[FIXED] Zlib is unable to extract a compress String in java, compression is done in python

Issue

Im trying to decompress a string in java, the string is compress in python with base64 encoding.

I tried a day to resolve the issue, The file can decode easily online and also in python. Find similar post that people have trouble compressing and decompressing in java and python.

zip.txt

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Base64;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;

public class CompressionUtils {
private static final int BUFFER_SIZE = 1024;

public static byte[] decompress(final byte[] data) {
    final Inflater inflater = new Inflater();
    inflater.setInput(data);
    ByteArrayOutputStream outputStream =
            new ByteArrayOutputStream(data.length);
    byte[] buffer = new byte[data.length];
    try {
        while (!inflater.finished()) {
            final int count = inflater.inflate(buffer);
            outputStream.write(buffer, 0, count);
        }
        outputStream.close();
    } catch (DataFormatException | IOException e) {
        e.printStackTrace();
        log.error("ZlibCompression decompress exception: {}", e.getMessage());
    }
    inflater.end();
    return outputStream.toByteArray();
}

public static void main(String[] args) throws IOException {
    decompress(Base64.getDecoder().decode(Files.readAllBytes(Path.of("zip.txt"))));
}
}

Error:

 java.util.zip.DataFormatException: incorrect header check
    at java.base/java.util.zip.Inflater.inflateBytesBytes(Native Method)
    at java.base/java.util.zip.Inflater.inflate(Inflater.java:378)
    at java.base/java.util.zip.Inflater.inflate(Inflater.java:464) 

Tried also this after @Mark Adler suggestion.

public static void main(String[] args) throws IOException {
    
    byte[] decoded = Base64.getDecoder().decode(Files.readAllBytes(Path.of("zip.txt")));
    ByteArrayInputStream in = new ByteArrayInputStream(decoded);
    GZIPInputStream gzStream = new GZIPInputStream(in);
    decompress(gzStream.readAllBytes());
    gzStream.close();
}

java.util.zip.DataFormatException: incorrect header check
at java.base/java.util.zip.Inflater.inflateBytesBytes(Native Method)
at java.base/java.util.zip.Inflater.inflate(Inflater.java:378)
at java.base/java.util.zip.Inflater.inflate(Inflater.java:464)
at efrisapi/com.efrisapi.util.CompressionUtils.decompress(CompressionUtils.java:51)
at efrisapi/com.efrisapi.util.CompressionUtils.main(CompressionUtils.java:67)

Solution

That is a gzip stream, not a zlib stream. Use GZIPInputStream.

Answered By - Mark Adler
Answer Checked By - Pedro (JavaFixing Volunteer)