A commentary on jfex.c

see ./system/examples/jfe/jfex.c

// J Front End Example
// define _WIN32 for Windows, __MACH__ for MAC, J64 for 64-bit
// JE is loaded from current working directory

#ifdef _WIN32
 #define _CRT_SECURE_NO_WARNINGS
 #include <windows.h>
 #include <direct.h>
 #define GETPROCADDRESS(h,p) GetProcAddress(h,p)
 #define JDLLNAME "\\j.dll"
#else
 #define _stdcall
 #include <dlfcn.h>
 #define GETPROCADDRESS(h,p)    dlsym(h,p)
 #ifdef __MACH__ 
  #define JDLLNAME "/libj.dylib"
 #else
  #define JDLLNAME "/libj.so"
 #endif
 #define _getcwd getcwd
#endif
#include <stdio.h>
#include <signal.h>
#include "jfex.h"
#include "jlib.h"

static JDoType jdo;
static JFreeType jfree;
static JgaType jga;
static JGetLocaleType jgetlocale;

static J jt;
static void* hjdll;

static char **adadbreak;
static void sigint(int k){**adadbreak+=1;signal(SIGINT,sigint);}
static char input[1000];

Jinput

Jinput is one of the callbacks set in JSM in main()

args:

• jt the handle returned from JInit()

// J calls for input (debug suspension and 1!:1[1) and we call for input
char* _stdcall Jinput(J jt,char* prompt)
{
        fputs(prompt,stdout);
        if(!fgets(input, sizeof(input), stdin))
        {
                fputs("\n",stdout);
                **adadbreak+=1;
        }
        return input;
}

Joutput

Joutput a callback set in main()

args:

• jt the handle returned from JInit()

• type from ./system/examples/jfe/jlib.h:

  // output type
  #define MTYOFM          1       /* formatted result array output */
  #define MTYOER          2       /* error output */
  #define MTYOLOG         3       /* output log */
  #define MTYOSYS         4       /* system assertion failure */
  #define MTYOEXIT        5       /* exit */
  #define MTYOFILE        6       /* output 1!:2[2 */

// J calls for output
void _stdcall Joutput(J jt,int type, char* s)
{
        if(MTYOEXIT==type) exit((int)(I)s);
        fputs(s,stdout);
        fflush(stdout);
}

Jwd

Jwd a callback set in main()

args:

• jt the handle returned from JInit()

don't understand this function

// J calls for 11!:x y - demonstrates all features of jwdw and jwdp
// pa is y and result array (if any) is returned in pz
// return  pz
//  0           - MTM i.0 0
// -1      A    - A result
// -2      A    - A is pairs of null terminated strings for event table
//  n           - EVDOMAIN etc
int _stdcall Jwd(J jt, int x, A pa, A* pz)
{
        A r; char c; I i;
        if(!AN(pa)) return EVDOMAIN;
        if(0==x)
        {
                if(LIT!=AT(pa)) return EVDOMAIN;
                c=*CAV(pa);
                if('0'==c) return 0;
                if('1'==c)
                {
                        char res[]="result";
                        I cnt=(I)strlen(res);
                        r=jga(jt,LIT,cnt,1,&cnt);
                        if(0==r) return EVDOMAIN;
                        strcpy(CAV(r),res);
                        *pz=r;
                        return -1; // string
                }
                if('2'==c)
                {
                        char res[]="a\0aa\0b\0bbb\0"; // null delimited pairs
                        I cnt=(I)sizeof(res);
                        r=jga(jt,LIT,cnt,1,&cnt);
                        memcpy(CAV(r),res,cnt);
                        *pz=r;
                        return -2; // event data table
                }
                if('3'==c)
                {
                        char* res=jgetlocale(jt);
                        I cnt=(I)strlen(res);
                        r=jga(jt,LIT,cnt,1,&cnt);
                        if(0==r) return EVDOMAIN;
                        strcpy(CAV(r),res);
                        *pz=r;
                        return -1; // string from current locale
                }
        }
        if(x==2000)
        {
                if(INT!=AT(pa)) return EVDOMAIN;
                i=*IAV(pa);
                if(0==i) return 0;
                if(1==i)
                {
                        I res[]={1,2,3,4,5};
                        I cnt=5;
                        r=jga(jt,INT,cnt,1,&cnt);
                        if(0==r) return EVDOMAIN;
                        memcpy(IAV(r),res,cnt*sizeof(I));
                        *pz=r;
                        return -1; // int vector
                }
        }
        return EVDOMAIN;
}

int main(int argc, char* argv[])
{

from ./system/examples/jfe/jlib.h

  #define SMWIN    0  /* j.exe    Jwdw (Windows) front end */
  #define SMJAVA   2  /* j.jar    Jwdp (Java) front end */
  #define SMCON    3  /* jconsole */

        void* callbacks[] = {Joutput,Jwd,Jinput,0,(void*)SMCON};
        char pathdll[1000];
        _getcwd(pathdll,sizeof(pathdll));
        strcat(pathdll,JDLLNAME);
#ifdef _WIN32
        hjdll=LoadLibraryA(pathdll);
#else
        hjdll=dlopen(pathdll,RTLD_LAZY);
#endif
        if(!hjdll)
        {
                fputs("Load library failed: ",stderr);
                fputs(pathdll,stderr);
                fputs("\n",stderr);
                return 1; // load library failed
        }
        jt=((JInitType)GETPROCADDRESS(hjdll,"JInit"))();
        if(!jt) return 1; // JE init failed
        ((JSMType)GETPROCADDRESS(hjdll,"JSM"))(jt,callbacks);
        jdo=(JDoType)GETPROCADDRESS(hjdll,"JDo");
        jfree=(JFreeType)GETPROCADDRESS(hjdll,"JFree");
        jga=(JgaType)GETPROCADDRESS(hjdll,"Jga");
        jgetlocale=(JGetLocaleType)GETPROCADDRESS(hjdll,"JGetLocale");
        adadbreak=(char**)jt; // first address in jt is address of breakdata
        signal(SIGINT,sigint);
        while(1){jdo(jt,Jinput(jt,"   "));}
        jfree(jt);
        return 0;
}