Minor class loading optimization.

In internal bug 1836311, the String.replace() in PathLoader.findClass
was identifed by traceview as 6.6% of startup time for an app.  This
adds a (hidden) alternative that takes a "binary name" like the
functions in ClassLoader, and we do the slash-to-dot conversion inside
the VM as we convert it to a descriptor.  (This is really how it should
have been done in the first place, but now it's part of the visible API
and engraved in stone.)

The original function now does a slash-to-dot conversion and calls the
new one.

(We may want to un-hide the method for the benefit of people writing
custom class loaders.  If so, we can do that in a separate API-update
commit.)

2 files changed, 31 insertions, 15 deletions

diff --git a/dalvik/src/main/java/dalvik/system/DexFile.java b/dalvik/src/main/java/dalvik/system/DexFile.java
index da51e45..00de314 100644
--- a/dalvik/src/main/java/dalvik/system/DexFile.java
+++ b/dalvik/src/main/java/dalvik/system/DexFile.java
@@ -38,11 +38,13 @@ public final class DexFile {
 
     /**
      * Opens a DEX file from a given File object. This will usually be a ZIP/JAR
-     * file with a "classes.dex" inside. The method should not be used for files
-     * inside the Dalvik cache.
-     * 
-     * @cts What will happen if we refer to the Dalvik cache? Should be either
-     *      specified or throw an exception...
+     * file with a "classes.dex" inside.
+     *
+     * The VM will generate the name of the coresponding file in
+     * /data/dalvik-cache and open it, possibly creating or updating
+     * it first if system permissions allow.  Don't pass in the name of
+     * a file in /data/dalvik-cache, as the named file is expected to be
+     * in its original (pre-dexopt) state.
      * 
      * @param file
      *            the File object referencing the actual DEX file
@@ -57,11 +59,13 @@ public final class DexFile {
 
     /**
      * Opens a DEX file from a given filename. This will usually be a ZIP/JAR
-     * file with a "classes.dex" inside. The method should not be used for files
-     * inside the Dalvik cache.
-     * 
-     * @cts What will happen if we refer to the Dalvik cache? Should be either
-     *      specified or throw an exception...
+     * file with a "classes.dex" inside.
+     *
+     * The VM will generate the name of the coresponding file in
+     * /data/dalvik-cache and open it, possibly creating or updating
+     * it first if system permissions allow.  Don't pass in the name of
+     * a file in /data/dalvik-cache, as the named file is expected to be
+     * in its original (pre-dexopt) state.
      * 
      * @param fileName
      *            the filename of the DEX file
@@ -190,11 +194,23 @@ public final class DexFile {
      * @cts Exception comment is a bit cryptic. What exception will be thrown?
      */
     public Class loadClass(String name, ClassLoader loader) {
+        String slashName = name.replace('.', '/');
+        return loadClassBinaryName(slashName, loader);
+    }
+
+    /**
+     * See {@link #loadClass(String, ClassLoader)}.
+     *
+     * This takes a "binary" class name to better match ClassLoader semantics.
+     *
+     * {@hide}
+     */
+    public Class loadClassBinaryName(String name, ClassLoader loader) {
         return defineClass(name, loader, mCookie,
             null);
             //new ProtectionDomain(name) /*DEBUG ONLY*/);
     }
-    
+
     native private static Class defineClass(String name, ClassLoader loader,
         int cookie, ProtectionDomain pd);
 
diff --git a/dalvik/src/main/java/dalvik/system/PathClassLoader.java b/dalvik/src/main/java/dalvik/system/PathClassLoader.java
index 55e61a9..597eb5b 100644
--- a/dalvik/src/main/java/dalvik/system/PathClassLoader.java
+++ b/dalvik/src/main/java/dalvik/system/PathClassLoader.java
@@ -179,8 +179,9 @@ public class PathClassLoader extends ClassLoader {
      * parent ClassLoader has failed to find a loaded class of the same name.
      * 
      * @param name
-     *            The name of the class to search for, in a human-readable form
-     *            like "java.lang.String" or "java.net.URLClassLoader$3$1".
+     *            The "binary name" of the class to search for, in a
+     *            human-readable form like "java.lang.String" or
+     *            "java.net.URLClassLoader$3$1".
      * @return the {@link Class} object representing the class
      * @throws ClassNotFoundException
      *             if the class cannot be found
@@ -199,8 +200,7 @@ public class PathClassLoader extends ClassLoader {
             //System.out.println("My path is: " + mPaths[i]);
 
             if (mDexs[i] != null) {
-                String slashName = name.replace('.', '/');
-                Class clazz = mDexs[i].loadClass(slashName, this);
+                Class clazz = mDexs[i].loadClassBinaryName(name, this);
                 if (clazz != null)
                     return clazz;
             } else if (mZips[i] != null) {