DataHandle: fix findString(..) and support handles with unknown length

The findString(..) method used to require the exact length of the
handle, this length can be unknown, e.g. for compressed handles.
This is	no longer the case.

Author: gab1one

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;
 	}