Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.206.2.13
diff -p -U 4 -r1.206.2.13 bootstrap.inc
--- includes/bootstrap.inc	14 Sep 2009 13:33:39 -0000	1.206.2.13
+++ includes/bootstrap.inc	2 Nov 2009 10:04:38 -0000
@@ -673,17 +673,21 @@ function drupal_page_cache_header($cache
   // The following headers force validation of cache:
   header("Expires: Sun, 19 Nov 1978 05:00:00 GMT");
   header("Cache-Control: must-revalidate");
 
-  if (variable_get('page_compression', TRUE)) {
+  if (variable_get('page_compression', TRUE) && extension_loaded('zlib')) {
     // Determine if the browser accepts gzipped data.
-    if (@strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') === FALSE && function_exists('gzencode')) {
-      // Strip the gzip header and run uncompress.
-      $cache->data = gzinflate(substr(substr($cache->data, 10), 0, -8));
-    }
-    elseif (function_exists('gzencode')) {
+    if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE) {
+      // $cache->data is already gzip'ed, so make sure zlib.output_compression
+      // does not compress it once more.
+      ini_set('zlib.output_compression', '0');
       header('Content-Encoding: gzip');
     }
+    else {
+      // The client does not support compression, so unzip the data in the
+      // cache. Strip the gzip header and run uncompress.
+      $cache->data = gzinflate(substr(substr($cache->data, 10), 0, -8));
+    }
   }
 
   // Send the original request's headers. We send them one after
   // another so PHP's header() function can deal with duplicate
Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.756.2.72
diff -p -U 4 -r1.756.2.72 common.inc
--- includes/common.inc	6 Oct 2009 12:03:11 -0000	1.756.2.72
+++ includes/common.inc	2 Nov 2009 10:04:39 -0000
@@ -2616,15 +2616,15 @@ function _drupal_bootstrap_full() {
 
 /**
  * Store the current page in the cache.
  *
- * We try to store a gzipped version of the cache. This requires the
- * PHP zlib extension (http://php.net/manual/en/ref.zlib.php).
- * Presence of the extension is checked by testing for the function
- * gzencode. There are two compression algorithms: gzip and deflate.
- * The majority of all modern browsers support gzip or both of them.
- * We thus only deal with the gzip variant and unzip the cache in case
- * the browser does not accept gzip encoding.
+ * If page_compression is enabled, a gzipped version of the page is stored in
+ * the cache to avoid compressing the output on each request. The cache entry
+ * is unzipped in the relatively rare event that the page is requested by a
+ * client without gzip support.
+ *
+ * Page compression requires the PHP zlib extension
+ * (http://php.net/manual/en/ref.zlib.php).
  *
  * @see drupal_page_header
  */
 function page_set_cache() {
@@ -2632,25 +2632,13 @@ function page_set_cache() {
 
   if (!$user->uid && $_SERVER['REQUEST_METHOD'] == 'GET' && page_get_cache(TRUE)) {
     // This will fail in some cases, see page_get_cache() for the explanation.
     if ($data = ob_get_contents()) {
-      $cache = TRUE;
-      if (variable_get('page_compression', TRUE) && function_exists('gzencode')) {
-        // We do not store the data in case the zlib mode is deflate.
-        // This should be rarely happening.
-        if (zlib_get_coding_type() == 'deflate') {
-          $cache = FALSE;
-        }
-        else if (zlib_get_coding_type() == FALSE) {
-          $data = gzencode($data, 9, FORCE_GZIP);
-        }
-        // The remaining case is 'gzip' which means the data is
-        // already compressed and nothing left to do but to store it.
+      if (variable_get('page_compression', TRUE) && extension_loaded('zlib')) {
+        $data = gzencode($data, 9, FORCE_GZIP);
       }
       ob_end_flush();
-      if ($cache && $data) {
-        cache_set($base_root . request_uri(), $data, 'cache_page', CACHE_TEMPORARY, drupal_get_headers());
-      }
+      cache_set($base_root . request_uri(), $data, 'cache_page', CACHE_TEMPORARY, drupal_get_headers());
     }
   }
 }