path: root/telephony/java/com/android/internal/telephony/gsm/SimUtils.java

/*
 * Copyright (C) 2006 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.internal.telephony.gsm;

import java.io.UnsupportedEncodingException;

import android.graphics.Bitmap;
import android.graphics.Color;
import android.util.Log;

/**
 * Various methods, useful for dealing with SIM data.
 */
public class SimUtils
{
    static final String LOG_TAG="GSM";

    /**
     * Many fields in GSM SIM's are stored as nibble-swizzled BCD
     *
     * Assumes left-justified field that may be padded right with 0xf 
     * values.
     *
     * Stops on invalid BCD value, returning string so far
     */
    public static String
    bcdToString(byte[] data, int offset, int length)
    {
        StringBuilder ret = new StringBuilder(length*2);
 
        for (int i = offset ; i < offset + length ; i++) {
            byte b;
            int v;
                        
            v = data[i] & 0xf;
            if (v > 9)  break;
            ret.append((char)('0' + v));

            v = (data[i] >> 4) & 0xf;
            if (v > 9)  break;
            ret.append((char)('0' + v));        
        }
        
        return ret.toString();    
    }


    /**
     * Decodes a GSM-style BCD byte, returning an int ranging from 0-99.
     *
     * In GSM land, the least significant BCD digit is stored in the most
     * significant nibble.
     *
     * Out-of-range digits are treated as 0 for the sake of the time stamp,
     * because of this: 
     *
     * TS 23.040 section 9.2.3.11
     * "if the MS receives a non-integer value in the SCTS, it shall
     * assume the digit is set to 0 but shall store the entire field
     * exactly as received"
     */
    public static int
    bcdByteToInt(byte b)
    {
        int ret = 0;

        // treat out-of-range BCD values as 0
        if ((b & 0xf0) <= 0x90) {
            ret = (b >> 4) & 0xf; 
        }

        if ((b & 0x0f) <= 0x09) {
            ret +=  (b & 0xf) * 10;
        }

        return ret;
    }


    /**
     * Decodes a string field that's formatted like the EF[ADN] alpha
     * identifier
     *
     * From TS 51.011 10.5.1:
     *   Coding:
     *   	this alpha tagging shall use either
     *      -	the SMS default 7 bit coded alphabet as defined in 
     *          TS 23.038 [12] with bit 8 set to 0. The alpha identifier 
     *          shall be left justified. Unused bytes shall be set to 'FF'; or
     *      -	one of the UCS2 coded options as defined in annex B.
     *
     * Annex B from TS 11.11 V8.13.0:
     *      1)  If the first octet in the alpha string is '80', then the
     *          remaining octets are 16 bit UCS2 characters ...
     *      2)  if the first octet in the alpha string is '81', then the
     *          second octet contains a value indicating the number of
     *          characters in the string, and the third octet contains an
     *          8 bit number which defines bits 15 to 8 of a 16 bit 
     *          base pointer, where bit 16 is set to zero and bits 7 to 1
     *          are also set to zero.  These sixteen bits constitute a
     *          base pointer to a "half page" in the UCS2 code space, to be
     *          used with some or all of the remaining octets in the string.
     *          The fourth and subsequent octets contain codings as follows:
     *          If bit 8 of the octet is set to zero, the remaining 7 bits
     *          of the octet contain a GSM Default Alphabet character,
     *          whereas if bit 8 of the octet is set to one, then the
     *          remaining seven bits are an offset value added to the
     *          16 bit base pointer defined earlier...
     *      3)  If the first octet of the alpha string is set to '82', then
     *          the second octet contains a value indicating the number of
     *          characters in the string, and the third and fourth octets
     *          contain a 16 bit number which defines the complete 16 bit
     *          base pointer to a "half page" in the UCS2 code space...
     */
    public static String
    adnStringFieldToString(byte[] data, int offset, int length)
    {
        if (length >= 1) {
            if (data[offset] == (byte) 0x80) {
                int ucslen = (length - 1) / 2;
                String ret = null;

                try {
                    ret = new String(data, offset + 1, ucslen * 2, "utf-16be");
                } catch (UnsupportedEncodingException ex) {
                    Log.e(LOG_TAG, "implausible UnsupportedEncodingException",
                          ex);
                }

                if (ret != null) {
                    // trim off trailing FFFF characters

                    ucslen = ret.length();
                    while (ucslen > 0 && ret.charAt(ucslen - 1) == '\uFFFF')
                        ucslen--;

                    return ret.substring(0, ucslen);
                }
            }
        }

        boolean isucs2 = false;
        char base = '\0';
        int len = 0;

        if (length >= 3 && data[offset] == (byte) 0x81) {
            len = data[offset + 1] & 0xFF;
            if (len > length - 3)
                len = length - 3;

            base = (char) ((data[offset + 2] & 0xFF) << 7);
            offset += 3;
            isucs2 = true;
        } else if (length >= 4 && data[offset] == (byte) 0x82) {
            len = data[offset + 1] & 0xFF;
            if (len > length - 4)
                len = length - 4;

            base = (char) (((data[offset + 2] & 0xFF) << 8) |
                            (data[offset + 3] & 0xFF));
            offset += 4;
            isucs2 = true;
        }

        if (isucs2) {
            StringBuilder ret = new StringBuilder();

            while (len > 0) {
                // UCS2 subset case

                if (data[offset] < 0) {
                    ret.append((char) (base + (data[offset] & 0x7F)));
                    offset++;
                    len--;
                }

                // GSM character set case

                int count = 0;
                while (count < len && data[offset + count] >= 0)
                    count++;

                ret.append(GsmAlphabet.gsm8BitUnpackedToString(data,
                           offset, count));

                offset += count;
                len -= count;
            }

            return ret.toString();
        }

        return GsmAlphabet.gsm8BitUnpackedToString(data, offset, length);
    }

    static int
    hexCharToInt(char c)
    {
        if (c >= '0' && c <= '9') return (c - '0');
        if (c >= 'A' && c <= 'F') return (c - 'A' + 10);
        if (c >= 'a' && c <= 'f') return (c - 'a' + 10);

        throw new RuntimeException ("invalid hex char '" + c + "'");
    }

    /**
     * Converts a hex String to a byte array.
     * 
     * @param s A string of hexadecimal characters, must be an even number of
     *          chars long
     *
     * @return byte array representation
     * 
     * @throws RuntimeException on invalid format
     */
    public static byte[]
    hexStringToBytes(String s)
    {
        byte[] ret;

        if (s == null) return null;

        int sz = s.length();

        ret = new byte[sz/2];

        for (int i=0 ; i <sz ; i+=2) {
            ret[i/2] = (byte) ((hexCharToInt(s.charAt(i)) << 4) 
                                | hexCharToInt(s.charAt(i+1)));
        }
        
        return ret;
    }


    /**
     * Converts a byte array into a String hexidecimal characters
     *
     * null returns null
     */
    public static String
    bytesToHexString(byte[] bytes)
    {
        if (bytes == null) return null;
        
        StringBuilder ret = new StringBuilder(2*bytes.length);

        for (int i = 0 ; i < bytes.length ; i++) {
            int b;

            b = 0x0f & (bytes[i] >> 4);

            ret.append("0123456789abcdef".charAt(b));

            b = 0x0f & bytes[i];

            ret.append("0123456789abcdef".charAt(b));
        }

        return ret.toString();
    }


    /**
     * Convert a TS 24.008 Section 10.5.3.5a Network Name field to a string
     * "offset" points to "octet 3", the coding scheme byte
     * empty string returned on decode error
     */
    public static String
    networkNameToString(byte[] data, int offset, int length)
    {
        String ret;
        
        if ((data[offset] & 0x80) != 0x80 || length < 1) {
            return "";
        }

        switch ((data[offset] >>> 4) & 0x7) {
            case 0:
                // SMS character set
                int countSeptets;
                int unusedBits = data[offset] & 7;
                countSeptets = (((length - 1) * 8) - unusedBits) / 7 ;
                ret =  GsmAlphabet.gsm7BitPackedToString(
                                data, offset + 1, countSeptets);
            break;
            case 1:
                // UCS2
                try {
                    ret = new String(data, 
                            offset + 1, length - 1, "utf-16");
                } catch (UnsupportedEncodingException ex) {
                    ret = "";
                    Log.e(LOG_TAG,"implausible UnsupportedEncodingException", ex);
                }
            break;

            // unsupported encoding
            default:
                ret = "";
            break;
        }

        // "Add CI"
        // "The MS should add the letters for the Country's Initials and
        //  a separator (e.g. a space) to the text string"

        if ((data[offset] & 0x40) != 0) {
            // FIXME(mkf) add country initials here

        }

        return ret;
    }
}