refactor file2 and add span with ownership

solanaceae/file/file2.hpp

@@ -5,6 +5,29 @@
 #include <vector>
 #include <variant>
 
+// TODO: move to/next-to span
+// a span that can also represent its ownership
+template<typename T>
+struct SpanWithOwnership : public Span<T> {
+	// TODO: allow for different owners
+	std::vector<T> _data_owner;
+
+	// self interactions
+	SpanWithOwnership(void) = delete;
+	constexpr SpanWithOwnership(const SpanWithOwnership&) = delete;
+	constexpr SpanWithOwnership(SpanWithOwnership&&) = default;
+
+	// non-owning
+	constexpr SpanWithOwnership(const Span<T>& span) : Span<T>(span) {}
+	constexpr SpanWithOwnership(const Span<T>&& span) : Span<T>(span) {}
+
+	// owning
+	constexpr SpanWithOwnership(std::vector<T>&& data) : Span<T>(data), _data_owner(std::move(data)) {}
+
+	bool isOwning(void) const { return !_data_owner.empty(); }
+};
+using ByteSpanWithOwnership = SpanWithOwnership<uint8_t>;
+
 struct File2I {
 	// read only
 	uint64_t _file_size {0};
@@ -20,6 +43,7 @@ struct File2I {
 
 	// pos -1 means stream, append to last written, or read position (independent, like FILE*s)
 	virtual bool write(const ByteSpan data, int64_t pos = -1) = 0;
-	[[nodiscard]] virtual std::variant<ByteSpan, std::vector<uint8_t>> read(uint64_t size, int64_t pos = -1) = 0;
+	//[[nodiscard]] virtual std::variant<ByteSpan, std::vector<uint8_t>> read(uint64_t size, int64_t pos = -1) = 0;
+	[[nodiscard]] virtual ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) = 0;
 };
 

solanaceae/file/file2_mem.cpp

@@ -25,8 +25,8 @@ bool File2MemW::write(const ByteSpan data, int64_t pos) {
 	return isGood();
 }
 
-std::variant<ByteSpan, std::vector<uint8_t>> File2MemW::read(uint64_t size, int64_t pos) {
-	return {};
+ByteSpanWithOwnership File2MemW::read(uint64_t size, int64_t pos) {
+	return ByteSpan{};
 }
 
 File2MemR::File2MemR(ByteSpan mem) : File2I(false, true), _mem(mem) {
@@ -44,9 +44,9 @@ bool File2MemR::write(const ByteSpan data, int64_t pos) {
 	return false;
 }
 
-std::variant<ByteSpan, std::vector<uint8_t>> File2MemR::read(uint64_t size, int64_t pos) {
+ByteSpanWithOwnership File2MemR::read(uint64_t size, int64_t pos) {
 	if (_read_pos >= _mem.size) {
-		return {};
+		return ByteSpan{};
 	}
 
 	ByteSpan ret {
@@ -54,6 +54,7 @@ std::variant<ByteSpan, std::vector<uint8_t>> File2MemR::read(uint64_t size, int6
 		std::min(size, _mem.size - _read_pos)
 	};
 	_read_pos += ret.size;
+	// return non-owning
 	return ret;
 }
 

solanaceae/file/file2_mem.hpp

@@ -14,7 +14,7 @@ struct File2MemW : public File2I {
 	bool isGood(void) override;
 
 	bool write(const ByteSpan data, int64_t pos = -1) override;
-	std::variant<ByteSpan, std::vector<uint8_t>> read(uint64_t size, int64_t pos = -1) override;
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override;
 };
 
 struct File2MemR : public File2I {
@@ -27,6 +27,6 @@ struct File2MemR : public File2I {
 	bool isGood(void) override;
 
 	bool write(const ByteSpan data, int64_t pos = -1) override;
-	std::variant<ByteSpan, std::vector<uint8_t>> read(uint64_t size, int64_t pos = -1) override;
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override;
 };
 

solanaceae/file/file2_stack.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "./file2.hpp"
+
+#include <stack>
+#include <memory>
+
+// wrapper/container for a file "stack"
+// has no file functionallity by itself
+
+struct File2Stack : public File2I {
+	std::stack<std::unique_ptr<File2I>> _stack;
+
+	// TODO: change interface again and make r/w non const data members!
+	File2Stack(void) : File2I(false, false), _stack() {}
+	File2Stack(std::stack<std::unique_ptr<File2I>>&& stack) : File2I(false, false), _stack(std::move(stack)) {}
+	File2Stack(std::unique_ptr<File2I>&& file) : File2I(false, false), _stack({std::move(file)}) {}
+	virtual ~File2Stack(void) {}
+
+	bool isGood(void) override {
+		return _stack.top()->isGood();
+	}
+
+	bool write(const ByteSpan data, int64_t pos = -1) override {
+		return _stack.top()->write(data, pos);
+	}
+
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override {
+		return _stack.top()->read(size, pos);
+	}
+};
+

solanaceae/file/file2_std.cpp

@@ -32,7 +32,6 @@ bool File2WFile::isGood(void) {
 	return _file.is_open() && _file.good();
 }
 
-	//bool write(const ByteSpan data, int64_t pos = -1) override;
 bool File2WFile::write(const ByteSpan data, int64_t pos) {
 	if (pos != -1) {
 		//std::cerr << "invalid pos\n";
@@ -49,7 +48,7 @@ bool File2WFile::write(const ByteSpan data, int64_t pos) {
 	return _file.good();
 }
 
-std::variant<ByteSpan, std::vector<uint8_t>> File2WFile::read(uint64_t, int64_t) {
+ByteSpanWithOwnership File2WFile::read(uint64_t, int64_t) {
 	return ByteSpan{};
 }
 
@@ -102,7 +101,7 @@ bool File2RWFile::write(const ByteSpan data, int64_t pos) {
 	return _file.good();
 }
 
-std::variant<ByteSpan, std::vector<uint8_t>> File2RWFile::read(uint64_t size, int64_t pos) {
+ByteSpanWithOwnership File2RWFile::read(uint64_t size, int64_t pos) {
 	if (pos >= int64_t(_file_size)) {
 		return ByteSpan{};
 	}
@@ -124,6 +123,8 @@ std::variant<ByteSpan, std::vector<uint8_t>> File2RWFile::read(uint64_t size, in
 		chunk.clear();
 	}
 
-	return chunk;
+	// return owning
+	return ByteSpanWithOwnership{std::move(chunk)};
+	//return chunk; // is this the same?
 }
 

solanaceae/file/file2_std.hpp

@@ -19,7 +19,7 @@ struct File2WFile : public File2I {
 	bool isGood(void) override;
 
 	bool write(const ByteSpan data, int64_t pos = -1) override;
-	std::variant<ByteSpan, std::vector<uint8_t>> read(uint64_t size, int64_t pos = -1) override;
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override;
 };
 
 // read write, requires an existing file, file size is fixed
@@ -35,7 +35,7 @@ struct File2RWFile : public File2I {
 	bool isGood(void) override;
 
 	bool write(const ByteSpan data, int64_t pos = -1) override;
-	std::variant<ByteSpan, std::vector<uint8_t>> read(uint64_t size, int64_t pos = -1) override;
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override;
 };
 
 // cut down interface (write disabled)

solanaceae/util/span.hpp

@@ -7,7 +7,7 @@
 
 // non owning view
 template<typename T>
-struct Span final {
+struct Span {
 	const T* ptr {nullptr};
 	uint64_t size {0};