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Hi
I know there's been loads of threads about this, but I searched for like an hour straight, an' couldn't find anythin'. :(
Anyway, I have a txt document saved in C: . It consists of many hex values, all strung together. I wish to simply read the file, take the first 14 characters, ( or use 14 characters to the middle of the document ) change them to ascii values, and store them to a string.
How can this be achieved ?
Many thanks.
not possible if there is nothing separating the hex values, unless you know that they were stored as pairs of hex values, ffff is really ff and ff. In that case it is pretty simple. read the first 14 characters into a buffer and convert them in memory.
You might be able to do it with stringstream c++ class, but I'm not proficient enough to show you how.Code:char buf[] = "fc";
int a;
sprintf(buf,"%x",&a);
Never really understood what buffers are / do.
Would it help if I say they were all separated by a full stop ?
You can read in different numbers from streams and stuff after you include a header called iomanip In that header is a function called setbase that allows you to change between number systems. You can still store them in normal variables too.
It works something like this:
Code:int num = 255;
cout <<"The number 255 in hexadecimal is " <<setbase(16) <<num <<"\n";
cout<<"Enter a new hex number: ";
cin>> setbase(16)>> num;
>>would it help if I say they were all separated by a full stop
nope -- I have no idea what a "full stop" is. They should be separated by spaces, tabe or CR/LF (Windows) or LF (*nix).
A buffer is nothing more than a consecutive set of memory that is used for odds and ends. See the code I posted for an example. There are all sorts of uses for them.
A buffer is simply temporary storage. In this case, it's a Character Array (C-style string).
You might find a hex editor helpful. I use XVI32 (FREE !!!). A hex editor will allow you to "look at" (and optionally edit) the data in any file. Most hex editors will also show the ASCII characters for any value that's in the ASCII range (i.e. 32 - 126). So, you can easily see if your program is altering the file as you expect.
You don't really change the value. You display the value's associated ASCII character. If you read-in 41 hex, that's an ASCII 'A'. If you if you increment it to 42 hex, it now represents an ASCII 'B'.Quote:
...change them to ascii values, and store them to a string.
Everything in the file (and your computer's memory) is a binary numerical value. That "number" might represent an ASCII character, the numerical value, or something else. You can display that number in decimal, octal, hex, as an ASCII character, or even in binary with a little more work.
You do need to read the data in as type char, or else you will get more than one character packed-into each integer.
Try this.Quote:
take the first 14 characters, ( or use 14 characters to the middle of the document ) change them to ascii values, and store them to a string.
Code:#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
string value("0123456789ABCDEF");
char array[14];
ifstream in("file.txt");
in.read(array, 14);
string hex(array, array+14);
string result;
for (string::size_type i=0; i<hex.length(); i+=2)
{
char ascii = value.find(hex[i]) * 16;
ascii += value.find(hex[i+1]);
cout << (int) ascii << endl;
result = result + ascii;
}
in.close();
cout << result << endl;
return 0;
}
Also, is there a simple way to invert strings ?
Thanks for all your help.Code:#include <iostream>
#include <string>
using namespace std;
int main()
{
string invertstring = "123456789"
invertstring.invert();
}
By far the easiest way is to use the reverse algorithm on the string. It's great.Code:// Reversing a string
#include <algorithm>
#include <iostream>
#include <string>
int main(void) {
std::string palindrome = "You can't reverse racecar!";
reverse(palindrome.begin(), palindrome.end());
std::cout<< palindrome <<std::endl;
return 0;
}
There are previous threads on this, a simple search of the boards would have answered your question. :)
No. But what would help is posting a small portion of the file so we can actually see what you are talking about. And maybe an example of what you want based on what you post.Quote:
Originally Posted by Necrofear
A picture is worth a thousand poorly explained questions and alleviates two thousand suggestions based on misinterpretation. ;)
Oh, right yeah. Forgot to search first.
But problems solved. Cheers people ! ;)
Oh, one more question :
What if I want to store the hex equivalent ( again I think that's the correct terminology, ) of a string inputted by the user into a completely different string. :confused:
If any methods require any other headers than the ones already needed, please tell me what the headers are.Code:
string string;
getline ( cin, string );
// Compute the hex equivalent of string.
// Store it in another string.
If you just want to print it, you can do:
If you want to store it in another string then one idea is:Code:for (string::size_type i=0; i<my_string.length(); i++)
cout << hex << static_cast<unsigned int> (my_string[i]) << endl;
Code:#include <sstream>
.
.
string my_string;
getline ( cin, my_string );
ostringstream ss;
for (string::size_type i=0; i<my_string.length(); i++)
{
ss << hex << uppercase << static_cast<unsigned int> (my_string[i]);
}
string hex_out = ss.str();
cout << hex_out << endl;
Oh, but is there a way to do it in lower case. I just tried to switch the uppercase to lowercase, but it said that lowercase was undeclared. Why's this ? :confused:
You people are amazing.
Cheers for ALL your help
The function for changing uppercase characters to lowercase characters is called tolower:
Code:int main()
{
locale loc;
string mystr("THIS IS ALL IN UPPERCASE");
cout << mystr.c_str() << endl;
for(string::size_type i = 0; i < mystr.length(); i++)
mystr[i] = tolower(mystr[i], loc);
cout << mystr.c_str() << endl;
What's
locale loc;
for? Can't you just do ...
Code:#include <iostream>
#include <string>
using namespace std;
int main()
{
string thing = "asdf";
cout<< endl << thing;
for ( int i=0; i<4; i++ )
{
thing[i] = toupper( (int) thing[i] );
}
cout<< endl << thing;
return 0;
}
Out of the two methods, only twormers worked.
But that one only converts the first letter.
How can I convert them all ?
(Sorry if i'm bieng stupid here, and have missed something obvious.)
Converts all the letters when I run it...
[update]
That locale loc seems very wrong - toupper takes only 1 argument
[/update]
Just incase this makes a difference, there are some numbers in between the letters I wish to convert.
Dunno if this matters or not.
No it shouldn't matter - you can test this in twomers program
by replacing the "asdf" with "1234" - output is unchanged for
numbers.
I think you can just use std::transform() here:
Code:#include <algorithm> // for std::transform
#include <string> // for std::string
#include <cctype> // for toupper
#include <iostream> // for std::cout and std::endl
int main()
{
std::string str = "asdf123";
std::cout << str << std::endl;
std::transform(str.begin(), str.end(), str.begin(), toupper);
std::cout << str << std::endl;
}
It's been a while since I googled this one, but I seem to remember some kind of issues with that.Quote:
Originally Posted by laserlight
http://groups.google.com/group/comp....f0e60773407338
Yep, on a hunch that there might be a problem I tested with both the MinGW port of GCC and MSVC8. std::toupper gave no compilation problems with MSVC8, but choked on GCC. The old C toupper worked in both cases.Quote:
It's been a while since I googled this one, but I seem to remember some kind of issues with that.
I did a check in Josuttis' The C++ Standard Library, and his example (chapter 11, section 2.13) was the same as my modified version, with the condition that the global locale is used.
How come transform only works if your'e not using namespace std ?
My guess would be that the using declaration brings std::toupper into scope, so you then face the same problem as I did with the MinGW port of GCC.Quote:
How come transform only works if your'e not using namespace std ?
>Oh, but is there a way to do it in lower case.
Are you wanting the hex output in lowercase? If yes, you can just leave out the uppercase flag:
At any rate, std::transform and std::tolower are worth learning.Code:ss << hex << static_cast<unsigned int> (my_string[i]);
Yeah, the previously mentioned method worked.
Cheers swoopy, owe you one.
You used 5 full stops in your post ;) I think they're known as "periods" in the US.Quote:
Originally Posted by Ancient Dragon
Ah. Sorry I'm from England.