utstring cloning

[Silvio Clecio]

Hello dudes.

What is the proper way to clone a utstring? I'm using:

utstring_clear(dst);
utstring_concat(src, dst);

but I'm not sure if it is the "elegant" way to do that. :-/ 

Thank you!

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Silvio Clecio

[Arthur O'Dwyer]

It appears to me that there is no such way, at the moment. Sounds like there would be a good case for adding something like `dst = utstring_clone(src)` — although I haven't looked closely at it.

Notice that the standard name for this operation is `strdup`; but `utstring_dup` seems like a worse name than `utstring_clone` just in terms of readability.

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[silvioprog]

+1 for utstring_clone(). :-)

Would it be nice to open a feature request at Github?

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Silvio Clécio

[silvioprog]

Possible macro?:

#define utstring_clone(dst, src)          \
do {                                      \
  if ((src)->d != NULL) {                 \
    utstring_new(dst);                    \
    (dst)->n = (src)->n;                  \
    (dst)->i = (src)->i;                  \
    memcpy((dst)->d, (src)->d, (src)->n); \
  } else {                                \
    (dst) = NULL;                         \
  }                                       \
} while (0)

---

#include <stdio.h>
#include <string.h>
#include "utstring.h"

int main() {
    UT_string *s, *c;
    utstring_new(s);
    utstring_printf(s, "hello world!");
    printf("source -> %s\n", utstring_body(s));
    utstring_clone(c, s);
    printf("cloned -> %s\n", utstring_body(c));
    utstring_free(s);
    utstring_free(c);
    return 0;
}

./a.out

source -> hello world!

cloned -> hello world!

(tested only on GCC)

I'm not sure if MSVC  allows macro returning. 🤔 But I'm going to test it in MSVC 15 2017:

#define utstring_clone(src)               \
({                                        \
  UT_string *dst = NULL;                  \
  if ((src)->d != NULL) {                 \
    utstring_new(dst);                    \
    (dst)->n = (src)->n;                  \
    (dst)->i = (src)->i;                  \
    memcpy((dst)->d, (src)->d, (src)->n); \
  }                                       \
  dst;                                    \
})

it allows to use as:

#include <stdio.h>
#include <string.h>
#include "utstring.h"

int main() {
    UT_string *s, *c;
    utstring_new(s);
    utstring_printf(s, "hello world!");
    printf("source -> %s\n", utstring_body(s));
    c = utstring_clone(s);
    printf("cloned -> %s\n", utstring_body(c));
    utstring_free(s);
    utstring_free(c);
    return 0;
}

./a.out

source -> hello world!

cloned -> hello world!

--

Silvio Clécio

[silvioprog]

Hm... the ({ }) construct is a GCC/Clang extension, so:

#ifdef __GNUC__

#define utstring_clone(src)               \
({                                        \
  UT_string *dst = NULL;                  \
  if ((src)->d != NULL) {                 \
    utstring_new(dst);                    \
    (dst)->n = (src)->n;                  \
    (dst)->i = (src)->i;                  \
    memcpy((dst)->d, (src)->d, (src)->n); \
  }                                       \
  dst;                                    \
})

#else
UT_string *utstring_clone(UT_string *src) {
  UT_string *dst = NULL;
  if (src->d != NULL) {
    utstring_new(dst);
    dst->n = src->n;
    dst->i = src->i;
    memcpy(dst->d, src->d, src->n);
  }
  return dst;
}
#endif

(successfully tested on GCC/Clang and MSVC)

What do you thing about this implementation?

On Fri, Feb 16, 2018 at 7:10 PM, silvioprog <silvi...@gmail.com> wrote:

[...]

I'm not sure if MSVC  allows macro returning. 🤔 But I'm going to test it in MSVC 15 2017:

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Silvio Clécio