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nbdkit_strdup_intern(3) NBDKIT nbdkit_strdup_intern(3)

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

LICENSE

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  • Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

2024-12-13 nbdkit-1.40.4