Start C++ rewrite.

abuf.h

@@ -0,0 +1,57 @@
+#ifndef ABUF_HPP
+#define ABUF_HPP
+
+#include <string>
+#include <string_view>
+#include <cstddef>
+
+namespace ke {
+
+/**
+ * Append buffer class for efficient string building.
+ * C++17 implementation with RAII memory management.
+ */
+class abuf {
+public:
+    // Constructors
+    abuf() noexcept = default;
+    
+    // Deleted copy constructor and assignment (use move semantics)
+    abuf(const abuf&) = delete;
+    abuf& operator=(const abuf&) = delete;
+    
+    // Move constructor and assignment
+    abuf(abuf&&) noexcept = default;
+    abuf& operator=(abuf&&) noexcept = default;
+    
+    // Destructor (automatic cleanup via std::string)
+    ~abuf() = default;
+    
+    // Append methods
+    void append(std::string_view s);
+    void append(const char* s, std::size_t len);
+    void append(char c);
+    
+    // Accessors
+    [[nodiscard]] const char* data() const noexcept { return buffer_.data(); }
+    [[nodiscard]] std::size_t size() const noexcept { return buffer_.size(); }
+    [[nodiscard]] std::size_t length() const noexcept { return buffer_.length(); }
+    [[nodiscard]] bool empty() const noexcept { return buffer_.empty(); }
+    [[nodiscard]] std::size_t capacity() const noexcept { return buffer_.capacity(); }
+    
+    // Get the underlying string
+    [[nodiscard]] const std::string& str() const noexcept { return buffer_; }
+    
+    // Clear the buffer
+    void clear() noexcept { buffer_.clear(); }
+    
+    // Reserve capacity
+    void reserve(std::size_t new_cap) { buffer_.reserve(new_cap); }
+
+private:
+    std::string buffer_;
+};
+
+} // namespace ke
+
+#endif // ABUF_HPP