Redundancy bytes when read file to byte array

Question

Here is some methods to read file to byte array that I use in my android app.

M1:

   private static byte[] readFileAsBytes(String filePath)
            throws java.io.IOException{   
        FileInputStream fisTargetFile = new FileInputStream(new File(filePath));
        String targetFileStr = IOUtils.toString(fisTargetFile, "UTF-8");
        byte[] inputData =  IOUtils.toByteArray(new StringReader(targetFileStr),"UTF-8");
        return inputData;
}

M2

 private static byte[] readFileAsBytes(String filePath)
            throws java.io.IOException{

        File file = new File(filePath);
        FileInputStream inputFile = new FileInputStream(file);
        byte inputData[] = new byte[(int)file.length()];
        inputFile.read(inputData);
        inputFile.close();
        return inputData;
    }

I also use method in this ...

But, when I debug, I dectect some redundant bytes, example:

File text: ABCDEF

When debug:
- In M1: inputData: {-17,-69,-65,65,66,67,68,69,70}

I know A -> 65, B -> 66,... But Why appear {-17,-69,-65}

-In M2: Appear many redundancy than M1.

I have searched, but not find same problem.

Any suggestions for me.

Thanks!!!

Please use hexadecimal notation for byte values. Decimal ones are unreadable. — greenapps, Mar 16 '17 at 11:08
`File text: ABCDEF`. Whith which program/app did you make the file? What is the size of the file? 6 or 9? 9 i believe as you have 9 values. But ABCDEF is only 6 characters. Most probably the first three values are a BOM. A byte order mark. — greenapps, Mar 16 '17 at 11:10
`-In M2: Appear many redundancy than M1.`??? What are you trying to tell? Dont understand a word of this. Please post the values when using M2. — greenapps, Mar 16 '17 at 11:12
@greenapps, I make app to encrypt/decrypt file with key 128 bit. Above example is short. Actual text key have 16 characters,,... So, with add first three values, it not make 128 bit. I will read about BOM, Thank you for your answer. — DustinPham, Mar 16 '17 at 12:00

greenapps · Accepted Answer · 2017-03-16T11:19:09.363

 String targetFileStr = IOUtils.toString(fisTargetFile, "UTF-8");
 byte[] inputData =  IOUtils.toByteArray(new StringReader(targetFileStr),"UTF-8");

Do not use intermediate String or StringReader to put the bytes of a file in a byte array.

For instance you cannot put a jpg file in a String as it's no text.

Put the bytes directly in a byte array as you do in the second readFileAsBytes(). That one should work. But you have to check the return value of inputFile.read(inputData); and eventually make a loop.

The three leading bytes are a BOM. A byte order mark. See: https://en.wikipedia.org/wiki/Byte_order_mark

 The UTF-8 representation of the BOM is the byte sequence 0xEF,0xBB,0xBF

The second one is not guranteed to work (though it often will) since the read call need not read the full array nor the full file. — Henry, Mar 16 '17 at 12:06

Redundancy bytes when read file to byte array

1 Answers1