---

CVMEptr.h

Go to the documentation of this file.

/*
                    GNU GENERAL PUBLIC LICENSE
                       Version 2, June 1991

 Copyright (C) 1989, 1991 Free Software Foundation, Inc.
                       59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

                            Preamble

  The licenses for most software are designed to take away your
freedom to share and change it.  By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users.  This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it.  (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.)  You can apply it to
your programs, too.

  When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it
in new free programs; and that you know you can do these things.

  To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.

  For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have.  You must make sure that they, too, receive or can get the
source code.  And you must show them these terms so they know their
rights.

  We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.

  Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software.  If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.

  Finally, any free program is threatened constantly by software
patents.  We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary.  To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.

  The precise terms and conditions for copying, distribution and
modification follow.

                    GNU GENERAL PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License.  The "Program", below,
refers to any such program or work, and a "work based on the Program"
means either the Program or any derivative work under copyright law:
that is to say, a work containing the Program or a portion of it,
either verbatim or with modifications and/or translated into another
language.  (Hereinafter, translation is included without limitation in
the term "modification".)  Each licensee is addressed as "you".

Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope.  The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.

  1. You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact all the
notices that refer to this License and to the absence of any warranty;
and give any other recipients of the Program a copy of this License
along with the Program.

You may charge a fee for the physical act of transferring a copy, and
you may at your option offer warranty protection in exchange for a fee.

  2. You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:

    a) You must cause the modified files to carry prominent notices
    stating that you changed the files and the date of any change.

    b) You must cause any work that you distribute or publish, that in
    whole or in part contains or is derived from the Program or any
    part thereof, to be licensed as a whole at no charge to all third
    parties under the terms of this License.

    c) If the modified program normally reads commands interactively
    when run, you must cause it, when started running for such
    interactive use in the most ordinary way, to print or display an
    announcement including an appropriate copyright notice and a
    notice that there is no warranty (or else, saying that you provide
    a warranty) and that users may redistribute the program under
    these conditions, and telling the user how to view a copy of this
    License.  (Exception: if the Program itself is interactive but
    does not normally print such an announcement, your work based on
    the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole.  If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works.  But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.

In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.

  3. You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:

    a) Accompany it with the complete corresponding machine-readable
    source code, which must be distributed under the terms of Sections
    1 and 2 above on a medium customarily used for software interchange; or,

    b) Accompany it with a written offer, valid for at least three
    years, to give any third party, for a charge no more than your
    cost of physically performing source distribution, a complete
    machine-readable copy of the corresponding source code, to be
    distributed under the terms of Sections 1 and 2 above on a medium
    customarily used for software interchange; or,

    c) Accompany it with the information you received as to the offer
    to distribute corresponding source code.  (This alternative is
    allowed only for noncommercial distribution and only if you
    received the program in object code or executable form with such
    an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for
making modifications to it.  For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable.  However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.

If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.

  4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.
However, parties who have received copies, or rights, from you under
this License will not have their licenses terminated so long as such
parties remain in full compliance.

  5. You are not required to accept this License, since you have not
signed it.  However, nothing else grants you permission to modify or
distribute the Program or its derivative works.  These actions are
prohibited by law if you do not accept this License.  Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.

  6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions.  You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.

  7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License.  If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all.  For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.

It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices.  Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.

This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.

  8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded.  In such case, this License incorporates
the limitation as if written in the body of this License.

  9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time.  Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number.  If the Program
specifies a version number of this License which applies to it and "any
later version", you have the option of following the terms and conditions 
either of that version or of any later version published by the Free Software 
Foundation.  If the Program does not specify a version number of this License,
 you may choose any version ever published by the Free Software Foundation.

  10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author to 
ask for permission.  For software which is copyrighted by the Free Software 
Foundation, write to the Free Software Foundation; we sometimes make 
exceptions for this.  Our decision will be guided by the two goals of 
preserving the free status of all derivatives of our free software and of 
promoting the sharing and reuse of software generally.

                            NO WARRANTY

  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN 
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE 
THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, 
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 
FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND 
PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, 
YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR 
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING 
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO 
LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR 
THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 
EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH 
DAMAGES.

                     END OF TERMS AND CONDITIONS
*/
/*
  \class CVMEptr
  \file CVMEptr.h

  Encapsulates a CVMEptr object. CVMEptrs are the lowest level of the
  vme module memory mapping hierarchy. They perform the actual mapping
  via the CVMEInterface class. They directly manipulate the registers
  and scale the pointer offsets.

  Author:
     Jason Venema
     NSCL
     Michigan State University
     East Lansing, MI 48824-1321
     mailto: venemaja@msu.edu
*/

#ifndef __CVMEPTR_H
#define __CVMEPTR_H

#ifndef __SYS_MMAN_H
#include <sys/mman.h>
#endif

#ifndef __UNISTD_H
#include <unistd.h>
#endif

#ifndef __TYPES_H
#include <sys/types.h>
#endif


#ifndef __HISTOTYPES_H
#include <histotypes.h>
#endif

#ifndef __RANGEERROR_H
#include <RangeError.h>
#endif

#ifndef __CVMEINTERFACE_H
#include <CVMEInterface.h>
#endif

#ifndef __STRING
#include <string>
#endif

#ifndef __MMAPERROR_H
#include <MmapError.h>
#endif

template<class T>
class CVMEptr
{
  UInt_t             m_nLength;  // the length of the mmap
  volatile Address_t m_pStart;      // the starting address of the mmap
  void*              m_pHandle; // Handle to VME interface device.
  Int_t              m_nOffset;
 public:
  // Default constructor and Copy Constructor 
  CVMEptr<T>(UInt_t space, UInt_t base, UInt_t length);
  CVMEptr<T>(const CVMEptr& aCVMEptr);
  CVMEptr<T>();

  // operator= Assignment operator
  CVMEptr<T>& operator= (const CVMEptr& aCVMEptr);

  // Operator== equality operator
  int operator== (const CVMEptr<T>& aCVMEptr)
    {
      return ((m_nOffset == aCVMEptr.m_nOffset) &&
              (m_nLength == aCVMEptr.m_nLength) &&
              (m_pStart  == aCVMEptr.m_pStart) &&
              (m_pActualBase == aCVMEptr.m_pActualBase));
    }

  // Destructor
  ~CVMEptr<T>();

 protected:

  // Protected function member:
  // This does the actual mmapping of the VME module
  void CreateMap(UInt_t space, UInt_t base, UInt_t length);

  // Public accessor functions to data members
 public:

  UInt_t getLength() const {
    return m_nLength;
  }
  Address_t getStart() const {
    return m_pStart;
  }
  Address_t getActualBase() const {
    return m_pActualBase;
  }
  Address_t getgenptr(UInt_t nOffset);

  // Protected mutator functions to data members
 public:
  void setLength(UInt_t am_nLength) {
    m_nLength = am_nLength;
  }
  void setStart(Address_t pStart) {
    m_pStart = pStart;
  }

  // Public member functions
 public:
  // Pointer dereference
  T& operator*();
  T* operator->();

  // Indexing
  T& operator[] (UInt_t nOffset);
  
  // Pointer addition/subtraction
  CVMEptr<T> operator+(UInt_t nOffset);
  CVMEptr<T> operator-(UInt_t nOffset);
  CVMEptr<T>& operator+=(UInt_t nOffset);
  CVMEptr<T>& operator-=(UInt_t nOffset);

  // Pointer pre-increment/decrement
  CVMEptr<T>& operator++();
  CVMEptr<T>& operator--();

  // Pointer post-increment/decrement
  CVMEptr<T> operator++(Int_t);
  CVMEptr<T> operator--(Int_t);

  // Type conversion operators
 public:
  CVMEptr<UChar_t> asChar();
  CVMEptr<UShort_t> asShort();
  CVMEptr<ULong_t> asLong();
};

#endif

/*
  \fn CVMEptr(VmeSpace space, UInt_t base, UInt_t length)

  Operation Type:
     Construction

  \param  VmeSpace space - enumeration indicating which vme address space 
                           to use
          UInt_t base - the base (offset) into the mapping
          UInt_t length - the length of the mapping
*/

template<class T>
CVMEptr<T>::CVMEptr<T>(UInt_t space, UInt_t base, UInt_t length) :
  m_nOffset(0),
  m_nLength(length)
{
  CreateMap(space, base, length);

}

/*
  \fn CVMEptr<T>::CVMEptr<T>()

  Operation Type:
     Constructor

  Purpose:
     Construct an object of this type. Note that no mapping is
     performed, and m_nOffset and m_nLength are both set to 0.
*/
template<class T>
CVMEptr<T>::CVMEptr<T>()
{
  m_nOffset = 0;
  m_nLength = 0;
}

/*
  \fn CVMEptr(const CVMEptr& aCVMEptr)

  Operation Type:
     Copy construction

  \param CVMEptr aCVMEptr - the CVMEptr to copy
*/
template<class T>
CVMEptr<T>::CVMEptr<T>(const CVMEptr& aCVMEptr)
{
  m_nOffset = aCVMEptr.m_nOffset;
  m_nLength = aCVMEptr.m_nLength;
  m_pStart  = aCVMEptr.m_pStart;
}

/*
  \fn CVMEptr& operator= (const CVMEptr& aCVMEptr)

  Operation type:
     operator= Assignment operator

  \param CVMEptr& aCVMEptr - reference to the CVMEptr to assign this to
*/
template<class T>
CVMEptr<T>&
CVMEptr<T>::operator= (const CVMEptr& aCVMEptr)
{
  if(this == &aCVMEptr) return *this;

  m_nOffset = aCVMEptr.m_nOffset;
  m_nLength = aCVMEptr.m_nLength;
  m_pStart  = aCVMEptr.m_pStart;

  return *this;
}

/*
  \fn CVMEptr<T>::~CVMEptr<T>()
  
  Operation type:
     Destructor

  Purpose: Destructor is responsible for munmapping the module
*/
template<class T>
CVMEptr<T>::~CVMEptr<T>()
{

  CVMEInterface::Unmap(m_pHandle, m_pStart, m_nLength);
  CVMEInterface::Close(m_pHandle);
}

/*
  \fn void CVMEptr<T>::CreateMap(UInt_t space, UInt_t base, UInt_t length)

  Operation Type:
     Map

  \param UInt_t space  - indicates which vme device to open 
                         (a16d16, a24d32 or a32d32)
         UInt_t base   - the base address of the module which we're mapping to
         UInt_t lenght - the length (bytes) of the map
*/
template<class T>
void
CVMEptr<T>::CreateMap(UInt_t space, UInt_t base, UInt_t length)
{

  m_nOffset = 0;

  // First open the specified vme device

  try {
    switch(space) {
    case 0:
      m_pHandle = CVMEInterface::Open(CVMEInterface::A16);
      break;
    case 1:
      m_pHandle = CVMEInterface::Open(CVMEInterface::A24);
      break;
    case 2:
      m_pHandle = CVMEInterface::Open(CVMEInterface::A24);
      break;
    case 3:
      m_pHandle = CVMEInterface::Open(CVMEInterface::A32);
      break;
    default:
      cerr << "Default condition in CVMEptr<T> CreateMap switch " << space 
           << endl;
      cerr.flush();
      
      break;
    }
  }
  catch(string& err) {
    string merr = "CVMEptr<T>::CreateMap - Opening connection to vme device";
    merr += '\n';
    merr += err;
    merr += "\n";
    CMmapError me(err.c_str());
    throw me; 
  }


  // Determine the page size and page offset

  m_nLength = length;
  try {
    m_pStart  = CVMEInterface::Map(m_pHandle, base, length);
  }
  catch (string& err) {
    string merr("CVMEptr<T>::CreateMap - Unable to perform CVMEInterface::Map");
    merr += '\n';
    merr += err;
    merr += "/n";
    throw CMmapError(merr.c_str());

  }

  
}


/*
  \fn T& CVMEptr<T>::operator*()

  Operation Type:
     Pointer dereference

  Purpose:
     Return the value stored at location m_nOffset in the mapped 
     address space. Throws an exception if the value is out of range.
*/
template<class T>
T&
CVMEptr<T>::operator*()
{
  if( (m_nOffset < 0) || (m_nOffset >= m_nLength)) {
    throw CRangeError (0, m_nLength, m_nOffset, 
                       "CVMEptr<T>::operator*() - outside of address window");

  }

  Address_t pVa = (Address_t)(m_nOffset*sizeof(T) + (UInt_t)m_pStart);
  return (*(T*)pVa);
}

/*
  \fn T* CVMEptr<T>::operator->()

  Operation Type:
     Pointer dereference

  Purpose:
     Return a pointer to the value at location m_nOffset
     into the mapped address space. Throws an exception if the value is
     out of range.
*/
template<class T>
T*
CVMEptr<T>::operator->()
{
  if((m_nOffset < 0) || (m_nOffset >= m_nLength)) {
    throw CRangeError(0, m_nLength, m_nOffset, 
                 "CVMEptr<T>::operator->() - outside of address window");
  }
  Address_t pVa = (Address_t)(m_nOffset*sizeof(T) + (UInt_t)m_pStart);
  
  return (T*)pVa;
}

/*
  \fn T& CVMEptr<T>::operator[] (UInt_t nOffset)

  Operation Type:
     Index read/write

  Purpose:
     Return the value stored at locaton nOffset into the mapped address
     space. Throws an exception if the value is out of range.

  \param UInt_t nOffset - the offset into the address space from which to read.
*/
template <class T>
T&
CVMEptr<T>::operator[] (UInt_t nOffset)
{
  if((m_nOffset < 0) || (m_nOffset >= m_nLength)) {
    throw CRangeError(0, m_nLength, m_nOffset, 
                      "CVMEptr<T>::operator[]() - outside of address window");
  }
  Address_t pVa = (Address_t)(nOffset*sizeof(T) + (UInt_t)m_pStart);

  return (*(T*)pVa);
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator+(UInt_t nOffset)

  Operation Type:
     Mutator

  Purpose:
     Add an offset to the current offset. Throws an exception if this
     puts us out of range of the memory map.

  \param UInt_t nOffset - the integer to add to the current offset
*/
template<class T>
CVMEptr<T>
CVMEptr<T>::operator+(UInt_t nOffset)
{
  if(nOffset+m_nOffset <= m_nLength) {  // make sure we're in bounds
    CVMEptr<T> temp = *this;
    temp += nOffset;
    return temp;
  }
  else {
    CRangeError re(0, m_nOffset, nOffset, 
                 "CVMEptr<T>::operator+() - outside of mapped address window");
    throw re;
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator-(UInt_t nOffset)

  Operation Type:
     Mutator

  Purpose:
     Subtracts an offset to the current offset. Throws an exception if this
     puts us out of range of the memory map.

  \param UInt_t nOffset - the integer to subtract from the current offset
*/
template<class T>
CVMEptr<T>
CVMEptr<T>::operator-(UInt_t nOffset)
{
  if(nOffset <= m_nOffset) {    // make sure we're in bounds
    CVMEptr<T> temp = *this;
    temp -= nOffset;
    return temp;
  }
  else {
    CRangeError re(0, m_nOffset, nOffset,
              "CVMEptr<T>::operator-() - outside of mapped addressed window");
    throw re;
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator+=(UInt_t nOffset)

  Operation Type:
     Mutator

  Purpose:
     Add an offset to the current offset. Throws an exception if this
     puts us out of range of the memory map.

  \param UInt_t nOffset - the integer to add to the current offset
*/
template<class T>
CVMEptr<T>&
CVMEptr<T>::operator+=(UInt_t nOffset)
{
  if(m_nOffset+nOffset <= m_nLength) {
    m_nOffset += nOffset;
    return *this;
  }
  else {
    CRangeError re(0, m_nOffset, nOffset,
               "CVMEptr<T>::operator+=() - outside of mapped address window");
    throw re;
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator-=(UInt_t nOffset)

  Operation Type:
     Mutator

  Purpose:
     Subtract an offset to the current offset. Throws an exception if this
     puts us out of range of the memory map.

  \param UInt_t nOffset - the integer to subtract from the current offset
*/
template<class T>
CVMEptr<T>&
CVMEptr<T>::operator-=(UInt_t nOffset)
{
  if(m_nOffset-nOffset > 0) {
    m_nOffset -= nOffset;
    return *this;
  }
  else {
    CRangeError re(0, m_nOffset, nOffset,
               "CVMEptr<T>::operator-=() - outside of mapped address window");
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator++()
  
  Operation Type:
     Mutator

  Purpose:
     (Pre)Increment the current offset. Throws an exception if this puts
     m_nOffset past the length of the memory map.
*/
template<class T>
CVMEptr<T>&
CVMEptr<T>::operator++()
{
  if(m_nOffset < m_nLength) {
    m_nOffset++;
    return *this;
  }
  else {
    string reason = "CVMEptr<T>::operator++() - reference to address which\n";
    reason += "is greater than map size";
    CRangeError re(0, m_nOffset, m_nOffset+1, reason);
    throw re;
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator--()
  
  Operation Type:
     Mutator

  Purpose:
     (Pre)Decrement the current offset. Throws an exception if this puts
     m_nOffset less than 0.
*/
template<class T>
CVMEptr<T>&
CVMEptr<T>::operator--()
{
  if(m_nOffset > 0) {
    m_nOffset--;
    return *this;
  }
  else {
    string reason = "CVMEptr<T>::operator--() - reference to address which\n";
    reason += "is less than map size";
    CRangeError re(0, m_nOffset, m_nOffset-1, reason);
    throw re;
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator++(Int_t)

  Operation type:
     Mutator

  Purpose:
     (Post)Increment the current offset. Throws an exception if this puts
     us past the length of the map.

  \param Int_t - dummy parameter indicates this is a 
                 post-increment operator
*/
template<class T>
CVMEptr<T>
CVMEptr<T>::operator++(Int_t)
{
  if(m_nOffset < m_nLength) {
    CVMEptr<T> p(*this);
    operator++();
    return p;
  }
  else {
    string reason = "CVMEptr<T>::operator++() - reference to memory address\n";
    reason += "which is greater than the size of the map";
    CRangeError re(0, m_nOffset, m_nOffset+1, reason);
    throw re;
  }
}

/*
  \fn CVMEptr<T>& CVMEptr<T>::operator--(Int_t)

  Operation type:
     Mutator

  Purpose:
     (Post)Decrement the current offset. Throws an exception if this puts
     us before the beginning of the memory map.

  \param Int_t - dummy parameter indicates this is a 
                 post-decrement operator
*/
template<class T>
CVMEptr<T>
CVMEptr<T>::operator--(Int_t)
{
  if(m_nOffset > 0) {
    CVMEptr<T> p(*this);
    operator--();
    return p;
  }
  else {
    string reason = "CVMEptr<T>::operator--() reference to memory address\n";
    reason += "which is less than the start address of the map";
    CRangeError re(0, m_nOffset, m_nOffset-1, reason);
    throw re;
  }
}

/*
  \fn Address_t CVMEptr<T>::getgenptr(UInt_t nOffset)

  Operation type:
     Selector

  Purpose:
     Return a pointer to the current address+offset into the module

  \param UInt_t nOffset - an offset to use to determine the pointer
*/
template<class T>
Address_t
CVMEptr<T>::getgenptr(UInt_t nOffset)
{
  Address_t p = (Address_t)(nOffset*sizeof(T) + (UInt_t)m_pStart);
  if(p) return p;
  else return (Address_t)kpNULL;
}

/*
  \fn CVMEptr<UChar_t> CVMEptr<T>::asChar()

  Operation Type:
     Type conversion operator

  Purpose:
     Returns this as a CVMEptr which maps m_pStart to an address space
     containing data of type UChar_t.
*/
template<class T>
CVMEptr<UChar_t>
CVMEptr<T>::asChar()
{
  //if(sizeof(T) == sizeof(UChar_t)) return *this;

  CVMEptr<UChar_t> temp;
  temp.setOffset(m_nOffset);
  temp.setLength(m_nLength);
  temp.setStart(m_pStart);
  temp.setActualBase(m_pActualBase);
  return temp;
}

/*
  \fn CVMEptr<UShort_t> CVMEptr<T>::asShort()

  Operation Type:
     Type conversion operator

  Purpose:
     Returns this as a CVMEptr which maps m_pStart to an address space
     containing data of type UShort_t.
*/
template<class T>
CVMEptr<UShort_t>
CVMEptr<T>::asShort()
{
  if(sizeof(T) == sizeof(UShort_t)) return *this;

  CVMEptr<UShort_t> temp;
  temp.setOffset(m_nOffset);
  temp.setLength(m_nLength);
  temp.setStart(m_pStart);

  return temp;
}

/*
  \fn CVMEptr<ULong_t> CVMEptr<T>::asLong()

  Operation Type:
     Type conversion operator

  Purpose:
     Returns this as a CVMEptr which maps m_pStart to an address space
     containing data of type ULong_t.
*/
template<class T>
CVMEptr<ULong_t>
CVMEptr<T>::asLong()
{
  if(sizeof(T) == sizeof(ULong_t)) return *this;

  CVMEptr<ULong_t> temp;
  temp.setOffset(m_nOffset);
  temp.setLength(m_nLength);
  temp.setStart(m_pStart);

  return temp;
}

---