#include <ShlObj.h>
#include <ComDef.h>

HRESULT SHBindToParent(
    LPCITEMIDLIST pidl,
    REFIID riid,
    VOID** ppv,
    LPCITEMIDLIST* ppidlLast)
{
    if (!ppv)
        return E_POINTER;

    // There must be at least one item ID.
    if (!pidl || !pidl->mkid.cb)
        return E_INVALIDARG;

    // Get the root folder.
    IShellFolderPtr desktop;
    HRESULT hr = SHGetDesktopFolder(&desktop);
    if (FAILED(hr))
        return hr;

    // Walk to the penultimate item ID.
    LPCITEMIDLIST marker = pidl;
    for (;;)
    {
        LPCITEMIDLIST next = reinterpret_cast<LPCITEMIDLIST>(
            marker->mkid.abID - sizeof(marker->mkid.cb) + marker->mkid.cb);
        if (!next->mkid.cb)
            break;
        marker = next;
    };

    if (marker == pidl)
    {
        // There was only a single item ID, so bind to the root folder.
        hr = desktop->QueryInterface(riid, ppv);
    }
    else
    {
        // Copy the ID list, truncating the last item.
        int length = marker->mkid.abID - pidl->mkid.abID;
        if (LPITEMIDLIST parent_id = reinterpret_cast<LPITEMIDLIST>(
            malloc(length + sizeof(pidl->mkid.cb))))
        {
            LPBYTE raw_data = reinterpret_cast<LPBYTE>(parent_id);
            memcpy(raw_data, pidl, length);
            memset(raw_data + length, 0, sizeof(pidl->mkid.cb));
            hr = desktop->BindToObject(parent_id, 0, riid, ppv);
            free(parent_id);
        }
        else
            return E_OUTOFMEMORY;
    }

    // Return a pointer to the last item ID.
    if (ppidlLast)
        *ppidlLast = marker;

    return hr;
}