Hex to UTF-8 Conversion Issue C++

[SSSS390]

Hi all,

I am converting hex to UTF-8 during that i am facing issue.

Input: %3d%22BoatsGreat%22

Output: =?oatsGreat"

Output should be : ="BoatsGreat"


Code:
#include <wchar.h>
#include <locale.h>
#include <stdlib.h>

void show(char* str)
{
while(str && *str)
if(*str != '%')
putwchar(btowc(*str++));
else
putwchar(strtoul(str+1, &str, 16));
}

int main()
{
setlocale(LC_ALL, "");
char str[] = "%3d%22BoatsGreat%22";
show(str);
}

[Peter87]

B is a valid hexadecimal digit so strtoul will read all three characters "22B".

[SSSS390]

@Peter87 any other option by which i can convert hex to UTF-8? as i dont want to convert B also other characters like A,B, C but it should decode.

[Peter87]

I don't think there is a similar function that let you specify the number of digits, but I don't know, I'm no expert on C string functions. It shouldn't be that hard to create your own. If you want to use strtoul you could copy the two digits to a null-terminated char array before using the function and then manually increment the str pointer by 2.

Note that UTF-8 uses 8-bit code units so when you're using putwchar, which outputs wide characters, your program is not really outputting UTF-8.

[SSSS390]

@Peter87 Yes its not outputting UTF-8 conversion really. If you know any code/function can you please tell me by which i can get UTF-8 conversion from Hex?

[Cubbi]

The title is misleading: based on the desired input/output, you're not working with UTF-8 in any capacity. You're simply reading a byte string where some bytes are encoded as three-byte sequences %xx where xx is hex.

Must it be in C? Here's a convenient way to set it up in C++:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

#include <iostream> #include <boost/spirit/include/qi.hpp> namespace qi = boost::spirit::qi; void show(const std::string& str) { std::string out; parse(str.begin(), str.end(), +('%' >> qi::int_parser<int,16,2,2>() | qi::char_), out); std::cout << out << '\n'; } int main() { show("%3d%22BoatsGreat%22"); show("%22%E7%8C%AB%F0%9F%90%B1%22"); // some UTf-8 for you }

="BoatsGreat" "猫🐱"

live demo: http://melpon.org/wandbox/permlink/cASmXQvlpTD997nm

[jonnin]

C just uses scanf.

scanf( "%x%x%s", intx, inty, str);

reads into an integer, another integer, and a string from input that is of the format 0x1 0x2 whateverrandomtext

Your input does not make sense to me, so I can't comment on the logic you need.

[SSSS390]

@cubbi Can you please show me how i can take input from user in your above code?

Because when i am doing it, giving me segmentation fault. its a large string of hex(hex string size greater than 4096) and while taking in cin it does not accept string greater than 4096.

[jonnin]

does cin.getline(var, MAXALLOWED) work?