mapped_struct.py 文件源码

def build(cls, initializer, destfile = None, tempdir = None, idmap = None,
            value_array_kwargs = {},
            id_mapper_kwargs = {}):
        if destfile is None:
            destfile = tempfile.NamedTemporaryFile(dir = tempdir)

        # Must dump values and keys to temporary files because
        # we don't know the size of the idmap before building it,
        # and it has to be at the beginning of the file
        with tempfile.NamedTemporaryFile(dir = tempdir, suffix = '.v',) as values_file:
            with tempfile.NamedTemporaryFile(dir = tempdir, suffix = '.k') as keys_file:
                initial_pos = destfile.tell()

                value_array = cls.ValueArray.build(
                    _iter_values_dump_keys(initializer, keys_file), values_file,
                    tempdir = tempdir, idmap = idmap, **value_array_kwargs)

                id_mapper = cls.IdMapper.build(
                    _iter_key_dump(keys_file), destfile, 
                    tempdir = tempdir, **id_mapper_kwargs)

            # pad to multiple of 32 for better cache alignment
            pos = destfile.tell()
            if pos & 31:
                destfile.write("\x00" * (32 - (pos & 31)))

            values_pos = destfile.tell()

            blocklen = 1 << 20
            for start in xrange(0, len(value_array.buf), blocklen):
                destfile.write(buffer(value_array.buf, start, blocklen))
            destfile.write(cls._Footer.pack(values_pos - initial_pos))
            destfile.flush()

            return cls(value_array, id_mapper)