qapi-types.py: Implement 'base' for unions
The new 'base' key in a union definition refers to a struct type, which
is inlined into the union definition and can represent fields common to
all kinds.
For example the following schema definition...
{ 'type': 'BlockOptionsBase', 'data': { 'read-only': 'bool' } }
{ 'union': 'BlockOptions',
'base': 'BlockOptionsBase',
'data': {
'raw': 'BlockOptionsRaw'
'qcow2': 'BlockOptionsQcow2'
} }
...would result in this generated C struct:
struct BlockOptions
{
BlockOptionsKind kind;
union {
void *data;
BlockOptionsRaw * raw;
BlockOptionsQcow2 * qcow2;
};
bool read_only;
};
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>