feat/test: add block position iterator for shard

* add ShardProperties test

src/main/java/org/janelia/saalfeldlab/n5/shard/Shard.java

@@ -116,6 +116,18 @@ default List<DataBlock<T>> getBlocks() {
 		return blocks;
 	}
 
+	/**
+	 * Returns an {@link Iterator} over block positions contained in this shard.
+	 * 
+	 * @return
+	 */
+	default Iterator<long[]> blockPositionIterator() {
+
+		final int nd = getSize().length;
+		long[] min = getDatasetAttributes().getBlockPositionFromShardPosition( getGridPosition(), new long[nd]);
+		return new GridIterator(GridIterator.int2long(getBlockGridSize()), min);
+	}
+
 	public ShardIndex getIndex();
 
 	public static <T,A extends DatasetAttributes & ShardParameters> Shard<T> createEmpty(final A attributes, long... shardPosition) {
@@ -158,4 +170,5 @@ public DataBlock<T> next() {
 			return shard.getBlock(it.next());
 		}
 	}
+
 }

src/main/java/org/janelia/saalfeldlab/n5/shard/ShardParameters.java

@@ -97,8 +97,10 @@ default int[] getBlockPositionInShard(final long[] shardPosition, final long[] b
 	/**
 	 * Given a block's position relative to a shard, returns its position in pixels
 	 * relative to the image.
-	 *
-	 * @return the block position
+	 * 
+	 * @param shardPosition shard position in the shard grid
+	 * @param blockPosition block position the 
+	 * @return the block's min pixel coordinate
 	 */
 	default long[] getBlockMinFromShardPosition(final long[] shardPosition, final long[] blockPosition) {
 
@@ -117,7 +119,9 @@ default long[] getBlockMinFromShardPosition(final long[] shardPosition, final lo
 	 * Given a block's position relative to a shard, returns its position relative
 	 * to the image.
 	 *
-	 * @return the block position
+	 * @param shardPosition shard position in the shard grid
+	 * @param blockPosition block position relative to the shard 
+	 * @return the block position in the block grid
 	 */
 	default long[] getBlockPositionFromShardPosition(final long[] shardPosition, final long[] blockPosition) {
 

src/main/java/org/janelia/saalfeldlab/n5/util/GridIterator.java

@@ -1,6 +1,5 @@
 package org.janelia.saalfeldlab.n5.util;
 
-import java.util.Arrays;
 import java.util.Iterator;
 
 /**
@@ -14,15 +13,18 @@ public class GridIterator implements Iterator<long[]> {
 
 	final protected long[] position;
 
+	final protected long[] min;
+
 	final protected int lastIndex;
 
 	protected int index = -1;
 
-	public GridIterator(final long[] dimensions) {
+	public GridIterator(final long[] dimensions, final long[] min) {
 
 		final int n = dimensions.length;
 		this.dimensions = new long[n];
 		this.position = new long[n];
+		this.min = min;
 		steps = new long[n];
 
 		final int m = n - 1;
@@ -38,6 +40,11 @@ public GridIterator(final long[] dimensions) {
 		lastIndex = (int)(k * dimm - 1);
 	}
 
+	public GridIterator(final long[] dimensions) {
+
+		this(dimensions, new long[dimensions.length]);
+	}
+
 	public GridIterator(final int[] dimensions) {
 
 		this(int2long(dimensions));
@@ -59,7 +66,7 @@ public boolean hasNext() {
 	@Override
 	public long[] next() {
 		fwd();
-		indexToPosition(index, dimensions, position);
+		indexToPosition(index, dimensions, min, position);
 		return position;
 	}
 
@@ -71,10 +78,10 @@ public int getIndex() {
 		return index;
 	}
 
-	final static public void indexToPosition(long index, final long[] dimensions, final long[] position) {
+	final static public void indexToPosition(long index, final long[] dimensions, final long[] min, final long[] position) {
 		final int maxDim = dimensions.length - 1;
 		for (int dim = maxDim; dim >= 0; dim--) {
-			position[dim] = index % dimensions[dim];
+			position[dim] = index % dimensions[dim] + min[dim];
 			index /= dimensions[dim];
 		}
 	}

src/test/java/org/janelia/saalfeldlab/n5/shard/ShardPropertiesTests.java

@@ -0,0 +1,90 @@
+package org.janelia.saalfeldlab.n5.shard;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import java.util.Iterator;
+
+import org.janelia.saalfeldlab.n5.DataType;
+import org.janelia.saalfeldlab.n5.ShardedDatasetAttributes;
+import org.janelia.saalfeldlab.n5.codec.Codec;
+import org.janelia.saalfeldlab.n5.codec.DeterministicSizeCodec;
+import org.janelia.saalfeldlab.n5.shard.ShardingCodec.IndexLocation;
+import org.junit.Test;
+
+public class ShardPropertiesTests {
+
+	@Test
+	public void testShardProperties() throws Exception {
+
+		final long[] arraySize = new long[]{16, 16};
+		final int[] shardSize = new int[]{16, 16};
+		final long[] shardPosition = new long[]{1, 1};
+		final int[] blkSize = new int[]{4, 4};
+
+		final ShardedDatasetAttributes dsetAttrs = new ShardedDatasetAttributes(
+				arraySize,
+				shardSize,
+				blkSize,
+				DataType.UINT8,
+				new Codec[]{},
+				new DeterministicSizeCodec[]{},
+				IndexLocation.END);
+
+		@SuppressWarnings({"rawtypes", "unchecked"})
+		final InMemoryShard shard = new InMemoryShard(dsetAttrs, shardPosition, null);
+
+		assertArrayEquals(new int[]{4, 4}, shard.getBlockGridSize());
+
+		assertArrayEquals(new long[]{0, 0}, shard.getShard(0, 0));
+		assertArrayEquals(new long[]{1, 1}, shard.getShard(5, 5));
+		assertArrayEquals(new long[]{1, 0}, shard.getShard(5, 0));
+		assertArrayEquals(new long[]{0, 1}, shard.getShard(0, 5));
+
+//		assertNull(shard.getBlockPosition(0, 0));
+//		assertNull(shard.getBlockPosition(3, 3));
+
+		assertArrayEquals(new int[]{0, 0}, shard.getBlockPosition(4, 4));
+		assertArrayEquals(new int[]{1, 1}, shard.getBlockPosition(5, 5));
+		assertArrayEquals(new int[]{2, 2}, shard.getBlockPosition(6, 6));
+		assertArrayEquals(new int[]{3, 3}, shard.getBlockPosition(7, 7));
+	}
+
+	@Test
+	public void testShardBlockPositionIterator() throws Exception {
+
+		final long[] arraySize = new long[]{16, 16};
+		final int[] shardSize = new int[]{16, 16};
+		final long[] shardPosition = new long[]{1, 1};
+		final int[] blkSize = new int[]{4, 4};
+
+		final ShardedDatasetAttributes dsetAttrs = new ShardedDatasetAttributes(
+				arraySize,
+				shardSize,
+				blkSize,
+				DataType.UINT8,
+				new Codec[]{},
+				new DeterministicSizeCodec[]{},
+				IndexLocation.END);
+
+		@SuppressWarnings({"rawtypes", "unchecked"})
+		final InMemoryShard shard = new InMemoryShard(dsetAttrs, shardPosition, null);
+
+		int i = 0;
+		Iterator<long[]> it = shard.blockPositionIterator();
+		long[] p = null;
+		while (it.hasNext()) {
+
+			p = it.next();
+			if( i == 0 )
+				assertArrayEquals(new long[]{4,4}, p);
+
+			i++;
+		}
+		assertEquals(16,i);
+		assertArrayEquals(new long[]{7,7}, p);
+
+	}
+
+}