Implement an output stream compressing with zstd

1 files changed, 88 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/compress/ZstdOuputStream.java b/vespajlib/src/main/java/com/yahoo/compress/ZstdOuputStream.java
new file mode 100644
index 00000000000..e81bcf6a465
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/compress/ZstdOuputStream.java
@@ -0,0 +1,88 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.compress;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * @author bjorncs
+ */
+public class ZstdOuputStream extends OutputStream {
+
+    private final ZstdCompressor compressor = new ZstdCompressor();
+
+    public static final int DEFAULT_INPUT_BUFFER_SIZE = 8*1024;
+
+    private final OutputStream out;
+    private final byte[] inputBuffer;
+    private final byte[] outputBuffer;
+    private int inputPosition = 0;
+    private boolean isClosed = false;
+
+    public ZstdOuputStream(OutputStream out, int inputBufferSize) {
+        this.out = out;
+        this.inputBuffer = new byte[inputBufferSize];
+        this.outputBuffer = new byte[ZstdCompressor.getMaxCompressedLength(inputBufferSize)];
+    }
+
+    public ZstdOuputStream(OutputStream out) {
+        this(out, DEFAULT_INPUT_BUFFER_SIZE);
+    }
+
+    @Override
+    public void write(int b) throws IOException {
+        throwIfClosed();
+        inputBuffer[inputPosition++] = (byte) b;
+        flushIfFull();
+    }
+
+    @Override
+    public void write(byte[] b) throws IOException {
+        throwIfClosed();
+        write(b, 0, b.length);
+    }
+
+    @Override
+    public void write(byte[] b, int off, int len) throws IOException {
+        throwIfClosed();
+        int end = off + len;
+        while (off < end) {
+            int copyLength = Math.min(end - off, inputBuffer.length - inputPosition);
+            System.arraycopy(b, off, inputBuffer, inputPosition, copyLength);
+            off += copyLength;
+            inputPosition += copyLength;
+            flushIfFull();
+        }
+    }
+
+    @Override
+    public void flush() throws IOException {
+        flushInternal();
+        out.flush();
+    }
+
+    @Override
+    public void close() throws IOException {
+        throwIfClosed();
+        flush();
+        out.close();
+        isClosed = true;
+    }
+
+    private void flushInternal() throws IOException {
+        throwIfClosed();
+        int compressedLength = compressor.compress(inputBuffer, 0, inputPosition, outputBuffer, 0, outputBuffer.length);
+        out.write(outputBuffer, 0, compressedLength);
+        inputPosition = 0;
+    }
+
+    private void flushIfFull() throws IOException {
+        if (inputPosition == inputBuffer.length) {
+            flushInternal();
+        }
+    }
+
+    private void throwIfClosed() {
+        if (isClosed) throw new IllegalArgumentException("Output stream is already closed");
+    }
+}