#255 implement decompression from direct buffer to heap buffer

src/main/java/org/xerial/snappy/Snappy.java

@@ -535,17 +535,19 @@ public static int uncompress(ByteBuffer compressed, ByteBuffer uncompressed)
         if (!compressed.isDirect()) {
             throw new SnappyError(SnappyErrorCode.NOT_A_DIRECT_BUFFER, "input is not a direct buffer");
         }
-        if (!uncompressed.isDirect()) {
-            throw new SnappyError(SnappyErrorCode.NOT_A_DIRECT_BUFFER, "destination is not a direct buffer");
-        }
 
         int cPos = compressed.position();
         int cLen = compressed.remaining();
 
         //         pos  limit
         // [ ......UUUUUU.........]
-        int decompressedSize = impl.rawUncompress(compressed, cPos, cLen, uncompressed,
-                uncompressed.position());
+        final int decompressedSize;
+        if (uncompressed.isDirect()) {
+            decompressedSize = impl.rawUncompress(compressed, cPos, cLen, uncompressed, uncompressed.position());
+        } else {
+            decompressedSize = impl.rawUncompressDirectToHeap(compressed, cPos, cLen,
+                    uncompressed.array(), uncompressed.position());
+        }
         uncompressed.limit(uncompressed.position() + decompressedSize);
 
         return decompressedSize;

src/main/java/org/xerial/snappy/SnappyNative.cpp

@@ -297,3 +297,35 @@ JNIEXPORT void JNICALL Java_org_xerial_snappy_SnappyNative_arrayCopy
 	env->ReleasePrimitiveArrayCritical((jarray) output, dest, 0);
 }
 
+/*
+ * Class:     org_xerial_snappy_SnappyNative
+ * Method:    rawUncompressDirectToHeap
+ * Signature: (Ljava/nio/ByteBuffer;IILjava/lang/Object;I)I
+ */
+JNIEXPORT jint JNICALL Java_org_xerial_snappy_SnappyNative_rawUncompressDirectToHeap
+  (JNIEnv* env, jobject self, jobject compressedBuffer, jint inputPos, jint inputLength,
+  jobject uncompressedArray, jint outputOffset)
+{
+    char* in = (char*) env->GetDirectBufferAddress(compressedBuffer);
+    if (in == 0) {
+        throw_exception(env, self, 3);
+        return (jint) 0;
+    }
+    char* out = (char*) env->GetPrimitiveArrayCritical((jarray) uncompressedArray, 0);
+    if (out == 0) {
+        // out of memory
+        throw_exception(env, self, 4);
+        return (jint) 0;
+    }
+    size_t decompressedLength;
+    snappy::GetUncompressedLength(in + inputPos, (size_t) inputLength, &decompressedLength);
+    bool ret = snappy::RawUncompress(in + inputPos, (size_t) inputLength, out + outputOffset);
+    env->ReleasePrimitiveArrayCritical((jarray) uncompressedArray, out, 0);
+    if(!ret) {
+        // failed to decompress
+        throw_exception(env, self, 5);
+        return (jint) 0;
+    }
+    return (jint) decompressedLength;
+}
+

src/main/java/org/xerial/snappy/SnappyNative.java

@@ -63,6 +63,10 @@ public native int rawUncompress(ByteBuffer compressed, int inputOffset, int inpu
             int outputOffset)
             throws IOException;
 
+    public native int rawUncompressDirectToHeap(ByteBuffer compressed, int inputOffset, int inputLength,
+                                                Object uncompressed, int outputOffset)
+            throws IOException;
+
     public native int rawUncompress(Object input, int inputOffset, int inputLength, Object output, int outputOffset)
             throws IOException;
 

src/test/java/org/xerial/snappy/SnappyGenerativeTest.java

@@ -0,0 +1,66 @@
+package org.xerial.snappy;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+
+import static org.junit.Assert.assertArrayEquals;
+
+@RunWith(Parameterized.class)
+public class SnappyGenerativeTest {
+
+  @Parameterized.Parameters
+  public static Iterable<Object[]> data() {
+    List<Object[]> testCases = new ArrayList<>(100);
+    for (int i = 0 ; i < 100; ++i) {
+      testCases.add(randomData());
+    }
+    return testCases;
+  }
+
+
+  private final byte[] input;
+
+  public SnappyGenerativeTest(byte[] input) {
+    this.input = input;
+  }
+
+  @Test
+  public void roundTripDirectToDirect() throws IOException {
+    ByteBuffer in = ByteBuffer.allocateDirect(input.length);
+    in.put(input);
+    ByteBuffer compressed = ByteBuffer.allocateDirect(input.length * 2);
+    Snappy.compress(in, compressed);
+    Snappy.uncompress(compressed, in);
+    byte[] result = new byte[input.length];
+    in.flip();
+    in.get(result);
+    assertArrayEquals(input, result);
+  }
+
+  @Test
+  public void roundTripDirectToHeap() throws IOException {
+    ByteBuffer in = ByteBuffer.allocateDirect(input.length);
+    in.put(input);
+    in.flip();
+    ByteBuffer compressed = ByteBuffer.allocateDirect(input.length * 2);
+    Snappy.compress(in, compressed);
+    ByteBuffer out = ByteBuffer.allocate(input.length);
+    Snappy.uncompress(compressed, out);
+    out.flip();
+    assertArrayEquals(input, out.array());
+  }
+
+  private static Object[] randomData() {
+    int length = Math.abs(ThreadLocalRandom.current().nextInt(10,10_000));
+    byte[] data = new byte[length];
+    ThreadLocalRandom.current().nextBytes(data);
+    return new Object[] {data};
+  }
+}

src/test/java/org/xerial/snappy/SnappyTest.java

@@ -113,6 +113,51 @@ public void directBuffer()
         assertEquals(origStr, decompressed);
     }
 
+
+    @Test
+    public void directBufferToHeapBuffer() throws Exception
+    {
+
+        StringBuilder s = new StringBuilder();
+        for (int i = 0; i < 20; ++i) {
+            s.append("Hello world!");
+        }
+        String origStr = s.toString();
+        byte[] orig = origStr.getBytes();
+        ByteBuffer src = ByteBuffer.allocateDirect(orig.length);
+        src.put(orig);
+        src.flip();
+        _logger.debug("input size: " + src.remaining());
+        int maxCompressedLen = Snappy.maxCompressedLength(src.remaining());
+        _logger.debug("max compressed length:" + maxCompressedLen);
+
+        ByteBuffer compressed = ByteBuffer.allocateDirect(maxCompressedLen);
+        int compressedSize = Snappy.compress(src, compressed);
+        _logger.debug("compressed length: " + compressedSize);
+
+        assertEquals(0, src.position());
+        assertEquals(orig.length, src.remaining());
+        assertEquals(orig.length, src.limit());
+
+        assertEquals(0, compressed.position());
+        assertEquals(compressedSize, compressed.limit());
+        assertEquals(compressedSize, compressed.remaining());
+
+        int uncompressedLen = Snappy.uncompressedLength(compressed);
+        _logger.debug("uncompressed length: " + uncompressedLen);
+        ByteBuffer extract = ByteBuffer.allocate(uncompressedLen);
+        int uncompressedLen2 = Snappy.uncompress(compressed, extract);
+        assertEquals(uncompressedLen, uncompressedLen2);
+        assertEquals(uncompressedLen, extract.remaining());
+
+        byte[] b = new byte[uncompressedLen];
+        extract.get(b);
+        String decompressed = new String(b);
+        _logger.debug(decompressed);
+
+        assertEquals(origStr, decompressed);
+    }
+
     @Test
     public void bufferOffset()
             throws Exception