Added code to check declared encodings first and check them

from kennethreitz/requests/utils.py.  Also I added some superset
encodings I have found in Chinese pages that are mishandled by
chardet/character declarations.

readability/encoding.py

@@ -2,20 +2,47 @@ import re
 import chardet
 
 def get_encoding(page):
+    # Regex for XML and HTML Meta charset declaration
+    charset_re = re.compile(r'<meta.*?charset=["\']*(.+?)["\'>]', flags=re.I)
+    pragma_re = re.compile(r'<meta.*?content=["\']*;?charset=(.+?)["\'>]', flags=re.I)
+    xml_re = re.compile(r'^<\?xml.*?encoding=["\']*(.+?)["\'>]')
+
+    declared_encodings = (charset_re.findall(page) +
+            pragma_re.findall(page) +
+            xml_re.findall(page))
+
+    # Try any declared encodings
+    if len(declared_encodings) > 0:
+        for declared_encoding in declared_encodings:
+            try:
+                page.decode(custom_decode(declared_encoding))
+                return custom_decode(declared_encoding)
+            except UnicodeDecodeError:
+                pass
+
+    # Fallback to chardet if declared encodings fail
     text = re.sub('</?[^>]*>\s*', ' ', page)
     enc = 'utf-8'
     if not text.strip() or len(text) < 10:
         return enc # can't guess
-    try:
-        diff = text.decode(enc, 'ignore').encode(enc)
-        sizes = len(diff), len(text)
-        if abs(len(text) - len(diff)) < max(sizes) * 0.01: # 99% of utf-8
-            return enc
-    except UnicodeDecodeError:
-        pass
     res = chardet.detect(text)
     enc = res['encoding']
     #print '->', enc, "%.2f" % res['confidence']
-    if enc == 'MacCyrillic':
-        enc = 'cp1251'
+    enc = custom_decode(enc)
     return enc
+
+def custom_decode(encoding):
+    """Overrides encoding when charset declaration
+       or charset determination is a subset of a larger
+       charset.  Created because of issues with Chinese websites"""
+    encoding = encoding.lower()
+    alternates = {
+        'big5': 'big5hkscs',
+        'gb2312': 'gb18030',
+        'ascii': 'utf-8',
+        'MacCyrillic': 'cp1251',
+    }
+    if encoding in alternates:
+        return alternates[encoding]
+    else:
+        return encoding