backport FernFlowerTask and relevant systems from 0.3

src/main/java/net/fabricmc/loom/util/ConsumingOutputStream.java

@@ -0,0 +1,64 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2016, 2017, 2018 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.util;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.function.Consumer;
+
+/**
+ * Created by covers1624 on 20/12/18.
+ */
+public class ConsumingOutputStream extends OutputStream {
+
+    private final Consumer<String> consumer;
+
+    private StringBuilder buffer = new StringBuilder();
+
+    public ConsumingOutputStream(Consumer<String> consumer) {
+        this.consumer = consumer;
+    }
+
+    @Override
+    public void write(int b) throws IOException {
+        char ch = (char) (b & 0xFF);
+        buffer.append(ch);
+        if (ch == '\n' || ch == '\r') {
+            flush();
+        }
+    }
+
+    @Override
+    public void flush() throws IOException {
+        String str = buffer.toString();
+        if (str.endsWith("\r") || str.endsWith("\n")) {
+            str = str.trim();
+            if (!str.isEmpty()) {
+                consumer.accept(str);
+            }
+            buffer = new StringBuilder();
+        }
+    }
+}