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dev:shared_strings

To minimize memory use, Crossfire uses a shared string mechanism. This is intended to be used for strings whose contents is not expected to change during the server's life. Using shared strings saves memory and improved performance.

Those strings are used like regular const char*, but should not be changed via strcpy, snprintf or other means because it would affect all structures using the shared string. Internally, they use a counter to track at how many places they are used. When it reaches 0, string is freed.

To alter such a string, the right behaviour is:

  • write new value in a char[] new_value variable
  • use free_string(str)
  • call str = add_string(new_value)

FIXME replace with sstring when done in code

To manipulate them, the following functions (defined in common/shstr.c) are available:

  • const char* add_string(const char *str), used to share a string. Returned value is a string with the same contents that can be shared with other objects
  • const char* add_refcount(const char *str), equivalent of add_string when the string is already a shared string
  • const char* find_string(const char *str), to search if a string is shared or not
  • void free_string(const char *str), to decrement the use counter. After it's called, str should not be used anymore.

Because shared strings will return a pointer to a string if it exists, one can see if the strings are equal by comparing the shared string address they point to (ie str == str2 directly).

dev/shared_strings.txt · Last modified: 2007/03/22 08:19 (external edit)