Source code for ccsdspy.utils

"""Utils for the CCSDSPy package."""

__author__ = "Daniel da Silva <mail@danieldasilva.org>"

from io import BytesIO
import warnings

import numpy as np


[docs]def split_by_apid(mixed_file, valid_apids=None): """Split a stream of mixed APIDs into separate streams by APID. Parameters ---------- mixed_file: str, file-like Path to file on the local file system, or file-like object valid_apids: list of int, None Optional list of valid APIDs. If specified, warning will be issued when an APID is encountered outside this list. Returns ------- Dictionary mapping integer apid number to BytesIO instance with the file pointer at the beginning of the stream. """ if hasattr(mixed_file, "read"): file_bytes = np.frombuffer(mixed_file.read(), "u1") else: file_bytes = np.fromfile(mixed_file, "u1") offset = 0 stream_by_apid = {} while offset < len(file_bytes): packet_nbytes = file_bytes[offset + 4] * 256 + file_bytes[offset + 5] + 7 apid = np.array([file_bytes[offset], file_bytes[offset + 1]], dtype=np.uint8) apid.dtype = ">u2" apid = apid[0] apid &= 0x07FF if valid_apids is not None and apid not in valid_apids: warnings.warn(f"Found unknown APID {apid}") if apid not in stream_by_apid: stream_by_apid[apid] = BytesIO() stream_by_apid[apid].write(file_bytes[offset : offset + packet_nbytes]) offset += packet_nbytes if offset != len(file_bytes): missing_bytes = offset - len(file_bytes) message = ( f"File appears truncated-- missing {missing_bytes} byte (or " "maybe garbage at end)" ) warnings.warn(message) for stream in stream_by_apid.values(): stream.seek(0) return stream_by_apid