asyncio.h

//------------------------------------------------------------------------------
// File: AsyncIo.h
//
// Desc: DirectShow sample code - base library for I/O functionality.
//
// Copyright (c) 1992-2001 Microsoft Corporation.  All rights reserved.
//------------------------------------------------------------------------------

#pragma once

//
// definition of CAsyncFile object that performs file access. It provides
// asynchronous, unbuffered, aligned reads from a file, using a worker thread
// on win95 and potentially overlapped i/o if available.

// !!! Need to use real overlapped i/o if available
// currently only uses worker thread, not overlapped i/o

class CAsyncIo;
class CAsyncStream;

//
//  Model the stream we read from based on a file-like interface
//
class CAsyncStream
{
public:
    virtual ~CAsyncStream() {};
    virtual HRESULT SetPointer(LONGLONG llPos) = 0;
    virtual HRESULT Read(PBYTE pbBuffer,
                         DWORD dwBytesToRead,
                         BOOL bAlign,
                         LPDWORD pdwBytesRead) = 0;
    virtual LONGLONG Size(LONGLONG *pSizeAvailable = NULL) = 0;
    virtual DWORD Alignment() = 0;
    virtual void Lock() = 0;
    virtual void Unlock() = 0;
    //virtual void SetStopHandle(HANDLE hevStop) {}
};

// represents a single request and performs the i/o. Can be called on either
// worker thread or app thread, but must hold pcsFile across file accesses.
// (ie across SetFilePointer/ReadFile pairs)
class CAsyncRequest
{
    CAsyncIo *m_pIo;
    CAsyncStream *m_pStream;
    LONGLONG      m_llPos;
    BOOL        m_bAligned;
    LONG        m_lLength;
    BYTE*       m_pBuffer;
    LPVOID      m_pContext;
    DWORD       m_dwUser;
    HRESULT     m_hr;

public:
    // init the params for this request. Issue the i/o
    // if overlapped i/o is possible.
    HRESULT Request(
        CAsyncIo *pIo,
        CAsyncStream *pStream,
        LONGLONG llPos,
        LONG lLength,
        BOOL bAligned,
        BYTE* pBuffer,
        LPVOID pContext,        // filter's context
        DWORD dwUser);          // downstream filter's context

    // issue the i/o if not overlapped, and block until i/o complete.
    // returns error code of file i/o
    HRESULT Complete();

    // cancels the i/o. blocks until i/o is no longer pending
    HRESULT Cancel()
    {
        return S_OK;
    };

    // accessor functions
    LPVOID GetContext()
    {
        return m_pContext;
    };

    DWORD GetUser()
    {
        return m_dwUser;
    };

    HRESULT GetHResult() {
        return m_hr;
    };

    // we set m_lLength to the actual length
    LONG GetActualLength() {
        return m_lLength;
    };

    LONGLONG GetStart() {
        return m_llPos;
    };
};


typedef CGenericList<CAsyncRequest> CRequestList;

// this class needs a worker thread, but the ones defined in classes\base
// are not suitable (they assume you have one message sent or posted per
// request, whereas here for efficiency we want just to set an event when
// there is work on the queue).
//
// we create CAsyncRequest objects and queue them on m_listWork. The worker
// thread pulls them off, completes them and puts them on m_listDone.
// The events m_evWork and m_evDone are set when the corresponding lists are
// not empty.
//
// Synchronous requests are done on the caller thread. These should be
// synchronised by the caller, but to make sure we hold m_csFile across
// the SetFilePointer/ReadFile code.
//
// Flush by calling BeginFlush. This rejects all further requests (by
// setting m_bFlushing within m_csLists), cancels all requests and moves them
// to the done list, and sets m_evDone to ensure that no WaitForNext operations
// will block. Call EndFlush to cancel this state.
//
// we support unaligned calls to SyncRead. This is done by opening the file
// twice if we are using unbuffered i/o (m_dwAlign > 1).
// !!!fix this to buffer on top of existing file handle?
class CAsyncIo
{

    CCritSec m_csReader;
    CAsyncStream *m_pStream;

    CCritSec m_csLists;      // locks access to the list and events
    BOOL m_bFlushing;        // true if between BeginFlush/EndFlush
    CRequestList m_listWork;
    CRequestList m_listDone;
    CAMEvent m_evWork;         // set when list is not empty
    CAMEvent m_evDone;

    // for correct flush behaviour: all protected by m_csLists
    LONG    m_cItemsOut;    // nr of items not on listDone or listWork
    BOOL    m_bWaiting;     // TRUE if someone waiting for m_evAllDone
    CAMEvent m_evAllDone;   // signal when m_cItemsOut goes to 0 if m_cWaiting


    CAMEvent m_evStop;         // set when thread should exit
    HANDLE m_hThread;

    LONGLONG Size() {
        ASSERT(m_pStream != NULL);
        return m_pStream->Size();
    };

    // start the thread
    HRESULT StartThread(void);

    // stop the thread and close the handle
    HRESULT CloseThread(void);

    // manage the list of requests. hold m_csLists and ensure
    // that the (manual reset) event hevList is set when things on
    // the list but reset when the list is empty.
    // returns null if list empty
    CAsyncRequest* GetWorkItem();

    // get an item from the done list
    CAsyncRequest* GetDoneItem();

    // put an item on the work list
    HRESULT PutWorkItem(CAsyncRequest* pRequest);

    // put an item on the done list
    HRESULT PutDoneItem(CAsyncRequest* pRequest);

    // called on thread to process any active requests
    void ProcessRequests(void);

    // initial static thread proc calls ThreadProc with DWORD
    // param as this
    static DWORD WINAPI InitialThreadProc(LPVOID pv) {
        CAsyncIo * pThis = (CAsyncIo*) pv;
        return pThis->ThreadProc();
    };

    DWORD ThreadProc(void);

public:

    CAsyncIo(CAsyncStream *pStream);
    ~CAsyncIo();

    // open the file
    HRESULT Open(LPCTSTR pName);

    // ready for async activity - call this before
    // calling Request
    HRESULT AsyncActive(void);

    // call this when no more async activity will happen before
    // the next AsyncActive call
    HRESULT AsyncInactive(void);

    // queue a requested read. must be aligned.
    HRESULT Request(
                LONGLONG llPos,
                LONG lLength,
                BOOL bAligned,
                BYTE* pBuffer,
                LPVOID pContext,
                DWORD dwUser);

    // wait for the next read to complete
    HRESULT WaitForNext(
                DWORD dwTimeout,
                LPVOID *ppContext,
                DWORD * pdwUser,
                LONG * pcbActual
                );

    // perform a read of an already aligned buffer
    HRESULT SyncReadAligned(
                LONGLONG llPos,
                LONG lLength,
                BYTE* pBuffer,
                LONG* pcbActual,
                PVOID pvContext
                );

    // perform a synchronous read. will be buffered
    // if not aligned.
    HRESULT SyncRead(
                LONGLONG llPos,
                LONG lLength,
                BYTE* pBuffer);

    // return length
    HRESULT Length(LONGLONG *pllTotal, LONGLONG* pllAvailable);

    // all Reader positions, read lengths and memory locations must
    // be aligned to this.
    HRESULT Alignment(LONG* pl);

    HRESULT BeginFlush();
    HRESULT EndFlush();

    LONG Alignment()
    {
        return m_pStream->Alignment();
    };

    BOOL IsAligned(LONG l) {
        if ((l & (Alignment() -1)) == 0) {
            return TRUE;
        } else {
            return FALSE;
        }
    };

    BOOL IsAligned(LONGLONG ll) {
        return IsAligned( (LONG) (ll & 0xffffffff));
    };

    //  Accessor
    HANDLE StopEvent() const { return m_evDone; }
};

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