DirCacheEntry: Speed up creation by avoiding string cast

The checkPath function is available as a byte[] form, in fact the
String form just converts to byte[] to run the algorithm.

Having DirCacheEntry take a byte[] -> String -> byte[] to check if
each path is valid is a huge waste of CPU time. On some systems it
can double the time required to read 38,999 files from trees to the
DirCache. This slows down any operation using a DirCache.

Expose the byte[] form and use it for DirCacheEntry creation.

Change-Id: I6db7bc793ece99ff3c356338d793c07c061aeac7

org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheEntryTest.java

@@ -69,9 +69,9 @@ public class DirCacheEntryTest {
 		assertFalse(isValidPath("a\u0000b"));
 	}
 
-	private static boolean isValidPath(final String path) {
+	private static boolean isValidPath(String path) {
 		try {
-			DirCacheCheckout.checkValidPath(path);
+			new DirCacheEntry(path);
 			return true;
 		} catch (InvalidPathException e) {
 			return false;

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java

@@ -1342,24 +1342,6 @@ public class DirCacheCheckout {
 			checkValidPathSegment(chk, i);
 	}
 
-	/**
-	 * Check if path is a valid path for a checked out file name or ref name.
-	 *
-	 * @param path
-	 * @throws InvalidPathException
-	 *             if the path is invalid
-	 * @since 3.3
-	 */
-	static void checkValidPath(String path) throws InvalidPathException {
-		try {
-			SystemReader.getInstance().checkPath(path);
-		} catch (CorruptObjectException e) {
-			InvalidPathException p = new InvalidPathException(path);
-			p.initCause(e);
-			throw p;
-		}
-	}
-
 	private static void checkValidPathSegment(ObjectChecker chk,
 			CanonicalTreeParser t) throws InvalidPathException {
 		try {

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheEntry.java

@@ -65,6 +65,7 @@ import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.util.IO;
 import org.eclipse.jgit.util.MutableInteger;
 import org.eclipse.jgit.util.NB;
+import org.eclipse.jgit.util.SystemReader;
 
 /**
  * A single file (or stage of a file) in a {@link DirCache}.
@@ -191,7 +192,7 @@ public class DirCacheEntry {
 		}
 
 		try {
-			DirCacheCheckout.checkValidPath(toString(path));
+			checkPath(path);
 		} catch (InvalidPathException e) {
 			CorruptObjectException p =
 				new CorruptObjectException(e.getMessage());
@@ -263,7 +264,7 @@ public class DirCacheEntry {
 	/**
 	 * Create an empty entry at the specified stage.
 	 *
-	 * @param newPath
+	 * @param path
 	 *            name of the cache entry, in the standard encoding.
 	 * @param stage
 	 *            the stage index of the new entry.
@@ -274,16 +275,16 @@ public class DirCacheEntry {
 	 *             range 0..3, inclusive.
 	 */
 	@SuppressWarnings("boxing")
-	public DirCacheEntry(final byte[] newPath, final int stage) {
-		DirCacheCheckout.checkValidPath(toString(newPath));
+	public DirCacheEntry(byte[] path, final int stage) {
+		checkPath(path);
 		if (stage < 0 || 3 < stage)
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().invalidStageForPath,
-					stage, toString(newPath)));
+					stage, toString(path)));
 
 		info = new byte[INFO_LEN];
 		infoOffset = 0;
-		path = newPath;
+		this.path = path;
 
 		int flags = ((stage & 0x3) << 12);
 		if (path.length < NAME_MASK)
@@ -730,6 +731,16 @@ public class DirCacheEntry {
 			return 0;
 	}
 
+	private static void checkPath(byte[] path) {
+		try {
+			SystemReader.getInstance().checkPath(path);
+		} catch (CorruptObjectException e) {
+			InvalidPathException p = new InvalidPathException(toString(path));
+			p.initCause(e);
+			throw p;
+		}
+	}
+
 	private static String toString(final byte[] path) {
 		return Constants.CHARSET.decode(ByteBuffer.wrap(path)).toString();
 	}

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

@@ -339,4 +339,19 @@ public abstract class SystemReader {
 	public void checkPath(String path) throws CorruptObjectException {
 		platformChecker.checkPath(path);
 	}
+
+	/**
+	 * Check tree path entry for validity.
+	 * <p>
+	 * Scans a multi-directory path string such as {@code "src/main.c"}.
+	 *
+	 * @param path
+	 *            path string to scan.
+	 * @throws CorruptObjectException
+	 *             path is invalid.
+	 * @since 4.2
+	 */
+	public void checkPath(byte[] path) throws CorruptObjectException {
+		platformChecker.checkPath(path, 0, path.length);
+	}
 }