From ab5312e7c035e76521140382b47113bcf50acbcf Mon Sep 17 00:00:00 2001
From: Matthew Somerville
Date: Fri, 29 Jan 2010 14:34:56 +0000
Subject: Speed up from_decimal and to_decimal by a lot (third to 50%ish).

---
 src/shorturls/baseconv.py | 52 ++++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/src/shorturls/baseconv.py b/src/shorturls/baseconv.py
index 0e62b83..1b4fd15 100644
--- a/src/shorturls/baseconv.py
+++ b/src/shorturls/baseconv.py
@@ -13,14 +13,25 @@ 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):
         if self.decode_mapping:
@@ -31,35 +42,20 @@ class BaseConverter(object):
                 else:
                     new += digit
             s = new
-        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 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(
-- 
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