Re: Question on a C++ string

From	Bo Persson <bo@bo-persson.se>
Newsgroups	comp.lang.c++
Subject	Re: Question on a C++ string
Date	2019-12-29 11:00 +0100
Message-ID	<h6rbpeF9oi1U1@mid.individual.net> (permalink)
References	<qu9hgc$nut$1@dont-email.me>

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On 2019-12-29 at 07:35, T wrote:
> Hi All,
> 
> I have four different way of converting a Raku/Perl6 string
> into a C++ string to pass to native call.  Three come out
> the same and one comes out with a 0x0000 (hex) at the end.
> 
> The "say" functions shows me each byte in the converted
> string.  Which one is correct?
> 
> The following is "abcdefg" converted to a C string,
> "wstr", etc. is the method I used and is not part
> of the C string:
> 
> 97 98 99 100 101 102 103       wstr
> 97 98 99 100 101 102 103 0     to-c-str
> 97 98 99 100 101 102 103       CArray[uint8].new
> 97 98 99 100 101 102 103       CArray[uint16].new
> 
> And why do I care if I am using "uint8" or "uint16"
> to convert visable text?  What about the one
> with the 0 at the end?
> 

A C string is always null-terminated, that is what *makes* it a string. 
Without the terminator it is an array of chars, which is something 
different.

The C language string-functions use the null to find the end of the 
string. For example, strlen:

"Returns the length of the given null-terminated byte string, that is, 
the number of characters in a character array whose first element is 
pointed to by str up to and not including the first null character.

The behavior is undefined if str is not a pointer to a null-terminated 
byte string."

https://en.cppreference.com/w/c/string/byte/strlen

     Bo Persson

Thread

Question on a C++ string T <T@invalid.invalid> - 2019-12-28 22:35 -0800
  Re: Question on a C++ string Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-12-29 09:33 +0000
    Re: Question on a C++ string Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2019-12-29 01:45 -0800
      Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 01:49 -0800
        Re: Question on a C++ string Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-12-29 11:04 +0000
        Re: Question on a C++ string Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2019-12-29 13:57 -0800
          Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 14:57 -0800
    Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 01:50 -0800
      Re: Question on a C++ string Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-12-29 11:08 +0000
        Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 11:50 -0800
          Re: Question on a C++ string Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2019-12-29 13:57 -0800
            Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 15:00 -0800
      Re: Question on a C++ string Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2019-12-29 13:57 -0800
        Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 15:02 -0800
          Re: Question on a C++ string Paavo Helde <myfirstname@osa.pri.ee> - 2019-12-30 01:28 +0200
      Re: Question on a C++ string Sam <sam@email-scan.com> - 2019-12-29 21:47 -0500
  Re: Question on a C++ string Bo Persson <bo@bo-persson.se> - 2019-12-29 11:00 +0100
    Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 02:33 -0800
      Re: Question on a C++ string Bart <bc@freeuk.com> - 2019-12-29 12:09 +0000
        Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 11:51 -0800
  Re: Question on a C++ string Paavo Helde <myfirstname@osa.pri.ee> - 2019-12-29 12:17 +0200
    Re: Question on a C++ string Barry Schwarz <schwarzb@delq.com> - 2019-12-29 08:45 -0800
      Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 11:54 -0800
  Re: Question on a C++ string Öö Tiib <ootiib@hot.ee> - 2019-12-29 02:56 -0800
    Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 12:02 -0800
  Re: Question on a C++ string Barry Schwarz <schwarzb@delq.com> - 2019-12-29 08:39 -0800
    Re: Question on a C++ string T <T@invalid.invalid> - 2019-12-29 12:10 -0800

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