should be it

external/duckdb/extension/parquet/include/resizable_buffer.hpp

@@ -0,0 +1,114 @@
+//===----------------------------------------------------------------------===//
+//                         DuckDB
+//
+// resizable_buffer.hpp
+//
+//
+//===----------------------------------------------------------------------===//
+
+#pragma once
+
+#include "duckdb.hpp"
+#include "duckdb/common/allocator.hpp"
+
+#include <exception>
+
+namespace duckdb {
+
+class ByteBuffer { // on to the 10 thousandth impl
+public:
+	ByteBuffer() {};
+	ByteBuffer(data_ptr_t ptr, uint64_t len) : ptr(ptr), len(len) {};
+
+	data_ptr_t ptr = nullptr;
+	uint64_t len = 0;
+
+public:
+	void inc(const uint64_t increment) {
+		available(increment);
+		unsafe_inc(increment);
+	}
+
+	void unsafe_inc(const uint64_t increment) {
+		len -= increment;
+		ptr += increment;
+	}
+
+	template <class T>
+	T read() {
+		available(sizeof(T));
+		return unsafe_read<T>();
+	}
+
+	template <class T>
+	T unsafe_read() {
+		T val = unsafe_get<T>();
+		unsafe_inc(sizeof(T));
+		return val;
+	}
+
+	template <class T>
+	T get() {
+		available(sizeof(T));
+		return unsafe_get<T>();
+	}
+
+	template <class T>
+	T unsafe_get() {
+		return Load<T>(ptr);
+	}
+
+	void copy_to(char *dest, const uint64_t len) const {
+		available(len);
+		unsafe_copy_to(dest, len);
+	}
+
+	void unsafe_copy_to(char *dest, const uint64_t len) const {
+		std::memcpy(dest, ptr, len);
+	}
+
+	void zero() const {
+		std::memset(ptr, 0, len);
+	}
+
+	void available(const uint64_t req_len) const {
+		if (!check_available(req_len)) {
+			throw std::runtime_error("Out of buffer");
+		}
+	}
+
+	bool check_available(const uint64_t req_len) const {
+		return req_len <= len;
+	}
+};
+
+class ResizeableBuffer : public ByteBuffer {
+public:
+	ResizeableBuffer() {
+	}
+	ResizeableBuffer(Allocator &allocator, const uint64_t new_size) {
+		resize(allocator, new_size);
+	}
+	void resize(Allocator &allocator, const uint64_t new_size) {
+		len = new_size;
+		if (new_size == 0) {
+			return;
+		}
+		if (new_size > alloc_len) {
+			alloc_len = NextPowerOfTwo(new_size);
+			allocated_data.Reset(); // Have to reset before allocating new buffer (otherwise we use ~2x the memory)
+			allocated_data = allocator.Allocate(alloc_len);
+			ptr = allocated_data.get();
+		}
+	}
+	void reset() {
+		ptr = allocated_data.get();
+		len = alloc_len;
+	}
+
+private:
+	AllocatedData allocated_data;
+	idx_t alloc_len = 0;
+};
+
+} // namespace duckdb