Data commit

Task/CRC-32/Python/crc-32-1.py

@@ -0,0 +1,8 @@
+>>> s = 'The quick brown fox jumps over the lazy dog'
+>>> import zlib
+>>> hex(zlib.crc32(s))
+'0x414fa339'
+
+>>> import binascii
+>>> hex(binascii.crc32(s))
+'0x414fa339'

Task/CRC-32/Python/crc-32-2.py

@@ -0,0 +1,19 @@
+def create_table():
+    a = []
+    for i in range(256):
+        k = i
+        for j in range(8):
+            if k & 1:
+                k ^= 0x1db710640
+            k >>= 1
+        a.append(k)
+    return a
+
+def crc_update(buf, crc):
+    crc ^= 0xffffffff
+    for k in buf:
+        crc = (crc >> 8) ^ crc_table[(crc & 0xff) ^ k]
+    return crc ^ 0xffffffff
+
+crc_table = create_table()
+print(hex(crc_update(b"The quick brown fox jumps over the lazy dog", 0)))

Task/CRC-32/Python/crc-32-3.py

@@ -0,0 +1,64 @@
+'''CRC-32 checksums for ascii strings'''
+
+from functools import (reduce)
+from itertools import (islice)
+
+
+# crc32 :: String -> Int
+def crc32(s):
+    '''CRC-32 checksum for an ASCII encoded string'''
+    def go(x):
+        x2 = x >> 1
+        return 0xedb88320 ^ x2 if x & 1 else x2
+    table = [
+        index(iterate(go)(n))(8)
+        for n in range(0, 256)
+    ]
+    return reduce(
+        lambda a, c: (a >> 8) ^ table[
+            (a ^ ord(c)) & 0xff
+        ],
+        s,
+        (0xffffffff)
+    ) ^ 0xffffffff
+
+
+# ------------------------- TEST -------------------------
+# main :: IO ()
+def main():
+    '''Test'''
+    print(
+        format(
+            crc32('The quick brown fox jumps over the lazy dog'),
+            '02x'
+        )
+    )
+
+
+# ----------------------- GENERIC ------------------------
+
+# index (!!) :: [a] -> Int -> a
+def index(xs):
+    '''Item at given (zero-based) index.'''
+    return lambda n: None if 0 > n else (
+        xs[n] if (
+            hasattr(xs, "__getitem__")
+        ) else next(islice(xs, n, None))
+    )
+
+
+# iterate :: (a -> a) -> a -> Gen [a]
+def iterate(f):
+    '''An infinite list of repeated
+       applications of f to x.
+    '''
+    def go(x):
+        v = x
+        while True:
+            yield v
+            v = f(v)
+    return go
+
+
+if __name__ == '__main__':
+    main()