1

In Java :

value = 1122;

public static final byte[] intToByteArray(int value) {
        return new byte[] {
                (byte)(value >>> 24),
                (byte)(value >>> 16),
                (byte)(value >>> 8),
                (byte)value};
    }

  public static int byteArrayToInt(byte[] data) {
        return (int)(
                (int)(0xff & data[0]) << 24  |
                (int)(0xff & data[1]) << 16  |
                (int)(0xff & data[2]) << 8   |
                (int)(0xff & data[3]) << 0
        );
    }

here it'll return [0, 0, 4, 98] so in C:

char* intToByteArray(int value){
        char* temp = new char[4];
         temp[0] = value >> 24,
         temp[1] = value >> 16,
         temp[2] = value >> 8, 
         temp[3] = value;
         return temp;
}

since there's no byte data type in c we can use char* instead of that but when i return temp value i am getting null so i checked values like this where = b\x04 'b'= 98, x04 = 4 i am not able to get data which is zero so while converting back how should i manage remaining values??

         char* where = new char[10];
         where[0] = temp[3];
         where[1] = temp[2];
         where[2] = temp[1];
         where[3] = temp[0];
         where[4] = 0;
poppy
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  • I'm not sure what your problem is, but this code works fine for me. The values of temp and where were both set properly. Are you sure you're using the "==" operator. I don't see why you can't do " where[3] == 0". There's no reason you shouldn't be able to get data that's 0. – steveg89 Aug 06 '12 at 13:55

2 Answers2

3

i am getting null

No you are not. You are getting a first byte which is a \0 nul byte. When you print this as a text string it will terminate the string. But its not a string, its an array of bytes.

If you were getting a NULL, you would get a segmentation fault or the like.

Peter Lawrey
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  • ya sorry getting \x00 value but what about remaining values how to get those and store in array.here only i am facing difficulty. – poppy Aug 06 '12 at 13:47
  • You can get those with `bytes[0]`, `bytes[1]` `bytes[2]` and `bytes[3]` like an array. ;) – Peter Lawrey Aug 06 '12 at 13:50
  • ya like this i can get all values int tt = temp[0];int tt1 = temp[1];int tt2 = temp[2];int tt3 = temp[3]; but i cant store all those values in array as bytes:(. is it possible to store like this \x00\x00\x04\x98?? – poppy Aug 06 '12 at 14:07
  • A `char*` is a pointer to an array of bytes. Doesn't `temp` have all those values in an array as bytes. – Peter Lawrey Aug 06 '12 at 14:11
0

While the above post is absolutely correct, you have one more serious problem with your porting effort. Your java produces

[ 0, 0, 4, 98 ]

while your C produces

[ 98, 4, 0, 0 ]

The code won't work when simply converted like that. Java is big-endian regardless of the hardware, but your C(++) unsurprisingly is low-endian. Worse still, you cannot be sure that it will be that way every time. With Carbide, i guess that you can perfectly stumble upon a big endian architecture (some ARMs? not an expert in this field). So you must either detect endian-ness of your Carbide platform or, replace the bitshift with an incremental modulo 256. Depends on how often you call the function. Modulo will take seriously more processor effort but doesn't care about endianness.

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Pavel Zdenek
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  • sorry,actually c also produces like java only but starting zero is there so rest of the values i am not able to see i made it reverse using other variable as mentioned in above code. – poppy Aug 07 '12 at 04:40