net/ToString: move UnmapV4() to class IPv6Address

src/net/IPv6Address.cxx

@@ -28,6 +28,7 @@
  */
 
 #include "IPv6Address.hxx"
+#include "IPv4Address.hxx"
 
 #include <assert.h>
 #include <string.h>
@@ -54,6 +55,20 @@ IPv6Address::IsAny() const noexcept
 		      &in6addr_any, sizeof(in6addr_any)) == 0;
 }
 
+IPv4Address
+IPv6Address::UnmapV4() const noexcept
+{
+	assert(IsV4Mapped());
+
+	struct sockaddr_in buffer{};
+	buffer.sin_family = AF_INET;
+	memcpy(&buffer.sin_addr, ((const char *)&address.sin6_addr) + 12,
+	       sizeof(buffer.sin_addr));
+	buffer.sin_port = address.sin6_port;
+
+	return buffer;
+}
+
 template<typename T>
 static void
 BitwiseAndT(T *dest, const T *a, const T *b, size_t n)

src/net/IPv6Address.hxx

@@ -43,6 +43,8 @@
 #include <netinet/in.h>
 #endif
 
+class IPv4Address;
+
 /**
  * An OO wrapper for struct sockaddr_in.
  */
@@ -183,6 +185,12 @@ public:
 		return IN6_IS_ADDR_V4MAPPED(&address.sin6_addr);
 	}
 
+	/**
+	 * Convert "::ffff:127.0.0.1" to "127.0.0.1".
+	 */
+	gcc_pure
+	IPv4Address UnmapV4() const noexcept;
+
 	/**
 	 * Bit-wise AND of two addresses.  This is useful for netmask
 	 * calculations.

src/net/SocketAddress.cxx

@@ -33,6 +33,7 @@
 #include "IPv6Address.hxx"
 #include "util/StringView.hxx"
 
+#include <assert.h>
 #include <string.h>
 
 #ifdef HAVE_UN
@@ -104,6 +105,14 @@ SocketAddress::IsV4Mapped() const noexcept
 	return GetFamily() == AF_INET6 && IPv6Address::Cast(*this).IsV4Mapped();
 }
 
+IPv4Address
+SocketAddress::UnmapV4() const noexcept
+{
+	assert(IsV4Mapped());
+
+	return IPv6Address::Cast(*this).UnmapV4();
+}
+
 unsigned
 SocketAddress::GetPort() const noexcept
 {

src/net/SocketAddress.hxx

@@ -43,6 +43,7 @@
 
 template<typename T> struct ConstBuffer;
 struct StringView;
+class IPv4Address;
 
 /**
  * An OO wrapper for struct sockaddr.
@@ -128,6 +129,12 @@ public:
 	gcc_pure
 	bool IsV4Mapped() const noexcept;
 
+	/**
+	 * Convert "::ffff:127.0.0.1" to "127.0.0.1".
+	 */
+	gcc_pure
+	IPv4Address UnmapV4() const noexcept;
+
 	/**
 	 * Extract the port number.  Returns 0 if not applicable.
 	 */

src/net/ToString.cxx

@@ -80,29 +80,6 @@ LocalAddressToString(const struct sockaddr_un &s_un, size_t size) noexcept
 
 #endif
 
-#if defined(HAVE_IPV6) && defined(IN6_IS_ADDR_V4MAPPED)
-
-/**
- * Convert "::ffff:127.0.0.1" to "127.0.0.1".
- */
-static IPv4Address
-UnmapV4(SocketAddress src) noexcept
-{
-	assert(src.IsV4Mapped());
-
-	const auto &src6 = *(const struct sockaddr_in6 *)src.GetAddress();
-
-	struct sockaddr_in buffer{};
-	buffer.sin_family = AF_INET;
-	memcpy(&buffer.sin_addr, ((const char *)&src6.sin6_addr) + 12,
-	       sizeof(buffer.sin_addr));
-	buffer.sin_port = src6.sin6_port;
-
-	return buffer;
-}
-
-#endif
-
 std::string
 ToString(SocketAddress address) noexcept
 {
@@ -116,7 +93,7 @@ ToString(SocketAddress address) noexcept
 #if defined(HAVE_IPV6) && defined(IN6_IS_ADDR_V4MAPPED)
 	IPv4Address ipv4_buffer;
 	if (address.IsV4Mapped())
-		address = ipv4_buffer = UnmapV4(address);
+		address = ipv4_buffer = address.UnmapV4();
 #endif
 
 	char host[NI_MAXHOST], serv[NI_MAXSERV];