• andrea9940 (14/14) Aug 07 2013 Hi, I have written a function to convert a C string to a D string.
• John Colvin (24/39) Aug 07 2013 Another way of doing this is lazily with a range. *Very*
• andrea9940 (1/1) Aug 07 2013 I hadn't tought of thath, thank you for the example.
• Andrej Mitrovic (9/14) Aug 07 2013 There's a small issue in your ternary operator, if 'cstr' is non-const
• andrea9940 (1/1) Aug 17 2013 Excellent discovery !

"andrea9940" <no mail.plz> writes:

Hi, I have written a function to convert a C string to a D string.
I did not use to!string because it allocates a new string while 
what I want is a dynamic array of type char[] pointing to the C 
string.

auto cstr2dstr(inout(char)* cstr)
{
     import core.stdc.string: strlen;
     return cstr ? cstr[0 .. strlen(cstr)] : "";
}

As D newbie I'd like to know if this is the correct usage of 
inout (it is needed to accept without distinction char*, 
const(char)* and immutable(char)* right ?) and if there is 
already a function in the standard D library which do that 
conversion.

"John Colvin" <john.loughran.colvin gmail.com> writes:

On Wednesday, 7 August 2013 at 18:50:21 UTC, andrea9940 wrote:
 Hi, I have written a function to convert a C string to a D 
 string.
 I did not use to!string because it allocates a new string while 
 what I want is a dynamic array of type char[] pointing to the C 
 string.

 auto cstr2dstr(inout(char)* cstr)
 {
     import core.stdc.string: strlen;
     return cstr ? cstr[0 .. strlen(cstr)] : "";
 }

 As D newbie I'd like to know if this is the correct usage of 
 inout (it is needed to accept without distinction char*, 
 const(char)* and immutable(char)* right ?) and if there is 
 already a function in the standard D library which do that 
 conversion.

Another way of doing this is lazily with a range. *Very* 
basically done, just for char* and read-only:

struct Cstring
{
     size_t i = 0;
     char* str;

     this(char* s)
     {
         str = s;
     }

      property bool empty()
     {
         return str[i] == '\0';
     }

      property char front()
     {
         return str[i];
     }

     void popFront()
     {
         ++i;
     }
}

"andrea9940" <no mail.plz> writes:

I hadn't tought of thath, thank you for the example.

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 8/7/13, andrea9940 <no mail.plz> wrote:
 auto cstr2dstr(inout(char)* cstr)
 {
      import core.stdc.string: strlen;
      return cstr ? cstr[0 .. strlen(cstr)] : "";
 }

There's a small issue in your ternary operator, if 'cstr' is non-const
but null, you will end up returning an immutable rather than a mutable
string. In fact your return type will always be const because of this
ternary (mutable and immutable both implicitly convert to const). I
suggest changing it to this:

return cstr ? cstr[0 .. strlen(cstr)] : cstr[0 .. 0];

You can also use inout(char)[] on the return type, it documents the
function better (and this is how I caught the ternary issue as well).

"andrea9940" <no mail.plz> writes:

Excellent discovery !