Serialize the given item, allocating buffers as needed
\rst
.. warning:: It is your responsibility to free the buffer using an
appropriate `free` implementation. \endrst
@param itemborrow A data item
@param bufferout Buffer containing the result
@param buffer_sizeout Size of the \p buffer
@return Length of the result. 0 on failure, in which case \p buffer is
`NULL`.
Serialize the given item, allocating buffers as needed
\rst .. warning:: It is your responsibility to free the buffer using an appropriate `free` implementation. \endrst
@param itemborrow A data item @param bufferout Buffer containing the result @param buffer_sizeout Size of the \p buffer @return Length of the result. 0 on failure, in which case \p buffer is `NULL`.