Add method to stream decompressed data

Author: xxDark

src/main/java/software/coley/lljzip/format/compression/MemorySegmentInputStream.java

@@ -0,0 +1,157 @@
+package software.coley.lljzip.format.compression;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+
+final class MemorySegmentInputStream extends InputStream {
+	private final MemorySegment data;
+	private long read;
+	private long markedOffset = -1;
+	private long markedLimit;
+	private volatile boolean closed;
+
+	MemorySegmentInputStream(MemorySegment data) {
+		this.data = data;
+	}
+
+	private void checkMarkLimit() {
+		if (markedOffset > -1) {
+			// Discard if we passed the read limit for our mark
+			long diff = read - markedOffset;
+			if (diff > markedLimit) {
+				markedOffset = -1;
+			}
+		}
+	}
+
+	@Override
+	public boolean markSupported() {
+		return true;
+	}
+
+	@Override
+	public synchronized void mark(int limit) {
+		// Record current position and read-limit
+		markedOffset = read;
+		markedLimit = limit;
+	}
+
+	@Override
+	public synchronized void reset() {
+		// Revert read to marked position.
+		read = markedOffset;
+	}
+
+	@Override
+	public int read() throws IOException {
+		ensureOpen();
+		MemorySegment data = this.data;
+		if (read >= data.byteSize()) {
+			return -1;
+		}
+		byte b = data.get(ValueLayout.JAVA_BYTE, read++);
+		checkMarkLimit();
+		return b & 0xff;
+	}
+
+	@Override
+	public int read(byte[] b, int off, int len) throws IOException {
+		ensureOpen();
+		MemorySegment data = this.data;
+		long read = this.read;
+		long length = data.byteSize();
+		if (read >= length) {
+			return -1;
+		}
+		long remaining = length - read;
+		len = (int) Math.min(remaining, len);
+		MemorySegment.copy(data, read, MemorySegment.ofArray(b), off, len);
+		this.read += len;
+		checkMarkLimit();
+		return len;
+	}
+
+	@Override
+	public byte[] readNBytes(int len) throws IOException {
+		ensureOpen();
+		MemorySegment data = this.data;
+		long read = this.read;
+		long length = data.byteSize();
+		if (read >= length) {
+			return new byte[0];
+		}
+		long remaining = length - read;
+		len = (int) Math.min(remaining, len);
+		byte[] buf = new byte[len];
+		MemorySegment.copy(data, read, MemorySegment.ofArray(buf), 0, len);
+		this.read += len;
+		checkMarkLimit();
+		return buf;
+	}
+
+	@Override
+	public long skip(long n) throws IOException {
+		ensureOpen();
+		MemorySegment data = this.data;
+		long read = this.read;
+		long length = data.byteSize();
+		if (read >= length) {
+			return 0;
+		}
+		n = Math.min(n, length - read);
+		this.read += n;
+		checkMarkLimit();
+		return n;
+	}
+
+	@Override
+	public int available() throws IOException {
+		ensureOpen();
+		MemorySegment data = this.data;
+		long length = data.byteSize();
+		long read = this.read;
+		if (read >= length) {
+			return 0;
+		}
+		long remaining = length - read;
+		if (remaining > Integer.MAX_VALUE)
+			return Integer.MAX_VALUE;
+		return (int) remaining;
+	}
+
+	@Override
+	public void close() throws IOException {
+		closed = true;
+	}
+
+	@Override
+	public long transferTo(OutputStream out) throws IOException {
+		ensureOpen();
+		MemorySegment data = this.data;
+		long length = data.byteSize();
+		long read = this.read;
+		if (read >= length) {
+			return 0L;
+		}
+		long remaining = length - read;
+		byte[] buffer = new byte[(int) Math.min(16384, remaining)];
+		MemorySegment bufferSegment = MemorySegment.ofArray(buffer);
+		while (read < length) {
+			int copyable = (int) Math.min(buffer.length, length - read);
+			MemorySegment.copy(data, read, bufferSegment, 0, copyable);
+			out.write(buffer, 0, copyable);
+			read += copyable;
+		}
+		this.read = length;
+		checkMarkLimit();
+		return remaining;
+	}
+
+	private void ensureOpen() throws IOException {
+		if (closed)
+			throw new IOException("Stream closed");
+	}
+}

src/main/java/software/coley/lljzip/format/compression/ZipCompressions.java

@@ -3,7 +3,9 @@
 import software.coley.lljzip.format.model.LocalFileHeader;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.lang.foreign.MemorySegment;
+import java.util.zip.DeflaterInputStream;
 
 /**
  * Constants for {@link LocalFileHeader#getCompressionMethod()}.
@@ -185,4 +187,27 @@ static MemorySegment decompress(LocalFileHeader header) throws IOException {
 			}
 		};
 	}
+
+	/**
+	 * @param header
+	 * 		Header with {@link LocalFileHeader#getFileData()} to decompress.
+	 *
+	 * @return Stream with decompressed data.
+	 *
+	 * @throws IOException
+	 * 		When the decompression failed.
+	 */
+	static InputStream decompressStream(LocalFileHeader header) throws IOException {
+		int method = header.getCompressionMethod();
+		InputStream in = new MemorySegmentInputStream(header.getFileData());
+		return switch (method) {
+			case STORED -> in;
+			case DEFLATED -> new DeflaterInputStream(in);
+			default -> {
+				// TODO: Support other decompressing techniques
+				String methodName = getName(method);
+				throw new IOException("Unsupported compression method: " + methodName);
+			}
+		};
+	}
 }