WriteProcessMemoryVlm

[This is preliminary documentation and subject to change.]

The WriteProcessMemoryVlm function writes memory in a specified process. The entire area to be written to must be accessible, or the operation fails.

BOOL WriteProcessMemoryVlm(
  HANDLE hProcess,  // handle to process whose memory is written to
  PVOID64 lpBaseAddress,
                    // address to start writing to
  PVOID64 lpBuffer,  // pointer to buffer to write data to
  DWORD nSize,      // number of bytes to write
  LPDWORD lpNumberOfBytesWritten 
                    // actual number of bytes written
);
 

Parameters

hProcess

Handle to the process whose memory is to be modified. The handle must have PROCESS_VM_WRITE and PROCESS_VM_OPERATION access to the process. For more information on PROCESS_VM_OPERATION, see OpenProcess.

lpBaseAddress

Pointer to the base address in the specified process to be written to. Before any data transfer occurs, the system verifies that all memory at the indicated base address for the specified size is accessible for write access. If the memory is not accessible for writing, no writing is done and WriteProcessMemoryVlm fails.

The address specified is 64 bits and can therefore be used to access memory in the process allocated using VirtualAllocVlm, or the address can be a sign-extended 32-bit address.

lpBuffer

Pointer to the buffer in the memory of the calling process that supplies data to be written to the address space of the specified process.

nSize

Number of bytes to write to the specified process.

lpNumberOfBytesWritten

Pointer to the actual number of bytes transferred into the specified process. The lpNumberOfBytesWritten parameter is optional. If lpNumberOfBytesWritten is NULL, it is ignored.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError. The function fails if the requested write operation crosses into an area of the process that is inaccessible.

Remarks

WriteProcessMemoryVlm copies the data from the specified buffer in the current process to the address range of the specified process. Any process that has a handle with PROCESS_VM_WRITE and PROCESS_VM_OPERATION access to the process to be written to can call WriteProcessMemoryVlm. The process whose address space is being written to is typically, but not necessarily, being debugged.

Before any data transfer occurs, the system verifies that all memory at the given base address for the specified size is accessible for write access. If the memory is not accessible for writing, no writing is done and WriteProcessMemoryVlm fails.

Note  To guard against an access violation, use structured exception handling to protect any code that writes to or reads from a memory-mapped view. For more information on structured exception handling, see Reading and Writing.

QuickInfo

  Windows NT: Requires version 5.0 or later.
  Windows: Unsupported.
  Windows CE: Unsupported.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.

See Also

Memory Management Overview, Memory Management Functions, Very Large Memory (VLM), OpenProcess, ReadProcessMemoryVlm, VirtualAllocVlm