lakesuperior_legacy/lakesuperior/store/ldp_rs/term.pyx

from rdflib import URIRef, BNode, Literal

#from cpython.mem cimport PyMem_Malloc, PyMem_Free
from libc.stdint cimport uint64_t
from libc.stdlib cimport free

from lakesuperior.cy_include cimport cytpl as tpl


DEF LSUP_TERM_TYPE_URIREF = 1
DEF LSUP_TERM_TYPE_BNODE = 2
DEF LSUP_TERM_TYPE_LITERAL = 3
DEF LSUP_TERM_PK_FMT = b'csss' # Reflects the Term structure
DEF LSUP_TERM_STRUCT_PK_FMT = b'S(' + LSUP_TERM_PK_FMT + b')'


cdef int serialize(const Term *term, tpl.tpl_bin *sterm) except -1:
    """
    Serialize a Term into a binary buffer.

    The returned result is dynamically allocated and must be manually freed.
    """
    tpl.tpl_jot(
            tpl.TPL_MEM, &(sterm.addr), &(sterm.sz),
            LSUP_TERM_STRUCT_PK_FMT, term)


cdef int deserialize(const Buffer *data, Term *term) except -1:
    """
    Return a term from serialized binary data.
    """
    _pk = tpl.tpl_peek(
            tpl.TPL_MEM | tpl.TPL_DATAPEEK, data[0].addr, data[0].sz,
            LSUP_TERM_PK_FMT, &(term[0].type), &(term[0].data),
            &(term[0].datatype), &(term[0].lang))

    if _pk is NULL:
        raise MemoryError('Error deserializing term.')
    else:
        free(_pk)


cdef int from_rdflib(term_obj, Term *term) except -1:
    """
    Return a Term struct obtained from a Python/RDFLiib term.
    """
    _data = str(term_obj).encode()
    term[0].data = _data

    if isinstance(term_obj, Literal):
        _datatype = (getattr(term_obj, 'datatype') or '').encode()
        _lang = (getattr(term_obj, 'language') or '').encode()
        term[0].type = LSUP_TERM_TYPE_LITERAL
        term[0].datatype = _datatype
        term[0].lang = _lang
    else:
        if isinstance(term_obj, URIRef):
            term[0].type = LSUP_TERM_TYPE_URIREF
        elif isinstance(term_obj, BNode):
            term[0].type = LSUP_TERM_TYPE_BNODE
        else:
            raise ValueError(f'Unsupported term type: {type(term_obj)}')


cdef Buffer *serialize_from_rdflib(term_obj) except NULL:
    """
    Return a Buffer struct from a Python/RDFLib term.
    """
    cdef:
        Term term
        Buffer data

    from_rdflib(term_obj, &term)
    serialize(&term, &data)

    return &data


cdef object to_rdflib(const Term *term):
    """
    Return an RDFLib term.
    """
    data = (<bytes>term[0].data).decode()
    if term[0].type == LSUP_TERM_TYPE_LITERAL:
        return Literal(data, datatype=term[0].datatype, lang=term[0].lang)
    else:
        if term[0].type == LSUP_TERM_TYPE_URIREF:
            return URIRef(data)
        elif term[0].type == LSUP_TERM_TYPE_BNODE:
            return BNode(data)
        else:
            raise IOError(f'Unknown term type code: {term[0].type}')


cdef object deserialize_to_rdflib(const Buffer *data):
    """
    Return a Python/RDFLib term from a serialized Cython term.
    """
    cdef Term *t

    deserialize(data, t)

    return to_rdflib(t)


cdef object to_bytes(const Term *term):
    """
    Return a Python bytes object of the serialized term.
    """
    cdef:
        Buffer pk_t
        unsigned char *bytestream

    serialize(term, &pk_t)
    bytestream = <unsigned char *>pk_t.addr

    return <bytes>(bytestream)[:pk_t.sz]