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.

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