1 files changed, 125 insertions, 127 deletions

diff --git a/src/common/StringUtil.cpp b/src/common/StringUtil.cpp
index 0ebfd85e..6b185a82 100644
--- a/src/common/StringUtil.cpp
+++ b/src/common/StringUtil.cpp
@@ -3,160 +3,158 @@
 #include <codecvt>
 
 namespace cru {
+namespace {
+
 template <typename UInt, int number_of_bit>
 inline std::enable_if_t<std::is_unsigned_v<UInt>, CodePoint> ExtractBits(
     UInt n) {
   return static_cast<CodePoint>(n & ((1u << number_of_bit) - 1));
 }
+}  // namespace
 
-CodePoint Utf16Iterator::Previous() {
-  if (position_ <= 0) return k_invalid_code_point;
-
-  const auto cu0 = static_cast<std::uint16_t>(string_[--position_]);
-
-  if (cu0 < 0xd800u || cu0 >= 0xe000u) {  // 1-length code point
-    return static_cast<CodePoint>(cu0);
-  } else if (cu0 >= 0xdc00u || cu0 <= 0xdfffu) {  // 2-length code point
-    if (position_ <= 0) {
-      throw TextEncodeException(
-          "Unexpected end when reading first code unit of surrogate pair "
-          "during backward.");
-    }
-    const auto cu1 = static_cast<std::uint16_t>(string_[--position_]);
+CodePoint Utf8NextCodePoint(std::string_view str, Index current,
+                            Index* next_position) {
+  CodePoint result;
 
-#ifdef CRU_DEBUG
-    if (cu1 < 0xd800u || cu1 > 0xdbffu) {
-      throw TextEncodeException(
-          "Unexpected bad-range first code unit of surrogate pair during "
-          "backward.");
+  if (current >= static_cast<Index>(str.length())) {
+    result = k_invalid_code_point;
+  } else {
+    const auto cu0 = static_cast<std::uint8_t>(str[current++]);
+
+    auto read_next_folowing_code = [&str, &current]() -> CodePoint {
+      if (current == static_cast<Index>(str.length()))
+        throw TextEncodeException(
+            "Unexpected end when read continuing byte of multi-byte code "
+            "point.");
+
+      const auto u = static_cast<std::uint8_t>(str[current]);
+      if (!(u & (1u << 7)) || (u & (1u << 6))) {
+        throw TextEncodeException(
+            "Unexpected bad-format (not 0b10xxxxxx) continuing byte of "
+            "multi-byte code point.");
+      }
+
+      return ExtractBits<std::uint8_t, 6>(str[current++]);
+    };
+
+    if ((1u << 7) & cu0) {
+      if ((1u << 6) & cu0) {      // 2~4-length code point
+        if ((1u << 5) & cu0) {    // 3~4-length code point
+          if ((1u << 4) & cu0) {  // 4-length code point
+            if (cu0 & (1u << 3)) {
+              throw TextEncodeException(
+                  "Unexpected bad-format begin byte (not 0b11110xxx) of 4-byte"
+                  "code point.");
+            }
+
+            const CodePoint s0 = ExtractBits<std::uint8_t, 3>(cu0) << (6 * 3);
+            const CodePoint s1 = read_next_folowing_code() << (6 * 2);
+            const CodePoint s2 = read_next_folowing_code() << 6;
+            const CodePoint s3 = read_next_folowing_code();
+            result = s0 + s1 + s2 + s3;
+          } else {  // 3-length code point
+            const CodePoint s0 = ExtractBits<std::uint8_t, 4>(cu0) << (6 * 2);
+            const CodePoint s1 = read_next_folowing_code() << 6;
+            const CodePoint s2 = read_next_folowing_code();
+            result = s0 + s1 + s2;
+          }
+        } else {  // 2-length code point
+          const CodePoint s0 = ExtractBits<std::uint8_t, 5>(cu0) << 6;
+          const CodePoint s1 = read_next_folowing_code();
+          result = s0 + s1;
+        }
+      } else {
+        throw TextEncodeException(
+            "Unexpected bad-format (0b10xxxxxx) begin byte of a code point.");
+      }
+    } else {
+      result = static_cast<CodePoint>(cu0);
     }
-#endif
+  }
 
-    const auto s0 = ExtractBits<std::uint16_t, 10>(cu1) << 10;
-    const auto s1 = ExtractBits<std::uint16_t, 10>(cu0);
+  if (next_position != nullptr) *next_position = current;
+  return result;
+}
 
-    return s0 + s1 + 0x10000;
+CodePoint Utf16NextCodePoint(std::u16string_view str, Index current,
+                             Index* next_position) {
+  CodePoint result;
 
+  if (current >= static_cast<Index>(str.length())) {
+    result = k_invalid_code_point;
   } else {
-    throw TextEncodeException(
-        "Unexpected bad-range second code unit of surrogate pair during "
-        "backward.");
-  }
-}
+    const auto cu0 = str[current++];
 
-CodePoint Utf16Iterator::Next() {
-  if (position_ >= static_cast<Index>(string_.length()))
-    return k_invalid_code_point;
+    if (!IsUtf16SurrogatePairCodeUnit(cu0)) {  // 1-length code point
+      result = static_cast<CodePoint>(cu0);
+    } else if (IsUtf16SurrogatePairLeading(cu0)) {  // 2-length code point
+      if (current >= static_cast<Index>(str.length())) {
+        throw TextEncodeException(
+            "Unexpected end when reading second code unit of surrogate pair.");
+      }
+      const auto cu1 = str[current++];
 
-  const auto cu0 = static_cast<std::uint16_t>(string_[position_++]);
+      if (!IsUtf16SurrogatePairTrailing(cu1)) {
+        throw TextEncodeException(
+            "Unexpected bad-range second code unit of surrogate pair.");
+      }
 
-  if (cu0 < 0xd800u || cu0 >= 0xe000u) {  // 1-length code point
-    return static_cast<CodePoint>(cu0);
-  } else if (cu0 <= 0xdbffu) {  // 2-length code point
-    if (position_ >= static_cast<Index>(string_.length())) {
-      throw TextEncodeException(
-          "Unexpected end when reading second code unit of surrogate pair "
-          "during forward.");
-    }
-    const auto cu1 = static_cast<std::uint16_t>(string_[position_++]);
+      const auto s0 = ExtractBits<std::uint16_t, 10>(cu0) << 10;
+      const auto s1 = ExtractBits<std::uint16_t, 10>(cu1);
+
+      result = s0 + s1 + 0x10000;
 
-#ifdef CRU_DEBUG
-    if (cu1 < 0xdc00u || cu1 > 0xdfffu) {
+    } else {
       throw TextEncodeException(
-          "Unexpected bad-format second code unit of surrogate pair during "
-          "forward.");
+          "Unexpected bad-range first code unit of surrogate pair.");
     }
-#endif
-
-    const auto s0 = ExtractBits<std::uint16_t, 10>(cu0) << 10;
-    const auto s1 = ExtractBits<std::uint16_t, 10>(cu1);
+  }
 
-    return s0 + s1 + 0x10000;
+  if (next_position != nullptr) *next_position = current;
+  return result;
+}
 
+CodePoint Utf16PreviousCodePoint(std::u16string_view str, Index current,
+                                 Index* previous_position) {
+  CodePoint result;
+  if (current <= 0) {
+    result = k_invalid_code_point;
   } else {
-    throw TextEncodeException(
-        "Unexpected bad-format first code unit of surrogate pair during "
-        "forward.");
-  }
-}
+    const auto cu0 = str[--current];
 
-Index PreviousIndex(std::u16string_view string, Index current) {
-  Utf16Iterator iterator{string, current};
-  iterator.Previous();
-  return iterator.CurrentPosition();
-}
+    if (!IsUtf16SurrogatePairCodeUnit(cu0)) {  // 1-length code point
+      result = static_cast<CodePoint>(cu0);
+    } else if (IsUtf16SurrogatePairTrailing(cu0)) {  // 2-length code point
+      if (current <= 0) {
+        throw TextEncodeException(
+            "Unexpected end when reading first code unit of surrogate pair.");
+      }
+      const auto cu1 = str[--current];
+
+      if (!IsUtf16SurrogatePairLeading(cu1)) {
+        throw TextEncodeException(
+            "Unexpected bad-range first code unit of surrogate pair.");
+      }
+
+      const auto s0 = ExtractBits<std::uint16_t, 10>(cu1) << 10;
+      const auto s1 = ExtractBits<std::uint16_t, 10>(cu0);
 
-Index NextIndex(std::u16string_view string, Index current) {
-  Utf16Iterator iterator{string, current};
-  iterator.Next();
-  return iterator.CurrentPosition();
+      result = s0 + s1 + 0x10000;
+
+    } else {
+      throw TextEncodeException(
+          "Unexpected bad-range second code unit of surrogate pair.");
+    }
+  }
+
+  if (previous_position != nullptr) *previous_position = current;
+  return result;
 }
 
 std::string ToUtf8(const std::u16string& s) {
-  // TODO: Implement this by myself.
+  // TODO: Implement this by myself. Remember to remove deprecation warning
+  // suppress macro.
   return std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}
       .to_bytes(s);
 }
-
-// CodePoint Utf8Iterator::Next() {
-//   if (position_ == static_cast<Index>(string_.length()))
-//     return k_invalid_code_point;
-
-//   const auto cu0 = static_cast<std::uint8_t>(string_[position_++]);
-
-//   auto read_next_folowing_code = [this]() -> CodePoint {
-//     if (this->position_ == static_cast<Index>(string_.length()))
-//       throw TextEncodeException(
-//           "Unexpected end when read continuing byte of multi-byte code
-//           point.");
-
-// #ifdef CRU_DEBUG
-//     const auto u = static_cast<std::uint8_t>(string_[position_]);
-//     if (!(u & (1u << 7)) || (u & (1u << 6))) {
-//       throw TextEncodeException(
-//           "Unexpected bad-format (not 0b10xxxxxx) continuing byte of "
-//           "multi-byte code point.");
-//     }
-// #endif
-
-//     return ExtractBits<std::uint8_t, 6>(string_[position_++]);
-//   };
-
-//   if ((1u << 7) & cu0) {
-//     if ((1u << 6) & cu0) {      // 2~4-length code point
-//       if ((1u << 5) & cu0) {    // 3~4-length code point
-//         if ((1u << 4) & cu0) {  // 4-length code point
-// #ifdef CRU_DEBUG
-//           if (cu0 & (1u << 3)) {
-//             throw TextEncodeException(
-//                 "Unexpected bad-format begin byte (not 0b10xxxxxx) of 4-byte
-//                 " "code point.");
-//           }
-// #endif
-
-//           const CodePoint s0 = ExtractBits<std::uint8_t, 3>(cu0) << (6 * 3);
-//           const CodePoint s1 = read_next_folowing_code() << (6 * 2);
-//           const CodePoint s2 = read_next_folowing_code() << 6;
-//           const CodePoint s3 = read_next_folowing_code();
-//           return s0 + s1 + s2 + s3;
-//         } else {  // 3-length code point
-//           const CodePoint s0 = ExtractBits<std::uint8_t, 4>(cu0) << (6 * 2);
-//           const CodePoint s1 = read_next_folowing_code() << 6;
-//           const CodePoint s2 = read_next_folowing_code();
-//           return s0 + s1 + s2;
-//         }
-//       } else {  // 2-length code point
-//         const CodePoint s0 = ExtractBits<std::uint8_t, 5>(cu0) << 6;
-//         const CodePoint s1 = read_next_folowing_code();
-//         return s0 + s1;
-//       }
-//     } else {
-//       throw TextEncodeException(
-//           "Unexpected bad-format (0b10xxxxxx) begin byte of a code point.");
-//     }
-//   } else {
-//     return static_cast<CodePoint>(cu0);
-//   }
-// }
-
 }  // namespace cru