From 41a972cd1efe22ba65b4dfdd2fcaad8af18a522c Mon Sep 17 00:00:00 2001
From: Andrey Loskutov <loskutov@gmx.de>
Date: Thu, 10 Sep 2015 00:04:38 +0200
Subject: [PATCH] [performance] Cache platform name in SystemReader

SystemReader.isMacOs() and SystemReader.isWindows() return values are
unlikely to change during the JVM lifetime (except tests). Don't read
system properties each time the methods are called, just use previously
calculated value.

Change-Id: I495521f67a8b544e7b7247d99bbd05a42ea16d20
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
---
 .../eclipse/jgit/junit/MockSystemReader.java  | 18 +++++++++
 .../org/eclipse/jgit/util/SystemReader.java   | 40 ++++++++++++-------
 2 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java
index 65551d657..d24dd44ff 100644
--- a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java
+++ b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java
@@ -47,6 +47,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.HashMap;
@@ -170,6 +171,7 @@ public DateFormat getDateTimeInstance(int dateStyle, int timeStyle) {
 	 * Assign some properties for the currently executing platform
 	 */
 	public void setCurrentPlatform() {
+		resetOsNames();
 		setProperty("os.name", System.getProperty("os.name"));
 		setProperty("file.separator", System.getProperty("file.separator"));
 		setProperty("path.separator", System.getProperty("path.separator"));
@@ -180,6 +182,7 @@ public void setCurrentPlatform() {
 	 * Emulate Windows
 	 */
 	public void setWindows() {
+		resetOsNames();
 		setProperty("os.name", "Windows");
 		setProperty("file.separator", "\\");
 		setProperty("path.separator", ";");
@@ -191,10 +194,25 @@ public void setWindows() {
 	 * Emulate Unix
 	 */
 	public void setUnix() {
+		resetOsNames();
 		setProperty("os.name", "*nix"); // Essentially anything but Windows
 		setProperty("file.separator", "/");
 		setProperty("path.separator", ":");
 		setProperty("line.separator", "\n");
 		setPlatformChecker();
 	}
+
+	private void resetOsNames() {
+		Field field;
+		try {
+			field = SystemReader.class.getDeclaredField("isWindows");
+			field.setAccessible(true);
+			field.set(null, null);
+			field = SystemReader.class.getDeclaredField("isMacOS");
+			field.setAccessible(true);
+			field.set(null, null);
+		} catch (Exception e) {
+			e.printStackTrace();
+		}
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
index b4233b6cc..4795c89e7 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
@@ -71,6 +71,11 @@
  */
 public abstract class SystemReader {
 	private static final SystemReader DEFAULT;
+
+	private static Boolean isMacOS;
+
+	private static Boolean isWindows;
+
 	static {
 		SystemReader r = new Default();
 		r.init();
@@ -148,6 +153,8 @@ public static SystemReader getInstance() {
 	 *            the default instance.
 	 */
 	public static void setInstance(SystemReader newReader) {
+		isMacOS = null;
+		isWindows = null;
 		if (newReader == null)
 			INSTANCE = DEFAULT;
 		else {
@@ -293,26 +300,31 @@ public DateFormat getDateTimeInstance(int dateStyle, int timeStyle) {
 	 * @return true if we are running on a Windows.
 	 */
 	public boolean isWindows() {
-		String osDotName = AccessController
-				.doPrivileged(new PrivilegedAction<String>() {
-					public String run() {
-						return getProperty("os.name"); //$NON-NLS-1$
-					}
-				});
-		return osDotName.startsWith("Windows"); //$NON-NLS-1$
+		if (isWindows == null) {
+			String osDotName = getOsName();
+			isWindows = Boolean.valueOf(osDotName.startsWith("Windows")); //$NON-NLS-1$
+		}
+		return isWindows.booleanValue();
 	}
 
 	/**
 	 * @return true if we are running on Mac OS X
 	 */
 	public boolean isMacOS() {
-		String osDotName = AccessController
-				.doPrivileged(new PrivilegedAction<String>() {
-					public String run() {
-						return getProperty("os.name"); //$NON-NLS-1$
-					}
-				});
-		return "Mac OS X".equals(osDotName) || "Darwin".equals(osDotName); //$NON-NLS-1$ //$NON-NLS-2$
+		if (isMacOS == null) {
+			String osDotName = getOsName();
+			isMacOS = Boolean.valueOf(
+					"Mac OS X".equals(osDotName) || "Darwin".equals(osDotName)); //$NON-NLS-1$ //$NON-NLS-2$
+		}
+		return isMacOS.booleanValue();
+	}
+
+	private String getOsName() {
+		return AccessController.doPrivileged(new PrivilegedAction<String>() {
+			public String run() {
+				return getProperty("os.name"); //$NON-NLS-1$
+			}
+		});
 	}
 
 	/**