bgneal@0: // Copyright (C) 2012 by Brian Neal.
bgneal@0: // This file is part of Cpp-Enigma, the Enigma Machine simulation.
bgneal@0: // Cpp-Enigma is released under the MIT License (see License.txt).
bgneal@0: //
bgneal@0: // rotor.cpp - Implementation file for the rotor class.
bgneal@0: 
bgneal@0: #include <set>
bgneal@0: #include <array>
bgneal@0: #include <algorithm>
bgneal@0: #include "rotor.h"
bgneal@1: #include "enigma_utils.h"
bgneal@0: 
bgneal@0: using namespace enigma;
bgneal@0: 
bgneal@1: ////////////////////////////////////////////////////////////////////////////////
bgneal@1: 
bgneal@0: namespace
bgneal@0: {
bgneal@0:    const char* const ucase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
bgneal@1: 
bgneal@1:    // Turned into a function to avoid translation unit initialization order problems.
bgneal@1:    const std::set<char>& get_ucase_set()
bgneal@1:    {
bgneal@1:       static const std::set<char> the_set(ucase, ucase + 26);
bgneal@1:       return the_set;
bgneal@1:    }
bgneal@0: }
bgneal@0: 
bgneal@1: ////////////////////////////////////////////////////////////////////////////////
bgneal@1: 
bgneal@0: rotor::rotor(const char* name, const char* wiring, int ring_setting, const char* stepping)
bgneal@1:  : rotor_name{name},
bgneal@1:    wiring_str{wiring},
bgneal@1:    ring_setting{ring_setting},
bgneal@1:    pos{0},
bgneal@1:    display_val{'A'},
bgneal@1:    entry_map(),
bgneal@1:    exit_map(),
bgneal@1:    display_map(),
bgneal@1:    pos_map(),
bgneal@1:    step_map()
bgneal@0: {
bgneal@0:    // check wiring length
bgneal@0:    if (wiring_str.size() != 26)
bgneal@0:    {
bgneal@0:       throw rotor_error("invalid wiring length");
bgneal@0:    }
bgneal@0: 
bgneal@0:    // ensure wiring contains only uppercase letters & every char must appear
bgneal@0:    // exactly once:
bgneal@1:    const std::set<char>& ucase_set(get_ucase_set());
bgneal@0: 
bgneal@1:    // g++ 4.6.3 warns about missing braces unless we double them up, below:
bgneal@1:    std::array<int, 26> letter_counts = {{ 0 }};
bgneal@0:    for (int i = 0; i < 26; ++i)
bgneal@0:    {
bgneal@1:       const char c{wiring_str[i]};
bgneal@0:       if (ucase_set.find(c) == ucase_set.end())
bgneal@0:       {
bgneal@0:          throw rotor_error("invalid wiring");
bgneal@0:       }
bgneal@0:       ++letter_counts[c - 'A'];
bgneal@0:    }
bgneal@0: 
bgneal@0:    if (std::find_if(letter_counts.begin(),
bgneal@0:                     letter_counts.end(),
bgneal@0:                     [](int n) { return n != 1; }) != letter_counts.end())
bgneal@0:    {
bgneal@0:       throw rotor_error("invalid wiring; duplicate letter");
bgneal@0:    }
bgneal@1: 
bgneal@1:    if (ring_setting < 0 || ring_setting >= 26)
bgneal@1:    {
bgneal@1:       throw rotor_error("invalid ring setting");
bgneal@1:    }
bgneal@1:    set_ring_setting(ring_setting);
bgneal@1: 
bgneal@1:    // Initialize our two arrays that describe the internal wiring. Arrays are used
bgneal@1:    // to do fast lookup from both entry (from the right) and exit (from the
bgneal@1:    // left).
bgneal@1: 
bgneal@1:    for (int i = 0; i < 26; ++i)
bgneal@1:    {
bgneal@1:       const int v = wiring_str[i] - 'A';
bgneal@1:       entry_map[i] = v;
bgneal@1:       exit_map[v] = i;
bgneal@1:    }
bgneal@1: 
bgneal@1:    // Build a lookup table that tells us when the pawls are allowed to step.
bgneal@1:    // The index to this array is the current display letter [A-Z] - 'A'.
bgneal@1: 
bgneal@1:    if (stepping != nullptr)
bgneal@1:    {
bgneal@2:       for (char c = *stepping; *stepping != '\0'; c = *(++stepping))
bgneal@1:       {
bgneal@1:          if (ucase_set.find(c) != ucase_set.end())
bgneal@1:          {
bgneal@1:             step_map[c - 'A'] = true;
bgneal@1:          }
bgneal@1:          else
bgneal@1:          {
bgneal@1:             throw rotor_error("invalid stepping");
bgneal@1:          }
bgneal@1:       }
bgneal@1:    }
bgneal@1: 
bgneal@1:    // set initial position
bgneal@1:    set_display('A');
bgneal@0: }
bgneal@1: 
bgneal@1: ////////////////////////////////////////////////////////////////////////////////
bgneal@1: 
bgneal@1: void rotor::set_ring_setting(int n)
bgneal@1: {
bgneal@1:    ring_setting = n;
bgneal@1: 
bgneal@1:    // Build a mapping from window display values to positions
bgneal@1:    // and a reverse mapping of position to display value:
bgneal@1:    for (int i = 0; i < 26; ++i)
bgneal@1:    {
bgneal@1:       const int n = alpha_mod(i - ring_setting);
bgneal@1:       display_map[i] = n;
bgneal@1:       pos_map[n] = i + 'A';
bgneal@1:    }
bgneal@1: }