Reverse hex value
Hi
I have a binaray file that is read in to a char vector. The problem is that the values that im interested in are somehow reversed.
cout << hex << static_cast<int>(myVector[4]) << endl;
The value from the vector formatted as hex is for example 87, but i want it reversed to 78.
Is that possible, if so could someone give me a hint.
I have a binaray file that is read in to a char vector. The problem is that the values that im interested in are somehow reversed.
cout << hex << static_cast<int>(myVector[4]) << endl;
The value from the vector formatted as hex is for example 87, but i want it reversed to 78.
Is that possible, if so could someone give me a hint.
I'm afraid what you observe is only a part of the iceberg. It's probably not as simple as "reversed".
The real mechanism, I believe, is the following:
you read data into memory in char, i.e. byte, 8 bits. You memory is byte addressed. Then you do a type cast when outputing the values in the vector. The new type is int, i.e. 32 bit (might not be true on all machines, but very likely to be true). So you program is outputing four bytes of binary values at a time.
As to reversing the observed 87 into 78, you might want to look into your program and find out the real reason. Simply doing a reverse is easy, but you need a good reason to support your reverse.
The real mechanism, I believe, is the following:
you read data into memory in char, i.e. byte, 8 bits. You memory is byte addressed. Then you do a type cast when outputing the values in the vector. The new type is int, i.e. 32 bit (might not be true on all machines, but very likely to be true). So you program is outputing four bytes of binary values at a time.
As to reversing the observed 87 into 78, you might want to look into your program and find out the real reason. Simply doing a reverse is easy, but you need a good reason to support your reverse.
Ok, thanks!!
I suspected it was not that easy and i have to look into it more thoroughly and do it right.
For now i could need some help with just doing a reverse. You say it is easy, can you give me an example, i would really appreciate it.
I suspected it was not that easy and i have to look into it more thoroughly and do it right.
For now i could need some help with just doing a reverse. You say it is easy, can you give me an example, i would really appreciate it.
@Fredic:
I don't know why you want this, but:
temp = static_cast<int>(myVector[4]);
cout << hex << (temp -16*6)*16+6;
I don't know why you want this, but:
temp = static_cast<int>(myVector[4]);
cout << hex << (temp -16*6)*16+6;
It's all right. Are you trying to convert numbers in hex?
If that's the case:
78 in hex means: 7*16^1 + 8*16^0.
Assume 0x78 is A in decimal, then:
A/16 gives you 7;
A - 7*16 gives you 8
If that's the case:
78 in hex means: 7*16^1 + 8*16^0.
Assume 0x78 is A in decimal, then:
A/16 gives you 7;
A - 7*16 gives you 8
Because no one mentioned it yet, if it is endianness, it would not become 87 --> 78. If that is what's happening, than it is not endianess. It would do more of the following style:
In that particular case, it would go from a positive value very close to 0, to more then halfway to the max negative value.
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In that particular case, it would go from a positive value very close to 0, to more then halfway to the max negative value.
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