Merge pull request #8 from bfirsh/crockford-base32

Add Crockford's base32 and performance improvements

1 files changed, 57 insertions, 29 deletions

diff --git a/src/shorturls/baseconv.py b/src/shorturls/baseconv.py
index 1e22ed1..1b4fd15 100644
--- a/src/shorturls/baseconv.py
+++ b/src/shorturls/baseconv.py
@@ -13,46 +13,74 @@ Sample usage:
 """
 
 class BaseConverter(object):
-    decimal_digits = "0123456789"
+    decode_mapping = {}
     
     def __init__(self, digits):
         self.digits = digits
+        self.length = len(digits)
     
     def from_decimal(self, i):
-        return self.convert(i, self.decimal_digits, self.digits)
+        if i < 0:
+            i, neg = -i, 1
+        else:
+            neg = 0
+        enc = ''
+        while i >= self.length:
+            i, mod = divmod(i, self.length)
+            enc = self.digits[mod] + enc
+        enc = self.digits[i] + enc
+        if neg:
+            enc = '-' + enc
+        return enc
     
     def to_decimal(self, s):
-        return int(self.convert(s, self.digits, self.decimal_digits))
-    
-    def convert(number, fromdigits, todigits):
-        # Based on http://code.activestate.com/recipes/111286/
-        if str(number)[0] == '-':
-            number = str(number)[1:]
-            neg = 1
+        if self.decode_mapping:
+            new = ''
+            for digit in s:
+                if digit in self.decode_mapping:
+                    new += self.decode_mapping[digit]
+                else:
+                    new += digit
+            s = new
+        if str(s)[0] == '-':
+            s, neg = str(s)[1:], 1
         else:
             neg = 0
-
-        # make an integer out of the number
-        x = 0
-        for digit in str(number):
-           x = x * len(fromdigits) + fromdigits.index(digit)
+        decoded = 0
+        multi = 1
+        while len(s) > 0:
+            decoded += multi * self.digits.index(s[-1:])
+            multi = multi * self.length
+            s = s[:-1]
+        if neg:
+            decoded = -decoded
+        return decoded
     
-        # create the result in base 'len(todigits)'
-        if x == 0:
-            res = todigits[0]
-        else:
-            res = ""
-            while x > 0:
-                digit = x % len(todigits)
-                res = todigits[digit] + res
-                x = int(x / len(todigits))
-            if neg:
-                res = '-' + res
-        return res
-    convert = staticmethod(convert)
-
 bin = BaseConverter('01')
 hexconv = BaseConverter('0123456789ABCDEF')
 base62 = BaseConverter(
     'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz'
-)
\ No newline at end of file
+)
+
+class Base32Converter(BaseConverter):
+    """
+    http://www.crockford.com/wrmg/base32.html
+    """
+    decode_mapping = {
+        'o': '0',
+        'i': '1',
+        'l': '1',
+    }
+    
+    def __init__(self):
+        super(Base32Converter, self).__init__('0123456789abcdefghjkmnpqrstvwxyz')
+    
+    def to_decimal(self, s):
+        return super(Base32Converter, self).to_decimal(s.lower())
+
+base32 = Base32Converter()
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+