Force libwpd backend to NOT run open or close session opcodes

Kind of unfortunate, but Windows already has the session open,
and freaks out with obscure errors if you try and open a new session.
So, the libwpd backend will simply give a fake response for these opcodes.

src/libwpd.c

@@ -13,13 +13,17 @@
 
 int ptp_comm_init(struct PtpRuntime *r) {
 	ptp_reset(r);
-	wpd_init(WPD_VERBOSE, L"Camlib WPD");
-
-	r->comm_backend = malloc(sizeof(struct WpdStruct));
 
 	// We are not using low-level I/O operations, so this is never used
 	r->max_packet_size = 512;
 
+	// in libwpd, this will only coinitalize the new thread. Orig thread may be dead.
+	wpd_init(WPD_VERBOSE, L"Camlib WPD");
+
+	if (r->comm_backend != NULL) return 0;
+
+	r->comm_backend = malloc(sizeof(struct WpdStruct));
+
 	return 0;	
 }
 
@@ -76,6 +80,10 @@ int ptp_send_bulk_packets(struct PtpRuntime *r, int length) {
 	struct LibWPDPtpCommand cmd;
 	struct PtpBulkContainer *bulk = (struct PtpBulkContainer*)(r->data);
 
+	if (bulk->code == PTP_OC_OpenSession || bulk->code == PTP_OC_CloseSession) {
+		return length;
+	}
+
 	if (bulk->type == PTP_PACKET_TYPE_COMMAND) {
 		cmd.code = bulk->code;
 		cmd.param_length = ptp_get_param_length(r);
@@ -131,33 +139,38 @@ int ptp_receive_bulk_packets(struct PtpRuntime *r) {
 	struct WpdStruct *wpd = (struct WpdStruct *)(r->comm_backend);
 	if (wpd == NULL) return PTP_IO_ERR;
 
+	// WPD doesn't let you send session opcodes
 	struct PtpBulkContainer *bulk = (struct PtpBulkContainer*)(r->data);
-	if (bulk->type == PTP_PACKET_TYPE_COMMAND) {
-		struct LibWPDPtpCommand cmd;
-		int b = wpd_receive_do_data(wpd, &cmd, (uint8_t *)(r->data + 12), r->data_length - 12);
-		if (b < 0) {
-			return PTP_IO_ERR;
-		}
-
-		if (b == 0) {
-			bulk->length = 12;
-			bulk->type = PTP_PACKET_TYPE_RESPONSE;
-			bulk->code = cmd.code;
-			bulk->transaction = r->transaction + 1;
-		} else {
-			bulk->length = 12 + b;
-			bulk->type = PTP_PACKET_TYPE_DATA;
-			bulk->code = cmd.code;
-			bulk->transaction = r->transaction + 1;
+	if (bulk->code == PTP_OC_OpenSession || bulk->code == PTP_OC_CloseSession) {
+		bulk->length = 12;
+		bulk->code = PTP_RC_OK;
+		bulk->type = PTP_PACKET_TYPE_RESPONSE;
+		memset(bulk->params, 5 * sizeof(uint32_t), 0);
+		return 12;
+	}
 
-			struct PtpBulkContainer *resp = (struct PtpBulkContainer*)(r->data + 12 + b);
-			resp->length = 12;
-			resp->type = PTP_PACKET_TYPE_RESPONSE;
-			resp->code = cmd.code;
-			resp->transaction = r->transaction + 1;
-		}
+	struct LibWPDPtpCommand cmd;
+	int b = wpd_receive_do_data(wpd, &cmd, (uint8_t *)(r->data + 12), r->data_length - 12);
+	if (b < 0) {
+		return PTP_IO_ERR;
+	}
+
+	if (b == 0) {
+		bulk->length = 12;
+		bulk->type = PTP_PACKET_TYPE_RESPONSE;
+		bulk->code = cmd.code;
+		bulk->transaction = r->transaction + 1;
 	} else {
-		// I remember doing this for a reason, need to figure out why
+		bulk->length = 12 + b;
+		bulk->type = PTP_PACKET_TYPE_DATA;
+		bulk->code = cmd.code;
+		bulk->transaction = r->transaction + 1;
+
+		struct PtpBulkContainer *resp = (struct PtpBulkContainer*)(r->data + 12 + b);
+		resp->length = 12;
+		resp->type = PTP_PACKET_TYPE_RESPONSE;
+		resp->code = cmd.code;
+		resp->transaction = r->transaction + 1;
 	}
 
 	return 0;