/*
* Licensed 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 com.facebook.presto.rcfile;
import com.facebook.presto.spi.type.CharType;
import com.facebook.presto.spi.type.Type;
import com.facebook.presto.spi.type.VarcharType;
import io.airlift.slice.Slice;
import io.airlift.slice.SliceInput;
import io.airlift.slice.SliceOutput;
import io.airlift.slice.Slices;
import java.io.IOException;
import static com.google.common.base.Preconditions.checkArgument;
import static io.airlift.slice.SizeOf.SIZE_OF_INT;
import static io.airlift.slice.SizeOf.SIZE_OF_LONG;
import static io.airlift.slice.SliceUtf8.offsetOfCodePoint;
import static java.lang.Math.min;
import static java.lang.Math.toIntExact;
import static java.util.Objects.requireNonNull;
// faster versions of org.apache.hadoop.io.WritableUtils methods adapted for Slice
public final class RcFileDecoderUtils
{
// 0xFFFF_FFFF + syncFirst(long) + syncSecond(long)
private static final int SYNC_SEQUENCE_LENGTH = SIZE_OF_INT + SIZE_OF_LONG + SIZE_OF_LONG;
private RcFileDecoderUtils()
{
}
public static int decodeVIntSize(Slice slice, int offset)
{
return decodeVIntSize(slice.getByte(offset));
}
public static int decodeVIntSize(byte value)
{
if (value >= -112) {
return 1;
}
if (value < -120) {
return -119 - value;
}
return -111 - value;
}
public static boolean isNegativeVInt(Slice slice, int offset)
{
return isNegativeVInt(slice.getByte(offset));
}
public static boolean isNegativeVInt(byte value)
{
return value < -120 || (value >= -112 && value < 0);
}
public static long readVInt(SliceInput in)
{
byte firstByte = in.readByte();
int length = decodeVIntSize(firstByte);
if (length == 1) {
return firstByte;
}
long value = 0;
for (int i = 1; i < length; i++) {
value <<= 8;
value |= (in.readByte() & 0xFF);
}
return isNegativeVInt(firstByte) ? ~value : value;
}
public static long readVInt(Slice slice, int start)
{
byte firstByte = slice.getByte(start);
int length = decodeVIntSize(firstByte);
if (length == 1) {
return firstByte;
}
return readVIntInternal(slice, start, length);
}
public static long readVInt(Slice slice, int start, int length)
{
if (length == 1) {
return slice.getByte(start);
}
return readVIntInternal(slice, start, length);
}
private static long readVIntInternal(Slice slice, int start, int length)
{
long value = 0;
for (int i = 1; i < length; i++) {
value <<= 8;
value |= (slice.getByte(start + i) & 0xFF);
}
return isNegativeVInt(slice.getByte(start)) ? ~value : value;
}
/**
* Find the beginning of the first full sync sequence that starts within the specified range.
*/
public static long findFirstSyncPosition(RcFileDataSource dataSource, long offset, long length, long syncFirst, long syncSecond)
throws IOException
{
requireNonNull(dataSource, "dataSource is null");
checkArgument(offset >= 0, "offset is negative");
checkArgument(length >= 1, "length must be at least 1");
checkArgument(offset + length <= dataSource.getSize(), "offset plus length is greater than data size");
// The full sync sequence is "0xFFFFFFFF syncFirst syncSecond". If
// this sequence begins the file range, the start position is returned
// even if the sequence finishes after length.
// NOTE: this decision must agree with RcFileReader.nextBlock
Slice sync = Slices.allocate(SIZE_OF_INT + SIZE_OF_LONG + SIZE_OF_LONG);
sync.setInt(0, 0xFFFF_FFFF);
sync.setLong(SIZE_OF_INT, syncFirst);
sync.setLong(SIZE_OF_INT + SIZE_OF_LONG, syncSecond);
// read 1 MB chunks at a time, but only skip ahead 1 MB - SYNC_SEQUENCE_LENGTH bytes
// this causes a re-read of SYNC_SEQUENCE_LENGTH bytes each time, but is much simpler code
byte[] buffer = new byte[toIntExact(min(1 << 20, length + (SYNC_SEQUENCE_LENGTH - 1)))];
Slice bufferSlice = Slices.wrappedBuffer(buffer);
for (long position = 0; position < length; position += bufferSlice.length() - (SYNC_SEQUENCE_LENGTH - 1)) {
// either fill the buffer entirely, or read enough to allow all bytes in offset + length to be a start sequence
int bufferSize = toIntExact(min(buffer.length, length + (SYNC_SEQUENCE_LENGTH - 1) - position));
// don't read off the end of the file
bufferSize = toIntExact(min(bufferSize, dataSource.getSize() - offset - position));
dataSource.readFully(offset + position, buffer, 0, bufferSize);
// find the starting index position of the sync sequence
int index = bufferSlice.indexOf(sync);
if (index >= 0) {
// If the starting position is before the end of the search region, return the
// absolute start position of the sequence.
if (position + index < length) {
long startOfSyncSequence = offset + position + index;
return startOfSyncSequence;
}
else {
// Otherwise, this is not a match for this region
// Note: this case isn't strictly needed as the loop will exit, but it is
// simpler to explicitly call it out.
return -1;
}
}
}
return -1;
}
public static void writeLengthPrefixedString(SliceOutput out, Slice slice)
{
writeVInt(out, slice.length());
out.writeBytes(slice);
}
public static void writeVInt(SliceOutput out, int value)
{
if (value >= -112 && value <= 127) {
out.writeByte(value);
return;
}
int length = -112;
if (value < 0) {
value ^= -1; // take one's complement'
length = -120;
}
int tmp = value;
while (tmp != 0) {
tmp = tmp >> 8;
length--;
}
out.writeByte(length);
length = (length < -120) ? -(length + 120) : -(length + 112);
for (int idx = length; idx != 0; idx--) {
int shiftBits = (idx - 1) * 8;
out.writeByte((value >> shiftBits) & 0xFF);
}
}
public static void writeVLong(SliceOutput out, long value)
{
if (value >= -112 && value <= 127) {
out.writeByte((byte) value);
return;
}
int length = -112;
if (value < 0) {
value ^= -1; // take one's complement'
length = -120;
}
long tmp = value;
while (tmp != 0) {
tmp = tmp >> 8;
length--;
}
out.writeByte(length);
length = (length < -120) ? -(length + 120) : -(length + 112);
for (int idx = length; idx != 0; idx--) {
int shiftBits = (idx - 1) * 8;
long mask = 0xFFL << shiftBits;
out.writeByte((byte) ((value & mask) >> shiftBits));
}
}
public static int calculateTruncationLength(Type type, Slice slice, int offset, int length)
{
requireNonNull(type, "type is null");
if (type instanceof VarcharType) {
return calculateTruncationLength(((VarcharType) type).getLength(), slice, offset, length);
}
if (type instanceof CharType) {
return calculateTruncationLength(((CharType) type).getLength(), slice, offset, length);
}
return length;
}
private static int calculateTruncationLength(int maxCharacterCount, Slice slice, int offset, int length)
{
requireNonNull(slice, "slice is null");
if (maxCharacterCount < 0) {
throw new IllegalArgumentException("Max length must be greater or equal than zero");
}
if (length <= maxCharacterCount) {
return length;
}
int indexEnd = offsetOfCodePoint(slice, offset, maxCharacterCount);
if (indexEnd < 0) {
return length;
}
return indexEnd - offset;
}
}