Fix #2398 (TokenBuffer.copyCurrentStructure() recursion -> iteration)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -16,6 +16,7 @@ Project: jackson-databind
  (reported by andreasbaus@github)
 #2393: `TreeTraversingParser.getLongValue()` incorrectly checks `canConvertToInt()`
  (reported by RabbidDog@github)
+#2398: Replace recursion in `TokenBuffer.copyCurrentStructure()` with iteration
 #2415: Builder-based POJO deserializer should pass builder instance, not type,
   to `handleUnknownVanilla()`
  (proposed by Vladimir T, follow up to #822)

src/main/java/com/fasterxml/jackson/databind/util/TokenBuffer.java

@@ -1103,37 +1103,142 @@ public void copyCurrentStructure(JsonParser p) throws IOException
             throw new IllegalStateException("No token available from argument `JsonParser`");
         }
 
-        if (_mayHaveNativeIds) {
-            _checkNativeIds(p);
-        }
-        
+        // We'll do minor handling here to separate structured, scalar values,
+        // then delegate appropriately
         switch (t) {
         case START_ARRAY:
-            writeStartArray();
-            while (p.nextToken() != JsonToken.END_ARRAY) {
-                copyCurrentStructure(p);
+            if (_mayHaveNativeIds) {
+                _checkNativeIds(p);
             }
-            writeEndArray();
+            writeStartArray();
+            _copyContents(p);
             break;
         case START_OBJECT:
-            writeStartObject();
-            while (p.nextToken() != JsonToken.END_OBJECT) {
-                copyCurrentStructure(p);
+            if (_mayHaveNativeIds) {
+                _checkNativeIds(p);
             }
-            writeEndObject();
+            writeStartObject();
+            _copyContents(p);
             break;
         default: // others are simple:
-            copyCurrentEvent(p);
+            _copyCurrentValue(p, t);
         }
     }
 
+    private final void _copyContents(JsonParser p) throws IOException
+    {
+        int depth = 1;
+        JsonToken t;
+
+        while ((t = p.nextToken()) != null) {
+            switch (t) {
+            case FIELD_NAME:
+                if (_mayHaveNativeIds) {
+                    _checkNativeIds(p);
+                }
+                writeFieldName(p.getCurrentName());
+                break;
+
+            case START_ARRAY:
+                if (_mayHaveNativeIds) {
+                    _checkNativeIds(p);
+                }
+                writeStartArray();
+                ++depth;
+                break;
+
+            case START_OBJECT:
+                if (_mayHaveNativeIds) {
+                    _checkNativeIds(p);
+                }
+                writeStartObject();
+                ++depth;
+                break;
+
+            case END_ARRAY:
+                if (--depth == 0) {
+                    return;
+                }
+                writeEndArray();
+                break;
+            case END_OBJECT:
+                if (--depth == 0) {
+                    return;
+                }
+                writeEndObject();
+                break;
+
+            default:
+                _copyCurrentValue(p, t);
+            }
+        }
+    }
+
+    // NOTE: Copied from earlier `copyCurrentEvent()`
+    private void _copyCurrentValue(JsonParser p, JsonToken t) throws IOException
+    {
+        if (_mayHaveNativeIds) {
+            _checkNativeIds(p);
+        }
+        switch (t) {
+        case VALUE_STRING:
+            if (p.hasTextCharacters()) {
+                writeString(p.getTextCharacters(), p.getTextOffset(), p.getTextLength());
+            } else {
+                writeString(p.getText());
+            }
+            break;
+        case VALUE_NUMBER_INT:
+            switch (p.getNumberType()) {
+            case INT:
+                writeNumber(p.getIntValue());
+                break;
+            case BIG_INTEGER:
+                writeNumber(p.getBigIntegerValue());
+                break;
+            default:
+                writeNumber(p.getLongValue());
+            }
+            break;
+        case VALUE_NUMBER_FLOAT:
+            if (_forceBigDecimal) {
+                writeNumber(p.getDecimalValue());
+            } else {
+                switch (p.getNumberType()) {
+                case BIG_DECIMAL:
+                    writeNumber(p.getDecimalValue());
+                    break;
+                case FLOAT:
+                    writeNumber(p.getFloatValue());
+                    break;
+                default:
+                    writeNumber(p.getDoubleValue());
+                }
+            }
+            break;
+        case VALUE_TRUE:
+            writeBoolean(true);
+            break;
+        case VALUE_FALSE:
+            writeBoolean(false);
+            break;
+        case VALUE_NULL:
+            writeNull();
+            break;
+        case VALUE_EMBEDDED_OBJECT:
+            writeObject(p.getEmbeddedObject());
+            break;
+        default:
+            throw new RuntimeException("Internal error: should never end up through this code path");
+        }
+    }
 
-    private final void _checkNativeIds(JsonParser jp) throws IOException
+    private final void _checkNativeIds(JsonParser p) throws IOException
     {
-        if ((_typeId = jp.getTypeId()) != null) {
+        if ((_typeId = p.getTypeId()) != null) {
             _hasNativeId = true;
         }
-        if ((_objectId = jp.getObjectId()) != null) {
+        if ((_objectId = p.getObjectId()) != null) {
             _hasNativeId = true;
         }
     }

src/test/java/com/fasterxml/jackson/failing/TokenBufferRecursion2398Test.java

@@ -8,8 +8,8 @@ public class TokenBufferRecursion2398Test extends BaseMapTest
 {
     private final ObjectMapper MAPPER = sharedMapper();
 
-    // 10k does it, 5k not
-    private final static int RECURSION = 9999;
+    // 10k does it, 5k not, but use bit higher values just in case
+    private final static int RECURSION = 25000;
 
     public void testDeeplyNestedArrays() throws Exception
     {