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Added new codec: bcd
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‎README.md‎

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@@ -20,6 +20,7 @@ This library extends the native `codecs` library and provides some new encodings
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`barbie-N` | text <-> barbie ciphertext | aka Barbie Typewriter (N belongs to [1, 4])
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`baseXX` | text <-> baseXX | see [base encodings](https://python-codext.readthedocs.io/en/latest/base.html)
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`baudot` | text <-> Baudot code bits | supports CCITT-1, CCITT-2, EU/FR, ITA1, ITA2, MTK-2 (Python3 only), UK, ...
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`bcd` | text <-> binary coded decimal text | encodes characters from their (zero-left-padded) ordinals
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`braille` | text <-> braille symbols | Python 3 only
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`dna` | text <-> DNA-N sequence | implements the 8 rules of DNA sequences (N belongs to [1,8])
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`excess3` | text <-> XS3 encoded text | uses Excess-3 (aka Stibitz code) binary encoding to convert characters from their ordinals
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:---: | :---: | ---
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`baudot-spaced` | text <-> Baudot code groups of bits | groups of 5 bits are whitespace-separated
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`baudot-tape` | text <-> Baudot code tape | outputs a string that looks like a perforated tape
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`bcd-extended0` | text <-> BCD-extended text | encodes characters from their (zero-left-padded) ordinals using prefix bits `0000`
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`bcd-extended1` | text <-> BCD-extended text | encodes characters from their (zero-left-padded) ordinals using prefix bits `1111`
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`manchester-inverted` | text <-> manchester encoded text | XORes each bit of the input with `10`
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`octal-spaced` | text <-> octal digits (whitespace-separated) | dummy octal conversion
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`ordinal-spaced` | text <-> ordinal digits (whitespace-separated) | dummy character ordinals conversion

‎codext/binary/__init__.py‎

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# -*- coding: UTF-8 -*-
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from .baudot import *
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from .bcd import *
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from .excess3 import *
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from .gray import *
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from .manchester import *

‎codext/binary/bcd.py‎

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# -*- coding: UTF-8 -*-
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"""BCD Codec - Binary Coded Decimal content encoding.
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This codec:
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- en/decodes strings from str to str
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- en/decodes strings from bytes to bytes
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- decodes file content to str (read)
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- encodes file content from str to bytes (write)
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"""
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from ..__common__ import *
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__examples1__ = {
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'enc(bcd|binary-coded-decimal|binary_coded_decimal)': {
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'This is a test!': "\x08A\x04\x10Q\x15\x03!\x05\x11P2\tp2\x11a\x01\x11Q\x16\x030",
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},
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'dec(binary-coded-decimal)': {
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'\xaf': None,
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'\xff': None,
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'\x08A\x04\x10Q\x15\x03!\x05\x11P2\tp2\x11a\x01\x11Q\x16\x030': "This is a test!",
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},
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}
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__examples2__ = {
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'enc(bcd-ext0|bcd_extended_zeros)': {
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'This is a test': "\x00\x08\x04\x01\x00\x04\x01\x00\x05\x01\x01\x05\x00\x03\x02\x01\x00\x05\x01\x01\x05\x00"
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"\x03\x02\x00\t\x07\x00\x03\x02\x01\x01\x06\x01\x00\x01\x01\x01\x05\x01\x01\x06\x00",
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},
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}
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__examples3__ = {
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'enc(bcd-ext1|bcd_extended_ones)': {
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'This is a test': "\xf0\xf8\xf4\xf1\xf0\xf4\xf1\xf0\xf5\xf1\xf1\xf5\xf0\xf3\xf2\xf1\xf0\xf5\xf1\xf1\xf5\xf0"
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"\xf3\xf2\xf0\xf9\xf7\xf0\xf3\xf2\xf1\xf1\xf6\xf1\xf0\xf1\xf1\xf1\xf5\xf1\xf1\xf6\xf0",
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},
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}
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CODE = {str(i): bin(i)[2:].zfill(4) for i in range(10)}
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class BCDDecodeError(ValueError):
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pass
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def bcd_encode(prefix=""):
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def encode(text, errors="strict"):
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r, bits = "", prefix
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for c in text:
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for i in str(ord(c)).zfill(3):
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bits += CODE[i]
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if len(bits) == 8:
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r += chr(int(bits, 2))
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bits = prefix
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if len(bits) > 0:
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r += chr(int(bits + "0000", 2))
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return r, len(b(text))
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return encode
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def bcd_decode(prefix=""):
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def decode(text, errors="strict"):
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code = {v: k for k, v in CODE.items()}
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r, d = "", ""
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for i, c in enumerate(text):
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bin_c = bin(ord(c))[2:].zfill(8)
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for k in range(len(prefix), 8, 4):
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hb = bin_c[k:k+4]
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try:
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d += code[hb]
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except KeyError:
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d += handle_error("bcd", errors, BCDDecodeError, decode=True)(hb, i)
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if len(d) == 3:
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r += chr(int(d))
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d = ""
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return r, len(b(text))
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return decode
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add("bcd", bcd_encode(), bcd_decode(), pattern=r"^(?:bcd|binary[-_]coded[-_]decimals?)$", examples=__examples1__)
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add("bcd-extended0", bcd_encode("0000"), bcd_decode("0000"), examples=__examples2__,
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pattern=r"^(?:bcd|binary[-_]coded[-_]decimals?)[-_]ext(?:ended)?(?:[-_]?0|[-_]zeros?)$")
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add("bcd-extended1", bcd_encode("1111"), bcd_decode("1111"), examples=__examples3__,
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pattern=r"^(?:bcd|binary[-_]coded[-_]decimals?)[-_]ext(?:ended)?(?:[-_]?1|[-_]ones?)$")
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‎docs/binary.md‎

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-----
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### Binary Coded Decimal (BCD)
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It converts characters to their odrinals, left-pads with zeros, converts digits to 4-bits groups and then make characters with the assembled groups. It can also use a 4-bits prefix for making new characters. It then allows to define extended versions of BCD.
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**Codec** | **Conversions** | **Aliases** | **Comment**
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:---: | :---: | --- | ---
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`bcd` | text <-> BCD encoded text | `binary_coded_decimals` |
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`bcd-extended0` | text <-> BCD encoded text using prefix `0000` | `bcd_ext0`, `bcd-extended-zeros`, `binary_coded_decimals_extended_0` |
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`bcd-extended1` | text <-> BCD encoded text using prefix `1111` | `bcd_ext1`, `bcd-extended-ones`, `binary_coded_decimals_extended_1` |
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```python
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>>> codext.encode("Test", "bcd")
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'\x08A\x01\x11Q\x16'
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>>> codext.decode("\x08A\x01\x11Q\x16", "binary_coded_decimal")
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'Test'
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>>> codext.encode("Test", "bcd_ext_zero")
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'\x00\x08\x04\x01\x00\x01\x01\x01\x05\x01\x01\x06\x00'
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>>> codext.decode("\x00\x08\x04\x01\x00\x01\x01\x01\x05\x01\x01\x06\x00", "bcd-ext0")
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'Test'
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>>> codext.encode("Test", "bcd_extended_ones")
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'\xf0\xf8\xf4\xf1\xf0\xf1\xf1\xf1\xf5\xf1\xf1\xf6\xf0'
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>>> codext.decode("\xf0\xf8\xf4\xf1\xf0\xf1\xf1\xf1\xf5\xf1\xf1\xf6\xf0", "bcd_ext1")
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'Test'
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```
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-----
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### Excess-3
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Also called *Stibitz code*, it converts letters to ordinals, left-pads with zeros and then applies Excess-3 (Stibitz) code to get groups of 4 bits that are finally reassembled into bytes.
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Also called *Stibitz code*, it converts characters to ordinals, left-pads with zeros and then applies Excess-3 (Stibitz) code to get groups of 4 bits that are finally reassembled into bytes.
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**Codec** | **Conversions** | **Aliases** | **Comment**
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:---: | :---: | --- | ---

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