Add initial dump() method to NetdNativeService

This is called by "dumpsys netd".

Bug: 27239233
Change-Id: I27fb308f8067243ff241a6f8fd6a83f406087d2a
diff --git a/server/DumpWriter.cpp b/server/DumpWriter.cpp
new file mode 100644
index 0000000..d96d47b
--- /dev/null
+++ b/server/DumpWriter.cpp
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "DumpWriter.h"
+
+#include <android-base/stringprintf.h>
+#include <utils/String8.h>
+
+using android::base::StringAppendV;
+using android::String16;
+using android::Vector;
+
+namespace {
+
+const char kIndentString[] = "  ";
+const size_t kIndentStringLen = strlen(kIndentString);
+
+}  // namespace
+
+
+DumpWriter::DumpWriter(int fd) : mIndentLevel(0), mFd(fd) {}
+
+void DumpWriter::incIndent() {
+    if (mIndentLevel < 255) {
+        mIndentLevel++;
+    }
+}
+
+void DumpWriter::decIndent() {
+    if (mIndentLevel > 0) {
+        mIndentLevel--;
+    }
+}
+
+void DumpWriter::println(const std::string& line) {
+    if (!line.empty()) {
+        for (int i = 0; i < mIndentLevel; i++) {
+            write(mFd, kIndentString, kIndentStringLen);
+        }
+        write(mFd, line.c_str(), line.size());
+    }
+    write(mFd, "\n", 1);
+}
+
+void DumpWriter::println(const char* fmt, ...) {
+    std::string line;
+    va_list ap;
+    va_start(ap, fmt);
+    StringAppendV(&line, fmt, ap);
+    va_end(ap);
+    println(line);
+}