Fixed GSM encoded network initiated position request

GSM encoded network initiated position requests were previously
not correctly decoded. The GSM encoded string was decoded as
ASCII but not all characters are encoded in the same way for
GSM and ASCII. These characters was not displayed.

Besides that, when the number of characters was evenly divided
by 8 the last character was lost. This is also corrected.

Change-Id: Ic70b7c28bbba1f2936a9cc99e78f8002cc5c8761

1 files changed, 21 insertions, 46 deletions

diff --git a/location/java/com/android/internal/location/GpsNetInitiatedHandler.java b/location/java/com/android/internal/location/GpsNetInitiatedHandler.java
index d539833..ffc3346 100755
--- a/location/java/com/android/internal/location/GpsNetInitiatedHandler.java
+++ b/location/java/com/android/internal/location/GpsNetInitiatedHandler.java
@@ -29,6 +29,7 @@ import android.os.RemoteException;
 import android.util.Log;
 
 import com.android.internal.R;
+import com.android.internal.telephony.GsmAlphabet;
 
 /**
  * A GPS Network-initiated Handler class used by LocationManager.
@@ -288,58 +289,32 @@ public class GpsNetInitiatedHandler {
      */
     static String decodeGSMPackedString(byte[] input)
     {
-        final char CHAR_CR = 0x0D;
-        int nStridx = 0;
-        int nPckidx = 0;
-        int num_bytes = input.length;
-        int cPrev = 0;
-        int cCurr = 0;
-        byte nShift;
-        byte nextChar;
-        byte[] stringBuf = new byte[input.length * 2];
-        String result = "";
-
-        while(nPckidx < num_bytes)
-        {
-            nShift = (byte) (nStridx & 0x07);
-            cCurr = input[nPckidx++];
-            if (cCurr < 0) cCurr += 256;
-
-            /* A 7-bit character can be split at the most between two bytes of packed
-             ** data.
-             */
-            nextChar = (byte) (( (cCurr << nShift) | (cPrev >> (8-nShift)) ) & 0x7F);
-            stringBuf[nStridx++] = nextChar;
-
-            /* Special case where the whole of the next 7-bit character fits inside
-             ** the current byte of packed data.
-             */
-            if(nShift == 6)
-            {
-                /* If the next 7-bit character is a CR (0x0D) and it is the last
-                 ** character, then it indicates a padding character. Drop it.
-                 */
-                if (nPckidx == num_bytes || (cCurr >> 1) == CHAR_CR)
-                {
-                    break;
+        final char PADDING_CHAR = 0x00;
+        int lengthBytes = input.length;
+        int lengthSeptets = (lengthBytes * 8) / 7;
+        String decoded;
+
+        /* Special case where the last 7 bits in the last byte could hold a valid
+         * 7-bit character or a padding character. Drop the last 7-bit character
+         * if it is a padding character.
+         */
+        if (lengthBytes % 7 == 0) {
+            if (lengthBytes > 0) {
+                if ((input[lengthBytes - 1] >> 1) == PADDING_CHAR) {
+                    lengthSeptets = lengthSeptets - 1;
                 }
-
-                nextChar = (byte) (cCurr >> 1);
-                stringBuf[nStridx++] = nextChar;
             }
-
-            cPrev = cCurr;
         }
 
-        try {
-            result = new String(stringBuf, 0, nStridx, "US-ASCII");
-        }
-        catch (UnsupportedEncodingException e)
-        {
-            Log.e(TAG, e.getMessage());
+        decoded = GsmAlphabet.gsm7BitPackedToString(input, 0, lengthSeptets);
+
+        // Return "" if decoding of GSM packed string fails
+        if (null == decoded) {
+            Log.e(TAG, "Decoding of GSM packed string failed");
+            decoded = "";
         }
 
-        return result;
+        return decoded;
     }
 
     static String decodeUTF8String(byte[] input)