[Biopython-dev] BioSQL upgrade [1 of 3]

[Yves Bastide]

The first patch creates a Bio.crc, with crc32 and crc64 methods; I 
needed a CRC64, and foud it clean to have it nicely with the usual CRC32 :-)

The crc64 code is a translation of the BioPerl one (I will only claim 
the errors).
-------------- next part --------------
--- /dev/null	1970-01-01 01:00:00.000000000 +0100
+++ Bio/crc.py	2002-11-22 21:34:16.000000000 +0100
@@ -0,0 +1,32 @@
+# crc32 and crc64
+# crc64 is adapted from BioPerl
+
+from binascii import crc32
+
+_table_h = []
+
+def crc64(s):
+    crcl = 0
+    crch = 0
+    for c in s:
+        shr = (crch & 0xFF) << 24
+        temp1h = crch >> 8
+        temp1l = (crcl >> 8) | shr
+        idx  = (crcl ^ ord(c)) & 0xFF
+        crch = temp1h ^ _table_h[idx]
+        crcl = temp1l
+
+    return "CRC-%08X%08X" % (crch, crcl)
+
+# Initialisation
+for i in range(256):
+    l = i
+    part_h = 0
+    for j in range(8):
+        rflag = l & 1
+        l >>= 1
+        if part_h & 1: l |= (1L << 31)
+        part_h >>= 1L
+        if rflag: part_h ^= 0xd8000000L
+    _table_h.append(part_h)
+