Add a util function that converts Text ndef record to text.

Add a unit test for it.

Change-Id: I5ce2020669150e3768a19354e951b6a54cc550d4

diff --git a/apps/Tag/src/com/android/apps/tag/NdefUtil.java b/apps/Tag/src/com/android/apps/tag/NdefUtil.java
index f2b01bb..3035c84 100644 (file)
--- a/apps/Tag/src/com/android/apps/tag/NdefUtil.java
+++ b/apps/Tag/src/com/android/apps/tag/NdefUtil.java
@@ -22,6 +22,7 @@ import com.google.common.collect.ImmutableBiMap;
 import com.google.common.primitives.Bytes;
 import com.trustedlogic.trustednfc.android.NdefRecord;
 
+import java.io.UnsupportedEncodingException;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.nio.charset.Charsets;
@@ -147,4 +148,44 @@ public class NdefUtil {
             return false;
         }
     }
+
+    /**
+     * Extracts payload text from Text type ndef record.
+     *
+     * @param record A ndef record. Must be {@link NdefRecord#TYPE_TEXT}.
+     * @return text payload.
+     */
+    public static String toText(NdefRecord record) {
+        Preconditions.checkArgument(record.getTnf() == NdefRecord.TNF_WELL_KNOWN_TYPE);
+        Preconditions.checkArgument(Arrays.equals(record.getType(), NdefRecord.TYPE_TEXT));
+        try {
+
+            byte[] payload = record.getPayload();
+
+            /*
+             * payload[0] contains the "Status Byte Encodings" field, per
+             * the NFC Forum "Text Record Type Definition" section 3.2.1.
+             *
+             * bit7 is the Text Encoding Field.
+             *
+             * if (Bit_7 == 0): The text is encoded in UTF-8
+             * if (Bit_7 == 1): The text is encoded in UTF16
+             *
+             * Bit_6 is reserved for future use and must be set to zero.
+             *
+             * Bits 5 to 0 are the length of the IANA language code.
+             */
+
+            String textEncoding = ((payload[0] & 0200) == 0) ? "UTF-8" : "UTF-16";
+            int languageCodeLength = payload[0] & 0077;
+
+            return new String(payload,
+                    languageCodeLength + 1,
+                    payload.length - languageCodeLength - 1,
+                    textEncoding);
+        } catch (UnsupportedEncodingException e) {
+            // should never happen unless we get a malformed tag.
+            throw new RuntimeException(e);
+        }
+    }
 }

diff --git a/apps/Tag/tests/src/com/android/apps/tag/NdefUtilTest.java b/apps/Tag/tests/src/com/android/apps/tag/NdefUtilTest.java
new file mode 100644 (file)
index 0000000..ee6e56b
--- /dev/null
+++ b/apps/Tag/tests/src/com/android/apps/tag/NdefUtilTest.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.apps.tag;
+
+import android.test.AndroidTestCase;
+import com.google.common.primitives.Bytes;
+import com.trustedlogic.trustednfc.android.NdefRecord;
+
+import java.io.UnsupportedEncodingException;
+
+public class NdefUtilTest extends AndroidTestCase {
+    public void testToText() throws UnsupportedEncodingException {
+        checkWord("Hello", "en-US", true);
+        checkWord("Hello", "en-US", false);
+        checkWord("abc\\u5639\\u563b", "cp1251", true);
+        checkWord("abc\\u5639\\u563b", "cp1251", false);
+    }
+
+    private static void checkWord(String word, String encoding, boolean isUtf8) throws UnsupportedEncodingException {
+        String utfEncoding = isUtf8 ? "UTF-8" : "UTF-16";
+
+        byte[] encodingBytes = encoding.getBytes("US-ASCII");
+        byte[] text = word.getBytes(utfEncoding);
+
+        int utfBit = isUtf8 ? 0 : (1 << 7);
+        char status = (char) (utfBit + encodingBytes.length);
+
+        byte[] data = Bytes.concat(
+           new byte[] { (byte) status },
+           encodingBytes,
+           text
+        );
+
+        NdefRecord record = new NdefRecord(NdefRecord.TNF_WELL_KNOWN_TYPE, NdefRecord.TYPE_TEXT, new byte[0], data);
+        assertEquals(word, NdefUtil.toText(record));
+    }
+}