...

2 files changed, 71 insertions, 0 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index d53b9740..6a18ef2b 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(CRU_BASE_INCLUDE_DIR ${CRU_INCLUDE_DIR}/cru/common)
 add_library(cru_base STATIC 
 	Logger.cpp
+	StringUtil.cpp
 )
 target_sources(cru_base PUBLIC
 	${CRU_BASE_INCLUDE_DIR}/Base.hpp
@@ -9,6 +10,7 @@ target_sources(cru_base PUBLIC
 	${CRU_BASE_INCLUDE_DIR}/Logger.hpp
 	${CRU_BASE_INCLUDE_DIR}/PreConfig.hpp
 	${CRU_BASE_INCLUDE_DIR}/SelfResolvable.hpp
+	${CRU_BASE_INCLUDE_DIR}/StringUtil.hpp
 )
 target_include_directories(cru_base PUBLIC ${CRU_INCLUDE_DIR})
 target_compile_definitions(cru_base PUBLIC $<$<CONFIG:Debug>:CRU_DEBUG>)
diff --git a/src/common/StringUtil.cpp b/src/common/StringUtil.cpp
new file mode 100644
index 00000000..31a5effd
--- /dev/null
+++ b/src/common/StringUtil.cpp
@@ -0,0 +1,69 @@
+#include "cru/common/StringUtil.hpp"
+
+namespace cru {
+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));
+}
+
+CodePoint Utf8Iterator::Next() {
+  if (position_ == static_cast<Index>(string_.length()))
+    return k_code_point_end;
+
+  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