NAME

       nbdkit_strdup_intern, nbdkit_strndup_intern, nbdkit_printf_intern, nbdkit_vprintf_intern -
       create a string with limited lifetime for nbdkit

SYNOPSIS

        #include <nbdkit-plugin.h>

        const char *nbdkit_strdup_intern (const char *str);
        const char *nbdkit_strndup_intern (const char *str, size_t n);
        const char *nbdkit_printf_intern (const char *fmt, ...);
        const char *nbdkit_vprintf_intern (const char *fmt, va_list ap);

DESCRIPTION

       Some callbacks are specified to return "const char *", even when a plugin may not have a
       suitable compile-time constant to return.  Returning dynamically-allocated memory for such
       a callback would induce a memory leak or otherwise complicate the plugin to perform
       additional bookkeeping.  For these cases, nbdkit provides several convenience functions
       for creating a copy of a string for better lifetime management.

   nbdkit_strdup_intern
   nbdkit_strndup_intern
       Returns a copy of "str", possibly limited to a maximum of "n" bytes.  After calling this,
       the plugin may free "str" and use this copy in its place.

       If the copy is created outside the scope of a connection (such as during ".load" or
       ".config"), the lifetime of the copy will last at least through ".unload".

       If the copy is created after a client has triggered a connection (such as during
       ".preconnect" or ".open"), the lifetime will last at least through ".close", but the copy
       is not safe to share with other connections.

   "nbdkit_printf_intern"
   "nbdkit_vprintf_intern"
       Return a string created from a format template, with a lifetime longer than the current
       connection.  These are shorthand for passing "fmt" to asprintf(3) on a temporary string,
       then passing that result to "nbdkit_strdup_intern".

RETURN VALUE

       These functions return a string.  This returned string must not be freed by the caller.
       It will be freed by nbdkit.

       If there is an error they call nbdkit_error(3) and return -1.

HISTORY

       The intern functions were added in nbdkit 1.24.

SEE ALSO

       nbdkit(1), nbdkit-plugin(3), nbdkit-filter(3).

AUTHORS

       Eric Blake

COPYRIGHT

       Copyright Red Hat

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