rntviewer/rntviewer.cpp

#include <ROOT/RNTupleReader.hxx>
#include <ROOT/RNTuple.hxx>
#include <TFile.h>

#include <cstdio>
#include <cstdint>

#include <sys/mman.h>
#include <unistd.h>

#ifdef DEBUG
#include <sanitizer/asan_interface.h>
#endif

#include "types.h"
#include "defer.hpp"
#include "mem.h"

#include "mem.cpp"

using namespace ROOT::Experimental;

static size_t file_size(FILE *f)
{
  fseek(f, 0, SEEK_END);
  size_t res = ftell(f);
  fseek(f, 0, SEEK_SET);
  return res;  
}

int main(int argc, char **argv)
{
  if (argc < 3) {
    fprintf(stderr, "Usage: %s <ntuple_name> <ntuple_file.root>\n", argv[0]);
    return 1;
  }

  // Collect arguments
  const char *ntpl_name = argv[1];
  const char *fname = argv[2];

  // Allocate memory
  Arena *arena = arena_alloc();
  if (!arena) {
    fprintf(stderr, "Failed to allocate memory\n");
    return 1;
  }
  defer { arena_release(arena); };

  // Open and map the file
  FILE *file = fopen(fname, "rb");
  defer { fclose(file); };

  const int fd = fileno(file);
  const size_t fsize = file_size(file);
  void *fmem = mmap(0, fsize, PROT_READ, MAP_SHARED_VALIDATE, fd, 0);
  if (!fmem) {
    fprintf(stderr, "Failed to open file %s\n", fname);
    return 1;
  }
  defer { munmap(fmem, fsize); };

  // Open the TFile
  TFile *tfile = TFile::Open(fname, "READ");
  if (!tfile) {
    fprintf(stderr, "Failed to open TFile.\n");
    return 1;
  }
  defer { delete tfile; };

  // Get the RNTuple information
  const RNTuple *anchor = tfile->Get<RNTuple>(ntpl_name);
  if (!anchor) {
    fprintf(stderr, "RNTuple '%s' not found in %s.\n", ntpl_name, fname);
    return 1;
  }

  return 0;
}