Documentation

A UrlRequest object contains a url to get, the file into which the contents at the given url should be written, the cachability of this request and the request's priority.

A UrlState object contains a map of url -> InProgressStatus, a Q of urls waiting to be started, the current pipe length and the unique junk to create unique filenames.

Q represents a prioritised queue, with two-tier priority. The left list contains higher priority items than the right list.

readQ will try and take an element from the Q, preferring elements from the high priority list.

insertQ inserts a low priority item into a Q.

pushQ inserts a high priority item into a Q.

Return a function for adding an element based on the priority.

deleteQ removes any instances of a given element from the Q.

deleteQ checks for membership in a Q.

emptyQ is an empty Q.

nullQ checks if the Q contains no items.

Data type to represent a connection error. The following are the codes from libcurl which map to each of the constructors: * 6 -> CouldNotResolveHost : The remote host was not resolved. * 7 -> CouldNotConnectToServer : Failed to connect() to host or proxy. * 28 -> OperationTimeout: the specified time-out period was reached.