Fix compressed id overlap in legacy block item rewriter

Fixes an edge case in ViaRewind where different data ints with the same item id are compressing to the same data int; (383 << 4) | (68 & 15) = 6132 (383 << 4) | (100 & 15) = 6132
ViaVersion · Aug 20, 2024 · 2f6c325 · 2f6c325
1 parent 0b3a792
commit 2f6c325
Showing 1 changed file with 13 additions and 8 deletions.
diff --git a/common/src/main/java/com/viaversion/viabackwards/api/rewriters/LegacyBlockItemRewriter.java b/common/src/main/java/com/viaversion/viabackwards/api/rewriters/LegacyBlockItemRewriter.java
@@ -103,9 +103,9 @@ private void addMapping(String key, JsonObject object, MappedLegacyBlockItem.Typ
                 // Include data
                 short unmappedData = Short.parseShort(key.substring(dataSeparatorIndex + 1));
                 unmappedId = Integer.parseInt(key.substring(0, dataSeparatorIndex));
-                unmappedId = IdAndData.toRawData(unmappedId, unmappedData);
+                unmappedId = compress(unmappedId, unmappedData);
             } else {
-                unmappedId = IdAndData.toRawData(Integer.parseInt(key), -1);
+                unmappedId = compress(Integer.parseInt(key), -1);
             }
 
             mappings.put(unmappedId, new MappedLegacyBlockItem(id, data, name, type));
@@ -120,12 +120,12 @@ private void addMapping(String key, JsonObject object, MappedLegacyBlockItem.Typ
         // Special block color handling
         if (name != null && name.contains("%color%")) {
             for (int i = from; i <= to; i++) {
-                mappings.put(IdAndData.toRawData(i, -1), new MappedLegacyBlockItem(id, data, name.replace("%color%", BlockColors1_11_1.get(i - from)), type));
+                mappings.put(compress(i, -1), new MappedLegacyBlockItem(id, data, name.replace("%color%", BlockColors1_11_1.get(i - from)), type));
             }
         } else {
             MappedLegacyBlockItem mappedBlockItem = new MappedLegacyBlockItem(id, data, name, type);
             for (int i = from; i <= to; i++) {
-                mappings.put(IdAndData.toRawData(i, -1), mappedBlockItem);
+                mappings.put(compress(i, -1), mappedBlockItem);
             }
         }
     }
@@ -360,13 +360,13 @@ protected CompoundTag getNamedTag(String text) {
     }
 
     private @Nullable MappedLegacyBlockItem getMappedBlock(int id, int data) {
-        MappedLegacyBlockItem mapping = blockReplacements.get(IdAndData.toRawData(id, data));
-        return mapping != null ? mapping : blockReplacements.get(IdAndData.toRawData(id, -1));
+        MappedLegacyBlockItem mapping = blockReplacements.get(compress(id, data));
+        return mapping != null ? mapping : blockReplacements.get(compress(id, -1));
     }
 
     private @Nullable MappedLegacyBlockItem getMappedItem(int id, int data) {
-        MappedLegacyBlockItem mapping = itemReplacements.get(IdAndData.toRawData(id, data));
-        return mapping != null ? mapping : itemReplacements.get(IdAndData.toRawData(id, -1));
+        MappedLegacyBlockItem mapping = itemReplacements.get(compress(id, data));
+        return mapping != null ? mapping : itemReplacements.get(compress(id, -1));
     }
 
     private @Nullable MappedLegacyBlockItem getMappedBlock(int rawId) {
@@ -379,6 +379,11 @@ protected JsonObject readMappingsFile(final String name) {
         return BackwardsMappingDataLoader.INSTANCE.loadFromDataDir(name);
     }
 
+    protected int compress(final int id, final int data) {
+        // Using IdAndData for the internal storage can cause id overlaps in edge cases and would lead to wrong data
+        return (id << 16) | (data & 0xFFFF);
+    }
+
     private record Pos(int x, short y, int z) {
 
         public Pos(int x, int y, int z) {