input/output buffering in TFile layer by setting the configuration parameters
* "tfile.fs.input.buffer.size" and "tfile.fs.output.buffer.size".
*
*
* Some design rationale behind TFile can be found at Hadoop-3315.
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class TFile {
static final Logger LOG = LoggerFactory.getLogger(TFile.class);
private static final String CHUNK_BUF_SIZE_ATTR = "tfile.io.chunk.size";
private static final String FS_INPUT_BUF_SIZE_ATTR =
"tfile.fs.input.buffer.size";
private static final String FS_OUTPUT_BUF_SIZE_ATTR =
"tfile.fs.output.buffer.size";
static int getChunkBufferSize(Configuration conf) {
int ret = conf.getInt(CHUNK_BUF_SIZE_ATTR, 1024 * 1024);
return (ret > 0) ? ret : 1024 * 1024;
}
static int getFSInputBufferSize(Configuration conf) {
return conf.getInt(FS_INPUT_BUF_SIZE_ATTR, 256 * 1024);
}
static int getFSOutputBufferSize(Configuration conf) {
return conf.getInt(FS_OUTPUT_BUF_SIZE_ATTR, 256 * 1024);
}
private static final int MAX_KEY_SIZE = 64 * 1024; // 64KB
static final Version API_VERSION = new Version((short) 1, (short) 0);
/** compression: gzip */
public static final String COMPRESSION_GZ = "gz";
/** compression: lzo */
public static final String COMPRESSION_LZO = "lzo";
/** compression: none */
public static final String COMPRESSION_NONE = "none";
/** comparator: memcmp */
public static final String COMPARATOR_MEMCMP = "memcmp";
/** comparator prefix: java class */
public static final String COMPARATOR_JCLASS = "jclass:";
/**
* Make a raw comparator from a string name.
*
* @param name
* Comparator name
* @return A RawComparable comparator.
*/
static public Comparator makeComparator(String name) {
return TFileMeta.makeComparator(name);
}
// Prevent the instantiation of TFiles
private TFile() {
// nothing
}
/**
* Get names of supported compression algorithms. The names are acceptable by
* TFile.Writer.
*
* @return Array of strings, each represents a supported compression
* algorithm. Currently, the following compression algorithms are
* supported.
*
* - "none" - No compression.
*
- "lzo" - LZO compression.
*
- "gz" - GZIP compression.
*
*/
public static String[] getSupportedCompressionAlgorithms() {
return Compression.getSupportedAlgorithms();
}
/**
* TFile Writer.
*/
@InterfaceStability.Evolving
public static class Writer implements Closeable {
// minimum compressed size for a block.
private final int sizeMinBlock;
// Meta blocks.
final TFileIndex tfileIndex;
final TFileMeta tfileMeta;
// reference to the underlying BCFile.
private BCFile.Writer writerBCF;
// current data block appender.
BlockAppender blkAppender;
long blkRecordCount;
// buffers for caching the key.
BoundedByteArrayOutputStream currentKeyBufferOS;
BoundedByteArrayOutputStream lastKeyBufferOS;
// buffer used by chunk codec
private byte[] valueBuffer;
/**
* Writer states. The state always transits in circles: READY -> IN_KEY ->
* END_KEY -> IN_VALUE -> READY.
*/
private enum State {
READY, // Ready to start a new key-value pair insertion.
IN_KEY, // In the middle of key insertion.
END_KEY, // Key insertion complete, ready to insert value.
IN_VALUE, // In value insertion.
// ERROR, // Error encountered, cannot continue.
CLOSED, // TFile already closed.
};
// current state of Writer.
State state = State.READY;
Configuration conf;
long errorCount = 0;
/**
* Constructor
*
* @param fsdos
* output stream for writing. Must be at position 0.
* @param minBlockSize
* Minimum compressed block size in bytes. A compression block will
* not be closed until it reaches this size except for the last
* block.
* @param compressName
* Name of the compression algorithm. Must be one of the strings
* returned by {@link TFile#getSupportedCompressionAlgorithms()}.
* @param comparator
* Leave comparator as null or empty string if TFile is not sorted.
* Otherwise, provide the string name for the comparison algorithm
* for keys. Two kinds of comparators are supported.
*
* - Algorithmic comparator: binary comparators that is language
* independent. Currently, only "memcmp" is supported.
*
- Language-specific comparator: binary comparators that can
* only be constructed in specific language. For Java, the syntax
* is "jclass:", followed by the class name of the RawComparator.
* Currently, we only support RawComparators that can be
* constructed through the default constructor (with no
* parameters). Parameterized RawComparators such as
* {@link WritableComparator} or
* {@link JavaSerializationComparator} may not be directly used.
* One should write a wrapper class that inherits from such classes
* and use its default constructor to perform proper
* initialization.
*
* @param conf
* The configuration object.
* @throws IOException
*/
public Writer(FSDataOutputStream fsdos, int minBlockSize,
String compressName, String comparator, Configuration conf)
throws IOException {
sizeMinBlock = minBlockSize;
tfileMeta = new TFileMeta(comparator);
tfileIndex = new TFileIndex(tfileMeta.getComparator());
writerBCF = new BCFile.Writer(fsdos, compressName, conf);
currentKeyBufferOS = new BoundedByteArrayOutputStream(MAX_KEY_SIZE);
lastKeyBufferOS = new BoundedByteArrayOutputStream(MAX_KEY_SIZE);
this.conf = conf;
}
/**
* Close the Writer. Resources will be released regardless of the exceptions
* being thrown. Future close calls will have no effect.
*
* The underlying FSDataOutputStream is not closed.
*/
@Override
public void close() throws IOException {
if ((state == State.CLOSED)) {
return;
}
try {
// First try the normal finish.
// Terminate upon the first Exception.
if (errorCount == 0) {
if (state != State.READY) {
throw new IllegalStateException(
"Cannot close TFile in the middle of key-value insertion.");
}
finishDataBlock(true);
// first, write out data:TFile.meta
BlockAppender outMeta =
writerBCF
.prepareMetaBlock(TFileMeta.BLOCK_NAME, COMPRESSION_NONE);
try {
tfileMeta.write(outMeta);
} finally {
outMeta.close();
}
// second, write out data:TFile.index
BlockAppender outIndex =
writerBCF.prepareMetaBlock(TFileIndex.BLOCK_NAME);
try {
tfileIndex.write(outIndex);
} finally {
outIndex.close();
}
writerBCF.close();
}
} finally {
IOUtils.cleanupWithLogger(LOG, blkAppender, writerBCF);
blkAppender = null;
writerBCF = null;
state = State.CLOSED;
}
}
/**
* Adding a new key-value pair to the TFile. This is synonymous to
* append(key, 0, key.length, value, 0, value.length)
*
* @param key
* Buffer for key.
* @param value
* Buffer for value.
* @throws IOException
*/
public void append(byte[] key, byte[] value) throws IOException {
append(key, 0, key.length, value, 0, value.length);
}
/**
* Adding a new key-value pair to TFile.
*
* @param key
* buffer for key.
* @param koff
* offset in key buffer.
* @param klen
* length of key.
* @param value
* buffer for value.
* @param voff
* offset in value buffer.
* @param vlen
* length of value.
* @throws IOException
* Upon IO errors.
*
* If an exception is thrown, the TFile will be in an inconsistent
* state. The only legitimate call after that would be close
*/
public void append(byte[] key, int koff, int klen, byte[] value, int voff,
int vlen) throws IOException {
if ((koff | klen | (koff + klen) | (key.length - (koff + klen))) < 0) {
throw new IndexOutOfBoundsException(
"Bad key buffer offset-length combination.");
}
if ((voff | vlen | (voff + vlen) | (value.length - (voff + vlen))) < 0) {
throw new IndexOutOfBoundsException(
"Bad value buffer offset-length combination.");
}
try {
DataOutputStream dosKey = prepareAppendKey(klen);
try {
++errorCount;
dosKey.write(key, koff, klen);
--errorCount;
} finally {
dosKey.close();
}
DataOutputStream dosValue = prepareAppendValue(vlen);
try {
++errorCount;
dosValue.write(value, voff, vlen);
--errorCount;
} finally {
dosValue.close();
}
} finally {
state = State.READY;
}
}
/**
* Helper class to register key after close call on key append stream.
*/
private class KeyRegister extends DataOutputStream {
private final int expectedLength;
private boolean closed = false;
public KeyRegister(int len) {
super(currentKeyBufferOS);
if (len >= 0) {
currentKeyBufferOS.reset(len);
} else {
currentKeyBufferOS.reset();
}
expectedLength = len;
}
@Override
public void close() throws IOException {
if (closed == true) {
return;
}
try {
++errorCount;
byte[] key = currentKeyBufferOS.getBuffer();
int len = currentKeyBufferOS.size();
/**
* verify length.
*/
if (expectedLength >= 0 && expectedLength != len) {
throw new IOException("Incorrect key length: expected="
+ expectedLength + " actual=" + len);
}
Utils.writeVInt(blkAppender, len);
blkAppender.write(key, 0, len);
if (tfileIndex.getFirstKey() == null) {
tfileIndex.setFirstKey(key, 0, len);
}
if (tfileMeta.isSorted() && tfileMeta.getRecordCount()>0) {
byte[] lastKey = lastKeyBufferOS.getBuffer();
int lastLen = lastKeyBufferOS.size();
if (tfileMeta.getComparator().compare(key, 0, len, lastKey, 0,
lastLen) < 0) {
throw new IOException("Keys are not added in sorted order");
}
}
BoundedByteArrayOutputStream tmp = currentKeyBufferOS;
currentKeyBufferOS = lastKeyBufferOS;
lastKeyBufferOS = tmp;
--errorCount;
} finally {
closed = true;
state = State.END_KEY;
}
}
}
/**
* Helper class to register value after close call on value append stream.
*/
private class ValueRegister extends DataOutputStream {
private boolean closed = false;
public ValueRegister(OutputStream os) {
super(os);
}
// Avoiding flushing call to down stream.
@Override
public void flush() {
// do nothing
}
@Override
public void close() throws IOException {
if (closed == true) {
return;
}
try {
++errorCount;
super.close();
blkRecordCount++;
// bump up the total record count in the whole file
tfileMeta.incRecordCount();
finishDataBlock(false);
--errorCount;
} finally {
closed = true;
state = State.READY;
}
}
}
/**
* Obtain an output stream for writing a key into TFile. This may only be
* called when there is no active Key appending stream or value appending
* stream.
*
* @param length
* The expected length of the key. If length of the key is not
* known, set length = -1. Otherwise, the application must write
* exactly as many bytes as specified here before calling close on
* the returned output stream.
* @return The key appending output stream.
* @throws IOException
*
*/
public DataOutputStream prepareAppendKey(int length) throws IOException {
if (state != State.READY) {
throw new IllegalStateException("Incorrect state to start a new key: "
+ state.name());
}
initDataBlock();
DataOutputStream ret = new KeyRegister(length);
state = State.IN_KEY;
return ret;
}
/**
* Obtain an output stream for writing a value into TFile. This may only be
* called right after a key appending operation (the key append stream must
* be closed).
*
* @param length
* The expected length of the value. If length of the value is not
* known, set length = -1. Otherwise, the application must write
* exactly as many bytes as specified here before calling close on
* the returned output stream. Advertising the value size up-front
* guarantees that the value is encoded in one chunk, and avoids
* intermediate chunk buffering.
* @throws IOException
*
*/
public DataOutputStream prepareAppendValue(int length) throws IOException {
if (state != State.END_KEY) {
throw new IllegalStateException(
"Incorrect state to start a new value: " + state.name());
}
DataOutputStream ret;
// unknown length
if (length < 0) {
if (valueBuffer == null) {
valueBuffer = new byte[getChunkBufferSize(conf)];
}
ret = new ValueRegister(new ChunkEncoder(blkAppender, valueBuffer));
} else {
ret =
new ValueRegister(new Chunk.SingleChunkEncoder(blkAppender, length));
}
state = State.IN_VALUE;
return ret;
}
/**
* Obtain an output stream for creating a meta block. This function may not
* be called when there is a key append stream or value append stream
* active. No more key-value insertion is allowed after a meta data block
* has been added to TFile.
*
* @param name
* Name of the meta block.
* @param compressName
* Name of the compression algorithm to be used. Must be one of the
* strings returned by
* {@link TFile#getSupportedCompressionAlgorithms()}.
* @return A DataOutputStream that can be used to write Meta Block data.
* Closing the stream would signal the ending of the block.
* @throws IOException
* @throws MetaBlockAlreadyExists
* the Meta Block with the same name already exists.
*/
public DataOutputStream prepareMetaBlock(String name, String compressName)
throws IOException, MetaBlockAlreadyExists {
if (state != State.READY) {
throw new IllegalStateException(
"Incorrect state to start a Meta Block: " + state.name());
}
finishDataBlock(true);
DataOutputStream outputStream =
writerBCF.prepareMetaBlock(name, compressName);
return outputStream;
}
/**
* Obtain an output stream for creating a meta block. This function may not
* be called when there is a key append stream or value append stream
* active. No more key-value insertion is allowed after a meta data block
* has been added to TFile. Data will be compressed using the default
* compressor as defined in Writer's constructor.
*
* @param name
* Name of the meta block.
* @return A DataOutputStream that can be used to write Meta Block data.
* Closing the stream would signal the ending of the block.
* @throws IOException
* @throws MetaBlockAlreadyExists
* the Meta Block with the same name already exists.
*/
public DataOutputStream prepareMetaBlock(String name) throws IOException,
MetaBlockAlreadyExists {
if (state != State.READY) {
throw new IllegalStateException(
"Incorrect state to start a Meta Block: " + state.name());
}
finishDataBlock(true);
return writerBCF.prepareMetaBlock(name);
}
/**
* Check if we need to start a new data block.
*
* @throws IOException
*/
private void initDataBlock() throws IOException {
// for each new block, get a new appender
if (blkAppender == null) {
blkAppender = writerBCF.prepareDataBlock();
}
}
/**
* Close the current data block if necessary.
*
* @param bForceFinish
* Force the closure regardless of the block size.
* @throws IOException
*/
void finishDataBlock(boolean bForceFinish) throws IOException {
if (blkAppender == null) {
return;
}
// exceeded the size limit, do the compression and finish the block
if (bForceFinish || blkAppender.getCompressedSize() >= sizeMinBlock) {
// keep tracks of the last key of each data block, no padding
// for now
TFileIndexEntry keyLast =
new TFileIndexEntry(lastKeyBufferOS.getBuffer(), 0, lastKeyBufferOS
.size(), blkRecordCount);
tfileIndex.addEntry(keyLast);
// close the appender
blkAppender.close();
blkAppender = null;
blkRecordCount = 0;
}
}
}
/**
* TFile Reader. Users may only read TFiles by creating TFile.Reader.Scanner.
* objects. A scanner may scan the whole TFile ({@link Reader#createScanner()}
* ) , a portion of TFile based on byte offsets (
* {@link Reader#createScannerByByteRange(long, long)}), or a portion of TFile with keys
* fall in a certain key range (for sorted TFile only,
* {@link Reader#createScannerByKey(byte[], byte[])} or
* {@link Reader#createScannerByKey(RawComparable, RawComparable)}).
*/
@InterfaceStability.Evolving
public static class Reader implements Closeable {
// The underlying BCFile reader.
final BCFile.Reader readerBCF;
// TFile index, it is loaded lazily.
TFileIndex tfileIndex = null;
final TFileMeta tfileMeta;
final BytesComparator comparator;
// global begin and end locations.
private final Location begin;
private final Location end;
/**
* Location representing a virtual position in the TFile.
*/
static final class Location implements Comparable, Cloneable {
private int blockIndex;
// distance/offset from the beginning of the block
private long recordIndex;
Location(int blockIndex, long recordIndex) {
set(blockIndex, recordIndex);
}
void incRecordIndex() {
++recordIndex;
}
Location(Location other) {
set(other);
}
int getBlockIndex() {
return blockIndex;
}
long getRecordIndex() {
return recordIndex;
}
void set(int blockIndex, long recordIndex) {
if ((blockIndex | recordIndex) < 0) {
throw new IllegalArgumentException(
"Illegal parameter for BlockLocation.");
}
this.blockIndex = blockIndex;
this.recordIndex = recordIndex;
}
void set(Location other) {
set(other.blockIndex, other.recordIndex);
}
/**
* @see java.lang.Comparable#compareTo(java.lang.Object)
*/
@Override
public int compareTo(Location other) {
return compareTo(other.blockIndex, other.recordIndex);
}
int compareTo(int bid, long rid) {
if (this.blockIndex == bid) {
long ret = this.recordIndex - rid;
if (ret > 0) return 1;
if (ret < 0) return -1;
return 0;
}
return this.blockIndex - bid;
}
/**
* @see java.lang.Object#clone()
*/
@Override
protected Location clone() {
return new Location(blockIndex, recordIndex);
}
/**
* @see java.lang.Object#hashCode()
*/
@Override
public int hashCode() {
final int prime = 31;
int result = prime + blockIndex;
result = (int) (prime * result + recordIndex);
return result;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
Location other = (Location) obj;
if (blockIndex != other.blockIndex) return false;
if (recordIndex != other.recordIndex) return false;
return true;
}
}
/**
* Constructor
*
* @param fsdis
* FS input stream of the TFile.
* @param fileLength
* The length of TFile. This is required because we have no easy
* way of knowing the actual size of the input file through the
* File input stream.
* @param conf
* @throws IOException
*/
public Reader(FSDataInputStream fsdis, long fileLength, Configuration conf)
throws IOException {
readerBCF = new BCFile.Reader(fsdis, fileLength, conf);
// first, read TFile meta
BlockReader brMeta = readerBCF.getMetaBlock(TFileMeta.BLOCK_NAME);
try {
tfileMeta = new TFileMeta(brMeta);
} finally {
brMeta.close();
}
comparator = tfileMeta.getComparator();
// Set begin and end locations.
begin = new Location(0, 0);
end = new Location(readerBCF.getBlockCount(), 0);
}
/**
* Close the reader. The state of the Reader object is undefined after
* close. Calling close() for multiple times has no effect.
*/
@Override
public void close() throws IOException {
readerBCF.close();
}
/**
* Get the begin location of the TFile.
*
* @return If TFile is not empty, the location of the first key-value pair.
* Otherwise, it returns end().
*/
Location begin() {
return begin;
}
/**
* Get the end location of the TFile.
*
* @return The location right after the last key-value pair in TFile.
*/
Location end() {
return end;
}
/**
* Get the string representation of the comparator.
*
* @return If the TFile is not sorted by keys, an empty string will be
* returned. Otherwise, the actual comparator string that is
* provided during the TFile creation time will be returned.
*/
public String getComparatorName() {
return tfileMeta.getComparatorString();
}
/**
* Is the TFile sorted?
*
* @return true if TFile is sorted.
*/
public boolean isSorted() {
return tfileMeta.isSorted();
}
/**
* Get the number of key-value pair entries in TFile.
*
* @return the number of key-value pairs in TFile
*/
public long getEntryCount() {
return tfileMeta.getRecordCount();
}
/**
* Lazily loading the TFile index.
*
* @throws IOException
*/
synchronized void checkTFileDataIndex() throws IOException {
if (tfileIndex == null) {
BlockReader brIndex = readerBCF.getMetaBlock(TFileIndex.BLOCK_NAME);
try {
tfileIndex =
new TFileIndex(readerBCF.getBlockCount(), brIndex, tfileMeta
.getComparator());
} finally {
brIndex.close();
}
}
}
/**
* Get the first key in the TFile.
*
* @return The first key in the TFile.
* @throws IOException
*/
public RawComparable getFirstKey() throws IOException {
checkTFileDataIndex();
return tfileIndex.getFirstKey();
}
/**
* Get the last key in the TFile.
*
* @return The last key in the TFile.
* @throws IOException
*/
public RawComparable getLastKey() throws IOException {
checkTFileDataIndex();
return tfileIndex.getLastKey();
}
/**
* Get a Comparator object to compare Entries. It is useful when you want
* stores the entries in a collection (such as PriorityQueue) and perform
* sorting or comparison among entries based on the keys without copying out
* the key.
*
* @return An Entry Comparator..
*/
public Comparator getEntryComparator() {
if (!isSorted()) {
throw new RuntimeException(
"Entries are not comparable for unsorted TFiles");
}
return new Comparator() {
/**
* Provide a customized comparator for Entries. This is useful if we
* have a collection of Entry objects. However, if the Entry objects
* come from different TFiles, users must ensure that those TFiles share
* the same RawComparator.
*/
@Override
public int compare(Scanner.Entry o1, Scanner.Entry o2) {
return comparator.compare(o1.getKeyBuffer(), 0, o1.getKeyLength(), o2
.getKeyBuffer(), 0, o2.getKeyLength());
}
};
}
/**
* Get an instance of the RawComparator that is constructed based on the
* string comparator representation.
*
* @return a Comparator that can compare RawComparable's.
*/
public Comparator getComparator() {
return comparator;
}
/**
* Stream access to a meta block.``
*
* @param name
* The name of the meta block.
* @return The input stream.
* @throws IOException
* on I/O error.
* @throws MetaBlockDoesNotExist
* If the meta block with the name does not exist.
*/
public DataInputStream getMetaBlock(String name) throws IOException,
MetaBlockDoesNotExist {
return readerBCF.getMetaBlock(name);
}
/**
* if greater is true then returns the beginning location of the block
* containing the key strictly greater than input key. if greater is false
* then returns the beginning location of the block greater than equal to
* the input key
*
* @param key
* the input key
* @param greater
* boolean flag
* @return
* @throws IOException
*/
Location getBlockContainsKey(RawComparable key, boolean greater)
throws IOException {
if (!isSorted()) {
throw new RuntimeException("Seeking in unsorted TFile");
}
checkTFileDataIndex();
int blkIndex =
(greater) ? tfileIndex.upperBound(key) : tfileIndex.lowerBound(key);
if (blkIndex < 0) return end;
return new Location(blkIndex, 0);
}
Location getLocationByRecordNum(long recNum) throws IOException {
checkTFileDataIndex();
return tfileIndex.getLocationByRecordNum(recNum);
}
long getRecordNumByLocation(Location location) throws IOException {
checkTFileDataIndex();
return tfileIndex.getRecordNumByLocation(location);
}
int compareKeys(byte[] a, int o1, int l1, byte[] b, int o2, int l2) {
if (!isSorted()) {
throw new RuntimeException("Cannot compare keys for unsorted TFiles.");
}
return comparator.compare(a, o1, l1, b, o2, l2);
}
int compareKeys(RawComparable a, RawComparable b) {
if (!isSorted()) {
throw new RuntimeException("Cannot compare keys for unsorted TFiles.");
}
return comparator.compare(a, b);
}
/**
* Get the location pointing to the beginning of the first key-value pair in
* a compressed block whose byte offset in the TFile is greater than or
* equal to the specified offset.
*
* @param offset
* the user supplied offset.
* @return the location to the corresponding entry; or end() if no such
* entry exists.
*/
Location getLocationNear(long offset) {
int blockIndex = readerBCF.getBlockIndexNear(offset);
if (blockIndex == -1) return end;
return new Location(blockIndex, 0);
}
/**
* Get the RecordNum for the first key-value pair in a compressed block
* whose byte offset in the TFile is greater than or equal to the specified
* offset.
*
* @param offset
* the user supplied offset.
* @return the RecordNum to the corresponding entry. If no such entry
* exists, it returns the total entry count.
* @throws IOException
*/
public long getRecordNumNear(long offset) throws IOException {
return getRecordNumByLocation(getLocationNear(offset));
}
/**
* Get a sample key that is within a block whose starting offset is greater
* than or equal to the specified offset.
*
* @param offset
* The file offset.
* @return the key that fits the requirement; or null if no such key exists
* (which could happen if the offset is close to the end of the
* TFile).
* @throws IOException
*/
public RawComparable getKeyNear(long offset) throws IOException {
int blockIndex = readerBCF.getBlockIndexNear(offset);
if (blockIndex == -1) return null;
checkTFileDataIndex();
return new ByteArray(tfileIndex.getEntry(blockIndex).key);
}
/**
* Get a scanner than can scan the whole TFile.
*
* @return The scanner object. A valid Scanner is always returned even if
* the TFile is empty.
* @throws IOException
*/
public Scanner createScanner() throws IOException {
return new Scanner(this, begin, end);
}
/**
* Get a scanner that covers a portion of TFile based on byte offsets.
*
* @param offset
* The beginning byte offset in the TFile.
* @param length
* The length of the region.
* @return The actual coverage of the returned scanner tries to match the
* specified byte-region but always round up to the compression
* block boundaries. It is possible that the returned scanner
* contains zero key-value pairs even if length is positive.
* @throws IOException
*/
public Scanner createScannerByByteRange(long offset, long length) throws IOException {
return new Scanner(this, offset, offset + length);
}
/**
* Get a scanner that covers a portion of TFile based on keys.
*
* @param beginKey
* Begin key of the scan (inclusive). If null, scan from the first
* key-value entry of the TFile.
* @param endKey
* End key of the scan (exclusive). If null, scan up to the last
* key-value entry of the TFile.
* @return The actual coverage of the returned scanner will cover all keys
* greater than or equal to the beginKey and less than the endKey.
* @throws IOException
*
* @deprecated Use {@link #createScannerByKey(byte[], byte[])} instead.
*/
@Deprecated
public Scanner createScanner(byte[] beginKey, byte[] endKey)
throws IOException {
return createScannerByKey(beginKey, endKey);
}
/**
* Get a scanner that covers a portion of TFile based on keys.
*
* @param beginKey
* Begin key of the scan (inclusive). If null, scan from the first
* key-value entry of the TFile.
* @param endKey
* End key of the scan (exclusive). If null, scan up to the last
* key-value entry of the TFile.
* @return The actual coverage of the returned scanner will cover all keys
* greater than or equal to the beginKey and less than the endKey.
* @throws IOException
*/
public Scanner createScannerByKey(byte[] beginKey, byte[] endKey)
throws IOException {
return createScannerByKey((beginKey == null) ? null : new ByteArray(beginKey,
0, beginKey.length), (endKey == null) ? null : new ByteArray(endKey,
0, endKey.length));
}
/**
* Get a scanner that covers a specific key range.
*
* @param beginKey
* Begin key of the scan (inclusive). If null, scan from the first
* key-value entry of the TFile.
* @param endKey
* End key of the scan (exclusive). If null, scan up to the last
* key-value entry of the TFile.
* @return The actual coverage of the returned scanner will cover all keys
* greater than or equal to the beginKey and less than the endKey.
* @throws IOException
*
* @deprecated Use {@link #createScannerByKey(RawComparable, RawComparable)}
* instead.
*/
@Deprecated
public Scanner createScanner(RawComparable beginKey, RawComparable endKey)
throws IOException {
return createScannerByKey(beginKey, endKey);
}
/**
* Get a scanner that covers a specific key range.
*
* @param beginKey
* Begin key of the scan (inclusive). If null, scan from the first
* key-value entry of the TFile.
* @param endKey
* End key of the scan (exclusive). If null, scan up to the last
* key-value entry of the TFile.
* @return The actual coverage of the returned scanner will cover all keys
* greater than or equal to the beginKey and less than the endKey.
* @throws IOException
*/
public Scanner createScannerByKey(RawComparable beginKey, RawComparable endKey)
throws IOException {
if ((beginKey != null) && (endKey != null)
&& (compareKeys(beginKey, endKey) >= 0)) {
return new Scanner(this, beginKey, beginKey);
}
return new Scanner(this, beginKey, endKey);
}
/**
* Create a scanner that covers a range of records.
*
* @param beginRecNum
* The RecordNum for the first record (inclusive).
* @param endRecNum
* The RecordNum for the last record (exclusive). To scan the whole
* file, either specify endRecNum==-1 or endRecNum==getEntryCount().
* @return The TFile scanner that covers the specified range of records.
* @throws IOException
*/
public Scanner createScannerByRecordNum(long beginRecNum, long endRecNum)
throws IOException {
if (beginRecNum < 0) beginRecNum = 0;
if (endRecNum < 0 || endRecNum > getEntryCount()) {
endRecNum = getEntryCount();
}
return new Scanner(this, getLocationByRecordNum(beginRecNum),
getLocationByRecordNum(endRecNum));
}
/**
* The TFile Scanner. The Scanner has an implicit cursor, which, upon
* creation, points to the first key-value pair in the scan range. If the
* scan range is empty, the cursor will point to the end of the scan range.
*
* Use {@link Scanner#atEnd()} to test whether the cursor is at the end
* location of the scanner.
*
* Use {@link Scanner#advance()} to move the cursor to the next key-value
* pair (or end if none exists). Use seekTo methods (
* {@link Scanner#seekTo(byte[])} or
* {@link Scanner#seekTo(byte[], int, int)}) to seek to any arbitrary
* location in the covered range (including backward seeking). Use
* {@link Scanner#rewind()} to seek back to the beginning of the scanner.
* Use {@link Scanner#seekToEnd()} to seek to the end of the scanner.
*
* Actual keys and values may be obtained through {@link Scanner.Entry}
* object, which is obtained through {@link Scanner#entry()}.
*/
public static class Scanner implements Closeable {
// The underlying TFile reader.
final Reader reader;
// current block (null if reaching end)
private BlockReader blkReader;
Location beginLocation;
Location endLocation;
Location currentLocation;
// flag to ensure value is only examined once.
boolean valueChecked = false;
// reusable buffer for keys.
final byte[] keyBuffer;
// length of key, -1 means key is invalid.
int klen = -1;
static final int MAX_VAL_TRANSFER_BUF_SIZE = 128 * 1024;
BytesWritable valTransferBuffer;
DataInputBuffer keyDataInputStream;
ChunkDecoder valueBufferInputStream;
DataInputStream valueDataInputStream;
// vlen == -1 if unknown.
int vlen;
/**
* Constructor
*
* @param reader
* The TFile reader object.
* @param offBegin
* Begin byte-offset of the scan.
* @param offEnd
* End byte-offset of the scan.
* @throws IOException
*
* The offsets will be rounded to the beginning of a compressed
* block whose offset is greater than or equal to the specified
* offset.
*/
protected Scanner(Reader reader, long offBegin, long offEnd)
throws IOException {
this(reader, reader.getLocationNear(offBegin), reader
.getLocationNear(offEnd));
}
/**
* Constructor
*
* @param reader
* The TFile reader object.
* @param begin
* Begin location of the scan.
* @param end
* End location of the scan.
* @throws IOException
*/
Scanner(Reader reader, Location begin, Location end) throws IOException {
this.reader = reader;
// ensure the TFile index is loaded throughout the life of scanner.
reader.checkTFileDataIndex();
beginLocation = begin;
endLocation = end;
valTransferBuffer = new BytesWritable();
// TODO: remember the longest key in a TFile, and use it to replace
// MAX_KEY_SIZE.
keyBuffer = new byte[MAX_KEY_SIZE];
keyDataInputStream = new DataInputBuffer();
valueBufferInputStream = new ChunkDecoder();
valueDataInputStream = new DataInputStream(valueBufferInputStream);
if (beginLocation.compareTo(endLocation) >= 0) {
currentLocation = new Location(endLocation);
} else {
currentLocation = new Location(0, 0);
initBlock(beginLocation.getBlockIndex());
inBlockAdvance(beginLocation.getRecordIndex());
}
}
/**
* Constructor
*
* @param reader
* The TFile reader object.
* @param beginKey
* Begin key of the scan. If null, scan from the first
* entry of the TFile.
* @param endKey
* End key of the scan. If null, scan up to the last entry
* of the TFile.
* @throws IOException
*/
protected Scanner(Reader reader, RawComparable beginKey,
RawComparable endKey) throws IOException {
this(reader, (beginKey == null) ? reader.begin() : reader
.getBlockContainsKey(beginKey, false), reader.end());
if (beginKey != null) {
inBlockAdvance(beginKey, false);
beginLocation.set(currentLocation);
}
if (endKey != null) {
seekTo(endKey, false);
endLocation.set(currentLocation);
seekTo(beginLocation);
}
}
/**
* Move the cursor to the first entry whose key is greater than or equal
* to the input key. Synonymous to seekTo(key, 0, key.length). The entry
* returned by the previous entry() call will be invalid.
*
* @param key
* The input key
* @return true if we find an equal key.
* @throws IOException
*/
public boolean seekTo(byte[] key) throws IOException {
return seekTo(key, 0, key.length);
}
/**
* Move the cursor to the first entry whose key is greater than or equal
* to the input key. The entry returned by the previous entry() call will
* be invalid.
*
* @param key
* The input key
* @param keyOffset
* offset in the key buffer.
* @param keyLen
* key buffer length.
* @return true if we find an equal key; false otherwise.
* @throws IOException
*/
public boolean seekTo(byte[] key, int keyOffset, int keyLen)
throws IOException {
return seekTo(new ByteArray(key, keyOffset, keyLen), false);
}
private boolean seekTo(RawComparable key, boolean beyond)
throws IOException {
Location l = reader.getBlockContainsKey(key, beyond);
if (l.compareTo(beginLocation) < 0) {
l = beginLocation;
} else if (l.compareTo(endLocation) >= 0) {
seekTo(endLocation);
return false;
}
// check if what we are seeking is in the later part of the current
// block.
if (atEnd() || (l.getBlockIndex() != currentLocation.getBlockIndex())
|| (compareCursorKeyTo(key) >= 0)) {
// sorry, we must seek to a different location first.
seekTo(l);
}
return inBlockAdvance(key, beyond);
}
/**
* Move the cursor to the new location. The entry returned by the previous
* entry() call will be invalid.
*
* @param l
* new cursor location. It must fall between the begin and end
* location of the scanner.
* @throws IOException
*/
private void seekTo(Location l) throws IOException {
if (l.compareTo(beginLocation) < 0) {
throw new IllegalArgumentException(
"Attempt to seek before the begin location.");
}
if (l.compareTo(endLocation) > 0) {
throw new IllegalArgumentException(
"Attempt to seek after the end location.");
}
if (l.compareTo(endLocation) == 0) {
parkCursorAtEnd();
return;
}
if (l.getBlockIndex() != currentLocation.getBlockIndex()) {
// going to a totally different block
initBlock(l.getBlockIndex());
} else {
if (valueChecked) {
// may temporarily go beyond the last record in the block (in which
// case the next if loop will always be true).
inBlockAdvance(1);
}
if (l.getRecordIndex() < currentLocation.getRecordIndex()) {
initBlock(l.getBlockIndex());
}
}
inBlockAdvance(l.getRecordIndex() - currentLocation.getRecordIndex());
return;
}
/**
* Rewind to the first entry in the scanner. The entry returned by the
* previous entry() call will be invalid.
*
* @throws IOException
*/
public void rewind() throws IOException {
seekTo(beginLocation);
}
/**
* Seek to the end of the scanner. The entry returned by the previous
* entry() call will be invalid.
*
* @throws IOException
*/
public void seekToEnd() throws IOException {
parkCursorAtEnd();
}
/**
* Move the cursor to the first entry whose key is greater than or equal
* to the input key. Synonymous to lowerBound(key, 0, key.length). The
* entry returned by the previous entry() call will be invalid.
*
* @param key
* The input key
* @throws IOException
*/
public void lowerBound(byte[] key) throws IOException {
lowerBound(key, 0, key.length);
}
/**
* Move the cursor to the first entry whose key is greater than or equal
* to the input key. The entry returned by the previous entry() call will
* be invalid.
*
* @param key
* The input key
* @param keyOffset
* offset in the key buffer.
* @param keyLen
* key buffer length.
* @throws IOException
*/
public void lowerBound(byte[] key, int keyOffset, int keyLen)
throws IOException {
seekTo(new ByteArray(key, keyOffset, keyLen), false);
}
/**
* Move the cursor to the first entry whose key is strictly greater than
* the input key. Synonymous to upperBound(key, 0, key.length). The entry
* returned by the previous entry() call will be invalid.
*
* @param key
* The input key
* @throws IOException
*/
public void upperBound(byte[] key) throws IOException {
upperBound(key, 0, key.length);
}
/**
* Move the cursor to the first entry whose key is strictly greater than
* the input key. The entry returned by the previous entry() call will be
* invalid.
*
* @param key
* The input key
* @param keyOffset
* offset in the key buffer.
* @param keyLen
* key buffer length.
* @throws IOException
*/
public void upperBound(byte[] key, int keyOffset, int keyLen)
throws IOException {
seekTo(new ByteArray(key, keyOffset, keyLen), true);
}
/**
* Move the cursor to the next key-value pair. The entry returned by the
* previous entry() call will be invalid.
*
* @return true if the cursor successfully moves. False when cursor is
* already at the end location and cannot be advanced.
* @throws IOException
*/
public boolean advance() throws IOException {
if (atEnd()) {
return false;
}
int curBid = currentLocation.getBlockIndex();
long curRid = currentLocation.getRecordIndex();
long entriesInBlock = reader.getBlockEntryCount(curBid);
if (curRid + 1 >= entriesInBlock) {
if (endLocation.compareTo(curBid + 1, 0) <= 0) {
// last entry in TFile.
parkCursorAtEnd();
} else {
// last entry in Block.
initBlock(curBid + 1);
}
} else {
inBlockAdvance(1);
}
return true;
}
/**
* Load a compressed block for reading. Expecting blockIndex is valid.
*
* @throws IOException
*/
private void initBlock(int blockIndex) throws IOException {
klen = -1;
if (blkReader != null) {
try {
blkReader.close();
} finally {
blkReader = null;
}
}
blkReader = reader.getBlockReader(blockIndex);
currentLocation.set(blockIndex, 0);
}
private void parkCursorAtEnd() throws IOException {
klen = -1;
currentLocation.set(endLocation);
if (blkReader != null) {
try {
blkReader.close();
} finally {
blkReader = null;
}
}
}
/**
* Close the scanner. Release all resources. The behavior of using the
* scanner after calling close is not defined. The entry returned by the
* previous entry() call will be invalid.
*/
@Override
public void close() throws IOException {
parkCursorAtEnd();
}
/**
* Is cursor at the end location?
*
* @return true if the cursor is at the end location.
*/
public boolean atEnd() {
return (currentLocation.compareTo(endLocation) >= 0);
}
/**
* check whether we have already successfully obtained the key. It also
* initializes the valueInputStream.
*/
void checkKey() throws IOException {
if (klen >= 0) return;
if (atEnd()) {
throw new EOFException("No key-value to read");
}
klen = -1;
vlen = -1;
valueChecked = false;
klen = Utils.readVInt(blkReader);
blkReader.readFully(keyBuffer, 0, klen);
valueBufferInputStream.reset(blkReader);
if (valueBufferInputStream.isLastChunk()) {
vlen = valueBufferInputStream.getRemain();
}
}
/**
* Get an entry to access the key and value.
*
* @return The Entry object to access the key and value.
* @throws IOException
*/
public Entry entry() throws IOException {
checkKey();
return new Entry();
}
/**
* Get the RecordNum corresponding to the entry pointed by the cursor.
* @return The RecordNum corresponding to the entry pointed by the cursor.
* @throws IOException
*/
public long getRecordNum() throws IOException {
return reader.getRecordNumByLocation(currentLocation);
}
/**
* Internal API. Comparing the key at cursor to user-specified key.
*
* @param other
* user-specified key.
* @return negative if key at cursor is smaller than user key; 0 if equal;
* and positive if key at cursor greater than user key.
* @throws IOException
*/
int compareCursorKeyTo(RawComparable other) throws IOException {
checkKey();
return reader.compareKeys(keyBuffer, 0, klen, other.buffer(), other
.offset(), other.size());
}
/**
* Entry to a <Key, Value> pair.
*/
public class Entry implements Comparable {
/**
* Get the length of the key.
*
* @return the length of the key.
*/
public int getKeyLength() {
return klen;
}
byte[] getKeyBuffer() {
return keyBuffer;
}
/**
* Copy the key and value in one shot into BytesWritables. This is
* equivalent to getKey(key); getValue(value);
*
* @param key
* BytesWritable to hold key.
* @param value
* BytesWritable to hold value
* @throws IOException
*/
public void get(BytesWritable key, BytesWritable value)
throws IOException {
getKey(key);
getValue(value);
}
/**
* Copy the key into BytesWritable. The input BytesWritable will be
* automatically resized to the actual key size.
*
* @param key
* BytesWritable to hold the key.
* @throws IOException
*/
public int getKey(BytesWritable key) throws IOException {
key.setSize(getKeyLength());
getKey(key.getBytes());
return key.getLength();
}
/**
* Copy the value into BytesWritable. The input BytesWritable will be
* automatically resized to the actual value size. The implementation
* directly uses the buffer inside BytesWritable for storing the value.
* The call does not require the value length to be known.
*
* @param value
* @throws IOException
*/
public long getValue(BytesWritable value) throws IOException {
DataInputStream dis = getValueStream();
int size = 0;
try {
int remain;
while ((remain = valueBufferInputStream.getRemain()) > 0) {
value.setSize(size + remain);
dis.readFully(value.getBytes(), size, remain);
size += remain;
}
return value.getLength();
} finally {
dis.close();
}
}
/**
* Writing the key to the output stream. This method avoids copying key
* buffer from Scanner into user buffer, then writing to the output
* stream.
*
* @param out
* The output stream
* @return the length of the key.
* @throws IOException
*/
public int writeKey(OutputStream out) throws IOException {
out.write(keyBuffer, 0, klen);
return klen;
}
/**
* Writing the value to the output stream. This method avoids copying
* value data from Scanner into user buffer, then writing to the output
* stream. It does not require the value length to be known.
*
* @param out
* The output stream
* @return the length of the value
* @throws IOException
*/
public long writeValue(OutputStream out) throws IOException {
DataInputStream dis = getValueStream();
long size = 0;
try {
int chunkSize;
while ((chunkSize = valueBufferInputStream.getRemain()) > 0) {
chunkSize = Math.min(chunkSize, MAX_VAL_TRANSFER_BUF_SIZE);
valTransferBuffer.setSize(chunkSize);
dis.readFully(valTransferBuffer.getBytes(), 0, chunkSize);
out.write(valTransferBuffer.getBytes(), 0, chunkSize);
size += chunkSize;
}
return size;
} finally {
dis.close();
}
}
/**
* Copy the key into user supplied buffer.
*
* @param buf
* The buffer supplied by user. The length of the buffer must
* not be shorter than the key length.
* @return The length of the key.
*
* @throws IOException
*/
public int getKey(byte[] buf) throws IOException {
return getKey(buf, 0);
}
/**
* Copy the key into user supplied buffer.
*
* @param buf
* The buffer supplied by user.
* @param offset
* The starting offset of the user buffer where we should copy
* the key into. Requiring the key-length + offset no greater
* than the buffer length.
* @return The length of the key.
* @throws IOException
*/
public int getKey(byte[] buf, int offset) throws IOException {
if ((offset | (buf.length - offset - klen)) < 0) {
throw new IndexOutOfBoundsException(
"Buffer not enough to store the key");
}
System.arraycopy(keyBuffer, 0, buf, offset, klen);
return klen;
}
/**
* Streaming access to the key. Useful for desrializing the key into
* user objects.
*
* @return The input stream.
*/
public DataInputStream getKeyStream() {
keyDataInputStream.reset(keyBuffer, klen);
return keyDataInputStream;
}
/**
* Get the length of the value. isValueLengthKnown() must be tested
* true.
*
* @return the length of the value.
*/
public int getValueLength() {
if (vlen >= 0) {
return vlen;
}
throw new RuntimeException("Value length unknown.");
}
/**
* Copy value into user-supplied buffer. User supplied buffer must be
* large enough to hold the whole value. The value part of the key-value
* pair pointed by the current cursor is not cached and can only be
* examined once. Calling any of the following functions more than once
* without moving the cursor will result in exception:
* {@link #getValue(byte[])}, {@link #getValue(byte[], int)},
* {@link #getValueStream}.
*
* @return the length of the value. Does not require
* isValueLengthKnown() to be true.
* @throws IOException
*
*/
public int getValue(byte[] buf) throws IOException {
return getValue(buf, 0);
}
/**
* Copy value into user-supplied buffer. User supplied buffer must be
* large enough to hold the whole value (starting from the offset). The
* value part of the key-value pair pointed by the current cursor is not
* cached and can only be examined once. Calling any of the following
* functions more than once without moving the cursor will result in
* exception: {@link #getValue(byte[])}, {@link #getValue(byte[], int)},
* {@link #getValueStream}.
*
* @return the length of the value. Does not require
* isValueLengthKnown() to be true.
* @throws IOException
*/
public int getValue(byte[] buf, int offset) throws IOException {
DataInputStream dis = getValueStream();
try {
if (isValueLengthKnown()) {
if ((offset | (buf.length - offset - vlen)) < 0) {
throw new IndexOutOfBoundsException(
"Buffer too small to hold value");
}
dis.readFully(buf, offset, vlen);
return vlen;
}
int nextOffset = offset;
while (nextOffset < buf.length) {
int n = dis.read(buf, nextOffset, buf.length - nextOffset);
if (n < 0) {
break;
}
nextOffset += n;
}
if (dis.read() >= 0) {
// attempt to read one more byte to determine whether we reached
// the
// end or not.
throw new IndexOutOfBoundsException(
"Buffer too small to hold value");
}
return nextOffset - offset;
} finally {
dis.close();
}
}
/**
* Stream access to value. The value part of the key-value pair pointed
* by the current cursor is not cached and can only be examined once.
* Calling any of the following functions more than once without moving
* the cursor will result in exception: {@link #getValue(byte[])},
* {@link #getValue(byte[], int)}, {@link #getValueStream}.
*
* @return The input stream for reading the value.
* @throws IOException
*/
public DataInputStream getValueStream() throws IOException {
if (valueChecked == true) {
throw new IllegalStateException(
"Attempt to examine value multiple times.");
}
valueChecked = true;
return valueDataInputStream;
}
/**
* Check whether it is safe to call getValueLength().
*
* @return true if value length is known before hand. Values less than
* the chunk size will always have their lengths known before
* hand. Values that are written out as a whole (with advertised
* length up-front) will always have their lengths known in
* read.
*/
public boolean isValueLengthKnown() {
return (vlen >= 0);
}
/**
* Compare the entry key to another key. Synonymous to compareTo(key, 0,
* key.length).
*
* @param buf
* The key buffer.
* @return comparison result between the entry key with the input key.
*/
public int compareTo(byte[] buf) {
return compareTo(buf, 0, buf.length);
}
/**
* Compare the entry key to another key. Synonymous to compareTo(new
* ByteArray(buf, offset, length)
*
* @param buf
* The key buffer
* @param offset
* offset into the key buffer.
* @param length
* the length of the key.
* @return comparison result between the entry key with the input key.
*/
public int compareTo(byte[] buf, int offset, int length) {
return compareTo(new ByteArray(buf, offset, length));
}
/**
* Compare an entry with a RawComparable object. This is useful when
* Entries are stored in a collection, and we want to compare a user
* supplied key.
*/
@Override
public int compareTo(RawComparable key) {
return reader.compareKeys(keyBuffer, 0, getKeyLength(), key.buffer(),
key.offset(), key.size());
}
/**
* Compare whether this and other points to the same key value.
*/
@Override
public boolean equals(Object other) {
if (this == other) return true;
if (!(other instanceof Entry)) return false;
return ((Entry) other).compareTo(keyBuffer, 0, getKeyLength()) == 0;
}
@Override
public int hashCode() {
return WritableComparator.hashBytes(keyBuffer, 0, getKeyLength());
}
}
/**
* Advance cursor by n positions within the block.
*
* @param n
* Number of key-value pairs to skip in block.
* @throws IOException
*/
private void inBlockAdvance(long n) throws IOException {
for (long i = 0; i < n; ++i) {
checkKey();
if (!valueBufferInputStream.isClosed()) {
valueBufferInputStream.close();
}
klen = -1;
currentLocation.incRecordIndex();
}
}
/**
* Advance cursor in block until we find a key that is greater than or
* equal to the input key.
*
* @param key
* Key to compare.
* @param greater
* advance until we find a key greater than the input key.
* @return true if we find a equal key.
* @throws IOException
*/
private boolean inBlockAdvance(RawComparable key, boolean greater)
throws IOException {
int curBid = currentLocation.getBlockIndex();
long entryInBlock = reader.getBlockEntryCount(curBid);
if (curBid == endLocation.getBlockIndex()) {
entryInBlock = endLocation.getRecordIndex();
}
while (currentLocation.getRecordIndex() < entryInBlock) {
int cmp = compareCursorKeyTo(key);
if (cmp > 0) return false;
if (cmp == 0 && !greater) return true;
if (!valueBufferInputStream.isClosed()) {
valueBufferInputStream.close();
}
klen = -1;
currentLocation.incRecordIndex();
}
throw new RuntimeException("Cannot find matching key in block.");
}
}
long getBlockEntryCount(int curBid) {
return tfileIndex.getEntry(curBid).entries();
}
BlockReader getBlockReader(int blockIndex) throws IOException {
return readerBCF.getDataBlock(blockIndex);
}
}
/**
* Data structure representing "TFile.meta" meta block.
*/
static final class TFileMeta {
final static String BLOCK_NAME = "TFile.meta";
final Version version;
private long recordCount;
private final String strComparator;
private final BytesComparator comparator;
// ctor for writes
public TFileMeta(String comparator) {
// set fileVersion to API version when we create it.
version = TFile.API_VERSION;
recordCount = 0;
strComparator = (comparator == null) ? "" : comparator;
this.comparator = makeComparator(strComparator);
}
// ctor for reads
public TFileMeta(DataInput in) throws IOException {
version = new Version(in);
if (!version.compatibleWith(TFile.API_VERSION)) {
throw new RuntimeException("Incompatible TFile fileVersion.");
}
recordCount = Utils.readVLong(in);
strComparator = Utils.readString(in);
comparator = makeComparator(strComparator);
}
@SuppressWarnings("unchecked")
static BytesComparator makeComparator(String comparator) {
if (comparator.length() == 0) {
// unsorted keys
return null;
}
if (comparator.equals(COMPARATOR_MEMCMP)) {
// default comparator
return new BytesComparator(new MemcmpRawComparator());
} else if (comparator.startsWith(COMPARATOR_JCLASS)) {
String compClassName =
comparator.substring(COMPARATOR_JCLASS.length()).trim();
try {
Class compClass = Class.forName(compClassName);
// use its default ctor to create an instance
return new BytesComparator((RawComparator