4 files changed, 104 insertions, 9 deletions
diff --git a/includes/image_io/utils/file_utils.h b/includes/image_io/utils/file_utils.h
index d1a469d..3a8d2c6 100644
--- a/includes/image_io/utils/file_utils.h
+++ b/includes/image_io/utils/file_utils.h
@@ -6,34 +6,35 @@
 #include <string>
 
 #include "image_io/base/data_segment.h"
+#include "image_io/base/message_handler.h"
 
 namespace photos_editing_formats {
 namespace image_io {
 
-/// A policy that controls whether an error is reported or not.
-enum class ReportErrorPolicy { kDontReportError, kReportError };
-
 /// @param file_name The name of the file to get the size in bytes of.
 /// @param size A pointer to a variable to receive the size.
 /// @return Whether file size was obtained properly.
 bool GetFileSize(const std::string& file_name, size_t* size);
 
 /// @param file_name The name of the file to open for output.
+/// @param message_handler Optional message handler to write messages to.
 /// @return An ostream pointer or nullptr if the open failed.
-std::unique_ptr<std::ostream> OpenOutputFile(
-    const std::string& file_name, ReportErrorPolicy report_error_policy);
+std::unique_ptr<std::ostream> OpenOutputFile(const std::string& file_name,
+                                             MessageHandler* message_handler);
 
 /// @param file_name The name of the file to open for input.
+/// @param message_handler Optional message handler to write messages to.
 /// @return An istream pointer or nullptr if the open failed.
-std::unique_ptr<std::istream> OpenInputFile(
-    const std::string& file_name, ReportErrorPolicy report_error_policy);
+std::unique_ptr<std::istream> OpenInputFile(const std::string& file_name,
+                                            MessageHandler* message_handler);
 
 /// Opens the named file for input, gets its size, and reads the entire contents
 /// into a data segment that is returned to the caller.
 /// @param file_name The name of the file to open for input.
+/// @param message_handler Optional message handler to write messages to.
 /// @return A DataSegment pointer or nullptr if the open and reading failed.
-std::shared_ptr<DataSegment> ReadEntireFile(
-    const std::string& file_name, ReportErrorPolicy report_error_policy);
+std::shared_ptr<DataSegment> ReadEntireFile(const std::string& file_name,
+                                            MessageHandler* message_handler);
 
 }  // namespace image_io
 }  // namespace photos_editing_formats
diff --git a/includes/image_io/utils/message_stats_writer.h b/includes/image_io/utils/message_stats_writer.h
new file mode 100644
index 0000000..24dd6b1
--- /dev/null
+++ b/includes/image_io/utils/message_stats_writer.h
@@ -0,0 +1,47 @@
+#ifndef IMAGE_IO_UTILS_MESSAGE_STATS_WRITER_H_  // NOLINT
+#define IMAGE_IO_UTILS_MESSAGE_STATS_WRITER_H_  // NOLINT
+
+#include <memory>
+#include <sstream>
+#include <string>
+
+#include "image_io/base/message_stats.h"
+#include "image_io/utils/string_outputter.h"
+
+namespace photos_editing_formats {
+namespace image_io {
+
+/// A class to write the message stats for error and warning counts. The output
+/// is written when the writer object is destroyed, making this a conveneient
+/// class to use in functions that have multiple return points and for which
+/// such output is desired at all return points.
+class MessageStatsWriter {
+ public:
+  /// @param message_stats The message stats object holding the counts.
+  /// @param outputter The outputter function to write the stats to.
+  /// @param name The name of the tool or function that is "finished".
+  MessageStatsWriter(const std::shared_ptr<MessageStats>& message_stats,
+                     const std::string& name, const StringOutputter& outputter)
+      : stats_(message_stats), outputter_(outputter), name_(name) {}
+
+  /// Writes the finished message with the stats to the outputter function.
+  ~MessageStatsWriter() {
+    const string kError = stats_->error_count == 1 ? "error" : "errors";
+    const string kWarning = stats_->warning_count == 1 ? "warning" : "warnings";
+    std::stringstream ss;
+    ss << std::endl
+       << name_ << " finished, " << stats_->error_count << " " << kError << ", "
+       << stats_->warning_count << " " << kWarning << std::endl;
+    outputter_(ss.str());
+  }
+
+ private:
+  std::shared_ptr<MessageStats> stats_;
+  StringOutputter outputter_;
+  std::string name_;
+};
+
+}  // namespace image_io
+}  // namespace photos_editing_formats
+
+#endif  // IMAGE_IO_UTILS_MESSAGE_STATS_WRITER_H_ // NOLINT
diff --git a/includes/image_io/utils/string_outputter.h b/includes/image_io/utils/string_outputter.h
new file mode 100644
index 0000000..b6ea013
--- /dev/null
+++ b/includes/image_io/utils/string_outputter.h
@@ -0,0 +1,19 @@
+#ifndef IMAGE_IO_UTILS_STRING_OUTPUTTER_H_  // NOLINT
+#define IMAGE_IO_UTILS_STRING_OUTPUTTER_H_  // NOLINT
+
+#include <functional>
+#include <string>
+
+namespace photos_editing_formats {
+namespace image_io {
+
+/// A typedef for a function that accepts a string and writes it somewhere.
+/// These types of functions are typically used in command line tools to write
+/// the output of the tool to stdout or some other location. The function
+/// should not write its own new line at the end of the str.
+using StringOutputter = std::function<void(const std::string& str)>;
+
+}  // namespace image_io
+}  // namespace photos_editing_formats
+
+#endif  // IMAGE_IO_UTILS_STRING_OUTPUTTER_H_  // NOLINT
diff --git a/includes/image_io/utils/string_outputter_message_writer.h b/includes/image_io/utils/string_outputter_message_writer.h
new file mode 100644
index 0000000..f34d975
--- /dev/null
+++ b/includes/image_io/utils/string_outputter_message_writer.h
@@ -0,0 +1,28 @@
+#ifndef IMAGE_IO_UTILS_STRING_OUTPUTTER_MESSAGE_WRITER_H_  // NOLINT
+#define IMAGE_IO_UTILS_STRING_OUTPUTTER_MESSAGE_WRITER_H_  // NOLINT
+
+#include "image_io/base/message_writer.h"
+#include "image_io/utils/string_outputter.h"
+
+namespace photos_editing_formats {
+namespace image_io {
+
+/// A MessageWriter that writes the messages to the StringOutputter function.
+class StringOutputterMessageWriter : public MessageWriter {
+ public:
+  /// @param outputter The outputter function to write messages to.
+  explicit StringOutputterMessageWriter(const StringOutputter& outputter)
+      : outputter_(outputter) {}
+  void WriteMessage(const Message& message) override {
+    outputter_(GetFormattedMessage(message));
+    outputter_("\n");
+  }
+
+ private:
+  StringOutputter outputter_;
+};
+
+}  // namespace image_io
+}  // namespace photos_editing_formats
+
+#endif  // IMAGE_IO_UTILS_STRING_OUTPUTTER_MESSAGE_WRITER_H_  // NOLINT