use utf8_length() instead of local function, isValidUtf8()

utf8_length() from libutils returns -1 when source not contains
valid sequence for UTF-8. Fixed to use it and removed the local
function isValidUtf8().

Change-Id: If2834ce1d1ae07fd8526ce8bc5df3fd3f44e85c8
Signed-off-by: Homin Lee <suapapa@insignal.co.kr>

Author: Homin Lee

media/jni/android_media_MediaScanner.cpp

@@ -19,6 +19,7 @@
 #define LOG_TAG "MediaScannerJNI"
 #include <utils/Log.h>
 #include <utils/threads.h>
+#include <utils/Unicode.h>
 #include <media/mediascanner.h>
 #include <media/stagefright/StagefrightMediaScanner.h>
 
@@ -56,53 +57,6 @@ static status_t checkAndClearExceptionFromCallback(JNIEnv* env, const char* meth
     return OK;
 }
 
-// stolen from dalvik/vm/checkJni.cpp
-static bool isValidUtf8(const char* bytes) {
-    while (*bytes != '\0') {
-        unsigned char utf8 = *(bytes++);
-        // Switch on the high four bits.
-        switch (utf8 >> 4) {
-        case 0x00:
-        case 0x01:
-        case 0x02:
-        case 0x03:
-        case 0x04:
-        case 0x05:
-        case 0x06:
-        case 0x07:
-            // Bit pattern 0xxx. No need for any extra bytes.
-            break;
-        case 0x08:
-        case 0x09:
-        case 0x0a:
-        case 0x0b:
-        case 0x0f:
-            /*
-             * Bit pattern 10xx or 1111, which are illegal start bytes.
-             * Note: 1111 is valid for normal UTF-8, but not the
-             * modified UTF-8 used here.
-             */
-            return false;
-        case 0x0e:
-            // Bit pattern 1110, so there are two additional bytes.
-            utf8 = *(bytes++);
-            if ((utf8 & 0xc0) != 0x80) {
-                return false;
-            }
-            // Fall through to take care of the final byte.
-        case 0x0c:
-        case 0x0d:
-            // Bit pattern 110x, so there is one additional byte.
-            utf8 = *(bytes++);
-            if ((utf8 & 0xc0) != 0x80) {
-                return false;
-            }
-            break;
-        }
-    }
-    return true;
-}
-
 class MyMediaScannerClient : public MediaScannerClient
 {
 public:
@@ -170,8 +124,11 @@ class MyMediaScannerClient : public MediaScannerClient
             mEnv->ExceptionClear();
             return NO_MEMORY;
         }
+
+        // Check if the value is valid UTF-8 string and replace
+        // any un-printable characters with '?' when it's not.
         char *cleaned = NULL;
-        if (!isValidUtf8(value)) {
+        if (utf8_length(value) == -1) {
             cleaned = strdup(value);
             char *chp = cleaned;
             char ch;