Sorry, I posted this message to the wrong forum by mistake. Please ignore it.
On Mon, Apr 7, 2008 at 1:27 PM, Jorge Arredondo
<[EMAIL PROTECTED]> wrote:
> I've started writing a J to Java interface and realized the following
> steps needed to be implemented:
> - Create C wrapper functions to expose J methods through JNI.
> - Create a Java wrapper class to call those JNI methods.
>
> Then, the methods of the wrapper class should be called in the following
> order:
> - JInit - creates the J instance
> - J method(s)
> - JFree - destroys the J instance (no more methods are going to be called).
>
>
> So, in order to call "JDo", I had to write the following code:
> === C code =============================================================
> #include "j_jwrapper.h"
> #include <windows.h>
> BOOL APIENTRY DllMain(HANDLE hInst, DWORD reason, LPVOID reserved){
> return TRUE; }
>
> #define JCALL(Method) long (CALLBACK* j_##Method)
>
> JCALL(Init)(void);
> JCALL(Free)(long jh);
> JCALL(Do)(long jh, const char *cmd);
>
> HMODULE jdll= NULL;
>
> JNIEXPORT jint JNICALL Java_j_JWrapper_JInit(JNIEnv *env, jobject this)
> {
> jdll = LoadLibrary("j.dll");
> if (!jdll)
> return 0;
> *(FARPROC*)&j_Init = GetProcAddress(jdll, "JInit");
> *(FARPROC*)&j_Free = GetProcAddress(jdll, "JFree");
> *(FARPROC*)&j_Do = GetProcAddress(jdll, "JDo");
> return j_Init();
> }
>
> JNIEXPORT jint JNICALL Java_j_JWrapper_JDo(JNIEnv *env, jobject this,
> jint j, jstring cmd)
> {
> const char *pcmd = (*env)->GetStringUTFChars(env, cmd, JNI_FALSE);
> jint ec = jdll_Do(j, pcmd);
> (*env)->ReleaseStringUTFChars(env, cmd, pcmd);
> return ec;
> }
>
> JNIEXPORT jint JNICALL Java_j_JWrapper_JFree(JNIEnv *env, jobject this, jint
> jh)
> {
> jint ec = j_Free(jh);
> FreeLibrary(jdll);
> return ec;
> }
>
> === Java wrapper =======================================================
> package j;
>
> public class JWrapper {
> private int jh = 0;
> static {System.loadLibrary("JayJNI");}
>
> native int JInit();
> native int JFree(int jh);
> native int JDo(int jh, String cmd);
>
> public JWrapper() {}
>
> public Init() throws Exception {
> jh = JInit();
> if (jh == 0) { throw new Exception("J DLL could not be
> loaded."); }
> }
>
> public int Free() {
> return JFree(jh);
> }
>
> public void Do(String cmd) throws Exception {
> int ec = JDo(jh, cmd);
> if (ec != 0) { throw new Exception("JDo failed with code:
> "+ec); }
> }
> }
>
> === Usage ==============================================================
> JWrapper J = new JWrapper();
> J.Init();
> J.Do("'hello'(1!:2)<'out.txt'");
> J.Free();
> ========================================================================
>
> It seems difficult that there isn't a Java API available, considering
> there is a Java front-end to J. Do we really need to write this kind
> of code, or am I missing something?
>
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