Added some rudimentary validity checking to host component.

* Proper verification of the host is difficult because older versions
  of Ruby do not support Unicode natively. This makes IRI support
  difficult when trying to validate.

lib/addressable/uri.rb

@@ -1019,6 +1019,14 @@ def host=(new_host)
       end
       @host = new_host ? new_host.to_str : nil
 
+      unreserved = CharacterClasses::UNRESERVED
+      sub_delims = CharacterClasses::SUB_DELIMS
+      if @host != nil && (@host =~ /[<>{}\/\?\#\@]/ ||
+          (@host[/^\[(.*)\]$/, 1] != nil && @host[/^\[(.*)\]$/, 1] !~
+          Regexp.new("^[#{unreserved}#{sub_delims}:]*$")))
+        raise InvalidURIError, "Invalid character in host: '#{@host.to_s}'"
+      end
+
       # Reset dependant values
       @authority = nil
       @normalized_host = nil

spec/addressable/uri_spec.rb

@@ -150,6 +150,14 @@ def to_s
   end
 end
 
+describe Addressable::URI, "when created with an invalid host" do
+  it "should raise an error" do
+    (lambda do
+      Addressable::URI.new(:host => "<invalid>")
+    end).should raise_error(Addressable::URI::InvalidURIError)
+  end
+end
+
 describe Addressable::URI, "when created from nil components" do
   before do
     @uri = Addressable::URI.new
@@ -1135,6 +1143,74 @@ def to_s
   end
 end
 
+describe Addressable::URI, "when parsing IPv6 addresses" do
+  it "should not raise an error for " +
+      "'http://[3ffe:1900:4545:3:200:f8ff:fe21:67cf]/'" do
+    Addressable::URI.parse("http://[3ffe:1900:4545:3:200:f8ff:fe21:67cf]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[fe80:0:0:0:200:f8ff:fe21:67cf]/'" do
+    Addressable::URI.parse("http://[fe80:0:0:0:200:f8ff:fe21:67cf]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[fe80::200:f8ff:fe21:67cf]/'" do
+    Addressable::URI.parse("http://[fe80::200:f8ff:fe21:67cf]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[::1]/'" do
+    Addressable::URI.parse("http://[::1]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[fe80::1]/'" do
+    Addressable::URI.parse("http://[fe80::1]/")
+  end
+
+  it "should raise an error for " +
+      "'http://[<invalid>]/'" do
+    (lambda do
+      Addressable::URI.parse("http://[<invalid>]/")
+    end).should raise_error(Addressable::URI::InvalidURIError)
+  end
+end
+
+describe Addressable::URI, "when parsing IPvFuture addresses" do
+  it "should not raise an error for " +
+      "'http://[v9.3ffe:1900:4545:3:200:f8ff:fe21:67cf]/'" do
+    Addressable::URI.parse("http://[v9.3ffe:1900:4545:3:200:f8ff:fe21:67cf]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[vff.fe80:0:0:0:200:f8ff:fe21:67cf]/'" do
+    Addressable::URI.parse("http://[vff.fe80:0:0:0:200:f8ff:fe21:67cf]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[v12.fe80::200:f8ff:fe21:67cf]/'" do
+    Addressable::URI.parse("http://[v12.fe80::200:f8ff:fe21:67cf]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[va0.::1]/'" do
+    Addressable::URI.parse("http://[va0.::1]/")
+  end
+
+  it "should not raise an error for " +
+      "'http://[v255.fe80::1]/'" do
+    Addressable::URI.parse("http://[v255.fe80::1]/")
+  end
+
+  it "should raise an error for " +
+      "'http://[v0.<invalid>]/'" do
+    (lambda do
+      Addressable::URI.parse("http://[v0.<invalid>]/")
+    end).should raise_error(Addressable::URI::InvalidURIError)
+  end
+end
+
 describe Addressable::URI, "when parsed from " +
     "'http://example.com/'" do
   before do