1 files changed, 141 insertions, 0 deletions
diff --git a/src/main/java/ftbsc/lll/utils/DescriptorBuilder.java b/src/main/java/ftbsc/lll/utils/DescriptorBuilder.java
new file mode 100644
index 0000000..541497b
--- /dev/null
+++ b/src/main/java/ftbsc/lll/utils/DescriptorBuilder.java
@@ -0,0 +1,141 @@
+package ftbsc.lll.utils;
+
+import org.objectweb.asm.Type;
+
+import java.util.ArrayList;
+
+/**
+ * Builds a method descriptor for you.
+ * See the <a href="https://asm.ow2.io/asm4-guide.pdf">documentation</a> to better understand what this is.
+ * Parameters must be given in a specific order.
+ * Return type should always be specified for clarity, but defaults to void.
+ */
+public class DescriptorBuilder {
+	/**
+	 * The descriptor of the return type.
+	 */
+	private String returnType;
+
+	/**
+	 * The descriptors of the parameters.
+	 */
+	private final ArrayList<String> params;
+
+	/**
+	 * Public constructor.
+	 * Initialises default values.
+	 */
+	public DescriptorBuilder() {
+		this.returnType = Type.getDescriptor(void.class);
+		this.params = new ArrayList<>();
+	}
+
+	/**
+	 * Sets the return type to the given type.
+	 * Passing a {@link Class} may cause problems if used with objects outside the Java
+	 * SDK. Pass the fully qualified name as a {@link String} rather than the {@link Class}
+	 * object for non-standard types.
+	 * @param returnType the Class object corresponding to the return type
+	 * @return the builder's state after the change
+	 */
+	public DescriptorBuilder setReturnType(Class<?> returnType) {
+		this.returnType = Type.getDescriptor(returnType);
+		return this;
+	}
+
+	/**
+	 * Sets the return type to the Object specified here as a fully
+	 * qualified name. Example: java.lang.String.
+	 * No validity checks are performed: it's up to the user to ensure the name is correct.
+	 * @param returnType the fully qualified name of the desired Object.
+	 * @return the builder's state after the change
+	 */
+	public DescriptorBuilder setReturnType(String returnType) {
+		return this.setReturnType(returnType, 0);
+	}
+
+	/**
+	 * Sets the return type to the Object specified here as a fully
+	 * qualified name (example: java.lang.String), with the specified array level.
+	 * No validity checks are performed: it's up to the user to ensure the name is correct.
+	 * @param returnType the fully qualified name of the desired Object.
+	 * @param arrayLevel how many levels of array are there
+	 *                   (example: String is 0, String[] is 1, String[][] is 2, etc.)
+	 * @return the builder's state after the change
+	 */
+	public DescriptorBuilder setReturnType(String returnType, int arrayLevel) {
+		this.returnType = nameToDescriptor(returnType, arrayLevel);
+		return this;
+	}
+
+	/**
+	 * Adds a parameter of the given class type to the method.
+	 * Parameter order matters.
+	 * Passing a {@link Class} may cause problems if used with objects outside the Java
+	 * SDK. Pass the fully qualified name as a {@link String} rather than the {@link Class}
+	 * object for non-standard types.
+	 * @param param the Class object corresponding to the parameter
+	 * @return the builder's state after the change
+	 */
+	public DescriptorBuilder addParameter(Class<?> param) {
+		this.params.add(Type.getDescriptor(param));
+		return this;
+	}
+
+	/**
+	 * Adds a parameter with the type specified by the given fully
+	 * qualified name to the method. Example: java.lang.String.
+	 * Parameter order matters.
+	 * No validity checks are performed: it's up to the user to ensure the name is correct.
+	 * @param param the fully qualified name of the parameter type
+	 * @return the builder's state after the change
+	 */
+	public DescriptorBuilder addParameter(String param) {
+		return this.addParameter(param, 0);
+	}
+
+	/**
+	 * Adds a parameter with the type specified by the given fully
+	 * qualified name (example: java.lang.String) to the method, with
+	 * the specified array level.
+	 * Parameter order matters.
+	 * No validity checks are performed: it's up to the user to ensure the name is correct.
+	 * @param param the fully qualified name of the parameter type
+	 * @param arrayLevel how many levels of array are there
+	 *                   (example: String is 0, String[] is 1, String[][] is 2, etc.)
+	 * @return the builder's state after the change
+	 */
+	public DescriptorBuilder addParameter(String param, int arrayLevel) {
+		this.params.add(nameToDescriptor(param, arrayLevel));
+		return this;
+	}
+
+	/**
+	 * Builds the descriptor into a string.
+	 * Example result: {@code int m(Object[] o)} becomes {@code ([Ljava/lang/Object;)I}
+	 * @return the resulting descriptor
+	 */
+	public String build() {
+		StringBuilder sb = new StringBuilder();
+		sb.append('(');
+		for(String p : params)
+			sb.append(p);
+		sb.append(')').append(returnType);
+		return sb.toString();
+	}
+
+	/**
+	 * Converts a fully qualified name and array level to a descriptor.
+	 * @param name the fully qualified name of the object type
+	 * @param arrayLevel how many levels of array are there
+	 *                   (example: String is 0, String[] is 1, String[][] is 2, etc.)
+	 * @return object descriptor
+	 */
+	public static String nameToDescriptor(String name, int arrayLevel) {
+		StringBuilder sb = new StringBuilder();
+		for(int i = 0; i < arrayLevel; i++)
+			sb.append('[');
+		sb.append('L').append(name.replace('.', '/')).append(';');
+		return sb.toString();
+	}
+}