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+// Copyright 2016 Simon Sapin.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This Rust crate implements IDNA
+//! [per the WHATWG URL Standard](https://url.spec.whatwg.org/#idna).
+//!
+//! It also exposes the underlying algorithms from [*Unicode IDNA Compatibility Processing*
+//! (Unicode Technical Standard #46)](http://www.unicode.org/reports/tr46/)
+//! and [Punycode (RFC 3492)](https://tools.ietf.org/html/rfc3492).
+//!
+//! Quoting from [UTS #46’s introduction](http://www.unicode.org/reports/tr46/#Introduction):
+//!
+//! > Initially, domain names were restricted to ASCII characters.
+//! > A system was introduced in 2003 for internationalized domain names (IDN).
+//! > This system is called Internationalizing Domain Names for Applications,
+//! > or IDNA2003 for short.
+//! > This mechanism supports IDNs by means of a client software transformation
+//! > into a format known as Punycode.
+//! > A revision of IDNA was approved in 2010 (IDNA2008).
+//! > This revision has a number of incompatibilities with IDNA2003.
+//! >
+//! > The incompatibilities force implementers of client software,
+//! > such as browsers and emailers,
+//! > to face difficult choices during the transition period
+//! > as registries shift from IDNA2003 to IDNA2008.
+//! > This document specifies a mechanism
+//! > that minimizes the impact of this transition for client software,
+//! > allowing client software to access domains that are valid under either system.
+
+#[macro_use] extern crate matches;
+extern crate unicode_bidi;
+extern crate unicode_normalization;
+
+pub mod punycode;
+pub mod uts46;
+
+/// The [domain to ASCII](https://url.spec.whatwg.org/#concept-domain-to-ascii) algorithm.
+///
+/// Return the ASCII representation a domain name,
+/// normalizing characters (upper-case to lower-case and other kinds of equivalence)
+/// and using Punycode as necessary.
+///
+/// This process may fail.
+pub fn domain_to_ascii(domain: &str) -> Result<String, uts46::Errors> {
+    uts46::to_ascii(domain, uts46::Flags {
+        use_std3_ascii_rules: false,
+        transitional_processing: true, // XXX: switch when Firefox does
+        verify_dns_length: false,
+    })
+}
+
+/// The [domain to Unicode](https://url.spec.whatwg.org/#concept-domain-to-unicode) algorithm.
+///
+/// Return the Unicode representation of a domain name,
+/// normalizing characters (upper-case to lower-case and other kinds of equivalence)
+/// and decoding Punycode as necessary.
+///
+/// This may indicate [syntax violations](https://url.spec.whatwg.org/#syntax-violation)
+/// but always returns a string for the mapped domain.
+pub fn domain_to_unicode(domain: &str) -> (String, Result<(), uts46::Errors>) {
+    uts46::to_unicode(domain, uts46::Flags {
+        use_std3_ascii_rules: false,
+
+        // Unused:
+        transitional_processing: true,
+        verify_dns_length: false,
+    })
+}