DataHandle: findString(..) add support handles with unknown length

src/main/java/org/scijava/io/handle/DataHandle.java

@@ -350,10 +350,7 @@ default String findString(final boolean saveString, final int blockSize,
 		final StringBuilder out = new StringBuilder();
 		final long startPos = offset();
 		long bytesDropped = 0;
-		final long inputLen = length();
-		long maxLen = inputLen - startPos;
-		final boolean tooLong = saveString && maxLen > MAX_SEARCH_SIZE;
-		if (tooLong) maxLen = MAX_SEARCH_SIZE;
+		final long maxLen = saveString ? MAX_SEARCH_SIZE : Long.MAX_VALUE;
 		boolean match = false;
 		int maxTermLen = 0;
 		for (final String term : terminators) {
@@ -366,7 +363,10 @@ default String findString(final boolean saveString, final int blockSize,
 			new DataHandleInputStream<>(this), getEncoding());
 		final char[] buf = new char[blockSize];
 		long loc = 0;
-		while (loc < maxLen && offset() < length() - 1) {
+		int r = 0;
+
+		// NB: we need at least 2 bytes to read a char
+		while (loc < maxLen && ((r = in.read(buf, 0, blockSize)) > 1)) {
 			// if we're not saving the string, drop any old, unnecessary output
 			if (!saveString) {
 				final int outLen = out.length();
@@ -378,16 +378,12 @@ default String findString(final boolean saveString, final int blockSize,
 					bytesDropped += dropIndex;
 				}
 			}
-
-			// read block from stream
-			final int r = in.read(buf, 0, blockSize);
-			if (r <= 0) throw new IOException("Cannot read from stream: " + r);
-
 			// append block to output
 			out.append(buf, 0, r);
 
 			// check output, returning smallest possible string
-			int min = Integer.MAX_VALUE, tagLen = 0;
+			int min = Integer.MAX_VALUE;
+			int tagLen = 0;
 			for (final String t : terminators) {
 				final int len = t.length();
 				final int start = (int) (loc - bytesDropped - len);
@@ -415,7 +411,9 @@ default String findString(final boolean saveString, final int blockSize,
 		}
 
 		// no match
-		if (tooLong) throw new IOException("Maximum search length reached.");
+		if (loc > MAX_SEARCH_SIZE) {
+			throw new IOException("Maximum search length reached.");
+		}
 		return saveString ? out.toString() : null;
 	}
 

src/test/java/org/scijava/io/handle/DataHandleEdgeCaseTests.java

@@ -0,0 +1,142 @@
+/*-
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2018 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
+ * Institute of Molecular Cell Biology and Genetics, University of
+ * Konstanz, and KNIME GmbH.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.io.handle;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.scijava.Context;
+import org.scijava.io.location.BytesLocation;
+import org.scijava.io.location.Location;
+
+/**
+ * Additional Tests for edge case behavior of {@link DataHandle}.
+ * 
+ * @author Gabriel Einsdorf
+ */
+public class DataHandleEdgeCaseTests {
+
+	private static final byte[] BYTES = { //
+		'H', 'e', 'l', 'l', 'o', ',', ' ', 'w', 'o', 'r', 'l', 'd', '\n', //
+		9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, -128, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, //
+		125, 127, -127, -125, -3, 'h', 'e' };
+
+	/**
+	 * Test to ensure {@link DataHandle#findString(String...)} and
+	 * {@link DataHandle#readCString()} work with {@link DataHandle}
+	 * implementations that have unknown length.
+	 * 
+	 * @throws IOException
+	 */
+	@Test
+	public void testFindStringsOnUnknonwLengthHandle() throws IOException {
+		final Context ctx = new Context();
+		final DataHandleService dhs = ctx.getService(DataHandleService.class);
+		final DummyHandle dummy = new DummyHandle(dhs.create(new BytesLocation(
+			BYTES)));
+
+		assertEquals("Hello,", dummy.findString(","));
+		assertEquals(" world\n", dummy.findString("\n"));
+
+		dummy.seek(41);
+		assertEquals("he", dummy.findString("\n"));
+
+		dummy.seek(16);
+		assertArrayEquals(Arrays.copyOfRange(BYTES, 16, 23), dummy.readCString()
+			.getBytes());
+		dummy.seek(42);
+		assertNull(dummy.readCString());
+	}
+
+	private class DummyHandle extends AbstractHigherOrderHandle<Location> {
+
+		public DummyHandle(final DataHandle<Location> handle) {
+			super(handle);
+		}
+
+		@Override
+		public long length() throws IOException {
+			return -1;
+		}
+
+		@Override
+		public long offset() throws IOException {
+			return handle().offset();
+		}
+
+		@Override
+		public void seek(final long pos) throws IOException {
+			handle().seek(pos);
+		}
+
+		@Override
+		public void setLength(final long length) throws IOException {
+			handle().setLength(length);
+		}
+
+		@Override
+		public int read(final byte[] b, final int off, final int len)
+			throws IOException
+		{
+			return handle().read(b, off, len);
+		}
+
+		@Override
+		public byte readByte() throws IOException {
+			return handle().readByte();
+		}
+
+		@Override
+		public void write(final int b) throws IOException {
+			handle().write(b);
+		}
+
+		@Override
+		public void write(final byte[] b, final int off, final int len)
+			throws IOException
+		{
+			handle().write(b, off, len);
+		}
+
+		@Override
+		protected void cleanup() throws IOException {
+			//
+		}
+	}
+
+}