package FlexibleEncoding.ORC;
/**
* 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.
*/
import java.io.EOFException;
import java.io.IOException;
/**
* A reader that reads a sequence of integers.
* */
public class RunLengthIntegerReader implements IntegerReader {
private final InStream input;
private final boolean signed;
private final long[] literals =
new long[RunLengthIntegerWriter.MAX_LITERAL_SIZE];
private int numLiterals = 0;
private int delta = 0;
private int used = 0;
private boolean repeat = false;
public RunLengthIntegerReader(InStream input, boolean signed) throws IOException {
this.input = input;
this.signed = signed;
}
public void readValues() throws IOException {
int control = input.read();
if (control == -1) {
throw new EOFException("Read past end of RLE integer from " + input);
} else if (control < 0x80) {
numLiterals = control + RunLengthIntegerWriter.MIN_REPEAT_SIZE;
used = 0;
repeat = true;
delta = input.read();
if (delta == -1) {
throw new EOFException("End of stream in RLE Integer from " + input);
}
// convert from 0 to 255 to -128 to 127 by converting to a signed byte
delta = (byte) (0 + delta);
if (signed) {
literals[0] = SerializationUtils.readVslong(input);
} else {
literals[0] = SerializationUtils.readVulong(input);
}
} else {
repeat = false;
numLiterals = 0x100 - control;
used = 0;
for(int i=0; i < numLiterals; ++i) {
if (signed) {
literals[i] = SerializationUtils.readVslong(input);
} else {
literals[i] = SerializationUtils.readVulong(input);
}
}
}
}
@Override
public boolean hasNext() throws IOException {
return used != numLiterals || input.available() > 0;
}
@Override
public long next() throws IOException {
long result;
if (used == numLiterals) {
readValues();
}
if (repeat) {
result = literals[0] + (used++) * delta;
} else {
result = literals[used++];
}
return result;
}
@Override
public void seek(PositionProvider index) throws IOException {
input.seek(index);
int consumed = (int) index.getNext();
if (consumed != 0) {
// a loop is required for cases where we break the run into two parts
while (consumed > 0) {
readValues();
used = consumed;
consumed -= numLiterals;
}
} else {
used = 0;
numLiterals = 0;
}
}
@Override
public void skip(long numValues) throws IOException {
while (numValues > 0) {
if (used == numLiterals) {
readValues();
}
long consume = Math.min(numValues, numLiterals - used);
used += consume;
numValues -= consume;
}
}
}