com.epam.parso.impl.CharDecompressor Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of parso Show documentation
Show all versions of parso Show documentation
Parso is a lightweight Java library designed to read SAS7BDAT datasets. The Parso interfaces
are analogous to libraries designed to read table-storing files, for example, CSVReader library.
Despite its small size, the Parso library is the only full-featured open-source solution to process SAS7BDAT
datasets, both uncompressed, CHAR-compressed and BIN-compressed. It is effective in processing clinical and
statistical data often stored in SAS7BDAT format. Parso allows converting data into CSV format.
The newest version!
/**
* *************************************************************************
* Copyright (C) 2015 EPAM
* 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.epam.parso.impl;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Implementation of the CHAR compression algorithm which corresponds to the literal "SASYZCRL".
* Refer the documentation for further details.
* It follows the general contract provided by the interface Decompressor.
*
*/
final class CharDecompressor implements Decompressor {
/**
* Unambiguous class instance.
*/
static final CharDecompressor INSTANCE = new CharDecompressor();
/**
* Object for writing logs.
*/
private static final Logger LOGGER = LoggerFactory.getLogger(CharDecompressor.class);
/**
* Empty private constructor for preventing multiple instances.
*/
private CharDecompressor() {
}
/**
* The function to decompress data. Compressed data are an array of bytes with control bytes and data bytes.
* The project documentation contains descriptions of the decompression algorithm.
*
* @param offset the offset of bytes array in {@link SasFileParser#cachedPage} that contains compressed data.
* @param length the length of bytes array that contains compressed data.
* @param resultLength the length of bytes array that contains decompressed data.
* @param page an array of bytes with compressed data.
* @return an array of bytes with decompressed data.
*/
@Override
public byte[] decompressRow(int offset, int length, int resultLength, byte[] page) {
byte[] resultByteArray = new byte[resultLength];
int currentResultArrayIndex = 0;
int currentByteIndex = 0;
while (currentByteIndex < length) {
int controlByte = page[offset + currentByteIndex] & 0xF0;
int endOfFirstByte = page[offset + currentByteIndex] & 0x0F;
int countOfBytesToCopy;
switch (controlByte) {
case 0x30://intentional fall through
case 0x20://intentional fall through
case 0x10://intentional fall through
case 0x00:
if (currentByteIndex != length - 1) {
countOfBytesToCopy = (page[offset + currentByteIndex + 1] & 0xFF) + 64
+ page[offset + currentByteIndex] * 256;
System.arraycopy(page, offset + currentByteIndex + 2, resultByteArray,
currentResultArrayIndex, countOfBytesToCopy);
currentByteIndex += countOfBytesToCopy + 1;
currentResultArrayIndex += countOfBytesToCopy;
}
break;
case 0x40:
int copyCounter = endOfFirstByte * 16 + (page[offset + currentByteIndex + 1] & 0xFF);
for (int i = 0; i < copyCounter + 18; i++) {
resultByteArray[currentResultArrayIndex++] = page[offset + currentByteIndex + 2];
}
currentByteIndex += 2;
break;
case 0x50:
for (int i = 0; i < endOfFirstByte * 256 + (page[offset + currentByteIndex + 1] & 0xFF) + 17; i++) {
resultByteArray[currentResultArrayIndex++] = 0x40;
}
currentByteIndex++;
break;
case 0x60:
for (int i = 0; i < endOfFirstByte * 256 + (page[offset + currentByteIndex + 1] & 0xFF) + 17; i++) {
resultByteArray[currentResultArrayIndex++] = 0x20;
}
currentByteIndex++;
break;
case 0x70:
for (int i = 0; i < endOfFirstByte * 256 + (page[offset + currentByteIndex + 1] & 0xFF) + 17; i++) {
resultByteArray[currentResultArrayIndex++] = 0x00;
}
currentByteIndex++;
break;
case 0x80:
case 0x90:
case 0xA0:
case 0xB0:
countOfBytesToCopy = Math.min(endOfFirstByte + 1 + (controlByte - 0x80),
length - (currentByteIndex + 1));
System.arraycopy(page, offset + currentByteIndex + 1, resultByteArray,
currentResultArrayIndex, countOfBytesToCopy);
currentByteIndex += countOfBytesToCopy;
currentResultArrayIndex += countOfBytesToCopy;
break;
case 0xC0:
for (int i = 0; i < endOfFirstByte + 3; i++) {
resultByteArray[currentResultArrayIndex++] = page[offset + currentByteIndex + 1];
}
currentByteIndex++;
break;
case 0xD0:
for (int i = 0; i < endOfFirstByte + 2; i++) {
resultByteArray[currentResultArrayIndex++] = 0x40;
}
break;
case 0xE0:
for (int i = 0; i < endOfFirstByte + 2; i++) {
resultByteArray[currentResultArrayIndex++] = 0x20;
}
break;
case 0xF0:
for (int i = 0; i < endOfFirstByte + 2; i++) {
resultByteArray[currentResultArrayIndex++] = 0x00;
}
break;
default:
LOGGER.error("Error control byte: {}", controlByte);
break;
}
currentByteIndex++;
}
return resultByteArray;
}
}