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GSM7Bit encoder / decoder
// based on: https://github.com/bsimic0001/AegisWallet/blob/master/mobile/src/main/java/com/aegiswallet/utils/MessagingUtils.java
public class MessagingUtils {
public static void main(String[] args) {
System.out.println("encode: " + encode("*100#"));
System.out.println("decode: " + decode("<<message to decode>>"));
}
/**
*
* @param ascci to be encoded to gsm7 bit
* @return encoded ascci to gsm 7 bit
*/
public static String encode(String ascci) {
StringBuilder sb = new StringBuilder();
int length = ascci.length();
int gsm7Length = GSM7CHARS.length;
for (int i = length; i > 0; i--) {
char c = ascci.charAt((i - 1));
for (int j = 0; j < gsm7Length; j++) {
if ((char) GSM7CHARS[j] == c) {
int num = GSM7CHARS[j];
sb.append(makeSevenBits(Integer.toBinaryString(num)));
}
}
}
String encoded = from7BitBinaryToHexReversed(sb.toString());
return encoded;
}
/**
*
* @param hex to be decoded
* @return decoded gsm 7 bit to ascci
*/
public static String decode(String hex) {
StringBuilder binary = new StringBuilder();
StringBuilder decoded = new StringBuilder();
int length = hex.length();
for (int i = length; i >= 2; i -= 2) {
String twos = hex.substring((i - 2), i);//2 characters at a time on reverse direction
binary.append(fromHexTo8BitBinary(twos));//Convert to 8 bit binary
}
int gsm7Length = GSM7CHARS.length;
for (int i = binary.length(); i >= 7; i -= 7) {
String seven = binary.substring((i - 7), i);//Chop into 7 bits binary in reverse direction
int decimalOfSeven = Integer.parseInt(seven, 2);
for (int j = 0; j < gsm7Length; j++) {
if (GSM7CHARS[j] == decimalOfSeven) {
decoded.append("").append((char) GSM7CHARS[j]);//Do translation
}
}
}
return decoded.toString();
}
/**
*
* @param hex hex be converted to 8 bit binary
* @return 8 bit binary
*/
private static String fromHexTo8BitBinary(String hex) {
StringBuilder ret = new StringBuilder();
String binary = Integer.toBinaryString(Integer.parseInt(hex, 16));//Convert hex to binary
int length = 8 - binary.length();
for (int i = 0; i < length; i++) {
ret.append("0");//Append missing 0's
}
ret.append(binary);
return ret.toString();
}
/**
*
* @param binary to be converted to hex
* @return hex string
*/
private static String from7BitBinaryToHexReversed(String binary) {
String ret = "";
String temp = "";
int length = binary.length();
int rem = length % 8;
int missingLenth = 8 - rem;
StringBuilder zeros = new StringBuilder();
for(int i = 0; i < missingLenth; i++) {
zeros.append("0");
}
binary = zeros.toString() + binary;
length = binary.length();
for (int i = length; i >= 8; i -= 8) {//read in reverse direction
temp = binary.substring((i - 8), i);//chop into 8 bits
int val = Integer.parseInt(temp, 2);//get decimal value of binary
String code = Integer.toHexString(val);
if (code.length() < 2) {
code = "0" + code;
}
ret += code;
}
return ret.toUpperCase();
}
/**
*
* @param binaryStr to be made 7 bits bianary
* @return 7 bit binary
*/
private static String makeSevenBits(String binaryStr) {
String ret = "";
StringBuilder zeros = new StringBuilder();
int length = binaryStr.length();
int appends = 7 - length;
for (int i = 0; i < appends; i++) {
zeros.append("0");//Append missing 0's to make 7 bits
}
ret = zeros + binaryStr;
return ret;
}
/**
* GSM 7 bit table
*/
static final int[] GSM7CHARS = {
0x0040, 0x00A3, 0x0024, 0x00A5, 0x00E8, 0x00E9, 0x00F9, 0x00EC,
0x00F2, 0x00E7, 0x000A, 0x00D8, 0x00F8, 0x000D, 0x00C5, 0x00E5,
0x0394, 0x005F, 0x03A6, 0x0393, 0x039B, 0x03A9, 0x03A0, 0x03A8,
0x03A3, 0x0398, 0x039E, 0x00A0, 0x00C6, 0x00E6, 0x00DF, 0x00C9,
0x0020, 0x0021, 0x0022, 0x0023, 0x00A4, 0x0025, 0x0026, 0x0027,
0x0028, 0x0029, 0x002A, 0x002B, 0x002C, 0x002D, 0x002E, 0x002F,
0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037,
0x0038, 0x0039, 0x003A, 0x003B, 0x003C, 0x003D, 0x003E, 0x003F,
0x00A1, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047,
0x0048, 0x0049, 0x004A, 0x004B, 0x004C, 0x004D, 0x004E, 0x004F,
0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057,
0x0058, 0x0059, 0x005A, 0x00C4, 0x00D6, 0x00D1, 0x00DC, 0x00A7,
0x00BF, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067,
0x0068, 0x0069, 0x006A, 0x006B, 0x006C, 0x006D, 0x006E, 0x006F,
0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077,
0x0078, 0x0079, 0x007A, 0x00E4, 0x00F6, 0x00F1, 0x00FC, 0x00E0,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,};
static final int[] GSM7CHARS_DEFAULT = {
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, 0x000C, -1, -1, -1, -1, -1,
-1, -1, -1, -1, 0x005E, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
0x007B, 0x007D, -1, -1, -1, -1, -1, 0x005C,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, 0x005B, 0x007E, 0x005D, -1,
0x007C, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, 0x20AC, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1,
};
}
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