Drop Swift 5.10 support

Motivation:

Swift 5.10 is outside of the support window for the project.

Modifications:

- Bump tools version to 6.0
- Avoid using the now-deprecated `String(cString:)` initializer for
  collections of `Int8` and instead use the one for `UInt8`.
- Add an inet_ntop helper

Result:

- 5.10 is dropped

Author: glbrntt

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.10
+// swift-tools-version: 6.0
 
 import PackageDescription
 

Sources/AsyncDNSResolver/c-ares/DNSResolver_c-ares.swift

@@ -637,18 +637,16 @@ private func toStringArray(_ arrayPointer: UnsafeMutablePointer<UnsafeMutablePoi
 extension IPAddress.IPv4 {
     init(_ address: in_addr) {
         var address = address
-        var addressBytes = [CChar](repeating: 0, count: Int(INET_ADDRSTRLEN))
-        inet_ntop(AF_INET, &address, &addressBytes, socklen_t(INET_ADDRSTRLEN))
-        self = .init(address: String(cString: addressBytes))
+        let addressString = sys_inet_ntop(family: AF_INET, bytes: &address, length: Int(INET_ADDRSTRLEN)) ?? ""
+        self = IPAddress.IPv4(address: addressString)
     }
 }
 
 extension IPAddress.IPv6 {
     init(_ address: ares_in6_addr) {
         var address = address
-        var addressBytes = [CChar](repeating: 0, count: Int(INET6_ADDRSTRLEN))
-        inet_ntop(AF_INET6, &address, &addressBytes, socklen_t(INET6_ADDRSTRLEN))
-        self = .init(address: String(cString: addressBytes))
+        let addressString = sys_inet_ntop(family: AF_INET6, bytes: &address, length: Int(INET6_ADDRSTRLEN)) ?? ""
+        self = IPAddress.IPv6(address: addressString)
     }
 }
 
@@ -665,3 +663,20 @@ extension AAAARecord {
         self.ttl = addrttl.ttl
     }
 }
+
+func sys_inet_ntop(family: CInt, bytes: UnsafeRawPointer, length: Int) -> String? {
+    var addressBytes: [Int8] = Array(repeating: 0, count: length)
+    return addressBytes.withUnsafeMutableBufferPointer { addressBytesPtr -> String? in
+        // The returned pointer is the same as addressBytesPtr.baseAddress but nil on error.
+        if inet_ntop(family, bytes, addressBytesPtr.baseAddress, socklen_t(length)) == nil {
+            return nil
+        }
+
+        return addressBytesPtr.baseAddress!.withMemoryRebound(
+            to: UInt8.self,
+            capacity: addressBytesPtr.count
+        ) {
+            String(cString: $0)
+        }
+    }
+}

Sources/AsyncDNSResolver/dnssd/DNSResolver_dnssd.swift

@@ -249,9 +249,7 @@ extension DNSSD {
                 throw AsyncDNSResolver.Error(code: .badResponse)
             }
 
-            var parsedAddressBytes = [CChar](repeating: 0, count: Int(INET_ADDRSTRLEN))
-            inet_ntop(AF_INET, ptr, &parsedAddressBytes, socklen_t(INET_ADDRSTRLEN))
-            let parsedAddress = String(cString: parsedAddressBytes)
+            let parsedAddress = sys_inet_ntop(family: AF_INET, bytes: ptr, length: Int(INET_ADDRSTRLEN)) ?? ""
             return ARecord(address: .init(address: parsedAddress), ttl: nil)
         }
 
@@ -272,9 +270,7 @@ extension DNSSD {
                 throw AsyncDNSResolver.Error(code: .badResponse)
             }
 
-            var parsedAddressBytes = [CChar](repeating: 0, count: Int(INET6_ADDRSTRLEN))
-            inet_ntop(AF_INET6, ptr, &parsedAddressBytes, socklen_t(INET6_ADDRSTRLEN))
-            let parsedAddress = String(cString: parsedAddressBytes)
+            let parsedAddress = sys_inet_ntop(family: AF_INET6, bytes: ptr, length: Int(INET6_ADDRSTRLEN)) ?? ""
             return AAAARecord(address: .init(address: parsedAddress), ttl: nil)
         }