I/O Module

The io class handles all reading and writing of physics data, supporting both CERN ROOT files (via TFile/TTree) and HDF5 files (via H5Cpp). It inherits from tools and notification and exposes a template-based read/write API for arbitrary C++ types.

Class: `io`

Header: <io/io.h>

Inheritance: tools, notification

HDF5 Methods

Signature	Description
`bool start(std::string filename, std::string read_write)`	Opens (or creates) an HDF5 file at filename. read_write is `"r"` (read), `"w"` (write), or `"rw"` (read-write). Returns `false` on failure.
`void end()`	Closes the currently open HDF5 file.
`template<g> void write(std::vector<g>* inpt, std::string set_name)`	Writes the vector inpt to HDF5 dataset set_name. g must be a trivially copyable POD type.
`template<g> void write(g* inpt, std::string set_name)`	Writes a single scalar inpt to HDF5 dataset set_name.
`template<g> void read(std::vector<g>* outpt, std::string set_name)`	Reads HDF5 dataset set_name into outpt (resized automatically).
`template<g> void read(g* out, std::string set_name)`	Reads a single scalar from HDF5 dataset set_name into out.
`void read(graph_hdf5_w* out, std::string set_name)`	Reads a `graph_hdf5_w` struct from HDF5 dataset set_name.
`std::vector<std::string> dataset_names()`	Returns a list of all dataset names in the open HDF5 file.

ROOT Methods

Signature	Description
`bool scan_keys()`	Scans all open ROOT files and builds the `keys` map. Must be called after setting `trees`, `branches`, and `leaves`. Returns `false` if no keys were found.
`void root_begin()`	Begins an iteration over the `keys` map, setting up `TTreeReader` instances.
`void root_end()`	Closes all open TTreeReader instances.
`void trigger_pcm()`	Triggers the pre-compiled macro (PCM) for object dictionaries.
`void check_root_file_paths()`	Validates that all file paths in `root_files` exist.
`std::map<std::string, long> root_size()`	Returns a map of tree-path → number of entries.
`std::map<std::string, data_t> get_data()`	Returns a pointer to the internal `data_t` map (populated by `root_begin` / `root_end`).
`void import_settings(settings_t* params)`	Copies `trees`, `branches`, `leaves`, and other settings from a `settings_t` struct.

Configuration Fields

Field	Type	Description
`enable_pyami`	`bool`	Enable AMI metadata fetching. Default `true`.
`metacache_path`	`std::string`	Path for the local metadata JSON cache. Default `"./"`.
`current_working_path`	`std::string`	Working directory used for relative file paths. Default `"."`.
`sow_name`	`std::string`	Name of the sum-of-weights branch in the ROOT file. Default `""`.
`trees`	`std::vector<std::string>`	List of ROOT tree names to scan (e.g. `{"nominal"}`).
`branches`	`std::vector<std::string>`	List of branch-path filter prefixes.
`leaves`	`std::vector<std::string>`	List of leaf-path filter suffixes.

Internal ROOT Maps (populated by `scan_keys`)

Field	Description
`files_open`	Map of filename → open `TFile*`.
`meta_data`	Map of filename → `meta*` objects.
`tree_data`	Map of filename → {tree-name → `TTree*`}.
`tree_entries`	Map of filename → {tree-name → entry count}.
`branch_data`	Map of path → {branch-name → `TBranch*`}.
`leaf_data`	Map of filename → {leaf-name → `TLeaf*`}.
`leaf_typed`	Map of filename → {leaf-name → ROOT type string}.
`keys`	Full nested map: filename → tree → branch → list of leaf names.

Example:

io reader;
reader.trees = {"nominal"};
reader.leaves = {"jet_pt"};
reader.root_files["sample.root"] = true;
reader.scan_keys();
reader.root_begin();
auto* data = reader.get_data();
// iterate entries via data map
reader.root_end();