move to read only memory mapped files

solanaceae/ngc_ft1_sha1/file2_mapped.hpp

@@ -0,0 +1,146 @@
+#pragma once
+
+#include <solanaceae/file/file2.hpp>
+
+#include "./mio.hpp"
+
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <cstring>
+#include <cassert>
+
+struct File2RWMapped : public File2I {
+	mio::ummap_sink _file_map;
+
+	// TODO: add truncate support?
+	// TODO: rw always true?
+	File2RWMapped(std::string_view file_path, int64_t file_size = -1) : File2I(true, true) {
+		std::filesystem::path native_file_path{file_path};
+
+		if (!std::filesystem::exists(native_file_path)) {
+			std::ofstream(native_file_path) << '\0'; // force create the file
+		}
+
+		_file_size = std::filesystem::file_size(native_file_path);
+		if (file_size >= 0 && _file_size != file_size) {
+			try {
+				std::filesystem::resize_file(native_file_path, file_size); // ensure size, usually sparse
+			} catch (...) {
+				std::cerr << "FileRWMapped error: resizing file failed\n";
+				return;
+			}
+
+			_file_size = std::filesystem::file_size(native_file_path);
+			if (_file_size != file_size) {
+				std::cerr << "FileRWMapped error: resizing file failed (size mismatch)\n";
+				return;
+			}
+		}
+
+		std::error_code err;
+		// sink, is also read
+		_file_map.map(native_file_path.u8string(), 0, _file_size, err);
+
+		if (err) {
+			std::cerr << "FileRWMapped error: mapping file failed: " << err.message() << " (" << err << ")\n";
+			return;
+		}
+	}
+
+	virtual ~File2RWMapped(void) {
+	}
+
+	bool isGood(void) override {
+		return _file_map.is_mapped();
+	}
+
+	bool write(const ByteSpan data, int64_t pos = -1) override {
+		// TODO: support streaming write
+		if (pos < 0) {
+			return false;
+		}
+
+		if (data.empty()) {
+			return true; // false?
+		}
+
+		// file size is fix for mmaped files
+		if (pos+data.size > _file_size) {
+			return false;
+		}
+
+		std::memcpy(_file_map.data()+pos, data.ptr, data.size);
+
+		return true;
+	}
+
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override {
+		// TODO: support streaming read
+		if (pos < 0) {
+			assert(false && "streaming not implemented");
+			return ByteSpan{};
+		}
+
+		if (pos+size > _file_size) {
+			assert(false && "read past end");
+			return ByteSpan{};
+		}
+
+		// return non-owning
+		return ByteSpan{_file_map.data()+pos, size};
+	}
+};
+
+struct File2RMapped : public File2I {
+	mio::ummap_source _file_map;
+
+	File2RMapped(std::string_view file_path) : File2I(false, true) {
+		std::filesystem::path native_file_path{file_path};
+
+		if (!std::filesystem::exists(native_file_path)) {
+			std::cerr << "FileRMapped error: file does not exist\n";
+			return;
+		}
+
+		_file_size = std::filesystem::file_size(native_file_path);
+
+		std::error_code err;
+		_file_map.map(native_file_path.u8string(), err);
+
+		if (err) {
+			std::cerr << "FileRMapped error: mapping file failed: " << err.message() << " (" << err << ")\n";
+			return;
+		}
+
+		if (_file_size != _file_map.length()) {
+			std::cerr << "FileRMapped warning: file size and mapped file size mismatch.\n";
+			_file_size = _file_map.length();
+		}
+	}
+
+	virtual ~File2RMapped(void) {
+	}
+
+	bool isGood(void) override {
+		return _file_map.is_mapped();
+	}
+
+	bool write(const ByteSpan, int64_t = -1) override { return false; }
+
+	ByteSpanWithOwnership read(uint64_t size, int64_t pos = -1) override {
+		// TODO: support streaming read
+		if (pos < 0) {
+			assert(false && "streaming not implemented");
+			return ByteSpan{};
+		}
+
+		if (pos+size > _file_size) {
+			assert(false && "read past end");
+			return ByteSpan{};
+		}
+
+		// return non-owning
+		return ByteSpan{_file_map.data()+pos, size};
+	}
+};