Improve URL generation by using region and improving virtual domain s…

…tyle addressing

See http://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region
for a list of all endpoints.

s3_file/libraries/s3_file.rb

@@ -87,15 +87,7 @@ def self.with_region_detect(region = nil)
   end
 
   def self.do_request(method, url, bucket, path, aws_access_key_id, aws_secret_access_key, token, region)
-    if url.nil?
-      url = 'https://' + (
-        if bucket =~ /\./
-          "s3.amazonaws.com/#{bucket}"
-        else
-          "#{bucket}.s3.amazonaws.com"
-        end
-      )
-    end
+    url = build_endpoint_url(bucket, region) if url.nil?
 
     with_region_detect(region) do |real_region|
       client.reset_before_execution_procs
@@ -110,6 +102,20 @@ def self.do_request(method, url, bucket, path, aws_access_key_id, aws_secret_acc
     end
   end
 
+  def self.build_endpoint_url(bucket, region)
+    endpoint = if region && region != "us-east-1"
+                 "s3-#{region}.amazonaws.com"
+               else
+                 "s3.amazonaws.com"
+               end
+
+    if bucket =~ /^[a-z0-9][a-z0-9-]+[a-z0-9]$/
+      "https://#{bucket}.#{endpoint}"
+    else
+      "https://#{endpoint}/#{bucket}"
+    end
+  end
+
   def self.get_md5_from_s3(bucket, url, path, aws_access_key_id, aws_secret_access_key, token, region = nil)
     get_digests_from_s3(bucket, url, path, aws_access_key_id, aws_secret_access_key, token, region)["md5"]
   end