A File Checksum Shell Menu Extension DLL

// VerifyHash.h : Declaration of the CVerifyHash

#pragma once
#include "resource.h"       // main symbols

#include "CtxVerifyHash.h"


#if defined(_WIN32_WCE) && !defined(_CE_DCOM) && !defined(_CE_ALLOW_SINGLE_THREADED_OBJECTS_IN_MTA)
#error "Single-threaded COM objects are not properly supported on Windows CE platform, such as the Windows Mobile platforms that do not include full DCOM support. Define _CE_ALLOW_SINGLE_THREADED_OBJECTS_IN_MTA to force ATL to support creating single-thread COM object's and allow use of it's single-threaded COM object implementations. The threading model in your rgs file was set to 'Free' as that is the only threading model supported in non DCOM Windows CE platforms."
#endif



// CVerifyHash

class ATL_NO_VTABLE CVerifyHash :
	public CComObjectRootEx<CComSingleThreadModel>,
	public CComCoClass<CVerifyHash, &CLSID_VerifyHash>,
	public IDispatchImpl<IVerifyHash, &IID_IVerifyHash, &LIBID_CtxVerifyHashLib,
           /*wMajor =*/ 1, /*wMinor =*/ 0>,
    public IShellExtInit,
    public IContextMenu
{
public:
    CVerifyHash() { }

    protected:

    // Parallel Vectors of various hashes and hash values
    //   (in string format, not byte) for a given file
    //
    //   file = "C:\Winnt\text.txt"
    //
    //   hashes[0] = "MD5"
    //   hashes[1] = "SHA-1"
    //   hashes[2] = "SHA-256"
    //
    //   filehashes[0] = "CD5B65B7ACDBA247EDE28FBA169F2F26"
    //   filehashes[1] = "5751B71EFED61D91B3AD048C0C81F15397DAF434"
    //   filehashes[2] = "9AE08AA516BA5739 ... 282C16841B9866F2"
    bool CalculateFileHashes( const std::wstring& filename,
                              std::vector< std::wstring >& hashes,
                              std::vector< std::wstring >& filehashes );

    // Transforms
    //   'CD4FE51FD1C9A4F311BA0E7E920FB957D2E6DB804AB00FDFEBDFDBA9BB586172'
    // to
    //   'CD4FE51FD1C9A4F3...EBDFDBA9BB586172
    //
    // Useful for MessageBoxes to keep the size down
    //   Starts snipping when hash.length() > 32
    std::wstring Snip( const std::wstring& hash );

    // Retrieves the text on the Clipboard
    bool GetClipboardText( std::wstring& ClipboardText );

protected:
    std::vector< std::wstring > files;

    UINT uID;

public:
  // IShellExtInit
  STDMETHODIMP Initialize(LPCITEMIDLIST, LPDATAOBJECT, HKEY);

public:
  // IContextMenu
  STDMETHODIMP InvokeCommand(LPCMINVOKECOMMANDINFO);
  STDMETHODIMP GetCommandString(UINT, UINT, UINT*, LPSTR, UINT);  
  STDMETHODIMP QueryContextMenu(HMENU, UINT, UINT, UINT, UINT);

DECLARE_REGISTRY_RESOURCEID(IDR_VERIFYHASH)

DECLARE_NOT_AGGREGATABLE(CVerifyHash)

BEGIN_COM_MAP(CVerifyHash)
	// COM_INTERFACE_ENTRY(IDispatch)
    COM_INTERFACE_ENTRY(IShellExtInit)
    COM_INTERFACE_ENTRY(IContextMenu)
END_COM_MAP()

	DECLARE_PROTECT_FINAL_CONSTRUCT()

	HRESULT FinalConstruct() { uID = -1; return S_OK; }

    void FinalRelease() { }

public:

};

OBJECT_ENTRY_AUTO(__uuidof(VerifyHash), CVerifyHash)