AAPT2: Better debugging output

Test: make aapt2_tests
Change-Id: I7778b773201381538dc1f2e376abee4eb33e44c0
diff --git a/tools/aapt2/text/Printer.cpp b/tools/aapt2/text/Printer.cpp
new file mode 100644
index 0000000..38b3585
--- /dev/null
+++ b/tools/aapt2/text/Printer.cpp
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2017 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 "text/Printer.h"
+
+#include <algorithm>
+
+#include "io/Util.h"
+
+using ::aapt::io::OutputStream;
+using ::android::StringPiece;
+
+namespace aapt {
+namespace text {
+
+void Printer::Println(const StringPiece& str) {
+  Print(str);
+  Print("\n");
+}
+
+void Printer::Println() {
+  Print("\n");
+}
+
+void Printer::Print(const StringPiece& str) {
+  if (error_) {
+    return;
+  }
+
+  auto remaining_str_begin = str.begin();
+  const auto remaining_str_end = str.end();
+  while (remaining_str_end != remaining_str_begin) {
+    // Find the next new-line.
+    const auto new_line_iter = std::find(remaining_str_begin, remaining_str_end, '\n');
+
+    // We will copy the string up until the next new-line (or end of string).
+    const StringPiece str_to_copy = str.substr(remaining_str_begin, new_line_iter);
+    if (!str_to_copy.empty()) {
+      if (needs_indent_) {
+        for (int i = 0; i < indent_level_; i++) {
+          if (!io::Copy(out_, "  ")) {
+            error_ = true;
+            return;
+          }
+        }
+        needs_indent_ = false;
+      }
+
+      if (!io::Copy(out_, str_to_copy)) {
+        error_ = true;
+        return;
+      }
+    }
+
+    // If we found a new-line.
+    if (new_line_iter != remaining_str_end) {
+      if (!io::Copy(out_, "\n")) {
+        error_ = true;
+        return;
+      }
+      needs_indent_ = true;
+      // Ok to increment iterator here because we know that the '\n' character is one byte.
+      remaining_str_begin = new_line_iter + 1;
+    } else {
+      remaining_str_begin = new_line_iter;
+    }
+  }
+}
+
+void Printer::Indent() {
+  ++indent_level_;
+}
+
+void Printer::Undent() {
+  --indent_level_;
+}
+
+}  // namespace text
+}  // namespace aapt