Implement Hamming code

Author: maxicot

hamming/__init__.py

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+from .lib import decode, encode
+
+__all__ = ["encode", "decode"]

hamming/src/__init__.py

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+from functools import reduce
+from math import ceil, log
+
+
+def encode(value: str) -> str:
+    code = [0] + [
+        int(i) for i in "".join(format(i, "b") for i in bytearray(value, "utf8"))
+    ]
+    length = len(code) - 1
+
+    r = 1
+    while 2**r < length + r + 1:
+        r += 1
+
+    for i in range(1, length + r + 1):
+        # check if power of 2
+        if log(i, 2) == ceil(log(i, 2)):
+            code.insert(i, 0)
+
+    for i in range(0, r):
+        x = 2**i
+
+        for j in range(1, len(code)):
+            if ((j >> i) & 1) == 1 and x != j:
+                code[x] = code[x] ^ code[j]
+
+    return "".join(str(i) for i in code)
+
+
+def decode(value: str) -> tuple[str, int]:
+    code = [int(i) for i in value]
+
+    def decoded():
+        for i in range(1, len(code)):
+            if log(i, 2) != ceil(log(i, 2)):
+                yield str(code[i])
+
+    decoded = "".join(decoded())
+    position = reduce(lambda x, y: x ^ y, [n for n, bit in enumerate(code) if bit])
+
+    if position == 0:
+        position = -1
+
+    return (decoded, position)

hamming/src/lib.py

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+from ..src import decode, encode
+
+
+def test_basic():
+    encoded = encode("abc")
+    _, error = decode(encoded)
+
+    assert error == -1