Add DNS component support and update hostname validation

Signed-off-by: Tushar Verma <tusharmyself06@gmail.com>

Author: vtushar06

.github/workflows/website-build.yml

@@ -29,6 +29,7 @@ jobs:
           -DSOURCEMETA_CORE_CRYPTO:BOOL=OFF
           -DSOURCEMETA_CORE_REGEX:BOOL=OFF
           -DSOURCEMETA_CORE_IP:BOOL=OFF
+          -DSOURCEMETA_CORE_DNS:BOOL=OFF
           -DSOURCEMETA_CORE_URI:BOOL=OFF
           -DSOURCEMETA_CORE_URITEMPLATE:BOOL=OFF
           -DSOURCEMETA_CORE_JSON:BOOL=OFF

.github/workflows/website-deploy.yml

@@ -39,6 +39,7 @@ jobs:
           -DSOURCEMETA_CORE_CRYPTO:BOOL=OFF
           -DSOURCEMETA_CORE_REGEX:BOOL=OFF
           -DSOURCEMETA_CORE_IP:BOOL=OFF
+          -DSOURCEMETA_CORE_DNS:BOOL=OFF
           -DSOURCEMETA_CORE_URI:BOOL=OFF
           -DSOURCEMETA_CORE_URITEMPLATE:BOOL=OFF
           -DSOURCEMETA_CORE_JSON:BOOL=OFF

config.cmake.in

@@ -15,6 +15,7 @@ if(NOT SOURCEMETA_CORE_COMPONENTS)
   list(APPEND SOURCEMETA_CORE_COMPONENTS crypto)
   list(APPEND SOURCEMETA_CORE_COMPONENTS regex)
   list(APPEND SOURCEMETA_CORE_COMPONENTS ip)
+  list(APPEND SOURCEMETA_CORE_COMPONENTS dns)
   list(APPEND SOURCEMETA_CORE_COMPONENTS uri)
   list(APPEND SOURCEMETA_CORE_COMPONENTS uritemplate)
   list(APPEND SOURCEMETA_CORE_COMPONENTS json)
@@ -61,6 +62,8 @@ foreach(component ${SOURCEMETA_CORE_COMPONENTS})
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_regex.cmake")
   elseif(component STREQUAL "ip")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_ip.cmake")
+  elseif(component STREQUAL "dns")
+    include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_dns.cmake")
   elseif(component STREQUAL "uri")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_ip.cmake")
     include("${CMAKE_CURRENT_LIST_DIR}/sourcemeta_core_uri.cmake")

src/core/dns/hostname.cc

@@ -29,7 +29,6 @@ auto is_hostname(const std::string_view value) -> bool {
   std::string_view::size_type position{0};
 
   while (position < value.size()) {
-    // Start of a new label
     const auto label_start{position};
 
     // RFC 1123 §2.1: first character is letter or digit
@@ -38,7 +37,6 @@ auto is_hostname(const std::string_view value) -> bool {
     }
     position += 1;
 
-    // Walk interior characters and the last character of the label
     while (position < value.size() && value[position] != '.') {
       // RFC 952 §B: interior characters are let-dig-hyp
       if (!is_let_dig_hyp(value[position])) {

src/core/dns/include/sourcemeta/core/dns.h

@@ -36,10 +36,10 @@ namespace sourcemeta::core {
 /// ```
 ///
 /// This function implements RFC 1123 §2.1 (ASCII only). It does not
-/// perform A-label or Punycode decoding — those belong to the separate
+/// perform A-label or Punycode decoding. Those belong to the separate
 /// `idn-hostname` format.
 SOURCEMETA_CORE_DNS_EXPORT
-auto is_hostname(std::string_view value) -> bool;
+auto is_hostname(const std::string_view value) -> bool;
 
 } // namespace sourcemeta::core
 

test/dns/hostname_test.cc

@@ -4,8 +4,6 @@
 
 #include <string>
 
-// VALID - RFC 1123 §2.1 / RFC 952 compliant inputs
-
 // RFC 952 §B: <hname> ::= <name>*["."<name>]  (three labels, TS d7+ #7)
 TEST(DNS_hostname, valid_simple_dotted) {
   EXPECT_TRUE(sourcemeta::core::is_hostname("www.example.com"));
@@ -121,8 +119,6 @@ TEST(DNS_hostname, valid_many_labels) {
   EXPECT_TRUE(sourcemeta::core::is_hostname("a.b.c.d.e.f"));
 }
 
-// INVALID - non-compliant inputs
-
 // RFC 952 §B: <hname> requires at least one <name> / label (TS d7+ #12)
 TEST(DNS_hostname, invalid_empty) {
   EXPECT_FALSE(sourcemeta::core::is_hostname(""));