BatteryStats: Decode wakeup reasons in Java

Wakeup reasons come from drivers and sometimes are malformed UTF-8.
Decode them in Java so we can easily replace malformed characters
and still have user visible strings.

Bug:22368519
Change-Id: Ifade1a7fcdf6545e7e344d74390200c329430e14

2 files changed, 53 insertions, 21 deletions

diff --git a/services/core/java/com/android/server/am/BatteryStatsService.java b/services/core/java/com/android/server/am/BatteryStatsService.java
index 4b0b924..4102f37 100644
--- a/services/core/java/com/android/server/am/BatteryStatsService.java
+++ b/services/core/java/com/android/server/am/BatteryStatsService.java
@@ -58,6 +58,11 @@ import java.io.File;
 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CodingErrorAction;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 
 /**
@@ -897,7 +902,10 @@ public final class BatteryStatsService extends IBatteryStats.Stub
     }
 
     final class WakeupReasonThread extends Thread {
-        final String[] mReason = new String[1];
+        private static final int MAX_REASON_SIZE = 512;
+        private CharsetDecoder mDecoder;
+        private ByteBuffer mUtf8Buffer;
+        private CharBuffer mUtf16Buffer;
 
         WakeupReasonThread() {
             super("BatteryStats_wakeupReason");
@@ -906,25 +914,53 @@ public final class BatteryStatsService extends IBatteryStats.Stub
         public void run() {
             Process.setThreadPriority(Process.THREAD_PRIORITY_FOREGROUND);
 
+            mDecoder = StandardCharsets.UTF_8
+                    .newDecoder()
+                    .onMalformedInput(CodingErrorAction.REPLACE)
+                    .onUnmappableCharacter(CodingErrorAction.REPLACE)
+                    .replaceWith("?");
+
+            mUtf8Buffer = ByteBuffer.allocateDirect(MAX_REASON_SIZE);
+            mUtf16Buffer = CharBuffer.allocate(MAX_REASON_SIZE);
+
             try {
-                int num;
-                while ((num = nativeWaitWakeup(mReason)) >= 0) {
+                String reason;
+                while ((reason = waitWakeup()) != null) {
                     synchronized (mStats) {
-                        // num will be either 0 or 1.
-                        if (num > 0) {
-                            mStats.noteWakeupReasonLocked(mReason[0]);
-                        } else {
-                            mStats.noteWakeupReasonLocked("unknown");
-                        }
+                        mStats.noteWakeupReasonLocked(reason);
                     }
                 }
             } catch (RuntimeException e) {
                 Slog.e(TAG, "Failure reading wakeup reasons", e);
             }
         }
+
+        private String waitWakeup() {
+            mUtf8Buffer.clear();
+            mUtf16Buffer.clear();
+            mDecoder.reset();
+
+            int bytesWritten = nativeWaitWakeup(mUtf8Buffer);
+            if (bytesWritten < 0) {
+                return null;
+            } else if (bytesWritten == 0) {
+                return "unknown";
+            }
+
+            // Set the buffer's limit to the number of bytes written.
+            mUtf8Buffer.limit(bytesWritten);
+
+            // Decode the buffer from UTF-8 to UTF-16.
+            // Unmappable characters will be replaced.
+            mDecoder.decode(mUtf8Buffer, mUtf16Buffer, true);
+            mUtf16Buffer.flip();
+
+            // Create a String from the UTF-16 buffer.
+            return mUtf16Buffer.toString();
+        }
     }
 
-    private static native int nativeWaitWakeup(String[] outReason);
+    private static native int nativeWaitWakeup(ByteBuffer outBuffer);
 
     private void dumpHelp(PrintWriter pw) {
         pw.println("Battery stats (batterystats) dump options:");
diff --git a/services/core/jni/com_android_server_am_BatteryStatsService.cpp b/services/core/jni/com_android_server_am_BatteryStatsService.cpp
index e257e89..dfc5ef6 100644
--- a/services/core/jni/com_android_server_am_BatteryStatsService.cpp
+++ b/services/core/jni/com_android_server_am_BatteryStatsService.cpp
@@ -59,9 +59,9 @@ static void wakeup_callback(bool success)
     }
 }
 
-static jint nativeWaitWakeup(JNIEnv *env, jobject clazz, jobjectArray outReasons)
+static jint nativeWaitWakeup(JNIEnv *env, jobject clazz, jobject outBuf)
 {
-    if (outReasons == NULL) {
+    if (outBuf == NULL) {
         jniThrowException(env, "java/lang/NullPointerException", "null argument");
         return -1;
     }
@@ -99,11 +99,11 @@ static jint nativeWaitWakeup(JNIEnv *env, jobject clazz, jobjectArray outReasons
         return -1;
     }
 
-    ALOGV("Reading wakeup reasons");
+    char* mergedreason = (char*)env->GetDirectBufferAddress(outBuf);
+    int remainreasonlen = (int)env->GetDirectBufferCapacity(outBuf);
 
-    char mergedreason[MAX_REASON_SIZE];
+    ALOGV("Reading wakeup reasons");
     char* mergedreasonpos = mergedreason;
-    int remainreasonlen = MAX_REASON_SIZE;
     char reasonline[128];
     int i = 0;
     while (fgets(reasonline, sizeof(reasonline), fp) != NULL) {
@@ -161,21 +161,17 @@ static jint nativeWaitWakeup(JNIEnv *env, jobject clazz, jobjectArray outReasons
     ALOGV("Got %d reasons", i);
     if (i > 0) {
         *mergedreasonpos = 0;
-        ScopedLocalRef<jstring> reasonString(env, env->NewStringUTF(mergedreason));
-        env->SetObjectArrayElement(outReasons, 0, reasonString.get());
-        i = 1;
     }
 
     if (fclose(fp) != 0) {
         ALOGE("Failed to close %s", LAST_RESUME_REASON);
         return -1;
     }
-
-    return i;
+    return mergedreasonpos - mergedreason;
 }
 
 static JNINativeMethod method_table[] = {
-    { "nativeWaitWakeup", "([Ljava/lang/String;)I", (void*)nativeWaitWakeup },
+    { "nativeWaitWakeup", "(Ljava/nio/ByteBuffer;)I", (void*)nativeWaitWakeup },
 };
 
 int register_android_server_BatteryStatsService(JNIEnv *env)