+++ /dev/null
-// Copyright (c) 2018-2020 Emil Dotchevski and Reverge Studios, Inc.
-
-// Distributed under the Boost Software License, Version 1.0. (See accompanying
-// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
-
-// This is the program presented in https://boostorg.github.io/leaf/#introduction-eh.
-
-// It reads a text file in a buffer and prints it to std::cout, using LEAF to handle errors.
-// This version uses exception handling. The version that does not use exception
-// handling is in print_file_result.cpp.
-
-#include <boost/leaf/exception.hpp>
-#include <boost/leaf/handle_errors.hpp>
-#include <boost/leaf/pred.hpp>
-#include <boost/leaf/on_error.hpp>
-#include <boost/leaf/common.hpp>
-#include <iostream>
-#include <memory>
-#include <stdio.h>
-
-namespace leaf = boost::leaf;
-
-
-// Error types
-struct bad_command_line { };
-struct input_error { };
-struct open_error { };
-struct read_error { };
-struct size_error { };
-struct eof_error { };
-struct output_error { };
-
-
-// We will handle all failures in our main function, but first, here are the declarations of the functions it calls, each
-// communicating failures by throwing exceptions
-
-// Parse the command line, return the file name.
-char const * parse_command_line( int argc, char const * argv[] );
-
-// Open a file for reading.
-std::shared_ptr<FILE> file_open( char const * file_name );
-
-// Return the size of the file.
-int file_size( FILE & f );
-
-// Read size bytes from f into buf.
-void file_read( FILE & f, void * buf, int size );
-
-
-// The main function, which handles all errors.
-int main( int argc, char const * argv[] )
-{
- return leaf::try_catch(
-
- [&]
- {
- char const * file_name = parse_command_line(argc,argv);
-
- auto load = leaf::on_error( leaf::e_file_name{file_name} );
-
- std::shared_ptr<FILE> f = file_open(file_name);
-
- int s = file_size(*f);
-
- std::string buffer(1 + s, '\0');
- file_read(*f, &buffer[0], buffer.size()-1);
-
- std::cout << buffer;
- std::cout.flush();
- if( std::cout.fail() )
- throw leaf::exception(output_error{}, leaf::e_errno{errno});
-
- return 0;
- },
-
- // Each of the lambdas below is an error handler. LEAF will consider them, in order, and call the first one that matches
- // the available error objects.
-
- // This handler will be called if the error includes:
- // - an object of type open_error, and
- // - an object of type leaf::e_errno that has .value equal to ENOENT, and
- // - an object of type leaf::e_file_name.
- []( open_error &, leaf::match_value<leaf::e_errno, ENOENT>, leaf::e_file_name const & fn )
- {
- std::cerr << "File not found: " << fn.value << std::endl;
- return 1;
- },
-
- // This handler will be called if the error includes:
- // - an object of type open_error, and
- // - an object of type leaf::e_errno (regardless of its .value), and
- // - an object of type leaf::e_file_name.
- []( open_error &, leaf::e_errno const & errn, leaf::e_file_name const & fn )
- {
- std::cerr << "Failed to open " << fn.value << ", errno=" << errn << std::endl;
- return 2;
- },
-
- // This handler will be called if the error includes:
- // - an object of type input_error, and
- // - an optional object of type leaf::e_errno (regardless of its .value), and
- // - an object of type leaf::e_file_name.
- []( input_error &, leaf::e_errno const * errn, leaf::e_file_name const & fn )
- {
- std::cerr << "Failed to access " << fn.value;
- if( errn )
- std::cerr << ", errno=" << *errn;
- std::cerr << std::endl;
- return 3;
- },
-
- // This handler will be called if the error includes:
- // - an object of type output_error, and
- // - an object of type leaf::e_errno (regardless of its .value),
- []( output_error &, leaf::e_errno const & errn )
- {
- std::cerr << "Output error, errno=" << errn << std::endl;
- return 4;
- },
-
- // This handler will be called if we've got a bad_command_line
- []( bad_command_line & )
- {
- std::cout << "Bad command line argument" << std::endl;
- return 5;
- },
-
- // This last handler matches any error: it prints diagnostic information to help debug logic errors in the program, since it
- // failed to match an appropriate error handler to the error condition it encountered. In this program this handler will
- // never be called.
- []( leaf::error_info const & unmatched )
- {
- std::cerr <<
- "Unknown failure detected" << std::endl <<
- "Cryptic diagnostic information follows" << std::endl <<
- unmatched;
- return 6;
- } );
-}
-
-
-// Implementations of the functions called by main:
-
-
-// Parse the command line, return the file name.
-char const * parse_command_line( int argc, char const * argv[] )
-{
- if( argc==2 )
- return argv[1];
- else
- throw leaf::exception(bad_command_line{});
-}
-
-
-// Open a file for reading.
-std::shared_ptr<FILE> file_open( char const * file_name )
-{
- auto load = leaf::on_error(input_error{});
-
- if( FILE * f = fopen(file_name, "rb") )
- return std::shared_ptr<FILE>(f, &fclose);
- else
- throw leaf::exception(open_error{}, leaf::e_errno{errno});
-}
-
-
-// Return the size of the file.
-int file_size( FILE & f )
-{
- auto load = leaf::on_error(input_error{}, size_error{}, []{ return leaf::e_errno{errno}; });
-
- if( fseek(&f, 0, SEEK_END) )
- throw leaf::exception();
-
- int s = ftell(&f);
- if( s==-1L )
- throw leaf::exception();
-
- if( fseek(&f,0,SEEK_SET) )
- throw leaf::exception();
-
- return s;
-}
-
-
-// Read size bytes from f into buf.
-void file_read( FILE & f, void * buf, int size )
-{
- auto load = leaf::on_error(input_error{});
-
- int n = fread(buf, 1, size, &f);
-
- if( ferror(&f) )
- throw leaf::exception(read_error{}, leaf::e_errno{errno});
-
- if( n!=size )
- throw leaf::exception(eof_error{});
-}
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