'================================================================
'= IPアドレスからホスト名を取得
'=    (gethostbyaddr.bas)
'================================================================
#include "Windows.bi"

#define WSADescription_Len 256
#define WSASYS_Status_Len 128
#define WS_VERSION_REQD &H101
#define IP_SUCCESS 0
#define SOCKET_ERROR  -1
#define AF_INET  2

Type WSADATA
    wVersion       As Integer
    wHighVersion   As Integer
    szDescription(WSADescription_Len) As Byte
    szSystemStatus(WSASYS_Status_Len) As Byte
    imaxsockets    As Integer
    imaxudp        As Integer
    lpszvEnderinfo As Long
End Type

' WinSockを初期化
Declare Function Api_WSAStartup& Lib "wsock32" Alias "WSAStartup" (ByVal VersionReq&, WSADataReturn As WSADATA)
  
' WinSock のリソースを解放
Declare Function Api_WSACleanup& Lib "wsock32" Alias "WSACleanup" ()

' 文字列を32ビットのバイナリ値に変換
Declare Function Api_inet_addr& Lib "wsock32" Alias "inet_addr" (ByVal s$)

' IP アドレスをホスト名に変換する関数
Declare Function Api_gethostbyaddr& Lib "wsock32" Alias "gethostbyaddr" (haddr&, ByVal hnlen&, ByVal addrtype&)

' メモリブロックのコピーを行うための関数
Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (xDest As Any, xSource As Any, ByVal nbytes&)

' 文字列の長さを調べる    
Declare Function Api_lstrlen& Lib "kernel32" Alias "lstrlenA" (lpString As Any)

Var Shared Edit1 As Object
Var Shared Text(2) As Object
Var Shared Button1 As Object

Edit1.Attach GetDlgItem("Edit1") : Edit1.SetFontSize 14
For i = 0 To 2
    Text(i).Attach GetDlgItem("Text" & Trim$(Str$(i + 1)))
    Text(i).SetFontSize 14
Next i
Button1.Attach GetDlgItem("Button1") : Button1.SetFontSize 14

'================================================================
'=
'================================================================
Declare Function SocketsInitialize () As Integer
Function SocketsInitialize() As Integer
    Var WSAD As WSADATA

    SocketsInitialize = Api_WSAStartup(WS_VERSION_REQD, WSAD) = IP_SUCCESS
End Function

'================================================================
'=
'================================================================
Declare Sub SocketsCleanup ()
Sub SocketsCleanup()
    If Api_WSACleanup() <> 0 Then
        A% = MessageBox("", "CleanUpエラー！", 0, 2)
    End If
End Sub

'================================================================
'=
'================================================================
Declare Function GetHostNameFromIP(sAddress As String) As String
Function GetHostNameFromIP(sAddress As String) As String
    Var ptrHosent As Long
    Var hAddress As Long
    Var nbytes As Long
    Var Ret As Long
   
    If SocketsInitialize() Then
        hAddress = Api_inet_addr(sAddress)

        If hAddress <> SOCKET_ERROR Then
            ptrHosent = Api_gethostbyaddr(hAddress, 4, AF_INET)

            If ptrHosent <> 0 Then
                CopyMemory ptrHosent, ByVal ptrHosent, 4
                nbytes = Api_lstrLen(ByVal ptrHosent)

                If nbytes > 0 Then
                    sAddress = Space$(nbytes)
                    CopyMemory sAddress, ByVal ptrHosent, nbytes
                    GetHostNameFromIP = sAddress
                End If
            Else
                A% = MessageBox("", "取得に失敗しました！", 0, 2)
            End If
      
            SocketsCleanup
        Else
            A% = MessageBox("", "無効のIPです！", 0, 2)
        End If
    Else
        A% = MessageBox("", "ソケットの初期化失敗！", 0, 2)
    End If
End Function

'================================================================
'=
'================================================================
Declare Sub Button1_on edecl ()
Sub Button1_on()
    Var hName As String

    Text(2).SetWindowText ""
    hName = GetHostNameFromIP(GetDlgItemText("Edit1"))
    Text(2).SetWindowText hName
End Sub

'================================================================
'=
'================================================================
While 1
    WaitEvent
Wend
Stop
End