cseg.h

研读AxCrypt对加解密的处理方法

#pragma once
#ifndef AXPIPE_CSEG_H
#define AXPIPE_CSEG_H
/*! \file CSeg.h
    \brief Reference counted memory buffers AxPipe::CSeg

    @(#) $Id: CSeg.h,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
    CSeg.h                          Reference counted memory buffers

    E-mail                          YYYY-MM-DD              Reason
    [e-mail]              2003-12-05              Initial
\endverbatim
*/
#include "AxPipe.h"

#include "AxAssert.h"
#define AXLIB_ASSERT_FILE "CSeg.h"

namespace AxPipe {
/// \brief Reference counted memory buffer objects.
///
/// Objects of this kind *must* not be instantiated by any other
/// means than 'new'. No arrays, no static, and no automatic. When
/// the reference count falls to zero, they are deleted automagically.
///
/// You must *never* reference a pointer after a call to Release().
/// You must *never* 'delete' a pointer manually. Let Release() do it.
///
/// The default is that these objects are read-write. You can determine
/// this by attempting to get a PtrWr(). If you get NULL, you must
/// copy. You set them read-only by specifying this in the constructor.
///
/// A CSeg consists of a buffer, referenced by a pointer. The buffer may be
/// owned by the CSeg object, or not. If it is, it'll be deleted when the last
/// reference to the object is Released() 'd.
///
/// Not all of the buffer may consist valid data, the start in the buffer may
/// be adjusted by an internally maintained offset, and the length of valid data
/// by an internally maintained length of valid data starting from the offset.
///
/// General rule of usage:
/// Always allocate with new - never create static or automatic CSeg objects, only through CAutoSeg
/// When you pass a copy elsewhere, especially if it is potentially a different thread, call AddRef().
/// When you're done with your instance, call Release().
/// Never perform a 'delete' on a CSeg *.
/// Never reference a CSeg after passing it anywhere without a prior AddRef() call!
///
/// CSeg's are thread safe in two ways. The reference count, m_iRefCnt, is only read and written
/// using the InterlockedIncrement()/InterlockedDecrement() API which are inherently thread safe.
/// In other functions, references to values that may be written at other times than object
/// construction and initialization, a critical section is used as necessary to ensure thread safeness.
class CSeg {
private:
    volatile LONG m_iRefCnt;                ///< Reference count. volatile due to InterlockedXXX req's
    CRITICAL_SECTION m_CritSect;            ///< This object may be shared among threads, thus needs this.

    unsigned char *m_pvBuf;                 ///< The raw data buffer pointer. Never changed once set.
    size_t m_cbBuf;                         ///< The raw data buffer size - not the same as how much valid data.
    CSeg *m_pMom;                           ///< Owning object, if this is a child.
    bool m_fOwnPtr;                         ///< True if this CSeg owns and manages the data buffer.
    bool m_fReadOnly;                       ///< True if this is a read-only object.
    int m_iType;                            ///< Opaque type indicator, free to use. Do note usage in AxPipe::eSegType

    size_t m_cbOff;                         ///< Current offset from start of raw buffer to valid data.
    size_t m_cbLen;                         ///< Current number of valid bytes of raw data, starting at CSeg::m_cbOff

    /// Constructor helper, init's a CSeg appropriately
    void Init(size_t cbBuf, void *pvBuf, bool fReadOnly, int iType);

    /// \brief Make a dependent copy of the original.
    CSeg& operator=(CSeg& rhs);

public:
    /// \brief Default, and full-function, ctor for non-owned (not deleted on destruction).
    CSeg(size_t cbBuf = 0, void *pvBuf = NULL, bool fReadOnly = false);

    /// \brief For constant data, and thus set ReadOnly true; Non-owned data (not deleted).
    CSeg(size_t cbBuf, const void *pvBuf);

    /// \brief Construct an owned buffer with a copy of provided data, possibly also in a larger buffer.
    CSeg(const void *pvBuf, size_t cbLen, size_t cbGrowBuf = 0);

    /// \brief Delete buffer if owned, Release() parent, if child and delete critical section.
    virtual ~CSeg();
    
    unsigned char *Ptr();                   ///< Get the raw buffer pointer.
    const unsigned char *PtrRd();           ///< Get a read-only pointer to the valid data in the buffer, using m_cbOff.
    unsigned char *PtrWr();                 ///< Get a writeable pointer to the valid data.
    unsigned char *PtrRelease();            ///< Get an independent free buffer with valid data and also Release().
    size_t Size(void);                      ///< Get the number of useable bytes in the buffer.
    size_t Len(void);                       ///< Get the length of valid data in bytes in the segment.
    CSeg *Len(size_t cbLen);                ///< Set the length of valid data in bytes in the segment.
    CSeg *Writeable();                      ///< Get a definitely writeable CSeg *, possibly a copy.
    CSeg *Drop(size_t cbOff);               ///< Drop cbOff bytes at the start of the buffer.
    CSeg *AddRef();                         ///< Increment the reference count of this object.
    int Release();                          ///< Decrement the reference count of this object.
    int Type();                             ///< Get the type, an opaque user-defined non-zero integer.
    CSeg *SetType(int iType);               ///< Set the type, an opaque user-defined non-zero integer.
    static bool IsSeg(CSeg *pSeg);          ///< Check if a segment pointer is valid reference to standard data.
    CSeg *Clone();                          ///< Make a clone of ourself
    static void *ClassId();                 ///< Run-time type identifcation.
    virtual void *RTClassId();              ///< Run-Time version of our type identification.
};

/// \brief std::auto_ptr like functionality with CSeg pointers.
///
/// If you really want auto_ptr-functionality with our reference counted CSeg's, use
/// this class like you would auto_ptr, with some limitations. You can't use auto_ptr,
/// as the proper way to dispose of a CSeg * is not to delete it, but to CSeg::Release() it.
/// \param T A CSeg-based class.
template<class T> class Auto_Seg {
private:
    T *m_p;                                 ///< The pointer to the CSeg-derived object.

    /// \brief Call CSeg::Release() if the pointer is valid.
    inline void Release() {
        if (m_p) {
            m_p->Release();
        }
    }
public:
    /// \brief Construct with a given CSeg-derived pointer, or NULL if none given.
    inline Auto_Seg(T *p = NULL) {
        m_p = p;
    }

    /// \brief Basically just CSeg::Release()
    inline ~Auto_Seg() {
        Release();
    }
    
    /// \brief Assign a new CSeg-derived pointer, CSeg::Release() the current, if any.
    inline Auto_Seg<T>& operator=(T *p) {
        Release();
        m_p = p;
        return *this;
    }
    
    /// \brief Assign a pointer to a CSeg object, CSeg::AddRef() the source first.
    inline Auto_Seg<T>& operator=(T& rhs) {
        rhs.AddRef();
        return *this = &rhs;
    }
    
    /// \brief Assign a Auto_Seg-derived reference.
    inline Auto_Seg<T>& operator=(Auto_Seg<T>& rhs) {
        if ((T *)rhs) {
            rhs->AddRef();
        }
        return *this = rhs.m_p;
    }
        
    /// \brief Reference the CSeg-derived pointer as a pointer.
    inline T* operator ->() {
        return m_p;
    }
    
    /// \brief Get the referenced CSeg-derived pointer.
    inline T* get() {
        return m_p;
    }
    
    /// \brief Get the reference CSeg-derived pointer, and then clear the reference here.
    inline T* release() {
        T *p = m_p;
        m_p = NULL;
        return p;
    }
};
/// \brief Use pretty much as you would auto_ptr<CSeg> if you could have done that, which you can't.
typedef Auto_Seg<CSeg> CAutoSeg;

}; // namespace AxPipe
#endif AXPIPE_CERROR_H