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;
import FlexibleEncoding.ORC.RunLengthIntegerWriterV2.EncodingType;
//import ORC.RunLengthIntegerWriterV2.EncodingType;
/**
* A reader that reads a sequence of light weight compressed integers. Refer
* {@link RunLengthIntegerWriterV2} for description of various lightweight
* compression techniques.
*/
public class RunLengthIntegerReaderV2 implements IntegerReader {
private final InStream input;
private final boolean signed;
private final long[] literals = new long[RunLengthIntegerWriterV2.MAX_SCOPE];
private int numLiterals = 0;
private int used = 0;
public RunLengthIntegerReaderV2(InStream input, boolean signed) throws IOException {
this.input = input;
this.signed = signed;
}
public void readValues() throws IOException {
// read the first 2 bits and determine the encoding type
int firstByte = input.read();
if (firstByte < 0) {
throw new EOFException("Read past end of RLE integer from " + input);
} else {
int enc = (firstByte >>> 6) & 0x03;
if (EncodingType.SHORT_REPEAT.ordinal() == enc) {
readShortRepeatValues(firstByte);
} else if (EncodingType.DIRECT.ordinal() == enc) {
readDirectValues(firstByte);
} else if (EncodingType.PATCHED_BASE.ordinal() == enc) {
readPatchedBaseValues(firstByte);
} else {
readDeltaValues(firstByte);
}
}
}
public void readDeltaValues(int firstByte) throws IOException {
// extract the number of fixed bits
int fb = (firstByte >>> 1) & 0x1f;
if (fb != 0) {
fb = SerializationUtils.decodeBitWidth(fb);
}
// extract the blob run length
int len = (firstByte & 0x01) << 8;
len |= input.read();
// read the first value stored as vint
long firstVal = 0;
if (signed) {
firstVal = SerializationUtils.readVslong(input);
} else {
firstVal = SerializationUtils.readVulong(input);
}
// store first value to result buffer
long prevVal = firstVal;
literals[numLiterals++] = firstVal;
// if fixed bits is 0 then all values have fixed delta
if (fb == 0) {
// read the fixed delta value stored as vint (deltas can be negative even
// if all number are positive)
long fd = SerializationUtils.readVslong(input);
// add fixed deltas to adjacent values
for(int i = 0; i < len; i++) {
literals[numLiterals++] = literals[numLiterals - 2] + fd;
}
} else {
long deltaBase = SerializationUtils.readVslong(input);
// add delta base and first value
literals[numLiterals++] = firstVal + deltaBase;
prevVal = literals[numLiterals - 1];
len -= 1;
// write the unpacked values, add it to previous value and store final
// value to result buffer. if the delta base value is negative then it
// is a decreasing sequence else an increasing sequence
SerializationUtils.readInts(literals, numLiterals, len, fb, input);
while (len > 0) {
if (deltaBase < 0) {
literals[numLiterals] = prevVal - literals[numLiterals];
} else {
literals[numLiterals] = prevVal + literals[numLiterals];
}
prevVal = literals[numLiterals];
len--;
numLiterals++;
}
}
}
public void readPatchedBaseValues(int firstByte) throws IOException {
// extract the number of fixed bits
int fbo = (firstByte >>> 1) & 0x1f;
int fb = SerializationUtils.decodeBitWidth(fbo);
// extract the run length of data blob
int len = (firstByte & 0x01) << 8;
len |= input.read();
// runs are always one off
len += 1;
// extract the number of bytes occupied by base
int thirdByte = input.read();
int bw = (thirdByte >>> 5) & 0x07;
// base width is one off
bw += 1;
// extract patch width
int pwo = thirdByte & 0x1f;
int pw = SerializationUtils.decodeBitWidth(pwo);
// read fourth byte and extract patch gap width
int fourthByte = input.read();
int pgw = (fourthByte >>> 5) & 0x07;
// patch gap width is one off
pgw += 1;
// extract the length of the patch list
int pl = fourthByte & 0x1f;
// read the next base width number of bytes to extract base value
long base = SerializationUtils.bytesToLongBE(input, bw);
long mask = (1L << ((bw * 8) - 1));
// if MSB of base value is 1 then base is negative value else positive
if ((base & mask) != 0) {
base = base & ~mask;
base = -base;
}
// unpack the data blob
long[] unpacked = new long[len];
SerializationUtils.readInts(unpacked, 0, len, fb, input);
// unpack the patch blob
long[] unpackedPatch = new long[pl];
SerializationUtils.readInts(unpackedPatch, 0, pl, pw + pgw, input);
// apply the patch directly when decoding the packed data
int patchIdx = 0;
long currGap = 0;
long currPatch = 0;
currGap = unpackedPatch[patchIdx] >>> pw;
currPatch = unpackedPatch[patchIdx] & ((1 << pw) - 1);
long actualGap = 0;
// special case: gap is >255 then patch value will be 0.
// if gap is <=255 then patch value cannot be 0
while (currGap == 255 && currPatch == 0) {
actualGap += 255;
patchIdx++;
currGap = unpackedPatch[patchIdx] >>> pw;
currPatch = unpackedPatch[patchIdx] & ((1 << pw) - 1);
}
// add the left over gap
actualGap += currGap;
// unpack data blob, patch it (if required), add base to get final result
for(int i = 0; i < unpacked.length; i++) {
if (i == actualGap) {
// extract the patch value
long patchedVal = unpacked[i] | (currPatch << fb);
// add base to patched value
literals[numLiterals++] = base + patchedVal;
// increment the patch to point to next entry in patch list
patchIdx++;
if (patchIdx < pl) {
// read the next gap and patch
currGap = unpackedPatch[patchIdx] >>> pw;
currPatch = unpackedPatch[patchIdx] & ((1 << pw) - 1);
actualGap = 0;
// special case: gap is >255 then patch will be 0. if gap is
// <=255 then patch cannot be 0
while (currGap == 255 && currPatch == 0) {
actualGap += 255;
patchIdx++;
currGap = unpackedPatch[patchIdx] >>> pw;
currPatch = unpackedPatch[patchIdx] & ((1 << pw) - 1);
}
// add the left over gap
actualGap += currGap;
// next gap is relative to the current gap
actualGap += i;
}
} else {
// no patching required. add base to unpacked value to get final value
literals[numLiterals++] = base + unpacked[i];
}
}
}
public void readDirectValues(int firstByte) throws IOException {
// extract the number of fixed bits
int fbo = (firstByte >>> 1) & 0x1f;
int fb = SerializationUtils.decodeBitWidth(fbo);
// extract the run length
int len = (firstByte & 0x01) << 8;
len |= input.read();
// runs are one off
len += 1;
// write the unpacked values and zigzag decode to result buffer
SerializationUtils.readInts(literals, numLiterals, len, fb, input);
if (signed) {
for(int i = 0; i < len; i++) {
literals[numLiterals] = SerializationUtils
.zigzagDecode(literals[numLiterals]);
numLiterals++;
}
} else {
numLiterals += len;
}
}
public void readShortRepeatValues(int firstByte) throws IOException {
// read the number of bytes occupied by the value
int size = (firstByte >>> 3) & 0x07;
// #bytes are one off
size += 1;
// read the run length
int len = firstByte & 0x07;
// run lengths values are stored only after MIN_REPEAT value is met
len += RunLengthIntegerWriterV2.MIN_REPEAT;
// read the repeated value which is store using fixed bytes
long val = SerializationUtils.bytesToLongBE(input, size);
if (signed) {
val = SerializationUtils.zigzagDecode(val);
}
// repeat the value for length times
for(int i = 0; i < len; i++) {
literals[numLiterals++] = val;
}
}
@Override
public boolean hasNext() throws IOException {
return used != numLiterals || input.available() > 0;
}
@Override
public long next() throws IOException {
long result;
if (used == numLiterals) {
numLiterals = 0;
used = 0;
readValues();
}
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) {
numLiterals = 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) {
numLiterals = 0;
used = 0;
readValues();
}
long consume = Math.min(numValues, numLiterals - used);
used += consume;
numValues -= consume;
}
}
}