Fixed get_error_msg for *nix

* Fixed undefined: get_error_msg

vlib/net/socket_win.v

@@ -3,3 +3,23 @@ module net
 #flag -lws2_32
 #include <winsock2.h>
 #include <Ws2tcpip.h>
+
+// Ref - https://docs.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-wsastartup
+const (
+    WSA_V1  = 0x100 // C.MAKEWORD(1, 0)
+    WSA_V11 = 0x101 // C.MAKEWORD(1, 1)
+    WSA_V2  = 0x200 // C.MAKEWORD(2, 0)
+    WSA_V21 = 0x201 // C.MAKEWORD(2, 1)
+    WSA_V22 = 0x202 // C.MAKEWORD(2, 2)
+)
+
+pub fn socket(family int, stype int, prototype int) Socket {
+	sockfd := C.socket(family, _type, proto)
+	s := Socket {
+		sockfd: sockfd
+		family: family
+		_type: _type
+		proto: proto
+	}
+	return s
+}

vlib/os/os.v

@@ -483,8 +483,6 @@ pub fn user_os() string {
 	return 'unknown'
 }
 
-
-
 // home_dir returns path to user's home directory.
 pub fn home_dir() string {
 	mut home := os.getenv('HOME')

vlib/os/os_nix.v

@@ -5,3 +5,12 @@ module os
 const (
 	PathSeparator = '/' 
 )
+
+// get_error_msg return error code representation in string.
+pub fn get_error_msg(code int) string {
+	_ptr_text := C.strerror(code) // voidptr?
+	if _ptr_text == 0 {
+		return ''
+	}
+	return tos(_ptr_text, C.strlen(_ptr_text))
+}

vlib/os/os_win.v

@@ -67,7 +67,9 @@ const (
     MAX_ERROR_CODE  = 15841 // ERROR_API_UNAVAILABLE
 )
 
-fn ptr_get_error_message(code u32) voidptr {
+// ptr_win_get_error_msg return string (voidptr) 
+// representation of error, only for windows. 
+fn ptr_win_get_error_msg(code u32) voidptr {
     mut buf := voidptr(0)
     // Check for code overflow
     if code > u32(MAX_ERROR_CODE) {
@@ -81,10 +83,14 @@ fn ptr_get_error_message(code u32) voidptr {
     return buf
 }
 
-pub fn get_error_msg(code u32) string {
-	_ptrdata := ptr_get_error_message(code)
-    if _ptrdata == voidptr(0) {
+// get_error_msg return error code representation in string.
+pub fn get_error_msg(code int) string {
+    if code < 0 { // skip negative
         return ''
     }
-	return tos(_ptrdata, C.strlen(_ptrdata))
+    _ptr_text := ptr_win_get_error_msg(u32(code))
+    if _ptr_text == 0 { // compare with null
+        return ''
+    }
+    return tos(_ptr_text, C.strlen(_ptr_text))
 }