mbedtls_ecp_write_key() function

\c 0 on success. #MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL or #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if the \p key representation is larger than the available space in \p buf. Another negative error code on different kinds of failure.

Note that although this function accepts an output buffer that is smaller or larger than the key, most key import interfaces require the output to have exactly key's nominal length. It is generally simplest to pass the key's nominal length as \c buflen, after checking that the output buffer is large enough. See the description of the \p buflen parameter for how to calculate the nominal length. If the private key was not set in \p key, the output is unspecified. Future versions may return an error in that case. This function does not support Curve448 yet.