Class: RUtilAnts::URLCache::URLCache

Inherits:
Object
  • Object
show all
Defined in:
lib/rUtilAnts/URLCache.rb

Overview

Class that caches every access to a URI (local file name, http, data…). This ensures just that several files are instantiated just once. For local files, it takes into account the file modification date/time to know if the Wx::Bitmap file has to be refreshed.

Defined Under Namespace

Classes: ServerDownError

Instance Method Summary collapse

Constructor Details

#initialize ⇒ URLCache

Constructor



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# File 'lib/rUtilAnts/URLCache.rb', line 20

def initialize
  # Map of known contents, interpreted in many flavors
  # map< Integer, [ Integer, Object ] >
  # map< URL's hash, [ CRC, Content ] >
  @URLs = {}
  # Map of hosts down (no need to try again such a host)
  # map< String >
  @HostsDown = {}
end

Instance Method Details

#getURLContent(iURL, iParameters = {}) ⇒ Object

Get a content from a URL. Here are the different formats the URL can have:

  • Local file name

  • http/https/ftp/ftps:// protocols

  • data:image URI

  • file:// protocol

It also handles redirections or zipped files

Parameters:

  • iURL (String): The URL

  • iParameters (map<Symbol,Object>): Additional parameters:

** :ForceLoad (Boolean): Do we force to refresh the cache ? [optional = false] ** :FollowRedirections (Boolean): Do we follow redirections ? [optional = true] ** :NbrRedirectionsAllowed (Integer): Number of redirections allowed [optional = 10] ** :LocalFileAccess (Boolean): Do we need a local file to read the content from ? If not, the content itslef will be given the code block. [optional = false]

  • CodeBlock: The code returning the object corresponding to the content:

** iContent (String): File content, or file name if :LocalFileAccess was true ** Returns: ** Object: Object read from the content, or nil in case of error ** Exception: The error encountered, or nil in case of success Return:

  • Object: The corresponding URL content, or nil in case of failure

  • Exception: The error, or nil in case of success



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# File 'lib/rUtilAnts/URLCache.rb', line 53

def getURLContent(iURL, iParameters = {})
  rObject = nil
  rError = nil

  # Parse parameters
  lForceLoad = iParameters[:ForceLoad]
  if (lForceLoad == nil)
    lForceLoad = false
  end
  # Get the URL handler corresponding to this URL
  lURLHandler = getURLHandler(iURL)
  lServerID = lURLHandler.getServerID
  if (@HostsDown.has_key?(lServerID))
    rError = ServerDownError.new("Server #{iURL} is currently down.")
  else
    lURLHash = iURL.hash
    # Check if it is in the cache, or if we force refresh, or if the URL was invalidated
    lCurrentCRC = lURLHandler.getCRC
    if ((@URLs[lURLHash] == nil) or
        (lForceLoad) or
        (@URLs[lURLHash][0] != lCurrentCRC))
      # Load it for real
      # Reset previous value if it was set
      @URLs[lURLHash] = nil
      # Get the object
      lObject = nil
      lAccessError = accessFile(iURL, iParameters.merge(:URLHandler => lURLHandler)) do |iContent, iBaseName|
        lObject, rError = yield(iContent)
      end
      if (lAccessError != nil)
        rError = lAccessError
      end
      # Put lObject in the cache if no error was found
      if (rError == nil)
        # OK, register it
        @URLs[lURLHash] = [ lCurrentCRC, lObject ]
      else
        if ((defined?(SocketError) != nil) and
            (rError.is_a?(SocketError)))
          # We have a server down
          @HostsDown[lServerID] = nil
        end
      end
    end
    # If no error was found (errors can only happen if it was not already in the cache), take it from the cache
    if (rError == nil)
      rObject = @URLs[lURLHash][1]
    end
  end

  return rObject, rError
end