When downloading metadata use the gzip transfer encoding when possible for a speedup. Fixes #749304 (metadata from google books not readable)

src/calibre/ebooks/metadata/google_books.py

@@ -193,6 +193,7 @@ class ResultList(list):
 def search(title=None, author=None, publisher=None, isbn=None,
            min_viewability='none', verbose=False, max_results=40):
     br   = browser()
+    br.set_handle_gzip(True)
     start, entries = 1, []
     while start > 0 and len(entries) <= max_results:
         new, start = Query(title=title, author=author, publisher=publisher,

src/calibre/ebooks/metadata/sources/amazon.py

@@ -283,6 +283,7 @@ class Amazon(Source):
     touched_fields = frozenset(['title', 'authors', 'identifier:amazon',
         'identifier:isbn', 'rating', 'comments', 'publisher', 'pubdate'])
     has_html_comments = True
+    supports_gzip_transfer_encoding = True
 
     AMAZON_DOMAINS = {
             'com': _('US'),

src/calibre/ebooks/metadata/sources/base.py

@@ -111,6 +111,12 @@ class Source(Plugin):
     #: Set this to True if your plugin return HTML formatted comments
     has_html_comments = False
 
+    #: Setting this to True means that the browser object will add
+    #: Accept-Encoding: gzip to all requests. This can speedup downloads
+    #: but make sure that the source actually supports gzip transfer encoding
+    #: correctly first
+    supports_gzip_transfer_encoding = False
+
     def __init__(self, *args, **kwargs):
         Plugin.__init__(self, *args, **kwargs)
         self._isbn_to_identifier_cache = {}
@@ -134,6 +140,8 @@ class Source(Plugin):
     def browser(self):
         if self._browser is None:
             self._browser = browser(user_agent=random_user_agent())
+            if self.supports_gzip_transfer_encoding:
+                self._browser.set_handle_gzip(True)
         return self._browser.clone_browser()
 
     # }}}

src/calibre/ebooks/metadata/sources/google.py

@@ -160,6 +160,7 @@ class GoogleBooks(Source):
     touched_fields = frozenset(['title', 'authors', 'tags', 'pubdate',
         'comments', 'publisher', 'identifier:isbn', 'rating',
         'identifier:google']) # language currently disabled
+    supports_gzip_transfer_encoding = True
 
     GOOGLE_COVER = 'http://books.google.com/books?id=%s&printsec=frontcover&img=1'
 

src/calibre/utils/browser.py

@@ -38,10 +38,10 @@ class Browser(B):
         self._clone_actions['set_handle_equiv'] = ('set_handle_equiv',
                 args, kwargs)
 
-    def set_handle_gzip(self, *args, **kwargs):
-        B.set_handle_gzip(self, *args, **kwargs)
+    def set_handle_gzip(self, handle):
+        self._set_handler('_gzip', handle)
         self._clone_actions['set_handle_gzip'] = ('set_handle_gzip',
-                args, kwargs)
+                (handle,), {})
 
     def set_debug_redirect(self, *args, **kwargs):
         B.set_debug_redirect(self, *args, **kwargs)