Add Range to represent (offset, length) pair

Author: tpietzsch

src/main/java/org/janelia/saalfeldlab/n5/readdata/Range.java

@@ -0,0 +1,94 @@
+package org.janelia.saalfeldlab.n5.readdata;
+
+import java.util.Comparator;
+
+/**
+ * A range specified as a {@link #offset}, {@link #length} pair.
+ */
+public interface Range {
+
+	/**
+	 * Order {@code Range}s by {@link #offset}.
+	 * Ranges with the same offset are ordered by {@link #length}.
+	 */
+	Comparator<Range> COMPARATOR = Comparator
+			.comparingLong(Range::offset)
+			.thenComparingLong(Range::length);
+
+	/**
+	 * @return start index (inclusive)
+	 */
+	long offset();
+
+	/**
+	 * @return number of elements
+	 */
+	long length();
+
+	/**
+	 * @return end index (exclusive)
+	 */
+	default long end() {
+		return offset() + length();
+	}
+
+	static boolean equals(final Range r0, final Range r1) {
+		if (r0 == null && r1==null) {
+			return true;
+		} else if (r0 == null || r1 == null) {
+			return false;
+		} else {
+			return r0.offset() == r1.offset() && r0.length() == r1.length();
+		}
+	}
+
+	static Range at(final long offset, final long length) {
+
+		class DefaultRange implements Range {
+
+			private final long offset;
+			private final long length;
+
+			public DefaultRange(final long offset, final long length) {
+				this.offset = offset;
+				this.length = length;
+			}
+
+			@Override
+			public long offset() {
+				return offset;
+			}
+
+			@Override
+			public long length() {
+				return length;
+			}
+
+			@Override
+			public final boolean equals(final Object o) {
+				if (!(o instanceof DefaultRange))
+					return false;
+
+				final DefaultRange that = (DefaultRange) o;
+				return offset == that.offset && length == that.length;
+			}
+
+			@Override
+			public int hashCode() {
+				int result = Long.hashCode(offset);
+				result = 31 * result + Long.hashCode(length);
+				return result;
+			}
+
+			@Override
+			public String toString() {
+				return "Range{" +
+						"offset=" + offset +
+						", length=" + length +
+						'}';
+			}
+		}
+
+		return new DefaultRange(offset, length);
+	}
+}

src/main/java/org/janelia/saalfeldlab/n5/readdata/ReadData.java

@@ -105,6 +105,18 @@ default ReadData slice(final long offset, final long length) throws N5IOExceptio
 		return materialize().slice(offset, length);
 	}
 
+	/**
+	 * Returns a new {@link ReadData} representing a slice, or subset
+	 * of this ReadData.
+	 *
+	 * @param range a range in this ReadData
+	 * @return a slice
+	 * @throws N5IOException an exception
+	 */
+	default ReadData slice(final Range range) throws N5IOException {
+		return slice(range.offset(), range.length());
+	}
+
 	/**
 	 * Open a {@code InputStream} on this data.
 	 * <p>