ROOT   Reference Guide
ROOT::Experimental::Internal::RFileNTupleAnchor Class Reference

Entry point for an RNTuple in a ROOT file.

The class points to the header and footer keys, which in turn have the references to the pages. Only the RNTuple key will be listed in the list of keys. Like TBaskets, the pages are "invisible" keys. Byte offset references in the RNTuple header and footer reference directly the data part of page records, skipping the TFile key part.

In the list of keys, this object appears as "ROOT::Experimental::RNTuple".

The RNTuple object is the user-facing representation of an RNTuple data set in a ROOT file. The RFileNTupleAnchor is the low-level entry point of an RNTuple in a ROOT file used by the page storage layer.

The ROOT::Experimental::RNTuple object has the same on-disk layout as the RFileNTupleAnchor. It only adds methods and transient members. Reading and writing RNTuple anchors with TFile and the minifile writer is thus fully interoperable (same on-disk information). TODO(jblomer): Remove unneeded fChecksum, fVersion, fSize, fReserved once ROOT::Experimental::RNTuple moves out of the experimental namespace.

Definition at line 65 of file RMiniFile.hxx.

## Public Attributes

std::int32_t fChecksum = 0
The ROOT streamer info checksum. More...

std::uint32_t fLenFooter = 0
The size of the uncompressed ntuple footer. More...

The size of the uncompressed ntuple header. More...

std::uint32_t fNBytesFooter = 0
The size of the compressed ntuple footer. More...

The size of the compressed ntuple header. More...

std::uint64_t fReserved = 0
Currently unused, reserved for later use. More...

std::uint64_t fSeekFooter = 0
The file offset of the footer excluding the TKey part. More...

The file offset of the header excluding the TKey part. More...

std::uint32_t fSize = sizeof(RFileNTupleAnchor)
Allows for skipping the struct. More...

std::uint32_t fVersion = 0
Allows for evolving the struct in future versions. More...

#include <ROOT/RMiniFile.hxx>

Inheritance diagram for ROOT::Experimental::Internal::RFileNTupleAnchor:
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## ◆ fChecksum

 std::int32_t ROOT::Experimental::Internal::RFileNTupleAnchor::fChecksum = 0

The ROOT streamer info checksum.

Older RNTuple versions used class version 0 and a serialized checksum, now we use class version 3 and "promote" the checksum as a class member

Definition at line 68 of file RMiniFile.hxx.

## ◆ fLenFooter

 std::uint32_t ROOT::Experimental::Internal::RFileNTupleAnchor::fLenFooter = 0

The size of the uncompressed ntuple footer.

Definition at line 84 of file RMiniFile.hxx.

The size of the uncompressed ntuple header.

Definition at line 78 of file RMiniFile.hxx.

## ◆ fNBytesFooter

 std::uint32_t ROOT::Experimental::Internal::RFileNTupleAnchor::fNBytesFooter = 0

The size of the compressed ntuple footer.

Definition at line 82 of file RMiniFile.hxx.

The size of the compressed ntuple header.

Definition at line 76 of file RMiniFile.hxx.

## ◆ fReserved

 std::uint64_t ROOT::Experimental::Internal::RFileNTupleAnchor::fReserved = 0

Currently unused, reserved for later use.

Definition at line 86 of file RMiniFile.hxx.

## ◆ fSeekFooter

 std::uint64_t ROOT::Experimental::Internal::RFileNTupleAnchor::fSeekFooter = 0

The file offset of the footer excluding the TKey part.

Definition at line 80 of file RMiniFile.hxx.

The file offset of the header excluding the TKey part.

Definition at line 74 of file RMiniFile.hxx.

## ◆ fSize

 std::uint32_t ROOT::Experimental::Internal::RFileNTupleAnchor::fSize = sizeof(RFileNTupleAnchor)

Allows for skipping the struct.

Definition at line 72 of file RMiniFile.hxx.

## ◆ fVersion

 std::uint32_t ROOT::Experimental::Internal::RFileNTupleAnchor::fVersion = 0

Allows for evolving the struct in future versions.

Definition at line 70 of file RMiniFile.hxx.

Collaboration diagram for ROOT::Experimental::Internal::RFileNTupleAnchor:
[legend]

The documentation for this class was generated from the following file: