UTF8 length calculation

Hello guys,
I am trying to write a code to find out no of characters in a multibyte UTF8 encoded string.

Code:

---

#include<stdio.h>
#include <stdlib.h>
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main(int argc, char** argv)
{
    string tring = argv[1];
    int count = 0;
    int length = 0;
    int number = 0;
    cout<<"Length of string"<<tring.length()<<'\n';
    cout<<"String iss " <<argv[1]<<'\n';
    length = mblen((char*)(ptr), 40);
    cout<<"Length  " << length <<'\n';
    cout<<"Total number is "<<number<<'\n';
  return 0;
}

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I have written the code above, used mblen to find out length/byte of the char being pointed. But it returns -1.

Any help/pointer will be appreciated.

OS : RHEL 4.0
Compiler : g++

What's ptr ?

I've never tried to use mblen(), but it strikes me that it's probably just as easy to write your own UTF8 version of strlen(). The rules of UTF8 are pretty simple; it would look something like

Code:

---

while (ptr)
{
    if (!(*ptr & 0x80))
        ptr++;
    else if (*ptr & 0xC0)
        ptr += 2;
    /// etc

---

mblen uses the current locale to return the length of a single multi-byte character. The default locale is 'C'.

Code:

---

#include <iostream>
#include <locale>
#include <cstdlib>
#include <cstring>
#include <climits>
using namespace std;

// taken from GNU LibC manual
// http://www.gnu.org/software/libc/manual/
size_t mbslen(const char *s)
{
    mbstate_t state;
    size_t result = 0;
    size_t nbytes;
    memset(&state, '\0', sizeof(state));
    while ((nbytes = mbrlen(s, MB_LEN_MAX, &state)) > 0)
    {
        if (nbytes >= (size_t) -2)
            return (size_t) -1; /* Something is wrong. */
        s += nbytes;
        ++result;
    }//while
    return result;
}//mbslen

int main(int argc, char **argv)
{
    if (argc < 2)
    {
        cerr << "missing parameter" << endl;
        return 1;
    }//if

    std::locale loc(""); // construct user-default locale
    std::locale::global(loc); // make it global, for std::mbrlen
    std::cout.imbue(loc); // have cout use as well

    const char *ptr = argv[1];
    string str = ptr;

    cout << "String is [" << ptr << "]" << endl;
    cout << "string::length = " << str.length() << endl;
    cout << "mbslen = " << mbslen(ptr) << endl;
    return 0;
}//main

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This assumes that the command line has the same encoding as specified by the user's default locale - which may not be the case (but is a reasonable assumption).

If you need "UTF8 length" regardless of the user's locale, you'll have to spin your own or use something like libiconv.

gg

Use mbrtowc() function, it will help you to check the length of every character.

Quote:

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Originally Posted by treuss

What's ptr ?

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Indeed, that code will not even compile, please copy & paste your actual program.