Fixed multi threading issues in gs_jni

15 files changed, 240 insertions, 177 deletions

diff --git a/demos/java/jni/gs_jni/callbacks.cpp b/demos/java/jni/gs_jni/callbacks.cpp
index 8d9ab2122..646219330 100644
--- a/demos/java/jni/gs_jni/callbacks.cpp
+++ b/demos/java/jni/gs_jni/callbacks.cpp
@@ -34,95 +34,92 @@ Lcom/artifex/gsjava/IntReference;)I"
 
 using namespace util;
 
-void callbacks::setJNIEnv(void *instance, JNIEnv *env)
+void callbacks::setJNIEnv(GSInstanceData *idata, JNIEnv *env)
 {
-	GSInstanceData *gsdata = findDataFromInstance(instance);
-	assert(gsdata);
-
-	gsdata->env = env;
+	idata->env = env;
 }
 
-void callbacks::setIOCallbacks(void *instance, jobject stdIn, jobject stdOut, jobject stdErr)
+void callbacks::setIOCallbacks(GSInstanceData *idata, jobject stdIn, jobject stdOut, jobject stdErr)
 {
-	GSInstanceData *gsdata = findDataFromInstance(instance);
-	assert(gsdata);
-
-	if (gsdata->env)
+	if (idata->env)
 	{
-		if (gsdata->stdIn)
-			gsdata->env->DeleteGlobalRef(gsdata->stdIn);
+		if (idata->stdIn)
+			idata->env->DeleteGlobalRef(idata->stdIn);
 
-		if (gsdata->stdOut)
-			gsdata->env->DeleteGlobalRef(gsdata->stdOut);
+		if (idata->stdOut)
+			idata->env->DeleteGlobalRef(idata->stdOut);
 
-		if (gsdata->stdErr)
-			gsdata->env->DeleteGlobalRef(gsdata->stdErr);
+		if (idata->stdErr)
+			idata->env->DeleteGlobalRef(idata->stdErr);
 
-		gsdata->stdIn = gsdata->env->NewGlobalRef(stdIn);
-		gsdata->stdOut = gsdata->env->NewGlobalRef(stdOut);
-		gsdata->stdErr = gsdata->env->NewGlobalRef(stdErr);
+		idata->stdIn = idata->env->NewGlobalRef(stdIn);
+		idata->stdOut = idata->env->NewGlobalRef(stdOut);
+		idata->stdErr = idata->env->NewGlobalRef(stdErr);
 	}
 }
 
 int callbacks::stdInFunction(void *callerHandle, char *buf, int len)
 {
-	int code = 0;
-
-	GSInstanceData *gsdata = findDataFromHandle(callerHandle);
+	GSInstanceData *gsdata = (GSInstanceData *)callerHandle;
 	assert(gsdata);
 
-	if (gsdata->env && gsdata->stdIn)
-	{
-		jbyteArray byteArray = gsdata->env->NewByteArray(len);
-		gsdata->env->SetByteArrayRegion(byteArray, 0, len, (jbyte *)buf);
-		code = callIntMethod(gsdata->env, gsdata->stdIn, "onStdIn", STDIN_SIG, (jlong)gsdata->stdioHandle, byteArray, (jint)len);
-	}
-	return code;
+	if (!gsdata->env || !gsdata->stdErr) return 0;
+
+	jbyteArray byteArray = gsdata->env->NewByteArray(len);
+	gsdata->env->SetByteArrayRegion(byteArray, 0, len, (jbyte *)buf);
+
+	jint result = callIntMethod(gsdata->env, gsdata->stdIn, "onStdIn", STDIN_SIG, (jlong)gsdata->stdioHandle, byteArray, (jint)len);
+	if (gsdata->env->ExceptionCheck()) return 0;
+
+	jboolean isCopy = JNI_FALSE;
+	jbyte *arr = gsdata->env->GetByteArrayElements(byteArray, &isCopy);
+
+	jsize copySize = result < len ? result : len;
+	memcpy(buf, arr, copySize);
+
+	return copySize;
 }
 
 int callbacks::stdOutFunction(void *callerHandle, const char *str, int len)
 {
-	int code = 0;
-
-	GSInstanceData *gsdata = findDataFromHandle(callerHandle);
+	GSInstanceData *gsdata = (GSInstanceData *)callerHandle;
 	assert(gsdata);
 
-	if (gsdata->env && gsdata->stdOut)
-	{
-		jbyteArray byteArray = gsdata->env->NewByteArray(len);
-		gsdata->env->SetByteArrayRegion(byteArray, 0, len, (const jbyte *)str);
-		code = callIntMethod(gsdata->env, gsdata->stdOut, "onStdOut", STDOUT_SIG, (jlong)gsdata->stdioHandle, byteArray, (jint)len);
-	}
-	return code;
+	if (!gsdata->env || !gsdata->stdOut) return len;
+
+	jbyteArray byteArray = gsdata->env->NewByteArray(len);
+	gsdata->env->SetByteArrayRegion(byteArray, 0, len, (const jbyte *)str);
+
+	jint result = callIntMethod(gsdata->env, gsdata->stdOut, "onStdOut", STDOUT_SIG, (jlong)gsdata->stdioHandle, byteArray, (jint)len);
+	if (gsdata->env->ExceptionCheck()) return 0;
+
+	return result;
 }
 
 int callbacks::stdErrFunction(void *callerHandle, const char *str, int len)
 {
-	int code = 0;
-
-	GSInstanceData *gsdata = findDataFromHandle(callerHandle);
+	GSInstanceData *gsdata = (GSInstanceData *)callerHandle;
 	assert(gsdata);
 
-	if (gsdata->env && gsdata->stdErr)
-	{
-		jbyteArray byteArray = gsdata->env->NewByteArray(len);
-		gsdata->env->SetByteArrayRegion(byteArray, 0, len, (const jbyte *)str);
-		code = callIntMethod(gsdata->env, gsdata->stdErr, "onStdErr", STDERR_SIG, (jlong)gsdata->stdioHandle, byteArray, (jint)len);
-	}
-	return code;
+	if (!gsdata->env || !gsdata->stdErr) return len;
+
+	jbyteArray byteArray = gsdata->env->NewByteArray(len);
+	gsdata->env->SetByteArrayRegion(byteArray, 0, len, (const jbyte *)str);
+
+	jint result = callIntMethod(gsdata->env, gsdata->stdErr, "onStdErr", STDERR_SIG, (jlong)gsdata->stdioHandle, byteArray, (jint)len);
+	if (gsdata->env->ExceptionCheck()) return 0;
+
+	return result;
 }
 
-void callbacks::setPollCallback(void *instance, jobject poll)
+void callbacks::setPollCallback(GSInstanceData *idata, jobject poll)
 {
-	GSInstanceData *gsdata = findDataFromInstance(instance);
-	assert(gsdata);
-
-	if (gsdata->env)
+	if (idata->env)
 	{
-		if (gsdata->poll)
-			gsdata->env->DeleteGlobalRef(gsdata->poll);
+		if (idata->poll)
+			idata->env->DeleteGlobalRef(idata->poll);
 
-		gsdata->poll = gsdata->env->NewGlobalRef(poll);
+		idata->poll = idata->env->NewGlobalRef(poll);
 	}
 }
 
@@ -130,7 +127,7 @@ int callbacks::pollFunction(void *callerHandle)
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(callerHandle);
+	GSInstanceData *gsdata = (GSInstanceData *)callerHandle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->poll)
@@ -140,35 +137,29 @@ int callbacks::pollFunction(void *callerHandle)
 	return code;
 }
 
-void callbacks::setDisplayCallback(void *instance, jobject displayCallback)
+void callbacks::setDisplayCallback(GSInstanceData *idata, jobject displayCallback)
 {
-	GSInstanceData *gsdata = findDataFromInstance(instance);
-	assert(gsdata);
-
-	if (gsdata->env)
+	if (idata->env)
 	{
-		if (gsdata->displayCallback)
+		if (idata->displayCallback)
 		{
-			gsdata->env->DeleteGlobalRef(gsdata->displayCallback);
-			gsdata->displayCallback = NULL;
+			idata->env->DeleteGlobalRef(idata->displayCallback);
+			idata->displayCallback = NULL;
 		}
 
-		gsdata->displayCallback = gsdata->env->NewGlobalRef(displayCallback);
+		idata->displayCallback = idata->env->NewGlobalRef(displayCallback);
 		//g_displayCallback = displayCallback;
 	}
 }
 
-void callbacks::setCalloutCallback(void *instance, jobject callout)
+void callbacks::setCalloutCallback(GSInstanceData *idata, jobject callout)
 {
-	GSInstanceData *gsdata = findDataFromInstance(instance);
-	assert(gsdata);
-
-	if (gsdata->env)
+	if (idata->env)
 	{
-		if (gsdata->callout)
-			gsdata->env->DeleteGlobalRef(gsdata->callout);
+		if (idata->callout)
+			idata->env->DeleteGlobalRef(idata->callout);
 
-		gsdata->callout = gsdata->env->NewGlobalRef(callout);
+		idata->callout = idata->env->NewGlobalRef(callout);
 	}
 }
 
@@ -193,7 +184,7 @@ int callbacks::display::displayOpenFunction(void *handle, void *device)
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -211,7 +202,7 @@ int callbacks::display::displayPrecloseFunction(void *handle, void *device)
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -226,7 +217,7 @@ int callbacks::display::displayCloseFunction(void *handle, void *device)
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -241,7 +232,7 @@ int callbacks::display::displayPresizeFunction(void *handle, void *device, int w
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -258,7 +249,7 @@ int callbacks::display::displaySizeFunction(void *handle, void *device, int widt
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -320,7 +311,7 @@ int callbacks::display::displaySyncFunction(void *handle, void *device)
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -335,7 +326,7 @@ int callbacks::display::displayPageFunction(void *handle, void *device, int copi
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -351,7 +342,7 @@ int callbacks::display::displayUpdateFunction(void *handle, void *device, int x,
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -368,7 +359,7 @@ int callbacks::display::displaySeparationFunction(void *handle, void *device, in
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -387,7 +378,7 @@ int callbacks::display::displayAdjustBandHeightFunction(void *handle, void *devi
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
@@ -404,7 +395,7 @@ int callbacks::display::displayRectangleRequestFunction(void *handle, void *devi
 {
 	int code = 0;
 
-	GSInstanceData *gsdata = findDataFromHandle(handle);
+	GSInstanceData *gsdata = (GSInstanceData *)handle;
 	assert(gsdata);
 
 	if (gsdata->env && gsdata->displayCallback)
diff --git a/demos/java/jni/gs_jni/callbacks.h b/demos/java/jni/gs_jni/callbacks.h
index f2a6bc75a..e8a23f938 100644
--- a/demos/java/jni/gs_jni/callbacks.h
+++ b/demos/java/jni/gs_jni/callbacks.h
@@ -2,6 +2,8 @@
 
 #include <jni.h>
 
+#include "instance_data.h"
+
 namespace callbacks
 {
 	/*!
@@ -10,17 +12,17 @@ namespace callbacks
 
 	@param env A JNIEnv.
 	*/
-	void setJNIEnv(void *instance, JNIEnv *env);
+	void setJNIEnv(GSInstanceData *idata, JNIEnv *env);
 
-	void setIOCallbacks(void *instance, jobject stdIn, jobject stdOut, jobject stdErr);
+	void setIOCallbacks(GSInstanceData *idata, jobject stdIn, jobject stdOut, jobject stdErr);
 	int stdInFunction(void *callerHandle, char *buf, int len);
 	int stdOutFunction(void *callerHandle, const char *str, int len);
 	int stdErrFunction(void *callerHandle, const char *str, int len);
 
-	void setPollCallback(void *instance, jobject poll);
+	void setPollCallback(GSInstanceData *idata, jobject poll);
 	int pollFunction(void *callerHandle);
 
-	void setDisplayCallback(void *instance, jobject displayCallback);
+	void setDisplayCallback(GSInstanceData *idata, jobject displayCallback);
 
 	namespace display
 	{
@@ -49,6 +51,6 @@ namespace callbacks
 			int *x, int *y, int *w, int *h);
 	}
 
-	void setCalloutCallback(void *instance, jobject calout);
+	void setCalloutCallback(GSInstanceData *idata, jobject callout);
 	int calloutFunction(void *instance, void *handle, const char *deviceName, int id, int size, void *data);
 }
\ No newline at end of file
diff --git a/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.cpp b/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.cpp
index 9830a00c7..b67c3ecb7 100644
--- a/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.cpp
+++ b/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.cpp
@@ -55,7 +55,10 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1new_1instance
 JNIEXPORT void JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1delete_1instance
 	(JNIEnv *env, jclass, jlong instance)
 {
-	callbacks::setJNIEnv((void *)instance, env);
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
+	callbacks::setJNIEnv(idata, env);
 	gsapi_delete_instance((void *)instance);
 
 	deleteDataFromInstance((void *)instance);
@@ -73,8 +76,8 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1stdio_1with_1ha
 		callbacks::stdOutFunction, callbacks::stdErrFunction, idata);
 	if (code == 0)
 	{
-		callbacks::setJNIEnv((void *)instance, env);
-		callbacks::setIOCallbacks((void *)instance, stdIn, stdOut, stdErr);
+		callbacks::setJNIEnv(idata, env);
+		callbacks::setIOCallbacks(idata, stdIn, stdOut, stdErr);
 	}
 	return code;
 }
@@ -91,8 +94,8 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1stdio
 		callbacks::stdOutFunction, callbacks::stdErrFunction, idata);
 	if (code == 0)
 	{
-		callbacks::setJNIEnv((void *)instance, env);
-		callbacks::setIOCallbacks((void *)instance, stdIn, stdOut, stdErr);
+		callbacks::setJNIEnv(idata, env);
+		callbacks::setIOCallbacks(idata, stdIn, stdOut, stdErr);
 	}
 	return code;
 }
@@ -100,11 +103,14 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1stdio
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1poll_1with_1handle
 	(JNIEnv *env, jclass, jlong instance, jobject poll, jlong callerHandle)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	int code = gsapi_set_poll_with_handle((void *)instance, callbacks::pollFunction, (void *)callerHandle);
 	if (code == 0)
 	{
-		callbacks::setJNIEnv((void *)instance, env);
-		callbacks::setPollCallback((void *)instance, poll);
+		callbacks::setJNIEnv(idata, env);
+		callbacks::setPollCallback(idata, poll);
 	}
 	return code;
 }
@@ -112,11 +118,14 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1poll_1with_1han
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1poll
 	(JNIEnv *env, jclass, jlong instance, jobject poll)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	int code = gsapi_set_poll((void *)instance, callbacks::pollFunction);
 	if (code == 0)
 	{
-		callbacks::setJNIEnv((void *)instance, env);
-		callbacks::setPollCallback((void *)instance, poll);
+		callbacks::setJNIEnv(idata, env);
+		callbacks::setPollCallback(idata, poll);
 	}
 	return code;
 }
@@ -124,6 +133,9 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1poll
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1display_1callback
 	(JNIEnv *env, jclass, jlong instance, jobject displayCallback)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	display_callback *cb = new display_callback;
 	cb->size = sizeof(display_callback);
 	cb->version_major = DISPLAY_VERSION_MAJOR;
@@ -146,8 +158,8 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1display_1callba
 	int code = gsapi_set_display_callback((void *)instance, cb);
 	if (code == 0)
 	{
-		callbacks::setJNIEnv((void *)instance, env);
-		callbacks::setDisplayCallback((void *)instance, displayCallback);
+		callbacks::setJNIEnv(idata, env);
+		callbacks::setDisplayCallback(idata, displayCallback);
 	}
 	return code;
 }
@@ -155,11 +167,14 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1display_1callba
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1register_1callout
 	(JNIEnv *env, jclass, jlong instance, jobject callout, jlong calloutHandle)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	int code = gsapi_register_callout((void *)instance, callbacks::calloutFunction, (void *)calloutHandle);
 	if (code == 0)
 	{
-		callbacks::setJNIEnv((void *)instance, env);
-		callbacks::setCalloutCallback((void *)instance, callout);
+		callbacks::setJNIEnv(idata, env);
+		callbacks::setCalloutCallback(idata, callout);
 	}
 	return code;
 }
@@ -179,10 +194,14 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1arg_1encoding
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1default_1device_1list
 	(JNIEnv *env, jclass, jlong instance, jbyteArray list, jint listlen)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (list == NULL)
 		return throwNullPointerException(env, "list");
+
 	jboolean isCopy = false;
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_set_default_device_list((void *)instance,
 		(const char *)env->GetByteArrayElements(list, &isCopy), listlen);
 	return code;
@@ -212,10 +231,14 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1get_1default_1device
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1init_1with_1args
 	(JNIEnv *env, jclass, jlong instance, jint argc, jobjectArray argv)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (argv == NULL)
 		return throwNullPointerException(env, "argv");
+
 	char **cargv = jbyteArray2DToCharArray(env, argv);
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_init_with_args((void *)instance, argc, cargv);
 	delete2DByteArray(argc, cargv);
 	return code;
@@ -224,8 +247,11 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1init_1with_1args
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1begin
 	(JNIEnv *env, jclass, jlong instance, jint userErrors, jobject pExitCode)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	int exitCode;
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_run_string_begin((void *)instance, userErrors, &exitCode);
 	if (pExitCode)
 		Reference::setValueField(env, pExitCode, toWrapperType(env, (jint)exitCode));
@@ -235,12 +261,16 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1begin
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1continue
 	(JNIEnv *env, jclass, jlong instance, jbyteArray str, jint length, jint userErrors, jobject pExitCode)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (str == NULL)
 		return throwNullPointerException(env, "str");
+
 	jboolean copy = false;
 	int exitCode;
 	const char *cstring = (const char *)env->GetByteArrayElements(str, &copy);
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_run_string_continue((void *)instance, cstring, length, userErrors, &exitCode);
 	if (pExitCode)
 		Reference::setValueField(env, pExitCode, toWrapperType(env, (jint)exitCode));
@@ -250,8 +280,11 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1continu
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1end
 	(JNIEnv *env, jclass, jlong instance, jint userErrors, jobject pExitCode)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	int exitCode;
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_run_string_end((void *)instance, userErrors, &exitCode);
 	if (pExitCode)
 		Reference::setValueField(env, pExitCode, toWrapperType(env, (jint)exitCode));
@@ -261,12 +294,16 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1end
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1with_1length
 	(JNIEnv *env, jclass, jlong instance, jbyteArray str, jint length, jint userErrors, jobject pExitCode)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (str == NULL)
 		return throwNullPointerException(env, "str");
+
 	jboolean copy = false;
 	int exitCode;
 	const char *cstring = (const char *)env->GetByteArrayElements(str, &copy);
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_run_string_with_length((void *)instance, cstring, length, userErrors, &exitCode);
 	if (pExitCode)
 		Reference::setValueField(env, pExitCode, toWrapperType(env, (jint)exitCode));
@@ -276,12 +313,16 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string_1with_1l
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string
 	(JNIEnv *env, jclass, jlong instance, jbyteArray str, jint userErrors, jobject pExitCode)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (str == NULL)
 		return throwNullPointerException(env, "str");
+
 	jboolean copy = false;
 	int exitCode;
 	const char *cstring = (const char *)env->GetByteArrayElements(str, &copy);
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_run_string((void *)instance, cstring, userErrors, &exitCode);
 	if (pExitCode)
 		Reference::setValueField(env, pExitCode, toWrapperType(env, (jint)exitCode));
@@ -291,12 +332,16 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1string
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1run_1file
 	(JNIEnv *env, jclass, jlong instance, jbyteArray fileName, jint userErrors, jobject pExitCode)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (fileName == NULL)
 		return throwNullPointerException(env, "fileName");
+
 	jboolean copy = false;
 	int exitCode;
 	const char *cstring = (const char *)env->GetByteArrayElements(fileName, &copy);
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_run_file((void *)instance, cstring, userErrors, &exitCode);
 	if (pExitCode)
 		Reference::setValueField(env, pExitCode, toWrapperType(env, (jint)exitCode));
@@ -312,11 +357,11 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1exit
 JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1param
 	(JNIEnv *env, jclass, jlong instance, jbyteArray param, jobject value, jint paramType)
 {
+	GSInstanceData *idata = findDataFromInstance((void *)instance);
+	assert(idata);
+
 	if (!param)
-	{
-		throwNullPointerException(env, "param");
-		return -1;
-	}
+		return throwNullPointerException(env, "param");
 
 	gs_set_param_type type = (gs_set_param_type)paramType;
 	bool paramSuccess;
@@ -330,7 +375,7 @@ JNIEXPORT jint JNICALL Java_com_artifex_gsjava_GSAPI_gsapi_1set_1param
 	jboolean copy = false;
 	const char *cstring = (const char *)env->GetByteArrayElements(param, &copy);
 
-	callbacks::setJNIEnv((void *)instance, env);
+	callbacks::setJNIEnv(idata, env);
 	int code = gsapi_set_param((void *)instance, cstring, data, type);
 	free(data);
 
diff --git a/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.h b/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.h
index 68c61e581..fd7e303aa 100644
--- a/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.h
+++ b/demos/java/jni/gs_jni/com_artifex_gsjava_GSAPI.h
@@ -2,6 +2,8 @@
 #include <jni.h>
 /* Header for class com_artifex_gsjava_GSAPI */
 
+#include "settings.h"
+
 #ifndef _Included_com_artifex_gsjava_GSAPI
 #define _Included_com_artifex_gsjava_GSAPI
 #ifdef __cplusplus
diff --git a/demos/java/jni/gs_jni/com_artifex_gsjava_util_NativePointer.h b/demos/java/jni/gs_jni/com_artifex_gsjava_util_NativePointer.h
index 8dd6a30b2..6c053df8d 100644
--- a/demos/java/jni/gs_jni/com_artifex_gsjava_util_NativePointer.h
+++ b/demos/java/jni/gs_jni/com_artifex_gsjava_util_NativePointer.h
@@ -2,6 +2,8 @@
 #include <jni.h>
 /* Header for class com_artifex_gsjava_util_NativePointer */
 
+#include "settings.h"
+
 #ifndef _Included_com_artifex_gsjava_util_NativePointer
 #define _Included_com_artifex_gsjava_util_NativePointer
 #ifdef __cplusplus
diff --git a/demos/java/jni/gs_jni/gs_jni.vcxproj b/demos/java/jni/gs_jni/gs_jni.vcxproj
index 201a59966..56f03d0ab 100644
--- a/demos/java/jni/gs_jni/gs_jni.vcxproj
+++ b/demos/java/jni/gs_jni/gs_jni.vcxproj
@@ -172,6 +172,7 @@
     <ClInclude Include="framework.h" />
     <ClInclude Include="instance_data.h" />
     <ClInclude Include="jni_util.h" />
+    <ClInclude Include="settings.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="callbacks.cpp" />
diff --git a/demos/java/jni/gs_jni/gs_jni.vcxproj.filters b/demos/java/jni/gs_jni/gs_jni.vcxproj.filters
index c69db33f9..ce1781b7a 100644
--- a/demos/java/jni/gs_jni/gs_jni.vcxproj.filters
+++ b/demos/java/jni/gs_jni/gs_jni.vcxproj.filters
@@ -33,6 +33,9 @@
     <ClInclude Include="instance_data.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="settings.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="dllmain.cpp">
diff --git a/demos/java/jni/gs_jni/instance_data.cpp b/demos/java/jni/gs_jni/instance_data.cpp
index 7543afdc6..8c9d1a05f 100644
--- a/demos/java/jni/gs_jni/instance_data.cpp
+++ b/demos/java/jni/gs_jni/instance_data.cpp
@@ -1,25 +1,30 @@
 #include "instance_data.h"
 
 #include <unordered_map>
-
 #include <assert.h>
-
-static GSInstanceData g_global; // Global instance for faster multithreading
+#include <mutex>
 
 #if defined(ALLOW_MT)
 
 static std::unordered_map<void *, GSInstanceData *> g_inst2Data; // instance -> data
-static std::unordered_map<void *, GSInstanceData *> g_hand2Data; // caller handle -> data
+static std::mutex g_mtx;
+
+#else
+
+static GSInstanceData g_global; // Global instance for faster multithreading
 
 #endif
 
 GSInstanceData *putInstanceData(GSInstanceData *data)
 {
 #if defined(ALLOW_MT)
-	assert(g_inst2Data.find(data->instance) == g_inst2Data.end() && g_hand2Data.find(data->callerHandle) == g_hand2Data.end());
+	g_mtx.lock();
+
+	assert(g_inst2Data.find(data->instance) == g_inst2Data.end());
 
 	g_inst2Data[data->instance] = data;
-	g_hand2Data[data->callerHandle] = data;
+
+	g_mtx.unlock();
 
 	return data;
 
@@ -32,18 +37,14 @@ GSInstanceData *putInstanceData(GSInstanceData *data)
 GSInstanceData *findDataFromInstance(void *instance)
 {
 #if defined(ALLOW_MT)
+	g_mtx.lock();
+
 	auto it = g_inst2Data.find(instance);
-	return it == g_inst2Data.end() ? NULL : it->second;
-#else
-	return &g_global;
-#endif
-}
+	GSInstanceData *result = it == g_inst2Data.end() ? NULL : it->second;
 
-GSInstanceData *findDataFromHandle(void *callerHandle)
-{
-#if defined(ALLOW_MT)
-	auto it = g_hand2Data.find(callerHandle);
-	return it == g_hand2Data.end() ? NULL : it->second;
+	g_mtx.unlock();
+
+	return result;
 #else
 	return &g_global;
 #endif
@@ -52,33 +53,12 @@ GSInstanceData *findDataFromHandle(void *callerHandle)
 void deleteDataFromInstance(void *instance)
 {
 #if defined(ALLOW_MT)
+	g_mtx.lock();
+
 	auto i2dit = g_inst2Data.find(instance);
 	if (i2dit != g_inst2Data.end())
-	{
-		GSInstanceData *idata = i2dit->second;
-		auto h2dit = g_hand2Data.find(idata->callerHandle);
-
-		assert(h2dit != g_hand2Data.end());
-
 		g_inst2Data.erase(i2dit);
-		g_hand2Data.erase(h2dit);
-	}
-#endif
-}
-
-void deleteDataFromHandle(void *callerHandle)
-{
-#if defined(ALLOW_MT)
-	auto h2dit = g_hand2Data.find(callerHandle);
-	if (h2dit != g_hand2Data.end())
-	{
-		GSInstanceData *idata = h2dit->second;
-		auto i2dit = g_inst2Data.find(idata->instance);
-
-		assert(i2dit != g_inst2Data.end());
 
-		g_hand2Data.erase(i2dit);
-		g_inst2Data.erase(h2dit);
-	}
+	g_mtx.unlock();
 #endif
-}
+}
\ No newline at end of file
diff --git a/demos/java/jni/gs_jni/instance_data.h b/demos/java/jni/gs_jni/instance_data.h
index 4274dbe24..22770daf4 100644
--- a/demos/java/jni/gs_jni/instance_data.h
+++ b/demos/java/jni/gs_jni/instance_data.h
@@ -2,6 +2,8 @@
 
 #include <jni.h>
 
+#include "settings.h"
+
 class GSInstanceData
 {
 public:
@@ -24,6 +26,4 @@ public:
 
 GSInstanceData *putInstanceData(GSInstanceData *data);
 GSInstanceData *findDataFromInstance(void *instance);
-GSInstanceData *findDataFromHandle(void *callerHandle);
-void deleteDataFromInstance(void *instance);
-void deleteDataFromHandle(void *callerHandle);
\ No newline at end of file
+void deleteDataFromInstance(void *instance);
\ No newline at end of file
diff --git a/demos/java/jni/gs_jni/jni_util.cpp b/demos/java/jni/gs_jni/jni_util.cpp
index 74852a95e..dfb570a8b 100644
--- a/demos/java/jni/gs_jni/jni_util.cpp
+++ b/demos/java/jni/gs_jni/jni_util.cpp
@@ -145,14 +145,14 @@ jint util::getIntField(JNIEnv *env, jobject object, const char *field)
     return env->GetIntField(object, fieldID);
 }
 
-int util::callIntMethod(JNIEnv *env, jobject object, const char *method, const char *sig, ...)
+jint util::callIntMethod(JNIEnv *env, jobject object, const char *method, const char *sig, ...)
 {
     jmethodID methodID = getMethodID(env, object, method, sig);
     if (methodID == NULL)
         return 0;
 
     va_list args;
-    int result;
+    jint result;
     va_start(args, sig);
     result = env->CallIntMethodV(object, methodID, args);
     va_end(args);
diff --git a/demos/java/jni/gs_jni/jni_util.h b/demos/java/jni/gs_jni/jni_util.h
index 6439712e9..2ea20fd47 100644
--- a/demos/java/jni/gs_jni/jni_util.h
+++ b/demos/java/jni/gs_jni/jni_util.h
@@ -2,6 +2,8 @@
 
 #include <jni.h>
 
+#include "settings.h"
+
 #define REFERENCE_VALUE_FILED_NAME "value"
 
 namespace util
@@ -141,7 +143,7 @@ namespace util
 	@param sig The method's signature.
 	@param ... The varargs representing the object's arguments in their respective order.
 	*/
-	int callIntMethod(JNIEnv *env, jobject object, const char *name, const char *sig, ...);
+	jint callIntMethod(JNIEnv *env, jobject object, const char *name, const char *sig, ...);
 
 	void setObjectField(JNIEnv *env, jobject object, const char *field, jobject value);
 
diff --git a/demos/java/mtdemo/Main.java b/demos/java/mtdemo/Main.java
index cdc3c9a01..bd3ef2f54 100644
--- a/demos/java/mtdemo/Main.java
+++ b/demos/java/mtdemo/Main.java
@@ -1,9 +1,11 @@
 import com.artifex.gsjava.GSInstance;
 
-import java.util.Scanner;
+import java.io.File;
 
 public class Main {
 
+	public static final String INFILE = "../../../examples/tiger.eps";
+
 	public static void main(String[] args) {
 		GSInstance.setAllowMultithreading(true);
 
@@ -14,19 +16,15 @@ public class Main {
 			} catch (NumberFormatException e) { }
 		}
 
-		//Scanner in = new Scanner(System.in);
-		//in.nextLine();
-
 		Worker[] workers = new Worker[workerCount];
 
 		for (int i = 0; i < workers.length; i++) {
-			workers[i] = new Worker("../../../examples/tiger.eps", "pdfout/out" + i + ".pdf");
+			workers[i] = new Worker(INFILE, "pdfout/out" + i + ".pdf");
 		}
 
 		System.out.println("Starting workers...");
 		for (int i = 0; i < workers.length; i++) {
 			workers[i].start();
 		}
-		System.out.println("Workers dispatched");
 	}
 }
\ No newline at end of file
diff --git a/demos/java/mtdemo/README.txt b/demos/java/mtdemo/README.txt
new file mode 100644
index 000000000..661a10e66
--- /dev/null
+++ b/demos/java/mtdemo/README.txt
@@ -0,0 +1,32 @@
+This directory contains files which demo multithreading in Ghostscript
+using the Java Language Bindings. The application here simply reads in
+the same EPS file and outputs it to multiple PDF files on different
+threads.
+
+What is here?
+
+* Main.java - Class containing Java main method
+* Worker.java - Class which handles concurrently running Ghostscript
+* build.bat - Builds the Java program
+
+Needed in this directory to run:
+
+* gpdldll64.dll (COMPILED FOR MULTITHREADING - use DGS_THREADSAFE)
+* gs_jni.dll
+* gsjava.jar
+
+How to run:
+
+Windows:
+
+The application can be started through the command line through the
+command:
+
+java -cp gsjava.jar;. Main
+
+OR
+
+java -cp gsjava.jar;. Main [thread count]
+
+where [thread count] is the number of threads (and files) which will
+be ran/written.
\ No newline at end of file
diff --git a/demos/java/mtdemo/Worker.java b/demos/java/mtdemo/Worker.java
index 2b7b960bd..3da333fd0 100644
--- a/demos/java/mtdemo/Worker.java
+++ b/demos/java/mtdemo/Worker.java
@@ -7,10 +7,13 @@ import com.artifex.gsjava.callbacks.*;
 
 import java.io.IOException;
 
+import java.util.Arrays;
+
 import static com.artifex.gsjava.GSAPI.*;
 
 public class Worker implements Runnable {
 
+	public static final boolean USE_CUSTOM_STDIO = true;
 	public static final boolean USE_STDOUT = false;
 
 	private static int ID = 0;
@@ -45,20 +48,19 @@ public class Worker implements Runnable {
 		try {
 			gsInstance = createGSInstance();
 
-			//StdIO io = new StdIO();
-			//gsInstance.set_stdio(io, null, null);
+			if (USE_CUSTOM_STDIO) {
+				StdIO io = new StdIO();
+				gsInstance.set_stdio(io, USE_STDOUT ? io : null, io);
+			}
 
 			if (!outPDF.exists())
 				outPDF.createNewFile();
 
-			final int FORMAT = GS_COLORS_RGB | GS_DISPLAY_DEPTH_8 | GS_DISPLAY_BIGENDIAN;
 			String[] args = {
 				"gs",
 				"-sDEVICE=pdfwrite",
-				//"dFirstPage=1",
-				//"dDisplayFormat=" + FORMAT,
-				"-o", outPDF.getAbsolutePath(),
-				"-f", inPS.getAbsolutePath()
+				"-o", outPDF.getPath(),
+				inPS.getPath()
 			};
 
 			int code = gsInstance.init_with_args(args);
diff --git a/demos/java/mtdemo/runmtd.bat b/demos/java/mtdemo/runmtd.bat
new file mode 100644
index 000000000..f23ce990d
--- /dev/null
+++ b/demos/java/mtdemo/runmtd.bat
@@ -0,0 +1,3 @@
+@echo off
+
+java -cp gsjava.jar;. Main %1
\ No newline at end of file