StrFormatByteSizeEx

// SHLWAPI.dll
#include <windows.h>

HRESULT StrFormatByteSizeEx(
    ULONGLONG ull,
    SFBS_FLAGS flags,
    LPWSTR pszBuf,
    DWORD cchBuf
);

<DllImport("SHLWAPI.dll", ExactSpelling:=True)>
Public Shared Function StrFormatByteSizeEx(
    ull As ULong,   ' ULONGLONG
    flags As Integer,   ' SFBS_FLAGS
    <MarshalAs(UnmanagedType.LPWStr)> pszBuf As System.Text.StringBuilder,   ' LPWSTR out
    cchBuf As UInteger   ' DWORD
) As Integer
End Function

' ull : ULONGLONG
' flags : SFBS_FLAGS
' pszBuf : LPWSTR out
' cchBuf : DWORD
Declare PtrSafe Function StrFormatByteSizeEx Lib "shlwapi" ( _
    ByVal ull As LongLong, _
    ByVal flags As Long, _
    ByVal pszBuf As LongPtr, _
    ByVal cchBuf As Long) As Long
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

StrFormatByteSizeEx = ctypes.windll.shlwapi.StrFormatByteSizeEx
StrFormatByteSizeEx.restype = ctypes.c_int
StrFormatByteSizeEx.argtypes = [
    ctypes.c_ulonglong,  # ull : ULONGLONG
    ctypes.c_int,  # flags : SFBS_FLAGS
    wintypes.LPWSTR,  # pszBuf : LPWSTR out
    wintypes.DWORD,  # cchBuf : DWORD
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('SHLWAPI.dll')
StrFormatByteSizeEx = Fiddle::Function.new(
  lib['StrFormatByteSizeEx'],
  [
    -Fiddle::TYPE_LONG_LONG,  # ull : ULONGLONG
    Fiddle::TYPE_INT,  # flags : SFBS_FLAGS
    Fiddle::TYPE_VOIDP,  # pszBuf : LPWSTR out
    -Fiddle::TYPE_INT,  # cchBuf : DWORD
  ],
  Fiddle::TYPE_INT)

#[link(name = "shlwapi")]
extern "system" {
    fn StrFormatByteSizeEx(
        ull: u64,  // ULONGLONG
        flags: i32,  // SFBS_FLAGS
        pszBuf: *mut u16,  // LPWSTR out
        cchBuf: u32  // DWORD
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("SHLWAPI.dll")]
public static extern int StrFormatByteSizeEx(ulong ull, int flags, [MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder pszBuf, uint cchBuf);
"@
$api = Add-Type -MemberDefinition $sig -Name 'SHLWAPI_StrFormatByteSizeEx' -Namespace Win32 -PassThru
# $api::StrFormatByteSizeEx(ull, flags, pszBuf, cchBuf)

#uselib "SHLWAPI.dll"
#func global StrFormatByteSizeEx "StrFormatByteSizeEx" sptr, sptr, sptr, sptr
; StrFormatByteSizeEx ull, flags, varptr(pszBuf), cchBuf   ; 戻り値は stat
; ull : ULONGLONG -> "sptr"
; flags : SFBS_FLAGS -> "sptr"
; pszBuf : LPWSTR out -> "sptr"
; cchBuf : DWORD -> "sptr"
; ※HSP3.7は int64 引数(64bit値渡し)に非対応です。
; ※HSP3.7は #func のため戻り値はシステム変数 stat に格納されます。

#uselib "SHLWAPI.dll"
#cfunc global StrFormatByteSizeEx "StrFormatByteSizeEx" int64, int, var, int
; res = StrFormatByteSizeEx(ull, flags, pszBuf, cchBuf)
; ull : ULONGLONG -> "int64"
; flags : SFBS_FLAGS -> "int"
; pszBuf : LPWSTR out -> "var"
; cchBuf : DWORD -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。
; ※int64 引数の DLL 値渡しは x64 ランタイム(hsp3_64)のみ対応(x86 は未対応)。

; HRESULT StrFormatByteSizeEx(ULONGLONG ull, SFBS_FLAGS flags, LPWSTR pszBuf, DWORD cchBuf)
#uselib "SHLWAPI.dll"
#cfunc global StrFormatByteSizeEx "StrFormatByteSizeEx" int64, int, var, int
; res = StrFormatByteSizeEx(ull, flags, pszBuf, cchBuf)
; ull : ULONGLONG -> "int64"
; flags : SFBS_FLAGS -> "int"
; pszBuf : LPWSTR out -> "var"
; cchBuf : DWORD -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

import (
	"golang.org/x/sys/windows"
	"unsafe"
)

var (
	shlwapi = windows.NewLazySystemDLL("SHLWAPI.dll")
	procStrFormatByteSizeEx = shlwapi.NewProc("StrFormatByteSizeEx")
)

// ull (ULONGLONG), flags (SFBS_FLAGS), pszBuf (LPWSTR out), cchBuf (DWORD)
r1, _, err := procStrFormatByteSizeEx.Call(
	uintptr(ull),
	uintptr(flags),
	uintptr(pszBuf),
	uintptr(cchBuf),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // HRESULT

function StrFormatByteSizeEx(
  ull: UInt64;   // ULONGLONG
  flags: Integer;   // SFBS_FLAGS
  pszBuf: PWideChar;   // LPWSTR out
  cchBuf: DWORD   // DWORD
): Integer; stdcall;
  external 'SHLWAPI.dll' name 'StrFormatByteSizeEx';

result := DllCall("SHLWAPI\StrFormatByteSizeEx"
    , "Int64", ull   ; ULONGLONG
    , "Int", flags   ; SFBS_FLAGS
    , "Ptr", pszBuf   ; LPWSTR out
    , "UInt", cchBuf   ; DWORD
    , "Int")   ; return: HRESULT

●StrFormatByteSizeEx(ull, flags, pszBuf, cchBuf) = DLL("SHLWAPI.dll", "int StrFormatByteSizeEx(qword, int, char*, dword)")
# 呼び出し: StrFormatByteSizeEx(ull, flags, pszBuf, cchBuf)
# ull : ULONGLONG -> "qword"
# flags : SFBS_FLAGS -> "int"
# pszBuf : LPWSTR out -> "char*"
# cchBuf : DWORD -> "dword"
# なでしこ1は32bit・ANSI(Shift_JIS)。文字列=char*(ANSI)、ポインタ/ハンドル=void*(4byte)。