MSDN Documentation

Creating and Opening Streams

Functions to create new files or open existing ones for stream-based access.

• CreateStreamOnFile

  Creates or opens a file for stream-based access. This function is a modern replacement for older Win32 file creation functions.

  HRESULT CreateStreamOnFile(PCWSTR pszFileName, DWORD dwDesiredAccess, DWORD dwShareMode, DWORD dwCreationDisposition, DWORD dwFlagsAndAttributes, IStream **ppstm);

• CreateFile2

  A more robust and feature-rich version of CreateFile that can be used to create file stream objects.

  HANDLE CreateFile2(LPCWSTR lpFileName, DWORD dwDesiredAccess, DWORD dwShareMode, DWORD dwCreationDisposition, LPCREATEFILE2_EXTENDED_PARAMETERS pCreateExParams);

Reading and Writing Data

Functions for performing asynchronous and synchronous read and write operations.

• ReadFile

  Reads data from a file or device into a buffer. Can be used asynchronously.

  BOOL ReadFile(HANDLE hFile, LPVOID lpBuffer, DWORD nNumberOfBytesToRead, LPDWORD lpNumberOfBytesRead, LPOVERLAPPED lpOverlapped);

• WriteFile

  Writes data from a buffer to a file or device. Can be used asynchronously.

  BOOL WriteFile(HANDLE hFile, LPCVOID lpBuffer, DWORD nNumberOfBytesToWrite, LPDWORD lpNumberOfBytesWritten, LPOVERLAPPED lpOverlapped);

• ReadClassStream

  Reads object data from a stream.

  HRESULT ReadClassStream(IStream *pstm, CLSID *pclsid);

• WriteClassStream

  Writes object data to a stream.

  HRESULT WriteClassStream(IStream *pstm, REFCLSID rclsid);

Seeking and Positioning

Functions to move the read/write pointer within the file stream.

• SetFilePointerEx

  Moves the file pointer to a specified location within a file.

  BOOL SetFilePointerEx(HANDLE hFile, LARGE_INTEGER liDistanceToMove, PLARGE_INTEGER lpNewFilePointer, DWORD dwMoveMethod);

• Seek

  Moves the seek pointer of the stream to a specified position.

  HRESULT Seek(IStream *pstm, LARGE_INTEGER dlibMove, DWORD dwOrigin, ULARGE_INTEGER *plibNewPosition);

Stream Properties and Control

Functions to get information about the stream and manage its state.

• GetFileSizeEx

  Retrieves the size of the specified file.

  BOOL GetFileSizeEx(HANDLE hFile, PLARGE_INTEGER lpFileSize);

• SetEndOfFile

  Sets the specified file to the specified size.

  BOOL SetEndOfFile(HANDLE hFile);

• LockFileEx

  Locks a specified portion of a file for exclusive access.

  BOOL LockFileEx(HANDLE hFile, DWORD dwFlags, DWORD dwReserved, DWORD nNumberOfBytesToLockHigh, DWORD nNumberOfBytesToLockLow, LPOVERLAPPED lpOverlapped);

#include <windows.h>
#include <objbase.h>
#include <stdio.h>

// Assume IStream is already defined and available

int main() {
    IStream *pStream = NULL;
    ULARGE_INTEGER ulSize;
    HRESULT hr;

    // Create a memory stream (e.g., using SHCreateMemStream)
    // For simplicity, let's assume pStream is already initialized with some data

    // Get the size of the stream
    if (SUCCEEDED(pStream->Seek(0, STREAM_SEEK_END, &ulSize))) {
        printf("Stream size: %llu bytes\n", ulSize.QuadPart);
    }

    // Reset stream position to the beginning
    if (SUCCEEDED(pStream->Seek(0, STREAM_SEEK_SET, NULL))) {
        // Read data from the stream
        char buffer[100];
        ULONG bytesRead;
        hr = pStream->Read(buffer, sizeof(buffer) - 1, &bytesRead);

        if (SUCCEEDED(hr) && bytesRead > 0) {
            buffer[bytesRead] = '\0'; // Null-terminate the buffer
            printf("Read from stream: %s\n", buffer);
        } else if (hr == S_FALSE) {
            printf("End of stream reached.\n");
        } else {
            printf("Error reading from stream: HRESULT = %08X\n", hr);
        }
    }

    // Release the stream
    if (pStream) {
        pStream->Release();
    }

    return 0;
}