From 30b1a77b6184fcee48c233a667e49380b0dfdb87 Mon Sep 17 00:00:00 2001
From: Rudi <rudi@nmare.net>
Date: Wed, 16 Sep 2026 21:08:22 +0000
Subject: [PATCH] Datastream bug fixes w/ not recognizing bytes

---
 .../datastream/DataStreamProcessor.java       |  2 +
 .../datastream/DataStreamProcessorTest.java   | 73 +++++++++++++++++++
 2 files changed, 75 insertions(+)

diff --git a/lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/DataStreamProcessor.java b/lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/DataStreamProcessor.java
index dcf28db..d25a790 100644
--- a/lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/DataStreamProcessor.java
+++ b/lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/DataStreamProcessor.java
@@ -548,6 +548,8 @@ public class DataStreamProcessor {
                             applyExtendedAttribute(ea, attrType, attrValue);
                         }
                     }
+                    baddr = (baddr + 1) % size;
+                    screen.setBufferAddress(baddr);
                     pos += 2 + nPairs * 2;
                     lastWasOrder = true;
                     break;
diff --git a/lib3270j/src/test/java/haus/nightmare/lib3270j/datastream/DataStreamProcessorTest.java b/lib3270j/src/test/java/haus/nightmare/lib3270j/datastream/DataStreamProcessorTest.java
index 7482ccb..9b8da4d 100644
--- a/lib3270j/src/test/java/haus/nightmare/lib3270j/datastream/DataStreamProcessorTest.java
+++ b/lib3270j/src/test/java/haus/nightmare/lib3270j/datastream/DataStreamProcessorTest.java
@@ -198,4 +198,77 @@ public class DataStreamProcessorTest {
         processor.processRecord(ewStream.toByteArray(), 0, ewStream.size(), true);
         assertEquals((byte) 0, screen.getCell(0).fg);
     }
+
+    @Test
+    public void testModifyFieldAdvancesBufferAddressAndPreservesFieldAttributes() throws java.io.IOException {
+        // Step 1: Initialize screen with an Erase/Write defining two fields
+        java.io.ByteArrayOutputStream initStream = new java.io.ByteArrayOutputStream();
+        initStream.write(CMD_EW);
+        initStream.write(0xC3);
+        // Field 1 at pos 0: SFE with FA_PRINTABLE, text "ABC"
+        initStream.write(ORDER_SBA);
+        initStream.write(0x40); initStream.write(0x40); // pos 0
+        initStream.write(ORDER_SFE);
+        initStream.write(0x01); // 1 pair
+        initStream.write(XA_3270);
+        initStream.write(FA_PRINTABLE);
+        initStream.write(translator.stringToEbcdic("ABC"));
+
+        // Field 2 at pos 10: SFE with FA_PRINTABLE, text "XYZ"
+        initStream.write(ORDER_SBA);
+        byte[] addr10 = encodeAddress(10, screen.getRows(), screen.getCols());
+        initStream.write(addr10);
+        initStream.write(ORDER_SFE);
+        initStream.write(0x01);
+        initStream.write(XA_3270);
+        initStream.write(FA_PRINTABLE);
+        initStream.write(translator.stringToEbcdic("XYZ"));
+
+        processor.processRecord(initStream.toByteArray(), 0, initStream.size(), true);
+
+        assertTrue(screen.getCell(0).isFieldAttribute());
+        assertEquals('A', screen.getCell(1).ucs4);
+        assertTrue(screen.getCell(10).isFieldAttribute());
+        assertEquals('X', screen.getCell(11).ucs4);
+
+        // Step 2: Issue a Write command that uses ORDER_MF on Field 1 and Field 2
+        java.io.ByteArrayOutputStream updateStream = new java.io.ByteArrayOutputStream();
+        updateStream.write(CMD_W);
+        updateStream.write(0xC1);
+        // SBA to pos 0
+        updateStream.write(ORDER_SBA);
+        updateStream.write(0x40); updateStream.write(0x40);
+        // MF on pos 0: set foreground to green (0xF4)
+        updateStream.write(ORDER_MF);
+        updateStream.write(0x01); // 1 pair
+        updateStream.write(XA_FOREGROUND);
+        updateStream.write(0xF4);
+        // Data "123" following MF directly
+        updateStream.write(translator.stringToEbcdic("123"));
+
+        // MF on pos 10
+        updateStream.write(ORDER_SBA);
+        updateStream.write(addr10);
+        updateStream.write(ORDER_MF);
+        updateStream.write(0x01);
+        updateStream.write(XA_FOREGROUND);
+        updateStream.write(0xF5); // turquoise
+        updateStream.write(translator.stringToEbcdic("789"));
+
+        processor.processRecord(updateStream.toByteArray(), 0, updateStream.size(), false);
+
+        // Verify Field 1: pos 0 MUST still be a field attribute, NOT overwritten by '1'
+        assertTrue(screen.getCell(0).isFieldAttribute(), "Position 0 must remain a field attribute");
+        assertEquals((byte) 0xF4, screen.getCell(0).fg, "Position 0 field attribute must have updated fg");
+        assertEquals('1', screen.getCell(1).ucs4, "Data must start at pos 1, not overwrite pos 0");
+        assertEquals('2', screen.getCell(2).ucs4);
+        assertEquals('3', screen.getCell(3).ucs4);
+
+        // Verify Field 2: pos 10 MUST still be a field attribute, NOT overwritten by '7'
+        assertTrue(screen.getCell(10).isFieldAttribute(), "Position 10 must remain a field attribute");
+        assertEquals((byte) 0xF5, screen.getCell(10).fg, "Position 10 field attribute must have updated fg");
+        assertEquals('7', screen.getCell(11).ucs4, "Data must start at pos 11, not overwrite pos 10");
+        assertEquals('8', screen.getCell(12).ucs4);
+        assertEquals('9', screen.getCell(13).ucs4);
+    }
 }