C++ Sample

This chapter contains two snippets that work as a sample for calling a COBOL program from C++ on Windows.

To build a COBOL program into a DLL requires Microsoft Visual Studio or another suitable C compiler. To call COBOL from C++ on Windows you use the isCOBOL C API which is available in the following files in the isCOBOL Evolve installation directory:

•	bin\iscobolc.dll

•	native\lib\iscobolc.lib

•	include\iscobolc.h

For example, here is a C++ class that can be built into a DLL to call COBOL:

 

#include <cstdio> #include <cstdlib> #include <cstring> #include "TestIsCobolDoc.h"   extern "C" { #include "iscobolc.h" }   CTestIsCobolDoc::CTestIsCobolDoc(void) { }   CTestIsCobolDoc::~CTestIsCobolDoc(void) { }   #define MAX_MSG_LEN 1024

void CTestIsCobolDoc::CallCobolProgram(void) {     long crc;   char errmsg[MAX_MSG_LEN + 1];   char **cobargv;   int *cobargl;     int retval;   int jvmoptnum = 2;   static char *jvmopts[2] = { "-Djava.class.path=C:\\Program Files (x86)\\Veryant\\isCOBOL\\lib\\iscobol.jar;C:\\Users\\dlubin\\Documents\\Visual Studio 2008\\Projects\\CallCOBOL\\debug",       "-Discobol.display_message=3" };   retval = isCobolInit(jvmoptnum, jvmopts, 0);   if(retval != ISCOBOLC_SUCCESS)   {     fprintf(stderr,"Error calling isCobolInit\n");     exit(1);   }   errmsg[MAX_MSG_LEN] = '\0';   int cobargc = 4;     cobargv = (char **)malloc(sizeof(char*) * cobargc);   cobargl = (int *)malloc (sizeof(int) * cobargc);     int error_val = 12345678;     cobargv[0] = (char *)&error_val;   cobargl[0] = sizeof(int);     cobargv[1] = _strdup("DB Service   ");   cobargl[1] = strlen(cobargv[1]);     cobargv[2] = _strdup("Username    ");   cobargl[2] = strlen(cobargv[2]);     cobargv[3] = _strdup("Password    ");   cobargl[3] = strlen(cobargv[2]);    if (isCobolCall("TESTPROG", cobargc, cobargv, cobargl, &crc) !=               ISCOBOLC_SUCCESS)   {     fprintf(stderr, "Error calling isCobolCall\n");     if ( isCobolError(errmsg, MAX_MSG_LEN) != ISCOBOLC_ERROR )     {       fprintf(stderr,"errmsg = %s\n", errmsg);     } }

free(cobargv[1]);   free(cobargv[2]);   free(cobargv[3]);      fprintf(stderr, "COBOL returned return-code = %ld, error-val = %d\n", crc, error_val);   fprintf(stderr, "Exit = %ld\n", isCobolTidy()); }

In this example, the called COBOL program is defined as follows:

id division. program-id. testprog. data division. linkage section. 01 error-val        pic s9(8) comp-5. 01 db-service       pic x(16). 01 username        pic x(16). 01 passwd         pic x(16). procedure division using error-val, db-service, username, passwd.   display "Hello from COBOL".   display "Received ERROR-VAL : " error-val.   display "Received DB-SERVICE: " db-service.   display "Received USERNAME : " username.   display "Received PASSWD  : " passwd.   move 87654321 to error-val.   display "MOVE " error-val " TO ERROR-VAL".   goback.