Merge pull request #8 from bfirsh/crockford-base32

Add Crockford's base32 and performance improvements

7 files changed, 121 insertions, 44 deletions

diff --git a/README.md b/README.md
index 797bd78..f933880 100644
--- a/README.md
+++ b/README.md
@@ -87,3 +87,16 @@ differ.
 If not defined, the redirect view will try to guess the proper domain by
 consulting the ``django.contrib.sites`` framework, if installed, or the
 requested domain, if not.
+
+#### ``SHORTURLS_DEFAULT_CONVERTER``
+
+The converter that is used to translate between short URLs and model IDs.
+Defaults to the built in base 62 conversion.
+
+Available converters:
+
+ - `shorturls.baseconv.base62` Base 62 encoding.
+ - `shorturls.baseconv.base32` [Douglas Crockford's base 32.](http://www.crockford.com/wrmg/base32.html)
+ - `shorturls.baseconv.hexconv` Hex encoding.
+ - `shorturls.baseconv.bin` Binary encoding, because why not.
+
diff --git a/src/shorturls/__init__.py b/src/shorturls/__init__.py
index e69de29..528e838 100644
--- a/src/shorturls/__init__.py
+++ b/src/shorturls/__init__.py
@@ -0,0 +1,19 @@
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.utils.importlib import import_module
+from shorturls import baseconv
+
+default_converter = baseconv.base62
+
+if hasattr(settings, 'SHORTURLS_DEFAULT_CONVERTER'):
+    mod_name, conv_name = settings.SHORTURLS_DEFAULT_CONVERTER.rsplit('.', 1)
+    try:
+        mod = import_module(mod_name)
+    except ImportError, e:
+        raise ImproperlyConfigured('Could not load converter specified by SHORTURLS_DEFAULT_CONVERTER. Error was: %s' % e)
+    try:
+        default_converter = getattr(mod, conv_name)
+    except AttributeError:
+        raise ImproperlyConfigured('Could not load converter specified by SHORTURLS_DEFAULT_CONVERTER. %s is not in %s.' % (conv_name, mod))
+
+    
\ No newline at end of file
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()
+
diff --git a/src/shorturls/templatetags/shorturl.py b/src/shorturls/templatetags/shorturl.py
index e1781cc..4c98d87 100644
--- a/src/shorturls/templatetags/shorturl.py
+++ b/src/shorturls/templatetags/shorturl.py
@@ -3,7 +3,7 @@ from django import template
 from django.conf import settings
 from django.core import urlresolvers
 from django.utils.safestring import mark_safe
-from shorturls.baseconv import base62
+from shorturls import default_converter as converter
 
 class ShortURL(template.Node):
     @classmethod
@@ -27,7 +27,7 @@ class ShortURL(template.Node):
         except (AttributeError, KeyError):
             return ''
         
-        tinyid = base62.from_decimal(obj.pk)
+        tinyid = converter.from_decimal(obj.pk)
                 
         if hasattr(settings, 'SHORT_BASE_URL') and settings.SHORT_BASE_URL:
             return urlparse.urljoin(settings.SHORT_BASE_URL, prefix+tinyid)
diff --git a/src/shorturls/tests/test_baseconv.py b/src/shorturls/tests/test_baseconv.py
index 5e203b7..24f944f 100644
--- a/src/shorturls/tests/test_baseconv.py
+++ b/src/shorturls/tests/test_baseconv.py
@@ -16,4 +16,19 @@ class BaseConvTests(unittest.TestCase):
         self._test_converter(baseconv.hexconv)
         
     def test_base62(self):
-        self._test_converter(baseconv.base62)
\ No newline at end of file
+        self._test_converter(baseconv.base62)
+    
+    def test_base32(self):
+        self._test_converter(baseconv.base32)
+    
+    def test_base32_mappings(self):
+        converter = baseconv.base32
+        self.assertEqual(
+            converter.from_decimal(converter.to_decimal('Fo9')),
+            'f09'
+        )
+        self.assertEqual(
+            converter.from_decimal(converter.to_decimal('43FG5i2L')),
+            '43fg5121'
+        )
+    
diff --git a/src/shorturls/tests/test_views.py b/src/shorturls/tests/test_views.py
index a2813f2..e2c7b63 100644
--- a/src/shorturls/tests/test_views.py
+++ b/src/shorturls/tests/test_views.py
@@ -1,5 +1,4 @@
 from django.conf import settings
-from django.http import Http404
 from django.test import TestCase
 from shorturls.baseconv import base62
 
diff --git a/src/shorturls/views.py b/src/shorturls/views.py
index d811fde..2d0a47b 100644
--- a/src/shorturls/views.py
+++ b/src/shorturls/views.py
@@ -4,9 +4,9 @@ from django.contrib.sites.models import Site, RequestSite
 from django.db import models
 from django.http import HttpResponsePermanentRedirect, Http404
 from django.shortcuts import get_object_or_404
-from shorturls.baseconv import base62
+from shorturls import default_converter
 
-def redirect(request, prefix, tiny):
+def redirect(request, prefix, tiny, converter=default_converter):
     """
     Redirect to a given object from a short URL.
     """
@@ -16,15 +16,18 @@ def redirect(request, prefix, tiny):
     # any of that stuff goes wrong.
     try:
         app_label, model_name = settings.SHORTEN_MODELS[prefix].split('.')
-        try:
-            model = models.get_model(app_label, model_name)
-        except LookupError:
-            raise Http404('Bad model.')
-        if not model:
-            raise ValueError
-        id = base62.to_decimal(tiny)
-    except (AttributeError, ValueError, KeyError):
-        raise Http404('Bad prefix, model, SHORTEN_MODELS, or encoded ID.')
+    except KeyError:
+        raise Http404('Bad prefix.')
+    try:
+        model = models.get_model(app_label, model_name)
+    except LookupError:
+        model = False
+    if not model:
+        raise Http404('Bad model specified in SHORTEN_MODELS.')
+    try:
+        id = converter.to_decimal(tiny)
+    except ValueError:
+        raise Http404('Bad encoded ID.')
     
     # Try to look up the object. If it's not a valid object, or if it doesn't
     # have an absolute url, bail again.