Don't use java.nio channel for file size determination

Java NIO has some problems (like files closing unexpectedly because the
thread was interrupted). To avoid those problems, don't use a NIO
channel to determine the size of a file, but rather ask the File itself.

We have to be prepared to handle wrong/outdated information in this case
too, as the inode of the File may change between opening and determining
file size.

Change-Id: Ic7aa6c3337480879efcce4a3058b548cd0e2cef0

org.eclipse.jgit/src/org/eclipse/jgit/util/IO.java

@@ -137,12 +137,38 @@ public class IO {
 			throws FileNotFoundException, IOException {
 		final FileInputStream in = new FileInputStream(path);
 		try {
-			final long sz = in.getChannel().size();
+			long sz = Math.max(path.length(), 1);
 			if (sz > max)
 				throw new IOException(MessageFormat.format(
 						JGitText.get().fileIsTooLarge, path));
-			final byte[] buf = new byte[(int) sz];
-			IO.readFully(in, buf, 0);
+
+			byte[] buf = new byte[(int) sz];
+			int valid = 0;
+			for (;;) {
+				if (buf.length == valid) {
+					if (buf.length == max) {
+						int next = in.read();
+						if (next < 0)
+							break;
+
+						throw new IOException(MessageFormat.format(
+								JGitText.get().fileIsTooLarge, path));
+					}
+
+					byte[] nb = new byte[Math.min(buf.length * 2, max)];
+					System.arraycopy(buf, 0, nb, 0, valid);
+					buf = nb;
+				}
+				int n = in.read(buf, valid, buf.length - valid);
+				if (n < 0)
+					break;
+				valid += n;
+			}
+			if (valid < buf.length) {
+				byte[] nb = new byte[valid];
+				System.arraycopy(buf, 0, nb, 0, valid);
+				buf = nb;
+			}
 			return buf;
 		} finally {
 			try {