CheckSumMappedFile function (imagehlp.h)

Computes the checksum of the specified image file.


  [in]  PVOID  BaseAddress,
  [in]  DWORD  FileLength,
  [out] PDWORD HeaderSum,
  [out] PDWORD CheckSum


[in] BaseAddress

The base address of the mapped file. This value is obtained by calling the MapViewOfFile function.

[in] FileLength

The size of the file, in bytes.

[out] HeaderSum

A pointer to a variable that receives the original checksum from the image file, or zero if there is an error.

[out] CheckSum

A pointer to the variable that receives the computed checksum.

Return value

If the function succeeds, the return value is a pointer to the IMAGE_NT_HEADERS structure contained in the mapped image.

If the function fails, the return value is NULL. To retrieve extended error information, call GetLastError.


The CheckSumMappedFile function computes a new checksum for the file and returns it in the CheckSum parameter. This function is used by any application that creates or modifies an executable image. Checksums are required for kernel-mode drivers and some system DLLs. The linker computes the original checksum at link time, if you use the appropriate linker switch. For more details, see your linker documentation.

It is recommended that all images have valid checksums. It is the caller's responsibility to place the newly computed checksum into the mapped image and update the on-disk image of the file.

All ImageHlp functions, such as this one, are single threaded. Therefore, calls from more than one thread to this function will likely result in unexpected behavior or memory corruption. To avoid this, you must synchronize all concurrent calls from more than one thread to this function.


Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header imagehlp.h
Library Imagehlp.lib
DLL Imagehlp.dll

See also


ImageHlp Functions