commit cee7b37eac2487c16c7b6772ed290152cb58241d
author Alexei Strots <alexei.strots@bluerivertech.com> Fri Apr 21 11:57:54 2023 -0700
committer James Kuszmaul <jabukuszmaul+collab@gmail.com> Fri Jul 21 08:11:41 2023 -0700
tree 3fc9f4acea5d9b7f77cff2149a894887cc232e82
parent f08b8fbe32592c79886b6813aa6a83f1116de3ac

Add ability to create SpanReader with known decoder

It will be used for passing memory decoder and generally it decouples
reading of data from construction of proper chains of decoders.

https://bluerivertechnology.atlassian.net/browse/PRO-20146

Change-Id: I09ac4104f84c04ea246f34d3a0d3321e0744edfc
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>

aos/events/logging/logfile_utils.cc

diff --git a/aos/events/logging/logfile_utils.cc b/aos/events/logging/logfile_utils.cc
index 304b3b3..3c8c50d 100644
--- a/aos/events/logging/logfile_utils.cc
+++ b/aos/events/logging/logfile_utils.cc
@@ -68,9 +68,39 @@
 
 namespace aos::logger {
 namespace {
-
 namespace chrono = std::chrono;
 
+std::unique_ptr<DataDecoder> ResolveDecoder(std::string_view filename,
+                                            bool quiet) {
+  static constexpr std::string_view kS3 = "s3:";
+
+  std::unique_ptr<DataDecoder> decoder;
+
+  if (filename.substr(0, kS3.size()) == kS3) {
+#if ENABLE_S3
+    decoder = std::make_unique<S3Fetcher>(filename);
+#else
+    LOG(FATAL) << "Reading files from S3 not supported on this platform";
+#endif
+  } else {
+    decoder = std::make_unique<DummyDecoder>(filename);
+  }
+
+  static constexpr std::string_view kXz = ".xz";
+  static constexpr std::string_view kSnappy = SnappyDecoder::kExtension;
+  if (filename.substr(filename.size() - kXz.size()) == kXz) {
+#if ENABLE_LZMA
+    decoder = std::make_unique<ThreadedLzmaDecoder>(std::move(decoder), quiet);
+#else
+    (void)quiet;
+    LOG(FATAL) << "Reading xz-compressed files not supported on this platform";
+#endif
+  } else if (filename.substr(filename.size() - kSnappy.size()) == kSnappy) {
+    decoder = std::make_unique<SnappyDecoder>(std::move(decoder));
+  }
+  return decoder;
+}
+
 template <typename T>
 void PrintOptionalOrNull(std::ostream *os, const std::optional<T> &t) {
   if (t.has_value()) {
@@ -1164,32 +1194,11 @@
 }
 
 SpanReader::SpanReader(std::string_view filename, bool quiet)
-    : filename_(filename) {
-  static constexpr std::string_view kS3 = "s3:";
-  if (filename.substr(0, kS3.size()) == kS3) {
-#if ENABLE_S3
-    decoder_ = std::make_unique<S3Fetcher>(filename);
-#else
-    LOG(FATAL) << "Reading files from S3 not supported on this platform";
-#endif
-  } else {
-    decoder_ = std::make_unique<DummyDecoder>(filename);
-  }
+    : SpanReader(filename, ResolveDecoder(filename, quiet)) {}
 
-  static constexpr std::string_view kXz = ".xz";
-  static constexpr std::string_view kSnappy = SnappyDecoder::kExtension;
-  if (filename.substr(filename.size() - kXz.size()) == kXz) {
-#if ENABLE_LZMA
-    decoder_ =
-        std::make_unique<ThreadedLzmaDecoder>(std::move(decoder_), quiet);
-#else
-    (void)quiet;
-    LOG(FATAL) << "Reading xz-compressed files not supported on this platform";
-#endif
-  } else if (filename.substr(filename.size() - kSnappy.size()) == kSnappy) {
-    decoder_ = std::make_unique<SnappyDecoder>(std::move(decoder_));
-  }
-}
+SpanReader::SpanReader(std::string_view filename,
+                       std::unique_ptr<DataDecoder> decoder)
+    : filename_(filename), decoder_(std::move(decoder)) {}
 
 absl::Span<const uint8_t> SpanReader::PeekMessage() {
   // Make sure we have enough for the size.

aos/events/logging/logfile_utils.h

diff --git a/aos/events/logging/logfile_utils.h b/aos/events/logging/logfile_utils.h
index 5d5d344..f8d6b8e 100644
--- a/aos/events/logging/logfile_utils.h
+++ b/aos/events/logging/logfile_utils.h
@@ -166,8 +166,13 @@
 // Class to read chunks out of a log file.
 class SpanReader {
  public:
+  // It creates a reader and makes proper decoder based on information encoded
+  // in the filename.
   SpanReader(std::string_view filename, bool quiet = false);
 
+  // Opens new reader from provided decoder.
+  SpanReader(std::string_view filename, std::unique_ptr<DataDecoder> decoder);
+
   std::string_view filename() const { return filename_; }
 
   size_t TotalRead() const { return total_read_; }