add in memory read and write for file2

solanaceae/file/file2_mem.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "./file2.hpp"
+
+// write to vector or read from span
+// no seeking for now (could make sense for read)
+
+struct File2MemW : public File2I {
+	std::vector<uint8_t>& _mem;
+
+	File2MemW(std::vector<uint8_t>& mem);
+	virtual ~File2MemW(void);
+
+	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;
+};
+
+struct File2MemR : public File2I {
+	ByteSpan _mem;
+	int64_t _read_pos{0};
+
+	File2MemR(ByteSpan mem);
+	virtual ~File2MemR(void);
+
+	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;
+};
+