在.h / .cpp文件中支持不同版本的boost

Question

I have a header and .cpp file (call it Foo.h/.cpp) that is structured like this (leaving out several irrelevant details for simplicity):

Foo.h

#include <boost/bimap.hpp>

const std::string & ToHeader(const int msgID);
int ToMsgID(const std::string & msgHdr);

typedef boost::bimap<int, std::string> MsgIDBimap;
MsgIDBimap & GetMessageIDToStringMap();

Foo.cpp

#include "Foo.h"
#include <boost/assign/list_of.hpp>

static MsgIDBimap msgIDBimap = boost::assign::list_of<MsgIDBimap::relation>
    ((int)ROM_MSG, "")
    ... // a whole bunch of other entries
; // end static bimap initialization

const std::string & ToHeader(const int msgID)
{
    MsgIDBimap::left_iterator foundIT = msgIDBimap.left.find(msgID);
    if(foundIT != msgIDBimap.left.end()) // found
    {
        return foundIT->second;
    }

    throw std::string("MSG_ID_NOT_FOUND");
}

int ToMsgID(const std::string & msgHdr)
{
    int msgID = (int)MSG_UNKNOWN; // unknown message header
    MsgIDBimap::right_iterator foundIT = msgIDBimap.right.find(msgHdr);
    if(foundIT != msgIDBimap.right.end()) // found
    {
        msgID = foundIT->second;
    }
    return msgID;
}

MsgIDBimap & GetMessageIdToStringMap()
{
    return msgIDBimap;
}

The problem is that now I need to support an earlier version of boost that does not support bimap (sucks, I know ... but I have no choice). So far, this is my solution:

Foo.h

#include <boost/version.hpp>
#define BOOST_VER_MAJOR (BOOST_VERSION/100000)        // ex.: 1   in  1_37_0
#define BOOST_VER_MINOR ((BOOST_VERSION/100) % 1000)  // ex.: 37  in  1_37_0
#define BOOST_VER_PATCH (BOOST_VERSION % 100)         // ex.: 0   in  1_37_0

/*************************************************************************************************/
#if ((BOOST_VER_MAJOR >= 1) && (BOOST_VER_MINOR >= 35)) // boost greater than or equal to 1.35 (bimap available)
#include <boost/bimap.hpp>
#endif
/*************************************************************************************************/

const std::string & ToHeader(const int msgID);
int ToMsgID(const std::string & msgHdr);

/*************************************************************************************************/
#if ((BOOST_VER_MAJOR >= 1) && (BOOST_VER_MINOR >= 35)) // boost greater than or equal to 1.35 (bimap available)
typedef boost::bimap<int, std::string> MsgIDBimap;
MsgIDBimap & GetMessageIdToStringMap();
#endif
/*************************************************************************************************/

Foo.cpp

#include "Foo.h"
#include <boost/assign/list_of.hpp>

#if ((BOOST_VER_MAJOR >= 1) && (BOOST_VER_MINOR >= 35)) // boost greater than or equal to 1.35 (bimap available)

static MsgIDBimap msgIDBimap = boost::assign::list_of<MsgIDBimap::relation>
    ((int)ROM_MSG,            "") // <ROM message> (no header)

; // end static msgIDBimap initialization

const std::string & ToHeader(const int msgID)
{
    MsgIDBimap::left_iterator foundIT = msgIDBimap.left.find(msgID);
    if(foundIT != msgIDBimap.left.end()) // found
    {
        return foundIT->second;
    }

    throw std::string("MSG_ID_NOT_FOUND");
}

int ToMsgID(const std::string & msgHdr)
{
    int msgID = (int)MSG_UNKNOWN; // unknown message header
    MsgIDBimap::right_iterator foundIT = msgIDBimap.right.find(msgHdr);
    if(foundIT != msgIDBimap.right.end()) // found
    {
        msgID = foundIT->second;
    }
    return msgID;
}

MsgIDBimap & GetMessageIdToStringMap()
{
    return msgIDBimap;
}

/*************************************************************************************************/
#else // boost less than 1.35, bimap not available

typedef std::map<int, std::string> MsgIDToStringMap;
static MsgIDToStringMap msgIDToStringMap = boost::assign::map_list_of<int, std::string>
    ((int)ROM_MSG,            "") // <ROM message> (no header)
; // end static msgIDToStringMap initialization

const std::string & ToHeader(const int msgID)
{
    const MsgIDToStringMap::const_iterator foundIT = msgIDToStringMap.find(msgID);
    if(foundIT != msgIDToStringMap.end()) // found
    {
        return foundIT->second;
    }

    throw std::string("MSG_ID_NOT_FOUND");
}

#define FLIP_ARGS(x,y) (y,x)
typedef std::map<std::string, int> StringToMsgIDMap;
static StringToMsgIDMap stringToMsgIDMap = boost::assign::map_list_of<std::string, int>
    FLIP_ARGS((int)ROM_MSG,            "") // <ROM message> (no header)

; // end static stringToMsgIDMap initialization

int ToMsgID(const std::string & msgHdr)
{
    int msgID = (int)MSG_UNKNOWN; // unknown message header
    const StringToMsgIDMap::const_iterator foundIT = stringToMsgIDMap.find(msgHdr);
    if(foundIT != stringToMsgIDMap.end()) // found
    {
        msgID = foundIT->second;
    }
    return msgID;
}
#endif

While this works, the problem is that the GetMessageIDToStringMap() function declaration/definition only exists in the later boost version scenario (the two scenarios are not 100% congruent to each other). I know that the GetMessageIDToStringMap() function itself will not ever be needed for the earlier boost version scenario.

Ideally, I would like to leave the static bimap inside the .cpp file and move the GetMessageIDToStringMap() to another file somewhere so that Foo.h/.cpp are 100% congruent for each #ifdef block. The issue is that the bimap is a static variable inside a .cpp file and no other file can access it. Even if I make the bimap a global variable instead of a static variable, I now have to expose a global variable in the header file which again would only exist in the later versions of boost.

Is there a way to resolve this so that the two versions of the file (boost >= 1.35 vs. earlier boost) are always 100% congruent to each other and yet the GetMessageIDToStringMap() function is available in another file?

Answer 1

In response to the comment in the question:

in foo.cpp:

typedef std::map<int, std::string> MsgIDToStringMap;
//you can remove the static
MsgIDToStringMap msgIDToStringMap = ...

Now in the other.cpp file:

extern MsgIDToStringMap msgIDToStringMap;
//and you can use the global variable.

But as I said in the 1st comment I would prefer a singleton class.