Experiments with std::string_view, argument dispatching, and stuff like that.

string_view_and_arguments.cpp

/// Experiments with string view, dispatching, and stuff like that.
/// J. Arrieta
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <locale>
#include <string>

// POSIX only
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

// An example of what NOT to do. Globals automatically render the program thread
// unsafe.
static std::size_t gNUMBER_WIDTH{12};
static std::size_t gTOTAL_SIZE{0};
static std::size_t gMAX_WIDTH{0};

auto size(std::string_view path) {
  struct stat stat_buffer;
  // An example of what NOT to do with string_view. string_view::data() will not
  // necessarily return a pointer to a null-terminated string, so this is
  // begging for a buffer overflow attack.
  ::stat(path.data(), &stat_buffer);
  return stat_buffer.st_size;
}

auto show_size(std::string_view path) {
  auto s     = size(path);
  gMAX_WIDTH = std::max(path.size(), gMAX_WIDTH);
  gTOTAL_SIZE += s;
  std::cout << std::setw(gNUMBER_WIDTH) << s << " " << path << "\n";
}

int main(int argc, char* argv[]) {
  std::cout.imbue(std::locale(""));  // add comma separator to numeric output

  // Elegant dispatching. Notice that the result of std::for_each is the
  // function itself. In this case I choose to pass the actual program name
  // (which is stupid). A cool use I can think of right of the bat is having the
  // function be a state machine, and the last call is the termination trigger.
  std::for_each(argv + 1, argv + argc, show_size)(argv[0]);

  // Just some stupid stuff.
  auto h = std::string(gNUMBER_WIDTH, '-') + " " + std::string(gMAX_WIDTH, '-');
  std::cout << h << "\n"
            << std::setw(gNUMBER_WIDTH) << gTOTAL_SIZE << " "
            << "Total bytes\n"
            << h << "\n";
}