Add BufferedWriter emulation to GWT

Change-Id: Ia7f7e66e404432d3ee32b4d06df704b09a7f2b4c

user/super/com/google/gwt/emul/java/io/BufferedWriter.java

@@ -0,0 +1,134 @@
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package java.io;
+
+import static javaemul.internal.InternalPreconditions.checkArgument;
+import static javaemul.internal.InternalPreconditions.checkNotNull;
+import static javaemul.internal.InternalPreconditions.checkState;
+
+/**
+ * See <a href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/BufferedWriter.html">the official
+ * Java API doc</a> for details.
+ */
+public class BufferedWriter extends Writer {
+  private static int defaultCharBufferSize = 8192;
+
+  private Writer out;
+  private char[] buf;
+  private int pos;
+  private int size;
+
+  public BufferedWriter(Writer out) {
+    this(out, defaultCharBufferSize);
+  }
+
+  public BufferedWriter(Writer out, int size) {
+    super(out);
+    checkArgument(size > 0, "Buffer size <= 0");
+    this.out = out;
+    this.buf = new char[size];
+    this.size = size;
+    this.pos = 0;
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (out == null) {
+      return;
+    }
+    try (Writer w = out) {
+      flushBuffer();
+    } finally {
+      out = null;
+      buf = null;
+    }
+  }
+
+  @Override
+  public void flush() throws IOException {
+    flushBuffer();
+    out.flush();
+  }
+
+  private void ensureOpen() throws IOException {
+    checkState(out != null, "stream closed");
+  }
+
+  private void flushBuffer() throws IOException {
+    ensureOpen();
+    if (pos > 0) {
+      out.write(buf, 0, pos);
+    }
+    pos = 0;
+  }
+
+  public void newLine() throws IOException {
+    write("\n");
+  }
+
+  @Override
+  public void write(char[] buffer, int offset, int count) throws IOException {
+    ensureOpen();
+    IOUtils.checkOffsetAndCount(buffer, offset, count);
+    if (count >= size) {
+      /* If the request length exceeds the size of the output buffer,
+      flush the buffer and then write the data directly.  In this
+      way buffered streams will cascade harmlessly. */
+      flushBuffer();
+      out.write(buffer, offset, count);
+      return;
+    }
+
+    int b = offset, t = offset + count;
+    while (b < t) {
+      int d = Math.min(size - pos, t - b);
+      System.arraycopy(buffer, b, buf, pos, d);
+      b += d;
+      pos += d;
+      if (pos >= size) {
+        flushBuffer();
+      }
+    }
+  }
+
+  @Override
+  public void write(int oneChar) throws IOException {
+    ensureOpen();
+    if (pos >= size) {
+      out.write(buf, 0, buf.length);
+      pos = 0;
+    }
+    buf[pos++] = (char) oneChar;
+  }
+
+  @Override
+  public void write(String str, int offset, int count) throws IOException {
+    ensureOpen();
+    // Ensure we throw a NullPointerException instead of a JavascriptException in case the
+    // given string is null.
+    checkNotNull(str);
+    int b = offset, t = offset + count;
+    while (b < t) {
+      int d = Math.min(size - pos, t - b);
+      str.getChars(b, b + d, buf, pos);
+      b += d;
+      pos += d;
+      if (pos >= size) {
+        flushBuffer();
+      }
+    }
+  }
+}

user/test/com/google/gwt/emultest/EmulSuite.java

@@ -16,6 +16,7 @@
 package com.google.gwt.emultest;
 
 import com.google.gwt.emultest.java.internal.CoercionsTest;
+import com.google.gwt.emultest.java.io.BufferedWriterTest;
 import com.google.gwt.emultest.java.io.ByteArrayInputStreamTest;
 import com.google.gwt.emultest.java.io.ByteArrayOutputStreamTest;
 import com.google.gwt.emultest.java.io.FilterInputStreamTest;
@@ -70,6 +71,7 @@
   CoercionsTest.class,
 
   // -- java.io
+  BufferedWriterTest.class,
   ByteArrayInputStreamTest.class,
   ByteArrayOutputStreamTest.class,
   FilterInputStreamTest.class,