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1 dashley 25 /* $Header: /cvsroot/esrg/sfesrg/esrgpcpj/shared/tclxtens/crchashextns.c,v 1.2 2001/07/26 23:18:07 dtashley Exp $ */
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3     //--------------------------------------------------------------------------------
4     //Copyright 2001 David T. Ashley
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682     //<http://www.gnu.org/philosophy/why-not-lgpl.html>.
683     //-------------------------------------------------------------------------------------------------
684     //--------------------------------------------------------------------------------
685     /* IJS_SM_FILE_PUBLIC */
686    
687     #define MODULE_CRCHASHEXTNS
688    
689     #include <string.h>
690    
691     #include "tcl.h"
692     #include "tcldecls.h"
693    
694     #include "crchashextns.h"
695     #include "crchashfuncs.h"
696    
697     #include "strfuncs.h"
698     #include "tclalloc.h"
699    
700    
701     //Procedure called when the "crc32" command is encountered in a Tcl script.
702     //
703     int CRCHASHEXTNS_Crc32extnCommand(ClientData dummy,
704     Tcl_Interp *interp,
705     int objc,
706     Tcl_Obj *objv[])
707     {
708     Tcl_Obj *rv;
709     //Value that will be returned.
710     Tcl_Obj *block_obj;
711     //Used for file reads.
712     char buffer[11];
713     //Space for "0x" followed by 8 hex chars and terminator.
714     struct CRCHASHFUNCS_Crc32StateStruct crc_state;
715     //CRC state structure, internals nominally known and accessible to another
716     //another software module.
717     unsigned long crc;
718     //Calculated CRC.
719     unsigned long bytearraysize;
720     //Size of block allocated or portion used.
721     char *bytearrayptr;
722     //Pointer to array of bytes.
723     char *fname;
724     //File name specified.
725     char *blockbuf;
726     //Pointer to array of bytes.
727     Tcl_Channel chan;
728     //Channel opened using the Tcl libraries.
729     int return_code, return_code_b;
730     //Return codes from Tcl library functions.
731     int loop_exit_flag;
732     //Looping exit flag.
733     int chars_read;
734     //Number of characters read (i.e. for short read).
735     int block_obj_n;
736    
737    
738     if (objc < 2 || objc > 3)
739     {
740     Tcl_WrongNumArgs(interp,
741     1,
742     objv,
743     "?-string? filename_or_string_value");
744    
745     return TCL_ERROR;
746     }
747     else if (objc == 2)
748     {
749     //Be sure that the internal crc table has been built. This function
750     //also returns a table correctness code. Error out severely if the
751     //CRC module believes its internal data has been corrupted.
752     if (!CRCHASHFUNCS_Crc32TableCheck())
753     {
754     //Serious internal error. Error out.
755    
756     //Create the return object.
757     rv = Tcl_NewStringObj("CRCHASHEXTNS.C: Serious internal error: CRC-32 lookup table corrupted.", -1);
758    
759     //Set the return value to be the error message.
760     Tcl_SetObjResult(interp, rv);
761    
762     //Error return.
763     return TCL_ERROR;
764     }
765    
766     //We need to open a channel, run it through the CRC algorithm, and
767     //return results.
768    
769     //Get the string representation of the object.
770     fname = Tcl_GetString(objv[1]);
771    
772     //Attempt to open a file channel. The error information, if any,
773     //will be placed in the interpreter's state.
774     chan = Tcl_OpenFileChannel(interp, fname, "r", 0);
775    
776     //There is the possibility that the channel could not be opened
777     //successfully. If there was an error, error out.
778     if (!chan)
779     {
780     //Create the return object.
781     rv = Tcl_NewStringObj("crc32: Tcl_OpenFileChannel() failure on file name: ", -1);
782    
783     //Tack on the offensive argument.
784     Tcl_AppendToObj(rv, fname, -1);
785    
786     //Set the return value to be the error message.
787     Tcl_SetObjResult(interp, rv);
788    
789     //Error return.
790     return TCL_ERROR;
791     }
792    
793     //Try to set the channel encoding to binary and record the return code.
794     return_code = Tcl_SetChannelOption(interp, chan, "-encoding", "binary");
795    
796     //Try to set the channel translation mode to binary and record the return
797     //code.
798     if (return_code == TCL_OK)
799     return_code_b = Tcl_SetChannelOption(interp, chan, "-translation", "binary");
800    
801     //If the attempt to set the channel encoding or translation
802     //didn't go well, error out. Must also try to chose the channel because
803     //it was successfully opened.
804     if ((return_code != TCL_OK) || (return_code_b != TCL_OK))
805     {
806     //Try to close the channel. "interp" not supplied so as not
807     //to overwrite error info.
808     Tcl_Close(NULL, chan);
809    
810     //Create the return object.
811     rv = Tcl_NewStringObj("crc32: Tcl_SetChannelOption() failure.", -1);
812    
813     //Set the return value to be the error message.
814     Tcl_SetObjResult(interp, rv);
815    
816     //Error return.
817     return TCL_ERROR;
818     }
819    
820     //Allocate the object to hold the block buffer. I've examined the
821     //function, and cannot do it with with a NULL pointer. Must instead
822     //allocate SOMETHING, although it will be destroyed immediately on
823     //the first read. This will have reference count zero.
824     block_obj = Tcl_NewByteArrayObj("Trash", 5);
825    
826     //Calculate the CRC. The essential process is to keep reading
827     //and adding to the CRC until end of file.
828     //Open and initialize the necessary structure.
829     CRCHASHFUNCS_Crc32StateStructOpen(&crc_state);
830    
831     loop_exit_flag = 0;
832    
833     do
834     {
835     //Grab as many chars as possible, up to 65536 of them.
836     //65536 was chosen because this is large enough for great
837     //performance, but small enough that it won't make a significant
838     //virtual memory impact.
839     chars_read = Tcl_ReadChars(chan, block_obj, 65536, 0);
840    
841     //If the characters read shows as <0, this is an error
842     //condition. Trap.
843     if (chars_read < 0)
844     {
845     //Try to close the channel. "interp" not supplied so as not
846     //to overwrite error info.
847     Tcl_Close(NULL, chan);
848    
849     //Deallocate the buffer used to accept block file reads. Because the
850     //creation process set the reference count to zero, a single
851     //decrement will destroy the object.
852     Tcl_DecrRefCount(block_obj);
853    
854     //Create the return object.
855     rv = Tcl_NewStringObj("crc32: Tcl_ReadChars() failure.", -1);
856    
857     //Set the return value to be the error message.
858     Tcl_SetObjResult(interp, rv);
859    
860     //Error return.
861     return TCL_ERROR;
862     }
863    
864     //Obtain a pointer to the binary block that was read.
865     blockbuf = Tcl_GetByteArrayFromObj(block_obj, &block_obj_n);
866    
867     //Add to the CRC for those chars read. Skip the zero case.
868     if (block_obj_n > 0)
869     {
870     CRCHASHFUNCS_Crc32StateStructAddData(&crc_state,
871     blockbuf,
872     block_obj_n);
873     }
874    
875     //We want to exit if EOF is true. A short read would
876     //also be an indication, but short read should imply
877     //EOF, so should not test both.
878     return_code = Tcl_Eof(chan);
879     loop_exit_flag = (return_code != 0);
880     } while(!loop_exit_flag);
881    
882     //Extract the CRC.
883     crc = CRCHASHFUNCS_Crc32Extract(&crc_state);
884    
885     //Postprocess the structure.
886     CRCHASHFUNCS_Crc32StateStructClose(&crc_state);
887    
888     //Close the channel.
889     return_code = Tcl_Close(interp, chan);
890    
891     //If there was an error closing the channel, error out.
892     if (return_code != TCL_OK)
893     {
894     //Create the return object.
895     rv = Tcl_NewStringObj("crc32: Tcl_Close() failure.", -1);
896    
897     //Set the return value to be the error message.
898     Tcl_SetObjResult(interp, rv);
899    
900     //Error return.
901     return TCL_ERROR;
902     }
903    
904     //Deallocate the buffer used to accept block file reads. Because the
905     //creation process set the reference count to zero, a single
906     //decrement will destroy the object.
907     Tcl_DecrRefCount(block_obj);
908    
909     //Return the CRC to the caller. No detectable errors
910     //are possible at this point.
911    
912     //Convert the long integer to a hexadecimal representation.
913     Strfuncs_UlToHexString(crc, buffer+2, 1);
914    
915     //Stuff the leading characters of the hexadecimal representation.
916     buffer[0] = '0';
917     buffer[1] = 'x';
918    
919     //Stuff the string terminator.
920     buffer[10] = 0;
921    
922     //Create the return object.
923     rv = Tcl_NewStringObj(buffer, -1);
924    
925     //Set the return value to be the hexadecimal representation of the
926     //CRC.
927     Tcl_SetObjResult(interp, rv);
928    
929     //Everything went well, return the OK code.
930     return TCL_OK;
931     }
932     else /* if (objc == 3) */
933     {
934     //The second parameter positively must be "-string" or a substring
935     //of that. At present, there are no competing option flags, so
936     //a simple substring lookup will handle it.
937     //Yank the string pointer.
938     bytearrayptr = Tcl_GetString(objv[1]);
939    
940     //If not a substring, error out.
941     if ((strlen(bytearrayptr)<2) || !Strfuncs_IsSubstring(bytearrayptr, "-string"))
942     {
943     //Create the return object.
944     rv = Tcl_NewStringObj("crc32: Unrecognized switch: ", -1);
945    
946     //Tack on the offensive argument.
947     Tcl_AppendToObj(rv, bytearrayptr, -1);
948    
949     //Set the return value to be the error message.
950     Tcl_SetObjResult(interp, rv);
951    
952     //Error return.
953     return TCL_ERROR;
954     }
955    
956     //Convert the last parameter to its byte representation and get a
957     //pointer to this representation and the length. This was the
958     //library call that Ajuba recommended.
959     bytearrayptr = Tcl_GetByteArrayFromObj(objv[2], &bytearraysize);
960    
961     //Be sure that the internal crc table has been built. This function
962     //also returns a table correctness code. Error out severely if the
963     //CRC module believes its internal data has been corrupted.
964     if (!CRCHASHFUNCS_Crc32TableCheck())
965     {
966     //Serious internal error. Error out.
967    
968     //Create the return object.
969     rv = Tcl_NewStringObj("CRCHASHEXTNS.C: Serious internal error: CRC-32 lookup table corrupted.", -1);
970    
971     //Set the return value to be the error message.
972     Tcl_SetObjResult(interp, rv);
973    
974     //Error return.
975     return TCL_ERROR;
976     }
977    
978     //Open and initialize the necessary structure.
979     CRCHASHFUNCS_Crc32StateStructOpen(&crc_state);
980    
981     //Process the string.
982     CRCHASHFUNCS_Crc32StateStructAddData(&crc_state,
983     bytearrayptr,
984     bytearraysize);
985     //Extract the CRC.
986     crc = CRCHASHFUNCS_Crc32Extract(&crc_state);
987    
988     //Postprocess the structure.
989     CRCHASHFUNCS_Crc32StateStructClose(&crc_state);
990    
991     //Convert the long integer to a hexadecimal representation.
992     Strfuncs_UlToHexString(crc, buffer+2, 1);
993    
994     //Stuff the leading characters of the hexadecimal representation.
995     buffer[0] = '0';
996     buffer[1] = 'x';
997    
998     //Stuff the string terminator.
999     buffer[10] = 0;
1000    
1001     //Create the return object.
1002     rv = Tcl_NewStringObj(buffer, -1);
1003    
1004     //Set the return value to be the hexadecimal representation of the
1005     //CRC.
1006     Tcl_SetObjResult(interp, rv);
1007    
1008     //Everything went well, return the OK code.
1009     return TCL_OK;
1010     }
1011     }
1012    
1013    
1014     //Performs initial registration to the hash table.
1015     //
1016     void CRCHASHEXTNS_Crc32extnInit(Tcl_Interp *interp)
1017     {
1018     //Register a command named "crc32".
1019     Tcl_CreateObjCommand(interp,
1020     "crc32",
1021     (Tcl_ObjCmdProc *)CRCHASHEXTNS_Crc32extnCommand,
1022     NULL,
1023     NULL);
1024     }
1025    
1026    
1027     //Returns version control string for file.
1028     //
1029     const char *CRCHASHEXTNS_cvcinfo(void)
1030     {
1031     return ("$Header: /cvsroot/esrg/sfesrg/esrgpcpj/shared/tclxtens/crchashextns.c,v 1.2 2001/07/26 23:18:07 dtashley Exp $");
1032     }
1033    
1034    
1035     //Returns version control string for associated .H file.
1036     //
1037     const char *CRCHASHEXTNS_hvcinfo(void)
1038     {
1039     return (CRCHASHEXTNS_H_VERSION);
1040     }
1041    
1042    
1043     // $Log: crchashextns.c,v $
1044     // Revision 1.2 2001/07/26 23:18:07 dtashley
1045     // Swap out of CRC modules and extensions.
1046     //
1047     //End of CRCHASHEXTNS.C

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