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author | Nao Pross <np@0hm.ch> | 2021-11-21 10:40:53 +0100 |
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committer | Nao Pross <np@0hm.ch> | 2021-11-21 10:40:53 +0100 |
commit | 2a3b0ef715d83c97ccb0c2b1eb63707a62ffe7a5 (patch) | |
tree | f45e5b6f5ec5a88456d94abc0a63173f355d2571 /src/gr-fadingui/python/frame_obj.py | |
parent | Change chapter title (diff) | |
parent | Merge branch 'master' of github.com:NaoPross/Fading (diff) | |
download | Fading-2a3b0ef715d83c97ccb0c2b1eb63707a62ffe7a5.tar.gz Fading-2a3b0ef715d83c97ccb0c2b1eb63707a62ffe7a5.zip |
Merge branch 'master' of github.com:NaoPross/Fading
Diffstat (limited to '')
-rw-r--r-- | src/gr-fadingui/python/frame_obj.py | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/src/gr-fadingui/python/frame_obj.py b/src/gr-fadingui/python/frame_obj.py new file mode 100644 index 0000000..136fce0 --- /dev/null +++ b/src/gr-fadingui/python/frame_obj.py @@ -0,0 +1,91 @@ +#!/usr/bin/env python +# -*- coding: utf-8 -*- +# +# Copyright 2021 Naoki Pross. + +from functools import reduce +import operator as op + +import numpy as np +from gnuradio import gr + + +class frame_obj: + """ + Frame Object: Contains informations about a data frame. + + ------------------------------------------------------------------------------- + | Preamble | Padding | ID | Data Length | Parity | Payload | Padding | + | k bytes | 1 bit | 5 bits | 21 bits | 5 bits | | if necessary | + ------------------------------------------------------------------------------- + | (31, 26) Hamming EC code | + --------------------------------- + + - The preamble is user defined. + - The ID (5 bits) + Data length (21 bits) together are a 26 bits, followed + by 5 parity bits computed using a (31,26) hamming code. + + This constraints the maximum payload size to 2 MiB and the number IDs to + 32, i.e. max file size is 64 MiB. + + """ + def __init__(self, preamble, payload_len): + self._preamble = np.array(preamble, dtype=np.uint8) + + self._preamble_len = len(self._preamble) + self._payload_len = payload_len + + @property + def header_length(self) -> int: + """Get header length in bytes""" + # 4 is the number of bytes for the hamming part + return self._preamble_len + 4 + + @property + def payload_length(self) -> int: + return self._payload_len + + @property + def length(self) -> int: + """Get frame lenght in bytes""" + # 8 is the size of the hamming ECC part + 1 bit + return self.header_length + self.payload_length + + @property + def preamble(self): + """Get preamble""" + return self._preamble + + def parity(self, bits): + """Compute the 5 parity bits for an unpacked array of 26 bits""" + assert(len(bits) == 26) + # FIXME: does not work + # return np.matmul(bits, gen) % 2 + return np.array([0, 0, 0, 0, 0]) + + def make(self, idv, data_len, data): + """Make a frame""" + # get lower 4 bits of idv + idv_bits = np.unpackbits([np.uint8(idv)])[:5] + + # get lower 22 bits of data_len + data_len_bytes = list(map(np.uint8, data_len.to_bytes(4, byteorder='little'))) + data_len_bits = np.unpackbits(data_len_bytes)[:21] + + # compute 5 parity bits + metadata = np.concatenate([idv_bits, data_len_bits]) + parity_bits = self.parity(metadata) + + # add padding + hamming_bits = np.concatenate([[0], metadata, parity_bits]) + assert(len(hamming_bits) == 32) + + # pack 32 bits into 4 bytes and add the rest + hamming = np.packbits(hamming_bits) + return np.concatenate([self.preamble, hamming, data]) + + def syndrome(self, bits): + """Compute the syndrome (check Hamming code) for an unpacked array of 31 bits""" + assert(len(bits) == 31) + return reduce(op.xor, [i for i, bit in enumerate(bits) if bit]) + |