Provides a CachingOuptutStream and a CachingWriter

src/main/java/org/codehaus/plexus/util/io/CachingOutputStream.java

@@ -0,0 +1,66 @@
+package org.codehaus.plexus.util.io;
+
+/*
+ * Copyright The Codehaus Foundation.
+ *
+ * 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.
+ */
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Objects;
+
+/**
+ * Caching OutputStream to avoid overwriting a file with
+ * the same content.
+ */
+public class CachingOutputStream extends ByteArrayOutputStream
+{
+    private final Path path;
+    private boolean modified;
+
+    public CachingOutputStream( File path )
+    {
+        this( Objects.requireNonNull( path ).toPath() );
+    }
+
+    public CachingOutputStream( Path path )
+    {
+        this.path = Objects.requireNonNull( path );
+    }
+
+    @Override
+    public void close() throws IOException
+    {
+        byte[] data = toByteArray();
+        if ( Files.exists( path ) && Files.size( path ) == data.length )
+        {
+            byte[] old = Files.readAllBytes( path );
+            if ( Arrays.equals( old, data ) )
+            {
+                return;
+            }
+        }
+        Files.write( path, data );
+        modified = true;
+    }
+
+    public boolean isModified()
+    {
+        return modified;
+    }
+}

src/main/java/org/codehaus/plexus/util/io/CachingWriter.java

@@ -0,0 +1,69 @@
+package org.codehaus.plexus.util.io;
+
+/*
+ * Copyright The Codehaus Foundation.
+ *
+ * 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.
+ */
+
+import java.io.File;
+import java.io.IOException;
+import java.io.StringWriter;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Objects;
+
+/**
+ * Caching Writer to avoid overwriting a file with
+ * the same content.
+ */
+public class CachingWriter extends StringWriter
+{
+    private final Path path;
+    private final Charset charset;
+    private boolean modified;
+
+    public CachingWriter( File path, Charset charset )
+    {
+        this( Objects.requireNonNull( path ).toPath(), charset );
+    }
+
+    public CachingWriter( Path path, Charset charset )
+    {
+        this.path = Objects.requireNonNull( path );
+        this.charset = Objects.requireNonNull( charset );
+    }
+
+    @Override
+    public void close() throws IOException
+    {
+        byte[] data = getBuffer().toString().getBytes( charset );
+        if ( Files.exists( path ) && Files.size( path ) == data.length )
+        {
+            byte[] ba = Files.readAllBytes( path );
+            if ( Arrays.equals( data, ba ) )
+            {
+                return;
+            }
+        }
+        Files.write( path, data );
+        modified = true;
+    }
+
+    public boolean isModified()
+    {
+        return modified;
+    }
+}