Raise a unique exception if libvirt C library not available.

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 0.2.1 (unreleased)
 
-
+  - `FFI::Libvirt::MissingLibError` is raised if libvirt C library
+    is not available.
 
 ## 0.2.0 (December 7, 2010)
 

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    libvirt (0.2.0)
+    libvirt (0.2.1.dev)
       ffi (~> 0.6.3)
       nokogiri (~> 1.4.3)
 

lib/ffi/libvirt.rb

@@ -7,10 +7,19 @@ module FFI
   # that it is up to you to manage all the pointers and so on that come
   # with this power.
   module Libvirt
+    autoload :MissingLibError, 'ffi/libvirt/exception'
+    autoload :Util, 'ffi/libvirt/util'
+
     extend FFI::Library
-    ffi_lib "libvirt"
 
-    autoload :Util, 'ffi/libvirt/util'
+    # Attempt to load the libvirt lib and raise a more specific exception
+    # if it doesn't exist. (Normally a LoadError, which is ambiguous, is
+    # raised)
+    begin
+      ffi_lib "libvirt"
+    rescue LoadError
+      raise MissingLibError
+    end
   end
 end
 

lib/ffi/libvirt/exception.rb

@@ -0,0 +1,10 @@
+module FFI
+  module Libvirt
+    # Error raised when the libvirt C library is missing.
+    class MissingLibError < StandardError
+      def initialize
+        super("The libvirt C library could not be loaded. Is it properly installed?")
+      end
+    end
+  end
+end