feat(stream): add CircularBitStreamReader

lib/kyut/BitStreamWriter.hpp

@@ -2,6 +2,7 @@
 #define INCLUDE_kyut_BitStreamWriter_hpp
 
 #include <cassert>
+#include <cstdint>
 #include <string_view>
 #include <vector>
 

lib/kyut/CircularBitStreamReader.hpp

+#ifndef INCLUDE_kyut_CircularBitStreamReader_hpp
+#define INCLUDE_kyut_CircularBitStreamReader_hpp
+
+#include <cassert>
+#include <cstdint>
+#include <string_view>
+#include <vector>
+
+namespace kyut {
+    class CircularBitStreamReader {
+    public:
+        explicit CircularBitStreamReader(std::vector<std::uint8_t>&& data)
+            : data_(std::move(data))
+            , pos_bits_(0) {
+        }
+
+        explicit CircularBitStreamReader(std::string_view data)
+            : data_(reinterpret_cast<const std::uint8_t*>(data.data()), reinterpret_cast<const std::uint8_t*>(data.data() + data.size()))
+            , pos_bits_(0) {
+        }
+
+        // Uncopyable and unmovable
+        CircularBitStreamReader(const CircularBitStreamReader&) = delete;
+        CircularBitStreamReader(CircularBitStreamReader&&) = delete;
+
+        CircularBitStreamReader& operator=(const CircularBitStreamReader&) = delete;
+        CircularBitStreamReader& operator=(CircularBitStreamReader&&) = delete;
+
+        ~CircularBitStreamReader() noexcept = default;
+
+        std::uint64_t read(std::size_t size_bits) {
+            std::uint64_t x = 0;
+            for (std::size_t i = 0; i < size_bits; i++) {
+                x <<= 1;
+                x |= read_bit() ? 1 : 0;
+            }
+
+            return x;
+        }
+
+        bool read_bit() {
+            const auto n = pos_bits_ >> 3;
+            const auto k = pos_bits_ & 7;
+
+            const auto bit = (data_[n] >> (7 - k)) & 1;
+
+            pos_bits_++;
+            pos_bits_ %= size_bits();
+
+            return bit != 0;
+        }
+
+        std::size_t size_bytes() const noexcept {
+            return data_.size();
+        }
+
+        std::size_t size_bits() const noexcept {
+            return size_bytes() * 8;
+        }
+
+        std::size_t position_bits() const noexcept {
+            return pos_bits_;
+        }
+
+    private:
+        std::vector<std::uint8_t> data_;
+        std::size_t pos_bits_;
+    };
+} // namespace kyut
+
+#endif // INCLUDE_kyut_CircularBitStreamReader_hpp

test/CMakeLists.txt

@@ -2,6 +2,7 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/test")
 
 add_executable(test_kyut
     test_BitStreamWriter.cpp
+    test_CircularBitStreamReader.cpp
 )
 
 target_link_libraries(test_kyut

test/test_CircularBitStreamReader.cpp

+#include "kyut/CircularBitStreamReader.hpp"
+
+#include <gtest/gtest.h>
+
+TEST(kyut, CircularBitStreamReader) {
+    kyut::CircularBitStreamReader r{"\x89\xAB\xCD\xEF"};
+    std::uint64_t a;
+
+    EXPECT_EQ(r.size_bytes(), 4);
+    EXPECT_EQ(r.size_bits(), 32);
+
+    EXPECT_EQ(r.position_bits(), 0);
+
+    a = r.read(4);
+    EXPECT_EQ(a, 0x8);
+    EXPECT_EQ(r.position_bits(), 4);
+
+    a = r.read(12);
+    EXPECT_EQ(a, 0x9AB);
+    EXPECT_EQ(r.position_bits(), 16);
+
+    a = r.read(20);
+    EXPECT_EQ(a, 0xCDEF8);
+    EXPECT_EQ(r.position_bits(), 4);
+}