Changing size of dynamic *char

Question

Is there way how to make my string to even size?

EDIT: I need a few string in struct that have even length. So something like:

struct msg { char * first; char * second; char * third; };

so it is in the end something like first string "hi\\0\\0" second string "hello\\0" third string "byebye\\0\\0" and i need to change them anytime+they are dynamic allocated.

Answer 1

Create a strdup_even() .

Allocate memory as needed to copy the string, plus maybe 1 more to make "even".

char *strdup_even(const char *str) {
  size_t len = strlen(str) + 1;  // Size needed for the _string_
  size_t len2 = len + len % 2;   // Even allocation size
  char *copy = malloc(len2);
  if (copy) {
    memcpy(copy, str, len);
    if (len2 > len) {
      copy[len] = '\0';
    }
  }
  return copy;
}

Sample usage

struct msg m;
m.first =  strdup_even("hi");
m.second = strdup_even("hello");

Answer 2

Use malloc() and realloc() :

char *string = malloc(STRING_SIZE);
strcpy(string, "hi");
string = realloc(string, STRING_SIZE+1);
string[STRING_SIZE] = '\0';