Scanning a File in Binary Mode and Interpret the Hex Characters as Actual Numbers in C++
I Know This Title Might Sound Confusing. I Have a Simple Question Which I Haven't Been Able to Solve Yet. Lets Imagine I Have a File, Opening It with an Hex...
I know this title might sound confusing. I have a simple question which I haven't been able to solve yet.
Lets imagine I have a file, opening it with an Hex Editor shows it has two characters inside, say 0x1B and 0x00 (obviously unprintable). I'd like to take that as 1B00 in HEX, which is 6912 in DEC, as opposed to directly converting the characters which would be wrong and is what all other questions I saw asked. Well, thats the task I want to do here. Seems simple, but everything I've tried just does it wrong! Even though I am obviously opening the file in binary mode.
I have only managed to read the characters individually, and mess around a bit, but never do what I actually want, which is as simple as taking those 2 hex characters, interpreting them as an Hex Number, and then convert it to Decimal.
Sorry for any unclear idea, Im not a native speaker. Any help will be appreciated, Im sure you'll think this was quite a noobish question :P
EDIT: Sorry, apparently I didn't explain myself properly. I know this might seem abstract, but it is a really concrete little thing which I have struggled to get solved, yet I haven't been able. Maybe I can ask it another way:
How can I scan a character in binary mode, lets say 0x1B, and convert that to actual 1B characters. Just that.
3 Answers
Sounds like you want to read the file as raw data, and then display it on the screen in decimal? Super easy!
int main() {
std::ifstream myfile("filename.data", std::ofstream::binary);
uint16_t number;
char* buffer = (char*)(&number);
while(myfile.read(buffer, sizeof(number))) {
std::cout << number << ' ';
}
}
The reason it's so easy is that there's no hexidecimal involved. The file is saved as a series of bytes, each byte holds one of 256 values. They aren't hex, they're just a series of values. If you read two bytes into the uint16_t, that is the easiest way to interpret two bytes as a single unsigned 2 byte value. And streaming out a uint16_t will, by default, display that value in decimal. There's no hexidecimal involved. The hexidecimal you saw in the hex editor was because a hex editor interprets the bytes as hex values.
If all you want to do is print a number in hexadecimal form, use std::hex
int i = 0x1B;
std::cout << std::hex << i << std::endl;
std::ifstream infile("test.bin", std::ofstream::binary);
while (true)
{
char c1 = ifs.get();
if (!infile.good())
{
break;
}
char c2 = ifs.get();
if (!infile.good())
{
break;
}
int num = (int)c1 |((int)c2 << 8);
// if you need the oppisite order then
// int num = (int)c2 &((int)c1 << 8);
cout << num;
}
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