csink.cpp

研读AxCrypt对加解密的处理方法

/*! \file
    \brief Implementation of AxPipe::CSink base class for sinks

    @(#) $Id: CSink.cpp,v 1.3 2004/02/02 12:10:47 svante Exp $

    AxPipe - Binary Stream Framework

    Copyright (C) 2003 Svante Seleborg/Axon Data, All rights reserved.

    This program is free software; you can redistribute it and/or modify it under the terms
    of the GNU General Public License as published by the Free Software Foundation;
    either version 2 of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
    without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along with this program;
    if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
    Boston, MA 02111-1307 USA

    The author may be reached at mailto:[e-mail] and http://axpipe.sourceforge.net

    Why is this framework released as GPL and not LGPL? See http://www.gnu.org/philosophy/why-not-lgpl.html

----
\verbatim
    CSink.cpp                       Implementation of CSink base class for sinks

    E-mail                          YYYY-MM-DD              Reason
    [e-mail]              2003-12-01              Initial
\endverbatim
*/
#include "stdafx.h"

#include "AxAssert.h"
#define AXLIB_ASSERT_FILE "CSink.cpp"

namespace AxPipe {
    /// Helper function that is also called by derived classes that want slightly
    /// different Work() logic, but can leverage this common base.
    /// Checks for special AxPipe::eSegType types, and calls the appropriate OutOpen(),
    /// OutClose(), OutFlush() and Out() functions depending on the case.
    /// Only in the case of Out() does the actual data segment get passed on. Any custom
    /// AxPipe::eSegType segment types gets passed as normal segments to Out().
    /// Ensures that the pipe is Open() at this stage before sending data etc.
    /// \return true if the caller should propagate the segment. The pSeg is never CSeg::Release()'d here. Caller must.
    bool
    CSink::DoSegWork(CSeg *pSeg) {
        bool fPropagate;                    // true if we propagate in band signals

        switch (pSeg->Type()) {
        case eSegTypeOpen:
            fPropagate = OutOpen();
            // Can't set this false before we've closed properly
            m_fIsOpen = true;
            return fPropagate;
            break;

        case eSegTypeFlush:
            return OutFlush();
            break;

        case eSegTypeClose:
            if (m_fIsOpen) {
                fPropagate = OutClose();
                // Can't set this false before we've closed properly
                m_fIsOpen = false;
            } else {
                // If we're not open doesn't make sense to propagate close
                fPropagate = false;
            }
            return fPropagate;
            break;

        case eSegTypePlug:
            // Set the exit so we can end if it's a thread etc.
            OutPlug();                      // Call this class's Plug-function
            fPropagate = m_fExit = true;
            return fPropagate;
            break;

        case 0:
            if (!m_fIsOpen) {
                SetError(ERROR_CODE_NOTOPEN, ERROR_MSG_NOTOPEN);
                break;
            }
            // Ignore zero-length segments.
            if (pSeg->Len()) {
                // non-zero length data segment.
                // Out() will not be called with anything else. CFilter derived classes have slightly
                // different rules.
                Out(pSeg->AddRef());
            }
            break;
        default:
            // It's an special/unknown segment type, call the handler (even with zero-length)
            // Note that we auto propagate special segments, even if they are semantially similar
            // to normal data segments.
            // CSeg::AddRef() it since the OutSpecial() handler is expected to CSeg::Release() it - as will the caller of DoSegWork()
            return OutSpecial(pSeg->AddRef());
            break;
        }
        return false;
    }

    /// Called with CSink::m_pSeg set to whatever needs to be processed.
    /// Work guarantees to never call Out() with anything but a valid, non-zero-length
    /// data segment. Other cases are handled by OutOpen(), OutClose() and OutFlush().
    /// A Plug() request causes nothing to be sent to Out().
    void
    CSink::Work() {
        CSeg *pSeg = m_pSeg;
        m_pSeg = NULL;

        (void)DoSegWork(pSeg);
        // DoSegWork() never releases, so we must.
        pSeg->Release();
    }

    /// Unless we're already exited, end processing and wait for it to reach
    /// idle state. Should not be called from Work() or Out(). Finally, we
    /// wait for the worker thread, if any, to actually exit, thus assuring
    /// that when Plug() returns, it is safe to call the destructor.
    /// The purpose of Plug is to finalize all processing and to ensure that
    /// any errors are found and reported. Final error checking for processing should
    /// thus not be done before Plug() is called. After Plug() is called, the
    /// only thing that should be done with the object and the pipe line is
    /// to destruct it.
    void
    CSink::OutPlug() {
        AxLib::OutputDebugStringF(_T("CSink::OutPlug() m_fExit=%d\n"), m_fExit);
    }

    /// Allocate a new segment, possibly from the next section of the pipe.
    ///
    /// Callable from user code in derived classes.
    ///
    /// Call this to get a segment if you suspect the next in line is a sink that
    /// might provide an efficient segment, such as for a memory mapped file.
    /// \return A writeable CSeg of the requested size, or NULL on error.
    CSeg *
    CSink::GetSeg(size_t cb)  {
        return new CSeg(cb);
    }

    /// \brief Send Out-of-band signal. Callable from user code in derived classes.
    ///
    /// Does nothing, this is a CSink.
    /// \see CPipe::Signal()
    void
    CSink::Signal(void *vId, void *p) {
    }

    /// Callable from user code in derived classes.
    ///
    /// \return The maximum output size in bytes. -1 if unknown or unlimited.
    /// \see OutSizeMax() The corresponding overrideable
    longlong
    CSink::SizeMax() {
        return OutSizeMax();
    }

    /// Do not call from user code, only from derived framework classes.
    /// The normal usage is to have the previous section up the line
    /// call this via it's CPipe::m_pSink pointer, the roundabout way is
    /// to enable seamless threading.
    /// Is frequently called from other library-internal classes, therefore public
    /// \param pSeg The segment to send off to Work(). Don't use it afterwards unless you've CSeg::AddRef()'d it.
    void
    CSink::OutPump(CSeg *pSeg) {
        WorkStart();
        m_pSeg = pSeg;
        WorkSignal();
    }
    
    /// Override this in user derived classes to return the maximum size
    /// of the sink, or -1 for expandable. The default CSink implementation
    /// always returns -1.
    /// \return The maximum output size in bytes. -1 if unknown or unlimited.
    /// \see SizeMax()
    longlong
    CSink::OutSizeMax() {
        return -1;
    }
    
    /// Override in user derived classes to provide an efficient memory segment
    /// output from a CSink, especially for memory mapped files.
    /// \see GetSeg() The User callable function.
    /// \return A writeable segment.
    CSeg *
    CSink::OutGetSeg(size_t cb) {
		CSeg *pSeg = new CSeg(cb);
		ASSPTR(pSeg);
        return pSeg;
    }
    
    /// Override in user derived classes to receive a out-of band signal sent from upstream.
    /// This will be called synchronized with the data stream, so previously sent
    /// data will have reached this section, unless some intermediate section buffers.
    /// No automatic Flush() request is sent though. This CSink default implementation
    /// does nothing and returns false to stop propagation, since it's CSink.
    /// \return false to stop the signal-propagation, true to continue it.
    /// \param vId A unique value identifying the signal, suggested is ClassId().
    /// \param p An opaque pointer value, interpretable by the receiver.
    /// \see CPipe::OutSignal()
    /// \sse CPipe::OutSpecial()
    bool
    CSink::OutSignal(void *vId, void *p) {
        return false;
    }

    /// Override in user derived classes. Called by the framework as a result of an
    /// Open() call here or upstream. Prepare for processing of a new stream, it must
    /// support being called again after a Close() call. No data may be processed by
    /// the stream without an Open() call.
    ///
    /// The default implementation for a CSink returns false, as it does not make
    /// sense to propagate downstream from a CSink()
    /// \return true if the framework should propagate the Open() request downstream.
    bool
    CSink::OutOpen() {
        return false;
    };
    
    /// You are not required to honor the request.
    /// \return true if the framework should propagate the Flush() request downstream.
    bool
    CSink::OutFlush() {
        return false;
    };
    
    /// The code should handle multiple (extra) calls to an already closed stream with
    /// no ill effects, i.e. silently ignore them. This default implementation returns
    /// false to stop propagation, since it's a CSink.
    /// \return true if the framework should propagate the Close() request downstream.
    bool
    CSink::OutClose() {
        return false;
    };
    /// Segments may be marked as special with a non-zero value based on AxPipe::eSegType types. These are
    /// filtered out of the stream by the framework and presented here instead of to Out(). Use
    /// this in derived classes to provide in band signalling and for other custom needs. Start
    /// numbering from AxPipe::eSegTypeDerived.
    ///
    /// The default implementation here just calls CSeg::Release() on the provided CSeg .
    ///
    /// These segements may be zero-length.
	/// \return false, since we're at the end of the line. No more propagation.
    /// \see AxPipe::eSegType
    bool
    CSink::OutSpecial(CSeg *pSeg) {
        pSeg->Release();
		return false;
    }

    /// Initialize member variables.
    CSink::CSink() {
        m_pSeg = NULL;
        m_fIsOpen = false;
    }

    /// Plug the pipe, destroy the sink and release remaining m_pSeg if any
    CSink::~CSink() {
        OutputDebugStringF(_T("CSink::~CSink() Initating... this=%p\n"), this);
        ASSCHK(m_fExit, _T("CSink::~CSink() called without Plug()"));
        if (CSeg::IsSeg(m_pSeg)) m_pSeg->Release();
        OutputDebugStringF(_T("CSink::~CSink() ...Done. this=%p\n"), this);
    }

    /// You can't append a CSink to a CSink, so this implements code to catch
    /// that error.
    void
    CSink::AppendSink(CSink *pSink, bool fAutoDelete) {
        SetError(ERROR_CODE_GENERIC, _T("Attempt to append to a sink"));
    }

    /// Synchronize all work downstream, ensuring
    /// that there is no work in progress.
    void
    CSink::Sync() {
        WaitForIdle();
        // Do no more, this is a CSink - It's the end of the line.
    }

    /// Called by the virtual destructor, the default implementation for CSink
    /// does nothing. The purpose of DestructSink() is to ensure that the
    /// whole chain gets destructed, also depending on if they should be
    /// auto deleted. It should be called by the destructor before it
    /// does the remaining destructing.
    void
    CSink::DestructSink() {
        OutputDebugString(_T("CSink::DestructSink()\n"));
    }
};