[rfile] set default compression to 505 and add SetCompressionSettings

Author: silverweed

io/io/inc/ROOT/RFile.hxx

@@ -8,6 +8,7 @@
 #ifndef ROOT7_RFile
 #define ROOT7_RFile
 
+#include <Compression.h>
 #include <ROOT/RError.hxx>
 
 #include <deque>
@@ -375,6 +376,13 @@ public:
 
    /// Prints the internal structure of this RFile to the given stream.
    void Print(std::ostream &out = std::cout) const;
+
+   /// Sets the compression algorithm and level used for all subsequent objects stored in this ROOT file.
+   /// See core/zip/inc/Compression.h for the meaning of the `compression` argument.
+   /// Default compression is 505 (ZSTD level 10).
+   void SetCompressionSettings(int compression);
+   /// \see SetCompressionSettings(int compression)
+   void SetCompressionSettings(RCompressionSetting::EAlgorithm::EValues algorithm, int level);
 };
 
 } // namespace Experimental

io/io/src/RFile.cxx

@@ -8,6 +8,7 @@
 #include "ROOT/RFile.hxx"
 
 #include <ROOT/StringUtils.hxx>
+#include <ROOT/RLogger.hxx>
 #include <ROOT/RError.hxx>
 
 #include <Byteswap.h>
@@ -30,6 +31,8 @@ ROOT::RLogChannel &ROOT::Experimental::Internal::RFileLog()
 using ROOT::Experimental::RFile;
 using ROOT::Experimental::Internal::RFileLog;
 
+static constexpr int kDefaultCompression = ROOT::RCompressionSetting::EDefaults::kUseGeneralPurpose;
+
 namespace {
 enum class ENameCycleError {
    kNoError,
@@ -224,7 +227,8 @@ std::unique_ptr<RFile> RFile::Update(std::string_view path)
 std::unique_ptr<RFile> RFile::Recreate(std::string_view path)
 {
    TDirectory::TContext ctx(nullptr); // XXX: probably not thread safe?
-   auto tfile = std::unique_ptr<TFile>(TFile::Open(std::string(path).c_str(), "RECREATE_WITHOUT_GLOBALREGISTRATION"));
+   auto tfile = std::unique_ptr<TFile>(
+      TFile::Open(std::string(path).c_str(), "RECREATE_WITHOUT_GLOBALREGISTRATION", "", kDefaultCompression));
    EnsureFileOpenAndBinary(tfile.get(), path);
 
    auto rfile = std::unique_ptr<RFile>(new RFile(std::move(tfile)));
@@ -235,6 +239,20 @@ RFile::RFile(std::unique_ptr<TFile> file) : fFile(std::move(file)) {}
 
 RFile::~RFile() = default;
 
+void RFile::SetCompressionSettings(int compression)
+{
+   if (fFile->IsWritable())
+      fFile->SetCompressionSettings(compression);
+   else
+      R__LOG_WARNING(RFileLog()) << "Tried to change compression settings on a non-writable file: this has no effect.";
+}
+
+void RFile::SetCompressionSettings(ROOT::RCompressionSetting::EAlgorithm::EValues algorithm, int level)
+{
+   int settings = ROOT::CompressionSettings(algorithm, level);
+   SetCompressionSettings(settings);
+}
+
 TKey *RFile::GetTKey(std::string_view path) const
 {
    // In RFile, differently from TFile, when dealing with a path like "a/b/c", we always consider it to mean

io/io/test/rfile.cxx

@@ -810,3 +810,18 @@ TEST(RFile, TTreeNoDoubleFree)
    // destructed once during writing, once during reading.
    EXPECT_EQ(TTreeDestructorCounter::GetTimesDestructed(), 2);
 }
+
+TEST(RFile, Compression)
+{
+   FileRaii fileGuard("test_rfile_compression.root");
+
+   {
+      auto file = RFile::Recreate(fileGuard.GetPath());
+      std::string s = "foo";
+      file->Put("foo", s);
+   }
+   {
+      auto file = std::unique_ptr<TFile>(TFile::Open(fileGuard.GetPath().c_str()));
+      EXPECT_EQ(file->GetCompressionSettings(), ROOT::RCompressionSetting::EDefaults::kUseGeneralPurpose);
+   }
+}