ucnv_getNextUChar

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

INT ucnv_getNextUChar(
    UConverter* converter,
    const CHAR** source,
    LPCSTR sourceLimit,
    UErrorCode* err
);

<DllImport("icuuc.dll", ExactSpelling:=True, CallingConvention:=CallingConvention.Cdecl)>
Public Shared Function ucnv_getNextUChar(
    ByRef converter As IntPtr,   ' UConverter* in/out
    source As IntPtr,   ' CHAR**
    <MarshalAs(UnmanagedType.LPStr)> sourceLimit As String,   ' LPCSTR
    ByRef err As Integer   ' UErrorCode* in/out
) As Integer
End Function

' converter : UConverter* in/out
' source : CHAR**
' sourceLimit : LPCSTR
' err : UErrorCode* in/out
Declare PtrSafe Function ucnv_getNextUChar Lib "icuuc" ( _
    ByRef converter As LongPtr, _
    ByVal source As LongPtr, _
    ByVal sourceLimit As String, _
    ByRef err 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

ucnv_getNextUChar = ctypes.cdll.icuuc.ucnv_getNextUChar
ucnv_getNextUChar.restype = ctypes.c_int
ucnv_getNextUChar.argtypes = [
    ctypes.c_void_p,  # converter : UConverter* in/out
    ctypes.c_void_p,  # source : CHAR**
    wintypes.LPCSTR,  # sourceLimit : LPCSTR
    ctypes.c_void_p,  # err : UErrorCode* in/out
]

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('icuuc.dll')
ucnv_getNextUChar = Fiddle::Function.new(
  lib['ucnv_getNextUChar'],
  [
    Fiddle::TYPE_VOIDP,  # converter : UConverter* in/out
    Fiddle::TYPE_VOIDP,  # source : CHAR**
    Fiddle::TYPE_VOIDP,  # sourceLimit : LPCSTR
    Fiddle::TYPE_VOIDP,  # err : UErrorCode* in/out
  ],
  Fiddle::TYPE_INT, Fiddle::Function::CDECL)

#[link(name = "icuuc")]
extern "C" {
    fn ucnv_getNextUChar(
        converter: *mut isize,  // UConverter* in/out
        source: *const *const i8,  // CHAR**
        sourceLimit: *const u8,  // LPCSTR
        err: *mut i32  // UErrorCode* in/out
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("icuuc.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int ucnv_getNextUChar(ref IntPtr converter, IntPtr source, [MarshalAs(UnmanagedType.LPStr)] string sourceLimit, ref int err);
"@
$api = Add-Type -MemberDefinition $sig -Name 'icuuc_ucnv_getNextUChar' -Namespace Win32 -PassThru
# $api::ucnv_getNextUChar(converter, source, sourceLimit, err)

#uselib "icuuc.dll"
#func global ucnv_getNextUChar "ucnv_getNextUChar" sptr, sptr, sptr, sptr
; ucnv_getNextUChar converter, varptr(source), sourceLimit, err   ; 戻り値は stat
; converter : UConverter* in/out -> "sptr"
; source : CHAR** -> "sptr"
; sourceLimit : LPCSTR -> "sptr"
; err : UErrorCode* in/out -> "sptr"
; ※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 "icuuc.dll"
#cfunc global ucnv_getNextUChar "ucnv_getNextUChar" int, var, str, int
; res = ucnv_getNextUChar(converter, source, sourceLimit, err)
; converter : UConverter* in/out -> "int"
; source : CHAR** -> "var"
; sourceLimit : LPCSTR -> "str"
; err : UErrorCode* in/out -> "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。

; INT ucnv_getNextUChar(UConverter* converter, CHAR** source, LPCSTR sourceLimit, UErrorCode* err)
#uselib "icuuc.dll"
#cfunc global ucnv_getNextUChar "ucnv_getNextUChar" int, var, str, int
; res = ucnv_getNextUChar(converter, source, sourceLimit, err)
; converter : UConverter* in/out -> "int"
; source : CHAR** -> "var"
; sourceLimit : LPCSTR -> "str"
; err : UErrorCode* in/out -> "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 (
	icuuc = windows.NewLazySystemDLL("icuuc.dll")
	procucnv_getNextUChar = icuuc.NewProc("ucnv_getNextUChar")
)

// converter (UConverter* in/out), source (CHAR**), sourceLimit (LPCSTR), err (UErrorCode* in/out)
r1, _, err := procucnv_getNextUChar.Call(
	uintptr(converter),
	uintptr(source),
	uintptr(unsafe.Pointer(windows.BytePtrFromString(sourceLimit))),
	uintptr(err),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // INT

function ucnv_getNextUChar(
  converter: Pointer;   // UConverter* in/out
  source: Pointer;   // CHAR**
  sourceLimit: PAnsiChar;   // LPCSTR
  err: Pointer   // UErrorCode* in/out
): Integer; cdecl;
  external 'icuuc.dll' name 'ucnv_getNextUChar';

result := DllCall("icuuc\ucnv_getNextUChar"
    , "Ptr", converter   ; UConverter* in/out
    , "Ptr", source   ; CHAR**
    , "AStr", sourceLimit   ; LPCSTR
    , "Ptr", err   ; UErrorCode* in/out
    , "Cdecl Int")   ; return: INT

●ucnv_getNextUChar(converter, source, sourceLimit, err) = DLL("icuuc.dll", "int ucnv_getNextUChar(void*, void*, char*, void*)")
# 呼び出し: ucnv_getNextUChar(converter, source, sourceLimit, err)
# converter : UConverter* in/out -> "void*"
# source : CHAR** -> "void*"
# sourceLimit : LPCSTR -> "char*"
# err : UErrorCode* in/out -> "void*"
# 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)。
# ※cdecl関数。DLL()宣言はstdcall前提。cdeclは EXEC_PTR(`cdecl`,…) を使用。