Need help in using JNI

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I want to access my c code from java and get data from C struct using JNI. I want to achieve this using hashtable or hashmap. Here is my C struct:

struct process
{
char str[];
char strr[];
int i;
}; 
struct process *ptr;

Now, I want to pass the data from the struct array(*ptr) to the java code. Can I pass the data using Hashtable or Hashmap? Or can I pass the struct array directly to java? Is there any decent way for doing this?

What I have tried:

I stored all data in a string array and passed it. But, it seems so cheap. So, suggest some ideas to pass it.

Posted 6-May-21 19:05pm

Member 15076657

Updated 6-May-21 21:27pm

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KarstenK · Accepted Answer · 2021-05-06T20:41:00

Be happy that it works and move on. Transfering complex objects between different runtimes isnt possible because of memory layout.
You may transfer some byte array in which the data is an reinterpret it. Like

C++

struct Data {
 int i;
 int lenstr;
 int lenstrr;
 char* data; // allocate with  lenstr + lenstr and copy the bits one and the other string
};

In Java you can fizzle the bytes out.

Richard MacCutchan · Accepted Answer · 2021-05-06T21:27:00

Quote:
Can I pass the data using Hashtable or Hashmap? Or can I pass the struct array directly to java? Is there any decent way for doing this?

Sadly, no. The Java Native Interface is designed to allow C programmers to write support libraries for Java programs. You cannot call a C library direct from Java unless it has been coded to the standard. So you would need to create an interface library that is callable from Java before you can access any of the C library functions.

Need help in using JNI

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