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digitalmars.D.bugs - [Issue 6878] New: Mutable result for toStringz()

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6878

           Summary: Mutable result for toStringz()
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



In some situations you have to call C functions that accept a char* (not
const). For simplify such usage cases I'd like std.string.toStringz to be
closer to this:


import core.stdc.string;

char* toStringz(immutable(char[]) s) pure nothrow
in
{
    // The assert below contradicts the unittests!
    //assert(memchr(s.ptr, 0, s.length) == null,
    //text(s.length, ": `", s, "'"));
}
out (result)
{
    if (result)
    {
        auto slen = s.length;
        while (slen > 0 && s[slen-1] == 0) --slen;
        assert(strlen(result) == slen);
        assert(memcmp(result, s.ptr, slen) == 0); // overkill?
    }
}
body
{
    /+ Unfortunately, this isn't reliable.
     We could make this work if string literals are put
     in read-only memory and we test if s[] is pointing into
     that.

     /* Peek past end of s[], if it's 0, no conversion necessary.
     * Note that the compiler will put a 0 past the end of static
     * strings, and the storage allocator will put a 0 past the end
     * of newly allocated char[]'s.
     */
     char* p = &s[0] + s.length;
     if (*p == 0)
     return s;
     +/

    // Need to make a copy
    auto copy = new char[s.length + 1];
    copy[0 .. s.length] = s[];
    copy[s.length] = '\0';

    return copy.ptr;
}

void main() {
    string t = "hello";
    char* s1 = toStringz(t);
    const(char*) s2 = toStringz(t);
    immutable(char*) s3 = toStringz(t);
    immutable(char)* s4 = toStringz(t);
}

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parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6878


Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |jmdavisProg gmx.com
         Resolution|                            |WONTFIX



PDT ---
Use std.utf.toUTFz. It allows you to get a pointer to whatever zero-terminate
string type you want (both in terms of character type and constness). toStringz
is simplified function for the common use case. We're not going to complicate
it further. toUTFz gives you the functionality that you're looking for.

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