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POJNI: From C code to Java and JNI
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  1. POJNI: From C code to Java and JNI
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    copied!<h3>Background</h3> <p>I am developing an application for android in eclipse and now I have a problem and I need your help. So I must Call function written in <strong><em>C</em></strong> from JAVA application. But on my way of writing code I have some <strong><em>Questions</em></strong> which you can see below. I am waiting for your answers and ideas ... </p> <h3>C Code:</h3> <pre><code>typdef struct blobData_s { unsigned long length; unsigned char data[1]; } blobData_t; unsigned int CheckEnrollmentExist ( unsigned long hdevice, blobData_t* pInputInfo ) { // Function code goes here .......................... return some_value; } </code></pre> <hr> <h3>JAVA Code:</h3> <p>In JAVA code instead of <code>unsigned long</code> I use <code>int</code> so I can write. </p> <pre><code>class jblobData_c { public int langth; *Question 1.* } public class ApplicationMainClass extends Activity { // Some code goes here ...................... public native int JCheckEnrollmentExist( int jhdevive, *Question 2.* ); } </code></pre> <p><strong><em>Question 1.</em></strong></p> <ul> <li>What I can use instead of <code>unsigned char</code> in JAVA Code ?</li> <li>What I must write in JAVA code instead of <code>unsigned char data[1];</code> ?</li> </ul> <p><strong><em>Question 2.</em></strong></p> <ul> <li>How I can use <code>class jblobData_c</code> instead of <code>blobData_t* pInputInfo</code> in the JAVA Code ?</li> <li>What I must write in JAVA instead of <code>blobData_t* pInputInfo</code> ?</li> </ul> <hr> <h3>JNI Code:</h3> <pre><code>JNIEXPORT jint JNICALL Java_com_Test_JCheckEnrollmentExist(JNIEnv* env, jobject obj, jint jhdevice, *Question 2.* ) { // Call the base function from C code. return CheckEnrollmentExist( jhdevice, *Question 3.*); } </code></pre> <p><strong><em>Question 3.</em></strong></p> <ul> <li>What I must write in <code>CheckEnrollmentExist</code> function that is C Code Function instead of <code>blobData_t* pInputInfo</code> in order this function works right and given parameter be the same </li> </ul> <h3>Reference</h3> <ol> <li><a href="https://stackoverflow.com/questions/3923299/how-to-pass-c-structs-back-and-forth-to-java-code-in-jni"><strong><em>How to pass C structs back and forth to Java code in JNI ?</em></strong></a></li> <li><a href="https://stackoverflow.com/questions/1571175/passing-large-c-structure-through-jni-efficiently"><strong><em>Passing large C structure through JNI efficiently</em></strong></a></li> <li><a href="http://www.coderanch.com/t/274504/java/java/Return-Structure-Object-Java-Through" rel="nofollow noreferrer"><strong><em>Return a Structure Object from C to Java Through JNI</em></strong></a></li> <li><a href="https://stackoverflow.com/questions/4324819/pass-data-between-java-and-c/4325678#4325678"><strong><em>Pass data between Java and C</em></strong></a></li> <li><a href="https://stackoverflow.com/questions/5802340/passing-a-pointer-from-jni-to-java-using-a-long"><strong><em>Passing a pointer from JNI to Java using a long</em></strong></a></li> <li><a href="https://stackoverflow.com/questions/1632367/passing-pointers-between-c-and-java-through-jni"><strong><em>Passing pointers between C and Java through JNI</em></strong></a></li> </ol>
 

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