NSIS，判断安装包是否管理员身份运行的代码

本篇文章属于《518超市播音软件开发日志》系列文章的一部分。
我在开发《518超市播音软件》（http://www.）的时候，用的NSIS打包制作安装包，安装的时候，需要确保是管理员权限的，不是的话，就提示需要管理员权限运行，然后退出。

Function un.onInit
  Call un.IsUserAdmin
  Pop $R0
  ${If} $R0 == "false"
    MessageBox MB_ICONEXCLAMATION|MB_OK|MB_TOPMOST|MB_SETFOREGROUND "需以管理员身份运行          $\n"
    Quit
  ${EndIf}



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Usage:
;   Call IsUserAdmin
;   Pop $R0   ; at this point $R0 is "true" or "false"
;
Function IsUserAdmin
Push $R0
Push $R1
Push $R2

ClearErrors
UserInfo::GetName
IfErrors Win9x
Pop $R1
UserInfo::GetAccountType
Pop $R2

StrCmp $R2 "Admin" 0 Continue
; Observation: I get here when running Win98SE. (Lilla)
; The functions UserInfo.dll looks for are there on Win98 too,
; but just don't work. So UserInfo.dll, knowing that admin isn't required
; on Win98, returns admin anyway. (per kichik)
; MessageBox MB_OK 'User "$R1" is in the Administrators group'
StrCpy $R0 "true"
Goto Done

Continue:
; You should still check for an empty string because the functions
; UserInfo.dll looks for may not be present on Windows 95. (per kichik)
StrCmp $R2 "" Win9x
StrCpy $R0 "false"
;MessageBox MB_OK 'User "$R1" is in the "$R2" group'
Goto Done

Win9x:
; comment/message below is by UserInfo.nsi author:
; This one means you don't need to care about admin or
; not admin because Windows 9x doesn't either
;MessageBox MB_OK "Error! This DLL can't run under Windows 9x!"
StrCpy $R0 "true"

Done:
;MessageBox MB_OK 'User= "$R1"  AccountType= "$R2"  IsUserAdmin= "$R0"'

Pop $R2
Pop $R1
Exch $R0
FunctionEnd
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;