I'm writing a C++ progr that requires a conversion, really a substitution, in HEX notation ...

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And currently I'm using "Uri" (Uniform Resource Identifier) method that's available to me as I use VS1010. Everything works ok now but I'm thinking there must be an older more C++ style method to convert a "15" to a "F".

Posted 20-Jan-12 9:48am

RedDk

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TRK3 · Answer 1 · 2012-01-20T11:18:00

Solution 4

It's not clear at all what you are looking for, but here's the standard "old school" answers:

Standard K&R C:

C++

char buffer[256];

sprintf(buffer,"%04x", integerValueYouWantToDisplayAsHex);

Seriously old school (if you don't have the C-runtime):

C++

char output_buffer[5];
char toHex[] = "0123456789ABCDEF";

for (int i = 3; i > 0; i--) {
    output_buffer[3-i] = toHex[(inputValue >> (i * 4)) & 0xff];
}
output_buffer[4] = 0;

Posted 20-Jan-12 11:18am

TRK3

Comments

JackDingler 20-Jan-12 17:34pm

The correct answer seems to be, that he didn't want an answer...

TRK3 20-Jan-12 17:40pm

Yeah. Oh well, I always like to dust of my K&R C...

RedDk 20-Jan-12 17:39pm

YES!

That is the type of thing I set out to do when I started. I ran into Uri::HexEscape by searching the assemblies through the VS2010 interface on "hex" and it's only thing that was returned. I thought, "where's the STL function"?

Thank-you for the code. Unicode is/has-been/always-will-be a thorn in my side.

TRK3 20-Jan-12 17:45pm

Great. I highly recommend the original Kernighan & Richie "C" book if you haven't read it.

http://www.amazon.com/Programming-Language-2nd-Brian-Kernighan/dp/0131103628

The original C is so simple and concise that I find it far easier to do things using the basic tools of C then it is to go searching through vast new frameworks and libraries to find the thing that does it -- especially when it's something like this that really ought to be simple to do.

Albert Holguin · Answer 2 · 2012-01-20T10:14:00

Solution 1

The number itself is stored as binary... the representation is just a human readable thing. So if you want to view it differently, use a string and display it however you want by just formatting your string accordingly.

Choose a string type that you want to use, and search for available format specifiers for details.

Posted 20-Jan-12 10:14am

Albert Holguin

Updated 20-Jan-12 10:16am

v2

Comments

RedDk 20-Jan-12 16:29pm

Without a note on "Uri" here in the answer I suspect that you're possibly suggesting I do something in C++ and leverage a lower level operator. Anyway, I probably should have flagged a key word ... How about Uri::HexEscape?

It works.

Albert Holguin 20-Jan-12 16:49pm

What I'm saying is.... your question is trivial... as posted, what do you mean you want to convert a 15 to F? ...is the 15 a string already? ...if it's an int value, then the decimal or hexadecimal representations are merely human readable representations.

JackDingler · Answer 3 · 2012-01-20T11:05:00

One old school way to do this, is to create a static array of 256 strings that denote the hex data.

C++

char szHexLookup[256][4] = 
{
"00","01","02","03","04","05","06","07","08","09","0A","0B","0C","0D","0E","0F", 
"10","11","12","13","14","15","16","17","18","19","1A","1B","1C","1D","1E","1F", 
"20","21","22","23","24","25","26","27","28","29","2A","2B","2C","2D","2E","2F", 
"30","31","32","33","34","35","36","37","38","39","3A","3B","3C","3D","3E","3F", 
"40","41","42","43","44","45","46","47","48","49","4A","4B","4C","4D","4E","4F", 
"50","51","52","53","54","55","56","57","58","59","5A","5B","5C","5D","5E","5F", 
"60","61","62","63","64","65","66","67","68","69","6A","6B","6C","6D","6E","6F", 
"70","71","72","73","74","75","76","77","78","79","7A","7B","7C","7D","7E","7F", 
"80","81","82","83","84","85","86","87","88","89","8A","8B","8C","8D","8E","8F", 
"90","91","92","93","94","95","96","97","98","99","9A","9B","9C","9D","9E","9F", 
"A0","A1","A2","A3","A4","A5","A6","A7","A8","A9","AA","AB","AC","AD","AE","AF", 
"B0","B1","B2","B3","B4","B5","B6","B7","B8","B9","BA","BB","BC","BD","BE","BF", 
"C0","C1","C2","C3","C4","C5","C6","C7","C8","C9","CA","CB","CC","CD","CE","CF", 
"D0","D1","D2","D3","D4","D5","D6","D7","D8","D9","DA","DB","DC","DD","DE","DF", 
"E0","E1","E2","E3","E4","E5","E6","E7","E8","E9","EA","EB","EC","ED","EE","EF", 
"F0","F1","F2","F3","F4","F5","F6","F7","F8","F9","FA","FB","FC","FD","FE","FF", 
};

You then walk through your source string, and use each character as an index to look up the corresponding hex representation.

I set the length of each string to 4 bytes so that they would all be aligned on a 4 byte boundary.

An alternative would be to make this just one 256 byte string and find the bytes by multiplying the index by 2 (shift left 1 bit for speed "Index << 1;) to find the string start.