A callback for rustls_connection_write_tls.
An implementation of this callback should attempt to write the n bytes in buf
to the network. If any bytes were written, the implementation should
set out_n to the number of bytes stored and return 0. If there was an error,
the implementation should return a nonzero rustls_io_result, which will be
passed through to the caller. On POSIX systems, returning errno is convenient.
On other systems, any appropriate error code works.
It's best to make one write attempt to the network per call. Additional writes will
be triggered by subsequent calls to rustls_connection_write_tls.
userdata is set to the value provided to rustls_connection_set_userdata. In most
cases that should be a struct that contains, at a minimum, a file descriptor.
The buf and out_n pointers are borrowed and should not be retained across calls.
A callback for rustls_connection_write_tls. An implementation of this callback should attempt to write the n bytes in buf to the network. If any bytes were written, the implementation should set out_n to the number of bytes stored and return 0. If there was an error, the implementation should return a nonzero rustls_io_result, which will be passed through to the caller. On POSIX systems, returning errno is convenient. On other systems, any appropriate error code works. It's best to make one write attempt to the network per call. Additional writes will be triggered by subsequent calls to rustls_connection_write_tls. userdata is set to the value provided to rustls_connection_set_userdata. In most cases that should be a struct that contains, at a minimum, a file descriptor. The buf and out_n pointers are borrowed and should not be retained across calls.