Move DumpWriter to libnetdutils

resolver related component in libnetd_resolv
needs it to easily print dump log.

Bug: 122564854
Test: built, flashed, booted
      system/netd/tests/runtests.sh pass
      adb shell dumpsys netd, worked fine

Change-Id: Ic97d5f21b738fc3074e9308f4846191e744ed479

3 files changed, 141 insertions, 0 deletions

diff --git a/libnetdutils/Android.bp b/libnetdutils/Android.bp
index f06087aa5..a1cbbbb5f 100644
--- a/libnetdutils/Android.bp
+++ b/libnetdutils/Android.bp
@@ -1,6 +1,7 @@
 cc_library {
     name: "libnetdutils",
     srcs: [
+        "DumpWriter.cpp",
         "Fd.cpp",
         "InternetAddresses.cpp",
         "Log.cpp",
diff --git a/libnetdutils/DumpWriter.cpp b/libnetdutils/DumpWriter.cpp
new file mode 100644
index 000000000..092ddbae2
--- /dev/null
+++ b/libnetdutils/DumpWriter.cpp
@@ -0,0 +1,72 @@
+/*
+ * 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 "netdutils/DumpWriter.h"
+
+#include <unistd.h>
+#include <limits>
+
+#include <android-base/stringprintf.h>
+#include <utils/String8.h>
+
+using android::base::StringAppendV;
+
+namespace android {
+namespace netdutils {
+
+namespace {
+
+const char kIndentString[] = "  ";
+const size_t kIndentStringLen = strlen(kIndentString);
+
+}  // namespace
+
+DumpWriter::DumpWriter(int fd) : mIndentLevel(0), mFd(fd) {}
+
+void DumpWriter::incIndent() {
+    if (mIndentLevel < std::numeric_limits<decltype(mIndentLevel)>::max()) {
+        mIndentLevel++;
+    }
+}
+
+void DumpWriter::decIndent() {
+    if (mIndentLevel > std::numeric_limits<decltype(mIndentLevel)>::min()) {
+        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);
+}
+
+// NOLINTNEXTLINE(cert-dcl50-cpp): Grandfathered C-style variadic function.
+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);
+}
+
+}  // namespace netdutils
+}  // namespace android
diff --git a/libnetdutils/include/netdutils/DumpWriter.h b/libnetdutils/include/netdutils/DumpWriter.h
new file mode 100644
index 000000000..a50b5e60a
--- /dev/null
+++ b/libnetdutils/include/netdutils/DumpWriter.h
@@ -0,0 +1,68 @@
+/*
+ * 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.
+ */
+
+#ifndef NETDUTILS_DUMPWRITER_H_
+#define NETDUTILS_DUMPWRITER_H_
+
+#include <string>
+
+namespace android {
+namespace netdutils {
+
+class DumpWriter {
+  public:
+    DumpWriter(int fd);
+
+    void incIndent();
+    void decIndent();
+
+    void println(const std::string& line);
+    template <size_t n>
+    void println(const char line[n]) {
+        println(std::string(line));
+    }
+    // Hint to the compiler that it should apply printf validation of
+    // arguments (beginning at position 3) of the format (specified in
+    // position 2). Note that position 1 is the implicit "this" argument.
+    void println(const char* fmt, ...) __attribute__((__format__(__printf__, 2, 3)));
+    void blankline() { println(""); }
+
+  private:
+    uint8_t mIndentLevel;
+    int mFd;
+};
+
+class ScopedIndent {
+  public:
+    ScopedIndent() = delete;
+    ScopedIndent(const ScopedIndent&) = delete;
+    ScopedIndent(ScopedIndent&&) = delete;
+    explicit ScopedIndent(DumpWriter& dw) : mDw(dw) { mDw.incIndent(); }
+    ~ScopedIndent() { mDw.decIndent(); }
+    ScopedIndent& operator=(const ScopedIndent&) = delete;
+    ScopedIndent& operator=(ScopedIndent&&) = delete;
+
+    // TODO: consider additional {inc,dec}Indent methods and a counter that
+    // can be used to unwind all pending increments on exit.
+
+  private:
+    DumpWriter& mDw;
+};
+
+}  // namespace netdutils
+}  // namespace android
+
+#endif  // NETDUTILS_DUMPWRITER_H_