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  1. #1
    radhika.putty is offline Member
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    Default Converting unsigned long to java

    I am trying to read a file written by C code in binary format. When i try to read data stored as unsigned long using Java i am getting wrong value because of the overflow caused by signed & unsigned probelm . I tried using BigInteger and also tried masking but nothing helped. is there any API available for this. I think we need to manually check the magnitude and do something but did anyone face this issue and found a work around

  2. #2
    lovelesh is offline Senior Member
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  3. #3
    toadaly is offline Senior Member
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    Create a BigInteger to hold the number. When you read it in, if it's negative, you know there was an overflow. In that case, add that negative BigInteger to another BigInteger that is Long.MAX_VALUE to get the unsigned value.

    Alternately, depending on what you're doing with the number, you might be able to simply deal with the negative values in a conditional, knowing they are really positive.

    As an alternate alternative, you could read the data into 2 java longs, with the upper 4 bytes in read into the lower 4 bytes of long1 and the lower 4 bytes read into the lower 4 bytes of long2.

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