#45 added controller to control evaluated values for array size

Author: raydac

jbbp/src/main/java/com/igormaznitsa/jbbp/JBBPParser.java

@@ -72,6 +72,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Properties;
 
 /**
@@ -93,6 +94,15 @@ public final class JBBPParser {
    * @since 1.4.0
    */
   public static final int FLAG_NEGATIVE_EXPRESSION_RESULT_AS_ZERO = 2;
+
+  /**
+   * Default expression array size controller. It is doing nothing.
+   *
+   * @since 2.1.0
+   */
+  public static final JBBPParserExpressionArraySizeController
+      DEFAULT_EXPRESSION_ARRAY_SIZE_CONTROLLER =
+      (parser, expressionEvaluator, fieldName, arraySize) -> arraySize;
   /**
    * Empty structure array
    */
@@ -113,11 +123,17 @@ public final class JBBPParser {
    * Custom field type processor for the parser, it can be null.
    */
   private final JBBPCustomFieldTypeProcessor customFieldTypeProcessor;
+  /**
+   * Controller to get and change values calculated by expressions as size for array fields.
+   *
+   * @since 2.1.0
+   */
+  private JBBPParserExpressionArraySizeController expressionArraySizeController =
+      DEFAULT_EXPRESSION_ARRAY_SIZE_CONTROLLER;
   /**
    * The Variable contains the last parsing counter value.
    */
   private long finalStreamByteCounter;
-
   /**
    * Constructor.
    *
@@ -248,6 +264,31 @@ public static JBBPParser prepare(final String script, final int flags) {
     return JBBPParser.prepare(script, JBBPBitOrder.LSB0, flags);
   }
 
+  /**
+   * Get current registered instance of controller to check array size calculated by expression.
+   *
+   * @return current instance of array size observer, can't be null
+   * @since 2.1.0
+   */
+  public JBBPParserExpressionArraySizeController getExpressionArraySizeController() {
+    return this.expressionArraySizeController;
+  }
+
+  /**
+   * Set current registered instance of controller to check array size calculated by expression.
+   *
+   * @param arraySizeObserver instance of array size observer, must not be null.
+   * @return instance of the parser.
+   * @throws NullPointerException if argument is null
+   * @see #DEFAULT_EXPRESSION_ARRAY_SIZE_CONTROLLER
+   * @since 2.1.0
+   */
+  public JBBPParser setExpressionArraySizeController(
+      final JBBPParserExpressionArraySizeController arraySizeObserver) {
+    this.expressionArraySizeController = Objects.requireNonNull(arraySizeObserver);
+    return this;
+  }
+
   /**
    * Inside method to parse a structure.
    *
@@ -355,6 +396,9 @@ private List<JBBPAbstractField> parseStruct(final JBBPBitInputStream inStream,
             if ((this.flags & FLAG_NEGATIVE_EXPRESSION_RESULT_AS_ZERO) != 0) {
               resultOfExpression = Math.max(resultOfExpression, 0);
             }
+            resultOfExpression =
+                this.expressionArraySizeController.onCalculatedArraySize(this, evaluator, name,
+                    resultOfExpression);
           } else {
             resultOfExpression = 0;
           }

jbbp/src/main/java/com/igormaznitsa/jbbp/JBBPParserExpressionArraySizeController.java

@@ -0,0 +1,26 @@
+package com.igormaznitsa.jbbp;
+
+import com.igormaznitsa.jbbp.compiler.JBBPNamedFieldInfo;
+import com.igormaznitsa.jbbp.compiler.varlen.JBBPIntegerValueEvaluator;
+
+/**
+ * Controller to get value for every array field which size calculated by expression.
+ *
+ * @see JBBPParser#setExpressionArraySizeController(JBBPParserExpressionArraySizeController)
+ * @see JBBPParser#getExpressionArraySizeController()
+ * @since 2.1.0
+ */
+@FunctionalInterface
+public interface JBBPParserExpressionArraySizeController {
+  /**
+   * Called for every calculation of an array size by expression.
+   *
+   * @param parser              source parser, must not be null
+   * @param expressionEvaluator expression evaluator used for calculation, must not be null
+   * @param fieldInfo           target field info, must not be null
+   * @param calculatedArraySize calculated array size
+   * @return array size which can be same as provided size or changed
+   */
+  int onCalculatedArraySize(JBBPParser parser, JBBPIntegerValueEvaluator expressionEvaluator,
+                            JBBPNamedFieldInfo fieldInfo, int calculatedArraySize);
+}

jbbp/src/test/java/com/igormaznitsa/jbbp/JBBPParserExpressionArraySizeControllerTest.java

@@ -0,0 +1,65 @@
+package com.igormaznitsa.jbbp;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import com.igormaznitsa.jbbp.model.JBBPFieldArrayByte;
+import java.io.ByteArrayInputStream;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.junit.jupiter.api.Test;
+
+class JBBPParserExpressionArraySizeControllerTest {
+
+  @Test
+  public void testGetterAndSetter() {
+    final JBBPParserExpressionArraySizeController controller =
+        (parser, expressionEvaluator, fieldInfo, calculatedArraySize) -> 0;
+    final JBBPParser parser = JBBPParser.prepare("ubyte len; byte [len*2] a;")
+        .setExpressionArraySizeController(controller);
+    assertSame(controller, parser.getExpressionArraySizeController());
+  }
+
+  @Test
+  public void testNoChangeSize() throws Exception {
+    final AtomicInteger calls = new AtomicInteger();
+    final JBBPParser parser =
+        JBBPParser.prepare("ubyte len; byte [len*2] a;").setExpressionArraySizeController(
+            (parser1, expressionEvaluator, fieldInfo, calculatedArraySize) -> {
+              calls.incrementAndGet();
+              assertEquals("a", fieldInfo.getFieldName());
+              assertEquals(4, calculatedArraySize);
+              return calculatedArraySize;
+            });
+    parser.parse(new ByteArrayInputStream(new byte[] {2, 1, 2, 3, 4}));
+    assertEquals(1, calls.get());
+  }
+
+  @Test
+  public void testThrowException() {
+    final JBBPParser parser =
+        JBBPParser.prepare("ubyte len; byte [len*2] a;").setExpressionArraySizeController(
+            (parser1, expressionEvaluator, fieldInfo, calculatedArraySize) -> {
+              assertEquals("a", fieldInfo.getFieldName());
+              if (calculatedArraySize > 2) {
+                throw new IllegalArgumentException();
+              }
+              return calculatedArraySize;
+            });
+    assertThrows(IllegalArgumentException.class,
+        () -> parser.parse(new ByteArrayInputStream(new byte[] {2, 1, 2, 3, 4})));
+  }
+
+  @Test
+  public void testChangeSize() throws Exception {
+    final JBBPParser parser =
+        JBBPParser.prepare("ubyte len; byte [len*2] a;").setExpressionArraySizeController(
+            (parser1, expressionEvaluator, fieldInfo, calculatedArraySize) -> {
+              assertEquals("a", fieldInfo.getFieldName());
+              return calculatedArraySize - 1;
+            });
+    assertEquals(3, parser.parse(new ByteArrayInputStream(new byte[] {2, 1, 2, 3, 4}))
+        .findFieldForNameAndType("a",
+            JBBPFieldArrayByte.class).size());
+  }
+}

jbbp/src/test/java/com/igormaznitsa/jbbp/JBBPParserTest.java

@@ -2611,7 +2611,6 @@ public JBBPAbstractField readCustomFieldType(JBBPBitInputStream in, JBBPBitOrder
             return new JBBPFieldArrayByte(fieldName, read);
           }
         });
-
   }
 
 }