/* System.Printing.dll
* MS.Internal.PrintWin32Thunk.PrinterThunkHandler.ThunkEnumPrinters();
*
* System.Drawing.dll:
* System.Drawing.Printing.PrinterSettings.InstalledPrinters.Get;
*/
internal static object[] ThunkEnumPrinters(PrinterFlags flags, string name, int level)
{
Type type = null;
switch (level)
{
case 1:
type = typeof(PrinterInfo1);
break;
case 2:
type = typeof(PrinterInfo2);
break;
case 4:
type = typeof(PrinterInfo4);
break;
case 5:
type = typeof(PrinterInfo5);
break;
default:
throw Error.ArgumentOutOfRange("level");
}
// 所需缓存字节数量
int pcbNeeded;
// 数据条目数量
int pcReturned;
// 首次调用 为了获知: 所需缓存字节数量
if (!EnumPrinters(flags, name, level, IntPtr.Zero, 0, out pcbNeeded, out pcReturned))
{
Error.ThrowIfLastErrorIsNotInsufficientBuffer();
}
if (pcbNeeded > 0)
{
var pBuffer = IntPtr.Zero;
try
{
// 分配本地内存
pBuffer = Marshal.AllocHGlobal(pcbNeeded);
if (!EnumPrinters(flags, name, level, pBuffer, pcbNeeded, out pcbNeeded, out pcReturned))
{
Error.ThrowLastError();
}
var p = pBuffer; // 当前数据起始指针
var size = Marshal.SizeOf(type); // 单个数据指针增量
var infos = new object[pcReturned];
for (int i = 0; i < pcReturned; i++)
{
infos[i] = Marshal.PtrToStructure(p, type);
p += size;
}
return(infos);
}
finally
{
// 释放本地内存
if (pBuffer != IntPtr.Zero)
{
Marshal.FreeHGlobal(pBuffer);
}
}
}
return(new object[0]);
}
static extern bool EnumPrinters(PrinterFlags Flags, string Name, int Level, IntPtr pPrinterEnum, int cbBuf, out int pcbNeeded, out int pcReturned);