Make writeBytes() return how many bytes actually got written

The core change is this one:

--- src/main/java/jssc/SerialNativeInterface.java
+++ src/main/java/jssc/SerialNativeInterface.java
@@ -278,5 +278,5 @@ public class SerialNativeInterface {
      * @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;

     /**

Essentially changing the return type of `writeBytes()` from `boolean` to
`int`. The reason behind this is that we can return how many bytes
actually got written, in place of just true/false.

Basically, this is a very small change. Nevertheless, there are some
consequences.

This is (kind of) a breaking change for the java API. But still not
really an issue, as it is a very easy migration. About how to migrate,
one can just do the same as done in `SerialPort.writeBytes1()` (notice
the '1' in the name). Just check if returned value matches the length of
the passed-in array. There is also a YAGNI approach (NOT RECOMMENDED!):
One could just use `writeBytes1()` instead. Which provides the old
behavior.

A more severe issue can arise because it potentially also breaks the ABI.
make sure to NOT mix usage of parts of jssc built before or after
this change! in most cases this shouldn't be an issue, as jssc unpacks
the correct version from its JAR anyway. BUT FOR THOSE WHO DID SEPARATE
THE JAVA CODE FROM THE NATIVE CODE AND INSTALL IT SEPARATELY, THEY
POTENTIALLY CAN END UP IN TROUBLE WHEN NOT TAKING CARE HERE.

In addition, this commit also contains some minor cleanups and fixes
some compiler warnings.

Related:
- #129

(wip @ 17cc247)

Author: hiddenalpha

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)
@@ -62,7 +60,16 @@
 #include <jssc_SerialNativeInterface.h>
 #include "version.h"
 
-//#include <iostream> //-lCstd use for Solaris linker
+#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
 
 /*
  * Get native library version
@@ -529,33 +536,31 @@ 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 +681,7 @@ 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/cpp/jssc_SerialNativeInterface.h

@@ -29,7 +29,16 @@
 #include <jssc_SerialNativeInterface.h>
 #include "version.h"
 
-//#include <iostream>
+#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 +241,61 @@ 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 +330,7 @@ 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/cpp/windows/jssc.cpp

@@ -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