libpcscxx/src/pcsc.hxx

/*! @file

    This file offers a C++ access to the PCSC library.

    @id $Id$
*/
//       1         2         3         4         5         6         7         8
// 45678901234567890123456789012345678901234567890123456789012345678901234567890

#ifndef PCSC_HXX
#define PCSC_HXX

#ifndef PCSC_LOG
//! Declare PCSC_LOG before #include in your code, if you want logging.
/*! PCSC_LOG passes its argument to a stream, so your definition must
    behave so that the argument can be streamed.

    Example, use std::log:
    @code
    #define PCSC_LOG(x) std::clog<<x<<" ("<<__PRETTY_FUNCTION__<<')'<<std::endl
    #include <pcsc.hxx>
    @endcode
    
    Example, use qDebug():
    @code
    #define PCSC_LOG(x) qDebug()<<x
    #include <pcsc.hxx>
    @endcode */
#define PCSC_LOG(x) // if unset, do nothing
#endif

#include <cryptaux.hxx>

#include <string>

#ifdef WIN32
  #undef UNICODE
  #include <WinSCard.h>
  #undef ERROR
  #ifndef MAX_ATR_SIZE
    #define MAX_ATR_SIZE 33
  #endif
  namespace pcsc {
    
    #ifdef UNICODE
      inline std::wstring strconv(std::string s) {
        return std::wstring(s.begin(), s.end());
      }
      inline std::string strconv(std::wstring s) {
        return std::string(s.begin(), s.end());
      }
      typedef wchar_t char_t;
      typedef std::wstring string;
    #else
      inline const std::string& strconv(const std::string& s) {
        return s;
      }
      typedef char char_t;
      typedef std::string string;
    #endif
  }
#else
  #include <PCSC/pcsclite.h>
  #include <PCSC/wintypes.h>
  #include <PCSC/winscard.h>
  namespace pcsc {
    inline const std::string& strconv(const std::string& s) {
      return s;
    }
    typedef char char_t;
    typedef std::string string;
  }
#endif

#include <boost/shared_ptr.hpp>
#include <vector>
#include <map>
#include <memory>

namespace pcsc {
  std::string version();
}

#include <sstream>
#include <iomanip>

/*! @defgroup gpcsc C++ Wrapper around pcsc-lite API

    This library is a C++ wrapper to the awful pcsc-lite interface.
    The reason for this wrapper is to get a nice object oriented
    interface written in C++ manner and using standard types and so to
    avoid the ugly M$-C-quirks. This interface is memory clean.
    @todo: Not implemented, not supported:
        - SCardGetStatusChange(hContext, 0, rgReaderStates, 1);
        - SCardReconnect(hCard, SCARD_SHARE_SHARED,
                         SCARD_PROTOCOL_T0 | SCARD_PROTOCOL_T1,
                         SCARD_LEAVE_CARD,
                         &dwActiveProtocol);
        - several other
    I do not need these, and I don't know the usecase where they are
    required.  If you need something that is not yet supported, please
    let me know, what you need and why. Then I'll add it so that it
    best fits the common needs. */
//@{
/*! @defgroup pcsclib PCSC C++ Library */
/*! @defgroup pcscexceptions PCSC Exceptions */

//! @see gpcsc
namespace pcsc {

  //============================================================================
  //! @addtogroup pcscexceptions
  //@{

  //----------------------------------------------------------------------------
  class exception: public std::exception {
    public:
      exception(const std::string& reason) throw(): _what("pcsc: "+reason) {}
      ~exception() throw() {}
      const char* what() const throw() {
        return _what.c_str();
      }
    private:
      std::string _what;
  };
  //----------------------------------------------------------------------------
  class not_implemented: public exception {
    public:
      not_implemented(const std::string& reason) throw():
          exception("feature is not implemented:\n"+reason) {
      }
  };
  //----------------------------------------------------------------------------
  class access_error: public exception {
    public:
      access_error(const std::string& reason) throw():
          exception("smardcard access error:\n"+reason) {
      }
  };
  //----------------------------------------------------------------------------
  class runtime_error: public exception {
    public:
      runtime_error(const std::string& reason, const std::string& data) throw():
          exception("runtime error,\n"+reason+":\n"+crypto::hex(data)) {}
  };
  //----------------------------------------------------------------------------
  class neesting_error: public exception {
    public:
      neesting_error() throw():
          exception("neesting error: more endTransaction than beginTransaction")
      {}
  };
  //@}

  //! @addtogroup pcsclib
  //@{
  
  //============================================================================
  class Connection {
      
      //...............................................................typedefs
    public:
      

      //------------------------------------------------------------------Reader
      friend class Reader;
      class Reader {

          //............................................................typedefs
        public:

          friend class Transaction;
          //! Scoped transaction.
          /*! This is a scoped transaction. That means, the
              transaction is started in the constructor and ended in
              the destructor, unless it is already ended before.  In
              case of an exception or leaving the block, the
              transaction is always cleaned up.

              There's a neesting counter to make sure, transaction is
              started only once and ended only once, even though the
              locking can be neested.

              @code
              pcsc::Connection c;
              {
              Transaction t(c.reader("name"));
              [...] // do some stuff, possible exceptions thrown
              if (problem) return; // automatically ended
              [...]
              t.end(); // ended if we reach this line
              [...]
              } // also ended, unless commit reaced
              @endcode */
          class Transaction {
            public:
              //! Begins a transaction.
              /*! @note Please note that the Reader is required in the
                  destructor und must therefore live longer than the
                  Transaction instance. */
              Transaction(Reader& r): _reader(r), _running(true) {
                _reader.beginTransaction();
              }
              //! Cancels the transaction if not yet finished.
              ~Transaction() try {
                end();
              } catch (...) {
                if (!std::uncaught_exception()) throw;
              }
              //! Ends the running transaction.
              void end() {
                if (_running) _reader.endTransaction();
                _running = false;
              }
            private:
              Reader& _reader;
              bool _running;
          };

          //! State and attribute list of a reader.
          class Status {
            public:
              Status(unsigned long s, const std::string& a): state(s), atr(a) {}
              const unsigned long state;
              const std::string atr;
          };
      
          //.............................................................methods
        public:

          //! Disconnects connection.
          ~Reader() {
            _state = SCardDisconnect(_id, SCARD_RESET_CARD);
            if (!std::uncaught_exception())
              _connection.check("disconnect smartcard");
          }

          //! Get reader status.
          Status status() {
            DWORD dummy(0);
            DWORD s;
            DWORD len(MAX_ATR_SIZE);
            unsigned char a[len];
            check(SCardStatus(_id, 0, &dummy, &s, &_protocol, a, &len),
                  "query smartcard status");
            return Status(s, std::string((char*)a, len));
          }

          //! Transmit data to reader.
          /*! @note Take care: Stings may contain embedded @c 0. */
          std::string transmit(char cla, char ins, char p1, char p2,
                               const std::string& lc = std::string(),
                               unsigned char le = 253) {
            std::string claInsP1P2;
            claInsP1P2.push_back(cla);
            claInsP1P2.push_back(ins);
            claInsP1P2.push_back(p1);
            claInsP1P2.push_back(p2);
            assert(claInsP1P2.size()==4);
            return transmit(claInsP1P2, lc, le);
          }

          //! Transmit data to reader.
          /*! @note Take care: Stings may contain embedded @c 0. */
          std::string transmit(char cla, char ins, char p1, char p2,
                               unsigned char le) {
            std::string claInsP1P2;
            claInsP1P2.push_back(cla);
            claInsP1P2.push_back(ins);
            claInsP1P2.push_back(p1);
            claInsP1P2.push_back(p2);
            assert(claInsP1P2.size()==4);
            return transmit(claInsP1P2, std::string(), le);
          }
          
          //! Transmit data to reader.
          /*! @note Take care: Stings may contain embedded @c 0. */
          std::string transmit(char cla, char ins, char p1, char p2,
                               const char* lc, int len,
                               unsigned char le = 253) {
            std::string claInsP1P2;
            claInsP1P2.push_back(cla);
            claInsP1P2.push_back(ins);
            claInsP1P2.push_back(p1);
            claInsP1P2.push_back(p2);
            assert(claInsP1P2.size()==4);
            return transmit(claInsP1P2, std::string(lc, len), le);
          }
          
          //! Transmit data to reader.
          /*! @note Take care: Stings may contain embedded @c 0.
              @note Prefer the transmit methods that passes @c cla, @c
                    ins, @c p1 and @c p2 separate.*/
          std::string transmit(const std::string& claInsP1P2,
                               const std::string& lc,
                               unsigned char le = 253) {
            if (claInsP1P2.size()!=4)
              throw runtime_error("transmit: claInsP1P2 must be 4 byte",
                                  claInsP1P2);
            if (lc.size()>255) throw runtime_error("transmit: lc too long", lc);
            std::string msg(claInsP1P2);
            if (lc.size()) (msg+=(char)lc.size())+=lc;
            msg+=le;
            return transmit(msg);
          }
          
          //! Transmit data to reader.
          /*! @note Take care: Stings may contain embedded @c 0.
              @note Prefer the transmit methods that passes @c cla, @c
                    ins, @c p1 and @c p2 separate.*/
          std::string transmit(std::string in) {
            DWORD len(1024); // arbitrary
            unsigned char buff[len];
            SCARD_IO_REQUEST rPci;
            rPci.dwProtocol  = pci()->dwProtocol;
            rPci.cbPciLength = sizeof(rPci);
            PCSC_LOG("SCardTransmit: "<<crypto::hex(in));
            check(SCardTransmit(_id, &rPci,
                                (unsigned char*)in.c_str(), in.size(),
                                0, buff, &len),
                  "smartcard transmit message "+crypto::hex(in));
            PCSC_LOG(" -> "<<crypto::hex(std::string((char*)buff, len)));
            return std::string((char*)buff, len);
          }

          //! @c false if last operation was not successful
          operator bool() const {
            //  Values are 32 bit values layed out as follows:
            //   3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
            //   1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
            //   ---+-+-+-----------------------+-------------------------------
            //   Sev|C|R|     Facility          |               Code            
            //   ---+-+-+-----------------------+-------------------------------
            //  where Sev - is the severity code
            //          00 - Success
            //          01 - Informational
            //          10 - Warning
            //          11 - Error
            // So everything with Sev=00 is successful
            // theoretically even with Sev=01, but that's still rejected
            //return (_state>>30&3)==0;
            return _state==SCARD_S_SUCCESS;
          }
          
          //...........................................................variables
        public:
      
          const std::string name;

          //.............................................................methods
        private:

          //! Use scoped transactions with @ref Transaction
          /*! Calls @c SCardBeginTransaction unless it's already inside
              a transaction. */
          void beginTransaction() {
            if (++_neesting==1)
              check(SCardBeginTransaction(_id), "smartcard begin transaction");
          }

          //! Use scoped transactions with @ref Transaction
          /*! Calls @c SCardEndTransaction if it's inside a transaction.
              
              @throws neesting_error if there are more calls to @c
              endTransaction than to @c beginTransaction. */
          void endTransaction() {
            if (--_neesting==0)
              check(SCardEndTransaction(_id, SCARD_LEAVE_CARD),
                    "smartcard end transaction");
            else if (_neesting<0) {
              _neesting = 0;
              throw neesting_error();
            }
          }

          /*! @throw not_implemented if _protocol is unknown. */
          const SCARD_IO_REQUEST* pci() {
            switch(_protocol) {
              case SCARD_PROTOCOL_T0: return SCARD_PCI_T0;
              case SCARD_PROTOCOL_T1: return SCARD_PCI_T1;
            }
            if (_connection._exc) throw not_implemented("unknown protocol");
            return 0;
          }
          
          //! Sets state and throws an exception if neccessary.
          /*! @throw access_error if it is instanciated for exceptions and
              an error occured in the last command. */
          bool check(long state, const std::string context="") {
            _state = state;
            return _connection.check(state, context);
          }

          //! Only Connection is allowed to instanciate.
          friend class Connection;
          
          //! Establishes a connection to the given named cardreader
          Reader(const std::string& nm, Connection& c,
                 DWORD mode=SCARD_SHARE_SHARED,
                 DWORD protocol=SCARD_PROTOCOL_T1):
              name(nm), _connection(c) {
            check(SCardConnect(_connection._id, strconv(name).c_str(),
                               mode, protocol,
                               &_id, &_protocol),
                  "connect smartcard \""+name);
          }

          //! forbidden
          Reader();

          //! forbidden
          Reader(const Reader&);

          //...........................................................variables
        private:

          Connection& _connection;
          SCARDHANDLE _id;
          DWORD _state;
          DWORD _protocol;
          static int _neesting;
      
      };
      //------------------------------------------------------------------Reader
      
      enum Scope {
        USER     = SCARD_SCOPE_USER,
        TERMINAL = SCARD_SCOPE_TERMINAL,
        SYSTEM   = SCARD_SCOPE_SYSTEM
      };

      typedef std::vector<std::string> Strings;
      
      //................................................................methods
    public:

      //! Opens a connection (establishes a smartcard context)
      /*! The errorhandling is defined with the @c exceptions flag:

          Using exceptions:
          @code
          try {
            pcsc::Connection c; // standard with exceptions
            pcsc::Connection::Strings r(c.scan());
          } catch (std::exception& x) {
            std::cout<<"Error with message: "<<x.what()<<std::endl;
          }
          @endcode

          Without exceptions:
          @code
          pcsc::Connection c(SYSTEM, false);
          if (!c) std::cout<<"Error with message: "<<c.error()<<std::endl;
          pcsc::Connection::Strings r(c.scan());
          if (!c) std::cout<<"Error with message: "<<c.error()<<std::endl;
          @endcode

          Recommendation: Use exceptions!

          @param s defines the scope of the connection
          @param exceptions
            - @c true:  class throws exceptions in case of an error
            - @c false: no exceptions, check your instance after each
                        operation */
      Connection(Scope s=USER, bool exceptions=true):
          _exc(exceptions), _id(0),
          _state(SCardEstablishContext(s, 0, 0, &_id)) {
        check("establish smartcard context");
      }

      //! Closes the connection (releases the smartcard context)
      ~Connection() {
        _state = SCardReleaseContext(_id);
        if (!std::uncaught_exception()) check("smartcard release context");
      }

      //! Scans for available readers from a specified list of groups.
      /*! Defaults to all groups. */
      Strings scan(const Strings& groups = Strings()) {
        Strings res;
        std::string grp(join(groups));
        DWORD num(0);
        if (!check(SCardListReaders(_id, groups.size()?strconv(grp).data():0, 0,
                                    &num),
                   "smartcard get size of readers of groups "+grp))
          return res;
        std::auto_ptr<char_t> nm(new char_t[num]);
        if (!check(SCardListReaders(_id, groups.size()?strconv(grp).data():0,
                                    nm.get(), &num),
                   "smartcard list reader names of groups "+grp))
          return res;
        return res = split(strconv(string(nm.get(), num-1)));
      }

      //! Get a reader, open a connection if not already open.
      /*! First use scan() to get a list of readers, then open a
          connection to the reader, then access it. */
      Reader& reader(const std::string& name) {
        if (_reader.find(name)==_reader.end())
          _reader.insert(std::make_pair(name, new Reader(name, *this)));
        return *_reader.find(name)->second;
      }

      //! Close connection of a named reader.
      /*! If you access the same reader through raeder() later, the
          connection will be reestablished. */
      void close(const std::string& s) {
        
      }

      //! @c false if last operation was not successful
      operator bool() const {
        //return (_state>>30&3)==0;
        return _state==SCARD_S_SUCCESS;
      }

      //! Get the describing text of the last error
      std::string error() const {
        std::stringstream ss;
        switch (_state) {
          case SCARD_E_CANCELLED:
            ss<<"The action was canceled by an SCardCancel request.";
            break;
          case SCARD_E_CANT_DISPOSE:
            ss<<"The system could not dispose of the media in the requested"
              <<" manner.";
            break;
          case SCARD_E_CARD_UNSUPPORTED:
            ss<<"The smart card does not meet minimal requirements for"
              <<" support.";
            break;
          case SCARD_E_DUPLICATE_READER:
            ss<<"The reader driver did not produce a unique reader name.";
            break;
          case SCARD_E_INSUFFICIENT_BUFFER:
            ss<<"The data buffer for returned data is too small for the"
              <<" returned data.";
            break;
          case SCARD_E_INVALID_ATR:
            ss<<"An ATR string obtained from the registry is not a valid"
              <<" ATR string.";
            break;
          case SCARD_E_INVALID_HANDLE:
            ss<<"The supplied handle was not valid.";
            break;
          case SCARD_E_INVALID_PARAMETER:
            ss<<"One or more of the supplied parameters could not be properly"
              <<" interpreted.";
            break;
          case SCARD_E_INVALID_TARGET:
            ss<<"Registry startup information is missing or not valid.";
            break;
          case SCARD_E_INVALID_VALUE:
            ss<<"One or more of the supplied parameters values could not"
              <<" be properly interpreted.";
            break;
          case SCARD_E_NOT_READY:
            ss<<"The reader or smart card is not ready to accept commands.";
            break;
          case SCARD_E_NOT_TRANSACTED:
            ss<<"An attempt was made to end a nonexistent transaction.";
            break;
          case SCARD_E_NO_MEMORY:
            ss<<"Not enough memory available to complete this command.";
            break;
          case SCARD_E_NO_SERVICE:
            ss<<"The smart card resource manager is not running.";
            break;
          case SCARD_E_NO_SMARTCARD:
            ss<<"The operation requires a smart card, but no smart card"
              <<" is currently in the device.";
            break;
          case SCARD_E_PCI_TOO_SMALL:
            ss<<"The PCI receive buffer was too small.";
            break;
          case SCARD_E_PROTO_MISMATCH:
            ss<<"The requested protocols are incompatible with the protocol"
              <<" currently in use with the smart card.";
            break;
          case SCARD_E_READER_UNAVAILABLE:
            ss<<"The specified reader is not currently available for use.";
            break;
          case SCARD_E_READER_UNSUPPORTED:
            ss<<"The reader driver does not meet minimal requirements for"
              <<" support.";
            break;
          case SCARD_E_SERVICE_STOPPED:
            ss<<"The smart card resource manager has shut down.";
            break;
          case SCARD_E_SHARING_VIOLATION:
            ss<<"The smart card cannot be accessed because of other outstanding"
              <<" connections.";
            break;
          case SCARD_E_SYSTEM_CANCELLED:
            ss<<"The action was cancelled by the system, presumably to log"
              <<" off or shut down.";
            break;
          case SCARD_E_TIMEOUT:
            ss<<"The user-specified time-out value has expired.";
            break;
          case SCARD_E_UNKNOWN_CARD:
            ss<<"The specified smart card name is not recognized.";
            break;
          case SCARD_E_UNKNOWN_READER:
            ss<<"The specified reader name is not recognized.";
            break;
          case SCARD_E_UNSUPPORTED_FEATURE:
            ss<<"This smart card does not support the requested feature.";
            break;
          case SCARD_F_COMM_ERROR:
            ss<<"An internal communications error has been detected.";
            break;
          case SCARD_F_INTERNAL_ERROR:
            ss<<"An internal consistency check failed.";
            break;
          case SCARD_F_UNKNOWN_ERROR:
            ss<<"An internal error has been detected, but the source is"
              <<" unknown.";
            break;
          case SCARD_F_WAITED_TOO_LONG:
            ss<<"An internal consistency timer has expired.";
            break;
          case SCARD_S_SUCCESS:
            ss<<"No error was encountered.";
            break;
          case SCARD_W_REMOVED_CARD:
            ss<<"The smart card has been removed, so that further communication"
              <<" is not possible.";
            break;
          case SCARD_W_RESET_CARD:
            ss<<"The smart card was reset.";
            break;
          case SCARD_W_UNPOWERED_CARD:
            ss<<"Power has been removed from the smart card, so that"
              <<" further communication is not possible.";
            break;
          case SCARD_W_UNRESPONSIVE_CARD:
            ss<<"The smart card is not responding to a reset.";
            break;
          case SCARD_W_UNSUPPORTED_CARD:
            ss<<"The reader cannot communicate with the smart card,"
              <<" due to ATR configuration conflicts.";
            break;
#ifndef __APPLE__
          case SCARD_E_NO_READERS_AVAILABLE:
            ss<<"No smart card reader is available.";
            break;
#endif
#ifdef WIN32
          case ERROR_BROKEN_PIPE:
            ss<<"The client attempted a smart card operation in a"
              <<" remote session, such as a client session running"
              <<" on a terminal server, and the operating system in"
              <<" use does not support smart card redirection.";
            break;
          case SCARD_E_BAD_SEEK:
            ss<<"There was an error trying to set the smart card file"
              <<" object pointer.";
            break;
          case SCARD_E_CERTIFICATE_UNAVAILABLE:
            ss<<"The requested certificate could not be obtained.";
            break;
          case SCARD_E_COMM_DATA_LOST:
            ss<<"A communications error with the smart card has been detected.";
            break;
          case SCARD_E_DIR_NOT_FOUND:
            ss<<"The specified directory does not exist in the smart card.";
            break;
          case SCARD_E_FILE_NOT_FOUND:
            ss<<"The specified file does not exist in the smart card.";
            break;
          case SCARD_E_ICC_CREATEORDER:
            ss<<"The requested order of object creation is not supported.";
            break;
          case SCARD_E_ICC_INSTALLATION:
            ss<<"No primary provider can be found for the smart card.";
            break;
          case SCARD_E_INVALID_CHV:
            ss<<"The supplied PIN is incorrect.";
            break;
          case SCARD_E_NO_ACCESS:
            ss<<"Access is denied to this file.";
            break;
          case SCARD_E_NO_DIR:
            ss<<"The supplied path does not represent a smart card directory.";
            break;
          case SCARD_E_NO_FILE:
            ss<<"The supplied path does not represent a smart card file.";
            break;
          case SCARD_E_NO_KEY_CONTAINER:
            ss<<"The requested key container does not exist on the smart card.";
            break;
          case SCARD_E_NO_SUCH_CERTIFICATE:
            ss<<"The requested certificate does not exist.";
            break;
          case SCARD_E_SERVER_TOO_BUSY:
            ss<<"The Smart card resource manager is too busy to complete this"
              <<" operation.";
            break;
          case SCARD_E_UNEXPECTED:
            ss<<"An unexpected card error has occurred.";
            break;
          case SCARD_E_UNKNOWN_RES_MNG:
            ss<<"An unrecognized error code was returned from a layered"
              <<" component.";
            break;
          case SCARD_E_WRITE_TOO_MANY:
            ss<<"The smartcard does not have enough memory to store the"
              <<" information.";
            break;
          case SCARD_P_SHUTDOWN:
            ss<<"The operation has been aborted to allow the server application"
              <<" to exit.";
            break;
          case SCARD_W_CANCELLED_BY_USER:
            ss<<"The action was cancelled by the user.";
            break;
          case SCARD_W_CARD_NOT_AUTHENTICATED:
            ss<<"No PIN was presented to the smart card.";
            break;
          case SCARD_W_CHV_BLOCKED:
            ss<<"The card cannot be accessed because the maximum number"
              <<" of PIN entry attempts has been reached.";
            break;
          case SCARD_W_EOF:
            ss<<"The end of the smart card file has been reached.";
            break;
          case SCARD_W_SECURITY_VIOLATION:
            ss<<"Access was denied because of a security violation.";
            break;
          case SCARD_W_WRONG_CHV:
            ss<<"The card cannot be accessed because the wrong PIN was"
              <<" presented.";
            break;
#endif
          default:
            ss<<"unknown PCSC state=0x"
              <<std::hex<<std::setfill('0')<<std::setw(8)<<_state;
            switch (_state>>30) {
              case 0: ss<<" means SUCCESS"; break;
              case 1: ss<<" means INFORMATIONAL"; break;
              case 2: ss<<" means WARNING"; break;
              case 3: ss<<" means ERROR"; break;
              default: ss<<" illegal value";
            }
            ss<<" C="<<(_state>>29&1);
            ss<<" R="<<(_state>>28&1);
            ss<<" Facility=0x"<<std::hex<<std::setfill('0')<<std::setw(3)
              <<(_state>>16&0xfff);
            ss<<" Code=0x"<<std::hex<<std::setfill('0')<<std::setw(4)
              <<(_state&0xffff);
        }
        return ss.str();
      }
      
      //................................................................methods
    private:
      
      //! Sets state and throws an exception if neccessary.
      /*! @throw access_error if it is instanciated for exceptions and
          an error occured in the last command. */
      bool check(long state, const std::string& context="") {
        _state = state;
        return check(context);
      }
      
      //! Throws an exception if neccessary.
      /*! @throw access_error if it is instanciated for exceptions and
          an error occured in the last command. */
      bool check(const std::string& context="") {
        if (_exc&&!*this)
          if (context.size())
            throw access_error(context+": "+error());
          else
            throw access_error(error());
        return *this;
      }

      //! Splits a buffer with 0 separators into a vector of strings.
      Strings split(const std::string& in) {
        Strings res;
        for (std::string::size_type pos(0); pos<in.size() && in[pos]!=0;
             pos+=res.rbegin()->size()+1)
          res.push_back(in.substr(pos).c_str());
        return res;
      }
      
      //!  Joins a vector of strings into a  buffer with 0 separators.
      std::string join(const Strings& in) {
        std::string res;
        if (in.size()) {
          for (Strings::const_iterator it(in.begin());
               it!=in.end(); ++it)
            res+=*it+'\0';
          res+='\0';
        }
        return res;
      }
      
      //..............................................................variables
    private:
      
      bool _exc;
      SCARDCONTEXT _id;
      long _state;
      std::map<std::string, boost::shared_ptr<Reader> > _reader;

  };

  //@}
  
}
//@}

#endif