[GitHub] [nifi-minifi-cpp] adamdebreceni commented on a change in pull request #987: MINIFICPP-1455: Fix FileStream error handling and reporting

[GitBox <gi...@apache.org>]

adamdebreceni commented on a change in pull request #987:
URL: https://github.com/apache/nifi-minifi-cpp/pull/987#discussion_r571994524



##########
File path: libminifi/src/io/FileStream.cpp
##########
@@ -31,21 +31,42 @@ namespace nifi {
 namespace minifi {
 namespace io {
 
+constexpr const char *FILE_OPENING_ERROR_MSG = "Error opening file: ";
+constexpr const char *READ_ERROR_MSG = "Error reading from file: ";
+constexpr const char *WRITE_ERROR_MSG = "Error writing to file: ";
+constexpr const char *SEEK_ERROR_MSG = "Error seeking in file: ";
+constexpr const char *INVALID_FILE_STREAM_ERROR_MSG = "invalid file stream";
+constexpr const char *TELLG_CALL_ERROR_MSG = "tellg call on file stream failed";
+constexpr const char *INVALID_BUFFER_ERROR_MSG = "invalid buffer";
+constexpr const char *FLUSH_CALL_ERROR_MSG = "flush call on file stream failed";
+constexpr const char *WRITE_CALL_ERROR_MSG = "write call on file stream failed";
+constexpr const char *EMPTY_MESSAGE_ERROR_MSG = "empty message";
+constexpr const char *SEEKG_CALL_ERROR_MSG = "seekg call on file stream failed";
+constexpr const char *SEEKP_CALL_ERROR_MSG = "seekp call on file stream failed";
+
 FileStream::FileStream(const std::string &path, bool append)
     : logger_(logging::LoggerFactory<FileStream>::getLogger()),
       path_(path),
       offset_(0) {
   file_stream_ = std::unique_ptr<std::fstream>(new std::fstream());
   if (append) {
     file_stream_->open(path.c_str(), std::fstream::in | std::fstream::out | std::fstream::app | std::fstream::binary);
-    file_stream_->seekg(0, file_stream_->end);
-    file_stream_->seekp(0, file_stream_->end);
-    std::streamoff len = file_stream_->tellg();
-    length_ = len > 0 ? gsl::narrow<size_t>(len) : 0;
-    seek(offset_);
+    if (file_stream_->is_open()) {
+      seekToEndOfFile(FILE_OPENING_ERROR_MSG);
+      auto len = file_stream_->tellg();
+      if (len < 0)

Review comment:
       as I understand the actual return type of `tellg` is implementation defined and might be unsigned, we should compare the result to `pos_type(-1)` to detect errors




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