Add gethostname to nativesockets (#5443)

lib/pure/nativesockets.nim

@@ -374,6 +374,22 @@ proc getHostByName*(name: string): Hostent {.tags: [ReadIOEffect].} =
   result.addrList = cstringArrayToSeq(s.h_addr_list)
   result.length = int(s.h_length)
 
+proc getHostname*(): string {.tags: [ReadIOEffect].} =
+  ## Returns the local hostname (not the FQDN)
+  # https://tools.ietf.org/html/rfc1035#section-2.3.1
+  # https://tools.ietf.org/html/rfc2181#section-11
+  const size = 64
+  result = newString(size)
+  when useWinVersion:
+    let success = winlean.getHostname(result, size)
+  else:
+    # Posix
+    let success = posix.getHostname(result, size)
+  if success != 0.cint:
+    raiseOSError(osLastError())
+  let x = len(cstring(result))
+  result.setLen(x)
+
 proc getSockDomain*(socket: SocketHandle): Domain =
   ## returns the socket's domain (AF_INET or AF_INET6).
   var name: SockAddr

lib/windows/winlean.nim

@@ -542,6 +542,9 @@ proc gethostbyaddr*(ip: ptr InAddr, len: cuint, theType: cint): ptr Hostent {.
 proc gethostbyname*(name: cstring): ptr Hostent {.
   stdcall, importc: "gethostbyname", dynlib: ws2dll.}
 
+proc gethostname*(hostname: cstring, len: cint): cint {.
+  stdcall, importc: "gethostname", dynlib: ws2dll.}
+
 proc socket*(af, typ, protocol: cint): SocketHandle {.
   stdcall, importc: "socket", dynlib: ws2dll.}
 

tests/stdlib/tnativesockets.nim

@@ -0,0 +1,8 @@
+import nativesockets, unittest
+
+suite "nativesockets":
+  test "getHostname":
+    let hostname = getHostname()
+    check hostname.len > 0
+    check hostname.len < 64
+