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#include <stdio.h>
void add (int, int, int *);
void main (void)
{
   int total;
   add (3, 5, &total);
   printf ("total = %d\n", total);
}
void add (int a, int b, int *sum)
{
   *sum = a + b;
}

// ---------------
// useSysInfo.java
//
// SysInfo Driver
// ---------------
public class useSysInfo
{
   public static void main (String [] args)
   {
      System.out.println ("----------\nuseSysInfo\n----------\n");
      // ----------------------------------------------------
      // Get and print the PATH environment variable setting.
      // ----------------------------------------------------
      System.out.println ("1. Get PATH environment variable setting.");
      System.out.println ("   Setting returned as a String object.\n");
      System.out.println ("PATH = " + SysInfo.getenv ("PATH") + "\n");
      // ------------------------------------------------------
      // Get the PATH environment variable setting by returning
      // setting in StringBuffer object referenced by evValue.
      // ------------------------------------------------------
      StringBuffer evValue = new StringBuffer ("");
      SysInfo.getenv ("PATH", evValue);
      // --------------------------------------------
      // Print the PATH environment variable setting.
      // --------------------------------------------
      System.out.println ("2.  Get PATH environment variable setting.");
      System.out.println ("    Setting returned in StringBuffer ref-");
      System.out.println ("    erence object.\n");
      System.out.println ("PATH = " + evValue + "\n");
      // -------------------------------------------
      // Get and print the native OS version number.
      // -------------------------------------------
      Version v = SysInfo.getVersion ();
      System.out.println ("3. Display native OS version info.");
      System.out.println ("   Info returned in Version object.\n");
      System.out.println ("Version Major = " + v.major);
      System.out.println ("Version Minor = " + v.minor);
   }
}

StringBuffer evValue = new StringBuffer ("");
SysInfo.getenv ("PATH", evValue);

public class SysInfo
{
   static
   {
      try
      {
         System.loadLibrary ("SysInfo");
      }
      catch (java.lang.UnsatisfiedLinkError e)
      {
         System.out.println (e);
      }
   }
   public static native String getenv (String evName);
   public static native void getenv (String evName, StringBuffer evValue);
   public static native Version getVersion ();
}

// ==========================
// SysInfo.cpp
//
// Obtain system information.
// ==========================
#include <windows.H>
#include "SysInfo.H"
// ========================================================================
// Java_SysInfo_getenv__Ljava_lang_String_2
//
// Obtain the value of an environment variable.
//
// Arguments:
//
// env    - pointer to pointer to JNI function table
// clazz  - handle of class that contains this method
// EVName - handle of Java String object that contains environment variable 
//          name
//
// Return:
//
// Java String object containing environment variable value
// ========================================================================
JNIEXPORT jstring JNICALL 
        Java_SysInfo_getenv__Ljava_lang_String_2 
        (JNIEnv *env, jclass clazz, jstring EVName)
{
        // Check Java String object argument (environment variable name) to see
    // if null reference passed.
    if (EVName == 0)
            return 0;
    // Get ASCII representation of environment variable name.
    const char *_EVName = env->GetStringUTFChars (EVName, 0);
    // Get environment variable value.
    const char *EVValue = getenv (_EVName);
    // Release memory used to hold ASCII representation.
        env->ReleaseStringUTFChars (EVName, _EVName);
    // Return a null reference if there is no environment variable value 
    // otherwise return this value.
    return (EVValue == 0) ? 0 : env->NewStringUTF (EVValue);
}
// =========================================================================
// Java_SysInfo_getenv__Ljava_lang_String_2Ljava_lang_StringBuffer_2
//
// Obtain the value of an environment variable.
//
// Arguments:
//
// env     - pointer to pointer to JNI function table
// clazz   - handle of class that contains this method
// EVName  - handle of Java String object that contains environment variable 
//           name
// EVValue - handle of Java StringBuffer object that will hold environment 
//           variable value
//
// Return:
//
// none
// =========================================================================
JNIEXPORT void JNICALL 
    Java_SysInfo_getenv__Ljava_lang_String_2Ljava_lang_StringBuffer_2 
        (JNIEnv *env, jclass clazz, jstring EVName, jobject EVValue)
{
    // Check Java String object argument (environment variable name) to see 
    // if null reference passed.
    if (EVName == 0)
            return;
    // Check Java StringBuffer object argument (environment variable value) 
    // to see if null reference passed.
    if (EVValue == 0)
            return;
    // Get ASCII representation of environment variable name.
    const char *_EVName = env->GetStringUTFChars (EVName, 0);
    // Get environment variable value.
    const char *_EVValue = getenv (_EVName);
    // Release memory used to hold ASCII representation.
        env->ReleaseStringUTFChars (EVName, _EVName);
    // Return if there is no environment variable value.
    if (_EVValue == 0)
            return;
    // Obtain the Java StringBuffer class handle that corresponds to the 
    // Java StringBuffer object handle.
    clazz = env->GetObjectClass (EVValue);
    // Obtain the method ID for the StringBuffer append method which takes 
    // a StringBuffer object reference argument and returns a String object 
    // reference.
    jmethodID mid = 
        env->GetMethodID (clazz, 
                          "append", 
                                  "(Ljava/lang/String;)Ljava/lang/StringBuffer;");
    // If this method does not exist then return.
    if (mid == 0)
            return;
    // Create a new Java String object and populate it with the environment
    // variable value.  Obtain a handle to this object.
    jstring _jstring = env->NewStringUTF ((const char *) _EVValue);
    // Call the StringBuffer object's append method passing the handle to 
    // the new Java String object.
    env->CallObjectMethod (EVValue, mid, _jstring);
}
// ====================================================
// Java_SysInfo_getVersion
//
// Get the native operating system's version.
//
// Arguments:
//
// env     - pointer to pointer to JNI function table
// clazz   - handle of class that contains this method
//
// Return:
//
// Version object containing native version information
// ====================================================
JNIEXPORT jobject JNICALL Java_SysInfo_getVersion (JNIEnv *env, jclass clazz)
{
    OSVERSIONINFO osVersionInfo;
    // Get operating system version information.
    osVersionInfo.dwOSVersionInfoSize = sizeof (OSVERSIONINFO);
    GetVersionEx (&osVersionInfo);
    // Attempt to find the Version class.
    clazz = env->FindClass ("Version");
    // If this class does not exist then return null.
    if (clazz == 0)
            return 0;
    // Allocate memory for a new Version class object.  Do not bother calling
    // the constructor (the default constructor does nothing).
    jobject obj = env->AllocObject (clazz);
    // Attempt to find the major field.
    jfieldID fid = env->GetFieldID (clazz, "major", "I");
    // If this field does not exist then return null.
    if (fid == 0)
            return 0;
    // Set the major field to the operating system's major version.
    env->SetIntField (obj, fid, osVersionInfo.dwMajorVersion);
    // Attempt to find the minor field.
    fid = env->GetFieldID (clazz, "minor", "I");
    // If this field does not exist then return null.
    if (fid == 0)
            return 0;
    // Set the minor field to the operating system's minor version.
    env->SetIntField (obj, fid, osVersionInfo.dwMinorVersion);
    return obj;
}