From 52d4375b10d920a59f1309c272a2e525feb1c25d Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sat, 1 Jan 2022 20:25:34 +0100
Subject: Separated out headers files; optimizations; type traits; better
 naming

---
 include/unicode/iso.h | 189 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 189 insertions(+)
 create mode 100644 include/unicode/iso.h

(limited to 'include/unicode/iso.h')

diff --git a/include/unicode/iso.h b/include/unicode/iso.h
new file mode 100644
index 0000000..9b20afd
--- /dev/null
+++ b/include/unicode/iso.h
@@ -0,0 +1,189 @@
+#pragma once
+
+#include "types.h"
+
+#include <stdexcept>
+#include <string>
+#include <unordered_map>
+
+namespace unicode::detail {
+
+ using namespace std::string_literals;
+
+ typedef std::unordered_map<iso_t, char32_t> iso_map_type;
+ typedef std::unordered_map<char32_t, iso_t> iso_map_type_reverse;
+
+ // ISO-8859-1 is lower 8-bit of Unicode, so no exceptions necessary
+ static inline iso_map_type iso_8859_1_map;
+
+ // ISO-8859-15 is lower 8-bit of Unicode, except for:
+ static inline iso_map_type iso_8859_15_map {
+  { '\xA4', U'\u20AC' }, // €
+  { '\xA6', U'\u0160' }, // Š
+  { '\xA8', U'\u0161' }, // š
+  { '\xB4', U'\u017D' }, // Ž
+  { '\xB8', U'\u017E' }, // ž
+  { '\xBC', U'\u0152' }, // Œ
+  { '\xBD', U'\u0153' }, // œ
+  { '\xBE', U'\u0178' }, // Ÿ
+ };
+
+ inline iso_map_type_reverse reverse_iso_map(const iso_map_type& map) {
+  iso_map_type_reverse result;
+  std::for_each(map.cbegin(), map.cend(),
+                [&](const iso_map_type::value_type& pair)
+                 {
+                  result.emplace(pair.second, pair.first);
+                  result.emplace(static_cast<char32_t>(static_cast<uint8_t>(pair.first)), 0); // map invalid characters to a known non-mapped value as marker
+                 });
+  return result;
+ }
+
+ static inline iso_map_type_reverse iso_8859_15_map_reverse { reverse_iso_map(iso_8859_15_map) };
+ static inline iso_map_type_reverse iso_8859_1_map_reverse { reverse_iso_map(iso_8859_1_map) };
+
+ template<unicode::detail::iso_map_type& Map=iso_8859_1_map, typename Container=std::basic_string<iso_t>>
+ struct iso_iterator {
+  typedef iso_t value_type;
+  typedef char32_t internal_type;
+  typedef char32_t& reference;
+  typedef char32_t* pointer;
+  typedef size_t difference_type;
+  typedef std::input_iterator_tag iterator_category;
+  typedef typename Container::const_iterator iterator;
+  typedef Container string_type;
+
+  iso_iterator(const iterator& it): m_it(it) {}
+
+  // pre-increment
+  iso_iterator& operator++()
+  {
+   ++m_it;
+   return *this;
+  }
+
+  bool operator!=(const iso_iterator& other) const
+  {
+   return m_it != other.m_it;
+  }
+
+  // return reference?
+  internal_type operator*() const
+  {
+   value_type value{*m_it};
+
+   if constexpr(std::addressof(Map) != std::addressof(iso_8859_1_map)) // mapping of 128 <= x <= 255 if needed
+   {
+    auto it{Map.find(value)};
+    if (it != Map.end())
+     return it->second;
+   }
+   return static_cast<internal_type>(static_cast<uint8_t>(value));
+  }
+
+  iso_iterator& operator+=(size_t distance)
+  {
+   std::advance(m_it, distance);
+   return *this;
+  }
+
+  difference_type operator-(const iso_iterator& other) const
+  {
+   return m_it - other.m_it;
+  }
+
+ private:
+  iterator m_it;
+ };
+
+ template<unicode::detail::iso_map_type_reverse& Map=iso_8859_1_map_reverse, typename Container=std::basic_string<iso_t>>
+ struct iso_back_insert_iterator {
+  typedef iso_back_insert_iterator& reference;
+  typedef iso_back_insert_iterator* pointer;
+  typedef size_t difference_type;
+  typedef iso_t value_type;
+  typedef char32_t internal_type;
+  typedef std::output_iterator_tag iterator_category;
+  typedef Container string_type;
+  
+  iso_back_insert_iterator(string_type& s): s(s) {}
+
+  iso_back_insert_iterator& operator=(const iso_back_insert_iterator& other)
+  {
+   if (std::addressof(other.s) != std::addressof(s))
+    throw std::runtime_error("iso_back_insert_iterator assignment operator actually called! Iterator should not be assigned to.");
+
+   return *this;
+  }
+
+  // no-op
+  reference operator++()
+  {
+   return *this;
+  }
+
+  // support *x = value, together with operator=()
+  reference operator*()
+  {
+   return *this;
+  }
+
+  reference operator=(const internal_type& value)
+  {
+   if constexpr(std::addressof(Map) != std::addressof(iso_8859_1_map_reverse)) // mapping back to 128 <= x <= 255 if needed
+   {
+    auto it{Map.find(value)};
+    if (it != Map.end()) {
+     if (it->second == 0) // marker for non-mappable character found
+      throw std::invalid_argument("Bad Unicode value to map to ISO 8859-15: "s + std::to_string(static_cast<uint32_t>(value)));
+     s.push_back(it->second);
+     return *this;
+    }
+   }
+
+   if (value > 255)
+    throw std::invalid_argument("Bad ISO 8859 value above 255: "s + std::to_string(static_cast<uint32_t>(value)));
+
+   s.push_back(static_cast<typename iso_back_insert_iterator::value_type>(value));
+   return *this;
+  }
+
+ private:
+  typename iso_back_insert_iterator::string_type& s;
+ };
+
+} // namespace unicode::detail
+
+namespace unicode {
+
+ using namespace detail;
+
+ // Encoding for convert() and ISO-8859-*
+ template<typename InputIt, typename OutputIt>
+ struct ISO_8859
+ {
+  typedef iso_t value_type;
+  typedef typename InputIt::string_type string_type;
+
+  static InputIt begin(const typename InputIt::string_type& s)
+  {
+   return InputIt(s.cbegin());
+  }
+
+  static InputIt end(const typename InputIt::string_type& s)
+  {
+   return InputIt(s.cend());
+  }
+
+  static OutputIt back_inserter(typename OutputIt::string_type& s)
+  {
+   return OutputIt(s);
+  }
+ };
+
+ // Encoding for convert()
+ typedef ISO_8859<iso_iterator<>, iso_back_insert_iterator<>> ISO_8859_1;
+ typedef ISO_8859<iso_iterator<iso_8859_15_map>, iso_back_insert_iterator<iso_8859_15_map_reverse>> ISO_8859_15;
+
+} // namespace unicode
+
-- 
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