In writeBytes return actual numBytesWritten

src/main/cpp/_nix_based/jssc.cpp

@@ -29,7 +29,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-#include <string.h>
 #include <sys/ioctl.h>
 #include <termios.h>
 #include <time.h>
@@ -40,7 +39,6 @@
 #endif
 #ifdef __sun
     #include <sys/filio.h>//Needed for FIONREAD in Solaris
-    #include <string.h>//Needed for select() function
 #endif
 #ifdef __APPLE__
     #include <serial/ioss.h>//Needed for IOSSIOSPEED in Mac OS X (Non standard baudrate)
@@ -62,8 +60,6 @@
 #include <jssc_SerialNativeInterface.h>
 #include "version.h"
 
-//#include <iostream> //-lCstd use for Solaris linker
-
 /*
  * Get native library version
  */
@@ -529,33 +525,31 @@ JNIEXPORT jboolean JNICALL Java_jssc_SerialNativeInterface_setDTR
 /*
  * Writing data to the port
  */
-JNIEXPORT jboolean JNICALL Java_jssc_SerialNativeInterface_writeBytes
+JNIEXPORT jint JNICALL Java_jssc_SerialNativeInterface_writeBytes
   (JNIEnv *env, jobject, jlong portHandle, jbyteArray buffer){
-    if( buffer == NULL ){
+    ssize_t ret = 0;
+    jbyte *jBuffer = NULL;
+    if( !buffer ){
         jclass exClz = env->FindClass("java/lang/NullPointerException");
-        if( exClz != NULL ) env->ThrowNew(exClz, "buffer");
-        return 0;
+        if( exClz ) env->ThrowNew(exClz, "buffer");
+        goto Finally;
     }
-    jboolean ret = JNI_FALSE;
-    jbyte* jBuffer = env->GetByteArrayElements(buffer, JNI_FALSE);
-    if( jBuffer == NULL ){
-        jclass exClz = env->FindClass("java/lang/RuntimeException");
-        if( exClz != NULL ) env->ThrowNew(exClz, "jni->GetByteArrayElements() failed");
-        return 0;
+    jBuffer = env->GetByteArrayElements(buffer, NULL);
+    if( !jBuffer ){
+        jclass exClz = env->ExceptionCheck() ? NULL : env->FindClass("java/lang/RuntimeException");
+        if( exClz ) env->ThrowNew(exClz, "jni->GetByteArrayElements() failed");
+        goto Finally;
     }
-    jint bufferSize = env->GetArrayLength(buffer);
-    jint result = write(portHandle, jBuffer, (size_t)bufferSize);
-    if( result == -1 ){
-        int err = errno; /*bakup errno*/
+    ret = write(portHandle, jBuffer, env->GetArrayLength(buffer));
+    if( ret == -1 ){
+        int err = errno;
         jclass exClz = env->FindClass("java/io/IOException");
-        assert(exClz != NULL);
-        env->ThrowNew(exClz, strerror(err));
+        if( exClz ) env->ThrowNew(exClz, strerror(err));
         goto Finally;
     }
-    ret = (result == bufferSize) ? JNI_TRUE : JNI_FALSE;
 Finally:
-    env->ReleaseByteArrayElements(buffer, jBuffer, 0);
-    return ret;
+    if( jBuffer ) env->ReleaseByteArrayElements(buffer, jBuffer, 0);
+    return (jint)ret;
 }
 
 /**
@@ -676,7 +670,7 @@ JNIEXPORT jbyteArray JNICALL Java_jssc_SerialNativeInterface_readBytes
     lpBuffer = (jbyte*)malloc(byteCount*sizeof*lpBuffer);
     if( !lpBuffer ){
         char emsg[32]; emsg[0] = '\0';
-        snprintf(emsg, sizeof emsg, "malloc(%d) failed", byteCount*sizeof*lpBuffer);
+        snprintf(emsg, sizeof emsg, "malloc(%zu) failed", byteCount*sizeof*lpBuffer);
         jclass exClz = env->FindClass("java/lang/RuntimeException");
         if( exClz ) env->ThrowNew(exClz, emsg);
         returnArray = NULL; goto Finally;

src/main/cpp/windows/jssc.cpp

@@ -29,7 +29,17 @@
 #include <jssc_SerialNativeInterface.h>
 #include "version.h"
 
-//#include <iostream>
+// For snprintf formatting
+#if defined(_MSC_VER) && _MSC_VER < 1800
+#   define PRIsz "Iu"
+#   define PRIssz "Id"
+#elif defined(__MINGW32__) && !defined(__MINGW64__)
+#   define PRIsz "u"
+#   define PRIssz "d"
+#else
+#   define PRIsz "zu"
+#   define PRIssz "zd"
+#endif
 
 #define MAX_PORT_NAME_STR_LEN 32
 
@@ -232,38 +242,61 @@ JNIEXPORT jboolean JNICALL Java_jssc_SerialNativeInterface_setDTR
  * portHandle - port handle
  * buffer - byte array for sending
  */
-JNIEXPORT jboolean JNICALL Java_jssc_SerialNativeInterface_writeBytes
+JNIEXPORT jint JNICALL Java_jssc_SerialNativeInterface_writeBytes
   (JNIEnv *env, jobject, jlong portHandle, jbyteArray buffer){
     HANDLE hComm = (HANDLE)portHandle;
     DWORD lpNumberOfBytesTransferred;
     DWORD lpNumberOfBytesWritten;
-    jboolean returnValue = JNI_FALSE;
-    if( buffer == NULL ){
+    jint returnValue = -1;
+    if( !buffer ){
         jclass exClz = env->FindClass("java/lang/NullPointerException");
-        if( exClz != NULL ) env->ThrowNew(exClz, "buffer");
+        if( exClz ) env->ThrowNew(exClz, "buffer");
         return 0;
     }
-    jbyte* jBuffer = env->GetByteArrayElements(buffer, JNI_FALSE);
-    if( jBuffer == NULL ){
-        jclass exClz = env->FindClass("java/lang/RuntimeException");
-        if( exClz != NULL ) env->ThrowNew(exClz, "jni->GetByteArrayElements() failed");
+    jbyte *jBuffer = env->GetByteArrayElements(buffer, NULL);
+    if( !jBuffer ){
+        jclass exClz = env->ExceptionCheck() ? NULL : env->FindClass("java/lang/RuntimeException");
+        if( exClz ) env->ThrowNew(exClz, "jni->GetByteArrayElements() failed");
         return 0;
     }
     OVERLAPPED *overlapped = new OVERLAPPED();
     overlapped->hEvent = CreateEventA(NULL, true, false, NULL);
-    if(WriteFile(hComm, jBuffer, (DWORD)env->GetArrayLength(buffer), &lpNumberOfBytesWritten, overlapped)){
-        returnValue = JNI_TRUE;
-    }
-    else if(GetLastError() == ERROR_IO_PENDING){
-        if(WaitForSingleObject(overlapped->hEvent, INFINITE) == WAIT_OBJECT_0){
-            if(GetOverlappedResult(hComm, overlapped, &lpNumberOfBytesTransferred, false)){
-                returnValue = JNI_TRUE;
-            }
+    DWORD err = 0;
+    do{
+        err = !WriteFile(hComm, jBuffer, (DWORD)env->GetArrayLength(buffer), &lpNumberOfBytesWritten, overlapped);
+        if( !err ){ /* successfully written. we're already done. */
+            returnValue = lpNumberOfBytesWritten;
+            break;
         }
-    }
+        err = GetLastError();
+        if( err != ERROR_IO_PENDING ){
+            break; /* some unknown error occurred. Go reporting it. */
+        }
+        /* our write above was async (IO_PENDING). So it was only fired off, but
+         * we do not know the result yet. Therefore we've to wait for the result. */
+        if( WaitForSingleObject(overlapped->hEvent, INFINITE) != WAIT_OBJECT_0 ){
+            /* too bad :( wait failed. */
+            err = GetLastError();
+            break;
+        }
+        /* waited successfully. Time to get the result. */
+        if( GetOverlappedResult(hComm, overlapped, &lpNumberOfBytesTransferred, false) ){
+            /* we know the result now */
+            returnValue = lpNumberOfBytesTransferred;
+            err = 0;
+        }else{ /* GetOverlappedResult has failed :( */
+            err = GetLastError();
+        }
+    }while(0);
     env->ReleaseByteArrayElements(buffer, jBuffer, 0);
     CloseHandle(overlapped->hEvent);
     delete overlapped;
+    if( err ){
+        char emsg[128];
+        snprintf(emsg, sizeof emsg, "Error %lu: https://learn.microsoft.com/en-us/windows/win32/debug/system-error-codes#system-error-codes", (long unsigned)err);
+        jclass exClz = env->FindClass("java/io/IOException");
+        if( exClz ) env->ThrowNew(exClz, emsg);
+    }
     return returnValue;
 }
 
@@ -298,7 +331,7 @@ JNIEXPORT jbyteArray JNICALL Java_jssc_SerialNativeInterface_readBytes
     lpBuffer = (jbyte*)malloc(byteCount*sizeof*lpBuffer);
     if( !lpBuffer ){
         char emsg[32]; emsg[0] = '\0';
-        snprintf(emsg, sizeof emsg, "malloc(%d) failed", byteCount*sizeof*lpBuffer);
+        snprintf(emsg, sizeof emsg, "malloc(%" PRIsz ") failed", byteCount*sizeof*lpBuffer);
         jclass exClz = env->FindClass("java/lang/RuntimeException");
         if( exClz ) env->ThrowNew(exClz, emsg);
         returnArray = NULL; goto Finally;

src/main/java/jssc/SerialNativeInterface.java

@@ -277,7 +277,7 @@ public static String getLibraryVersion() {
      * 
      * @return If the operation is successfully completed, the method returns true, otherwise false
      */
-    public native boolean writeBytes(long handle, byte[] buffer) throws IOException;
+    public native int writeBytes(long handle, byte[] buffer) throws IOException;
 
     /**
      * Get bytes count in buffers of port

src/main/java/jssc/SerialPort.java

@@ -28,6 +28,8 @@
 import java.io.UnsupportedEncodingException;
 import java.lang.reflect.Method;
 
+import static jssc.SerialPortException.wrapNativeException;
+
 /**
  *
  * @author scream3r
@@ -397,15 +399,15 @@ public boolean setDTR(boolean enabled) throws SerialPortException {
     }
 
     /**
-     * Write byte array to port
+     * Write byte array to port.
      *
-     * @param buffer <code>byte[]</code> array to write
+     * @param buffer <code>byte[]</code> array to write.
      *
-     * @return If the operation is successfully completed, the method returns true, otherwise false
-     * 
-     * @throws SerialPortException if exception occurred
+     * @return number of bytes written.
+     *
+     * @throws SerialPortException
      */
-    public boolean writeBytes(byte[] buffer) throws SerialPortException {
+    public int writeBytes(byte[] buffer) throws SerialPortException {
         checkPortOpened("writeBytes()");
         try {
             return serialInterface.writeBytes(portHandle, buffer);
@@ -419,13 +421,13 @@ public boolean writeBytes(byte[] buffer) throws SerialPortException {
      *
      * @param singleByte single <code>byte</code> value to write
      *
-     * @return If the operation is successfully completed, the method returns true, otherwise false
+     * @return Number of bytes written.
      *
      * @throws SerialPortException if exception occurred
      *
      * @since 0.8
      */
-    public boolean writeByte(byte singleByte) throws SerialPortException {
+    public int writeByte(byte singleByte) throws SerialPortException {
         checkPortOpened("writeByte()");
         return writeBytes(new byte[]{singleByte});
     }
@@ -435,46 +437,67 @@ public boolean writeByte(byte singleByte) throws SerialPortException {
      *
      * @param string <code>String</code> value to write
      *
-     * @return If the operation is successfully completed, the method returns true, otherwise false
+     * @return
+     *      Number of bytes written. WARN: Number of BYTES, NOT number of CHARS!
+     *      This may differ from <code>string.length()</code> if passed in string
+     *      contains chars outside the english alphabet. If you need reliable
+     *      return lengths, consider calling
+     *      {@link java.lang.String#getBytes(java.nio.charset.Charset)}
+     *      yourself and then passing result to
+     *      {@link #writeBytes(byte[])}
+     *      instead. This gives you the chance to verify the expected return
+     *      value correctly.
      *
      * @throws SerialPortException if exception occurred
      *
      * @since 0.8
      */
-    public boolean writeString(String string) throws SerialPortException {
+    public int writeString(String string) throws SerialPortException {
         checkPortOpened("writeString()");
-        return writeBytes(string.getBytes());
+        byte[] bytes = string.getBytes();
+        return writeBytes(bytes);
     }
 
     /**
      * Write String to port
      *
      * @param string <code>String</code> value to write
      * @param charsetName valid <code>Charset</code> name, e.g. <code>"UTF-8"</code>
-     * @return If the operation is successfully completed, the method returns true, otherwise false
+     *
+     * @return
+     *      Number of bytes written. WARN: Number of BYTES, NOT number of CHARS!
+     *      This may differ from <code>string.length()</code> if passed in string
+     *      contains chars outside the english alphabet. If you need reliable
+     *      return lengths, consider calling
+     *      {@link java.lang.String#getBytes(java.nio.charset.Charset)}
+     *      yourself and then passing result to
+     *      {@link #writeBytes(byte[])}
+     *      instead. This gives you the chance to verify the expected return
+     *      value correctly.
      *
      * @throws SerialPortException if exception occurred
      * @throws UnsupportedEncodingException if encoding exception occurred
      *
      * @since 2.8.0
      */
-    public boolean writeString(String string, String charsetName) throws SerialPortException, UnsupportedEncodingException {
+    public int writeString(String string, String charsetName) throws SerialPortException, UnsupportedEncodingException {
         checkPortOpened("writeString()");
-        return writeBytes(string.getBytes(charsetName));
+        byte[] bytes = string.getBytes(charsetName);
+        return writeBytes(bytes);
     }
 
     /**
      * Write int value (in range from 0 to 255 (0x00 - 0xFF)) to port
      *
      * @param singleInt single <code>int</code> value to write
      *
-     * @return If the operation is successfully completed, the method returns true, otherwise false
+     * @return Number of bytes written.
      *
      * @throws SerialPortException if exception occurred
      *
      * @since 0.8
      */
-    public boolean writeInt(int singleInt) throws SerialPortException {
+    public int writeInt(int singleInt) throws SerialPortException {
         checkPortOpened("writeInt()");
         return writeBytes(new byte[]{(byte)singleInt});
     }
@@ -484,13 +507,13 @@ public boolean writeInt(int singleInt) throws SerialPortException {
      *
      * @param buffer <code>int[]</code> array to write
      *
-     * @return If the operation is successfully completed, the method returns true, otherwise false
+     * @return Number of bytes written.
      *
      * @throws SerialPortException if exception occurred
      *
      * @since 0.8
      */
-    public boolean writeIntArray(int[] buffer) throws SerialPortException {
+    public int writeIntArray(int[] buffer) throws SerialPortException {
         checkPortOpened("writeIntArray()");
         byte[] byteArray = new byte[buffer.length];
         for(int i = 0; i < buffer.length; i++){
@@ -1415,4 +1438,5 @@ public void run() {
             }
         }
     }
+
 }