Function deserialize_binary_event

pywebio/platform/utils.py:56–123

Binary event message is used to submit form data with files upload to server. Data message format: | event | file_header | file_data | file_header | file_data | ... The 8 bytes at the beginning of each segment indicate the number of bytes remaining in the segment. event: {

(data: bytes)

def deserialize_binary_event(data: bytes):
    """
    Binary event message is used to submit form data with files upload to server.

    Data message format:
    | event | file_header | file_data | file_header | file_data | ...

    The 8 bytes at the beginning of each segment indicate the number of bytes remaining in the segment.

    event: {
        ...
        data: {
            input_name => input_data,
            ...
        }
    }

    file_header: {
        'filename': file name,
        'size': file size,
        'mime_type': file type,
        'last_modified': last_modified timestamp,
        'input_name': name of input field
    }

    file_data is the file content in bytes.

     - When a form field is not a file input, the `event['data'][input_name]` will be the value of the form field.
     - When a form field is a single file, the `event['data'][input_name]` is None,
        and there will only be one file_header+file_data for the field.
     - When a form field is a multiple files, the `event['data'][input_name]` is [],
        and there may be multiple file_header+file_data for the field.

    Example:
        b'\x00\x00\x00\x00\x00\x00\x00E{"event":"from_submit","task_id":"main-4788341456","data":{"data":1}}\x00\x00\x00\x00\x00\x00\x00Y{"filename":"hello.txt","size":2,"mime_type":"text/plain","last_modified":1617119937.276}\x00\x00\x00\x00\x00\x00\x00\x02ss'
    """
    # split data into segments
    parts = []
    start_idx = 0
    while start_idx < len(data):
        size = int.from_bytes(data[start_idx:start_idx + 8], "big")
        start_idx += 8
        content = data[start_idx:start_idx + size]
        parts.append(content)
        start_idx += size

    event = json.loads(parts[0])

    # deserialize file data
    files = defaultdict(list)
    for idx in range(1, len(parts), 2):
        file_header = json.loads(parts[idx])
        file_header['content'] = parts[idx + 1]

        # Security fix: to avoid interpreting file name as path
        file_header['filename'] = os.path.basename(file_header['filename'])

        input_name = file_header.pop('input_name')