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dhondtadhondta
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Added new codec: excess3
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Lines changed: 33 additions & 10 deletions

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‎README.md‎

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@@ -22,6 +22,7 @@ This library extends the native `codecs` library and provides some new encodings
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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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`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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`gray` | text <-> gray encoded text | aka reflected binary code
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`html` | text <-> HTML entities | implements entities according to [this reference](https://dev.w3.org/html5/html-author/charref)
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`leetspeak` | text <-> leetspeak encoded text | based on minimalistic elite speaking rules

‎codext/binary/excess3.py‎

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from ..__common__ import *
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__examples__ = {'enc(excess3|xs-3|stibitz)': {'This is a test': ";t7C\x84H6T8D\x83e<£eD\x944D\x84I"}}
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__examples__ = {
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'enc(excess3|xs-3|stibitz)': {
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'This is a test!': ";t7C\x84H6T8D\x83e<\xa3eD\x944D\x84I6`",
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'This is another test ': ";t7C\x84H6T8D\x83e<\xa4CDDICt4DseD\x944D\x84I6P",
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},
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}
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CODE = {
@@ -28,25 +33,25 @@ def excess3_encode(text, errors="strict"):
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r += chr(int(b, 2))
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b = ""
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if len(b) > 0:
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b += "0000"
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r += chr(int(b, 2))
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r += chr(int(b + "0000", 2))
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return r, len(text)
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def excess3_decode(text, errors="strict"):
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code = {v: k for k, v in CODE}
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code = {v: k for k, v in CODE.items()}
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r, d = "", ""
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for c in text:
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b = bin(ord(c))[2:].zfill(8)
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bin_c = bin(ord(c))[2:].zfill(8)
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for i in range(0, 8, 4):
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d += code[b[i:i+4]]
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try:
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d += code[bin_c[i:i+4]]
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except KeyError: # (normal case) occurs when 0000 was used for padding
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break
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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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if len(d) > 0:
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r += chr(int(d))
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return r, len(text)
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return r, len(b(text))
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add("excess3", excess3_encode, excess3_decode, pattern=r"^(?:excess\-3|xs\-?3|stibitz)$")
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add("excess3", excess3_encode, excess3_decode, pattern=r"^(?:excess\-?3|xs\-?3|stibitz)$", text=False)
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‎docs/encodings.md‎

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@@ -129,6 +129,23 @@ CACTCGGTCGGCCATATGTTCGGCCATATGTTCGTCTGTTCACTCGCCCATACACT
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-----
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### Excess-3 Code
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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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**Codec** | **Conversions** | **Aliases** | **Comment**
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:---: | :---: | --- | ---
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`excess3` | text <-> XS3 encoded text | `excess-3`, `xs3`, `stibitz` |
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```python
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>>> codext.encode("This is a test!", "excess-3")
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';t7C\x84H6T8D\x83e<£eD\x944D\x84I6`'
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>>> codext.decode(";t7C\x84H6T8D\x83e<£eD\x944D\x84I6`", "stibitz")
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'This is a test!'
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```
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-----
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### Gray Code
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Also called *reflected binary code*, it implements the Gray code applied to characters while converted to bytes.

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