net/InetAddress: add method Format()

Author: MaxKellermann

src/net/IPv4Address.cxx

@@ -4,10 +4,37 @@
 #include "IPv4Address.hxx"
 
 #include <cassert>
+#include <cstring> // for strlen()
+#include <cstdio> // for sprintf()
+
+#ifndef _WIN32
+#include <arpa/inet.h> // for inet_ntop()
+#endif
 
 IPv4Address::IPv4Address(SocketAddress src) noexcept
 	:address(src.CastTo<struct sockaddr_in>())
 {
 	assert(!src.IsNull());
 	assert(src.GetFamily() == AF_INET);
 }
+
+const char *
+IPv4Address::Format(std::span<char> buffer) const noexcept
+{
+	if (buffer.size() <= 7) [[unlikely]]
+		return nullptr;
+
+	char *p = buffer.data();
+
+	if (inet_ntop(AF_INET, &address.sin_addr,
+		      p, buffer.size() - 7) == nullptr)
+		return nullptr;
+
+	const unsigned port = GetPort();
+	if (port != 0) {
+		p += std::strlen(p);
+		std::sprintf(p, ":%u", port);
+	}
+
+	return buffer.data();
+}

src/net/IPv4Address.hxx

@@ -232,4 +232,12 @@ public:
 		return IPv4Address(ConstructInAddrBE(GetNumericAddressBE() & other.GetNumericAddressBE()),
 				   GetPort() & other.GetPort());
 	}
+
+	/**
+	 * Format this object as a C string into the given buffer.
+	 *
+	 * @return the C string on success, nullptr on error
+	 */
+	[[nodiscard]]
+	const char *Format(std::span<char> buffer) const noexcept;
 };

src/net/IPv6Address.cxx

@@ -5,8 +5,12 @@
 #include "IPv4Address.hxx"
 
 #include <cassert>
+#include <cstring> // for strlen()
+#include <cstdio> // for sprintf()
 
-#include <string.h>
+#ifndef _WIN32
+#include <arpa/inet.h> // for inet_ntop()
+#endif
 
 IPv6Address::IPv6Address(SocketAddress src) noexcept
 	:address(src.CastTo<struct sockaddr_in6>())
@@ -65,3 +69,27 @@ IPv6Address::operator&(const IPv6Address &other) const
 		     sizeof(result));
 	return result;
 }
+
+const char *
+IPv6Address::Format(std::span<char> buffer) const noexcept
+{
+	if (buffer.size() <= 9) [[unlikely]]
+		return nullptr;
+
+	char *p = buffer.data();
+
+	const unsigned port = GetPort();
+	if (port != 0)
+		*p++ = '[';
+
+	if (inet_ntop(AF_INET6, &address.sin6_addr,
+		      p, buffer.size() - 9) == nullptr)
+		return nullptr;
+
+	if (port != 0) {
+		p += std::strlen(p);
+		std::sprintf(p, "]:%u", port);
+	}
+
+	return buffer.data();
+}

src/net/IPv6Address.hxx

@@ -212,6 +212,14 @@ public:
 	[[gnu::pure]]
 	IPv6Address operator&(const IPv6Address &other) const;
 
+	/**
+	 * Format this object as a C string into the given buffer.
+	 *
+	 * @return the C string on success, nullptr on error
+	 */
+	[[nodiscard]]
+	const char *Format(std::span<char> buffer) const noexcept;
+
 private:
 	/**
 	 * Helper function for MaskFromPrefix().

src/net/InetAddress.hxx

@@ -10,6 +10,8 @@
 #include "IPv6Address.hxx"
 #endif
 
+#include <span>
+
 /**
  * A class that can store either an IPv4 or an IPv6 address.
  */
@@ -116,4 +118,26 @@ public:
 			return {};
 		}
 	}
+
+	/**
+	 * Format this object as a C string into the given buffer.
+	 *
+	 * @return the C string on success, nullptr on error
+	 */
+	[[nodiscard]]
+	const char *Format(std::span<char> buffer) const noexcept {
+		switch (GetFamily()) {
+		case AF_INET:
+			return v4.Format(buffer);
+
+#ifdef HAVE_IPV6
+		case AF_INET6:
+			return v6.Format(buffer);
+#endif
+
+		default:
+			[[unlikely]]
+			return nullptr;
+		}
+	}
 };