Config system v1

Roughly inspired by what I've learned from my work on Space Station 14, without some of the unnecessary cruft and complexity.

Implementation is relatively simple once I figured out all the template order shenanigans.

src/dusk/io.cpp

@@ -0,0 +1,143 @@
+#include "dusk/io.hpp"
+#include <cstdio>
+#include <filesystem>
+
+using namespace dusk::io;
+
+#if _WIN32
+#define MODE_TYPE wchar_t
+#define MODE(val) L##val
+#define ftell(file) _ftelli64(file)
+#define fseek(a, b, c) _fseeki64(a, b, c)
+#else
+#define MODE_TYPE char
+#define MODE(val) ##val
+#endif
+
+static FILE* ThrowIfNotOpen(const FileStream& file) {
+    if (!file.GetFileHandle()) {
+        throw std::runtime_error("Invalid file handle!");
+    }
+
+    return static_cast<FILE*>(file.GetFileHandle());
+}
+
+[[noreturn]] static void ThrowForError(int code) {
+    throw std::system_error(std::make_error_code(static_cast<std::errc>(code)));
+}
+
+static FILE* OpenCore(const std::filesystem::path& path, const MODE_TYPE* mode) {
+    FILE* file;
+
+    int err;
+#if _WIN32
+    static_assert(std::is_same_v<std::filesystem::path::value_type, wchar_t>);
+    err = _wfopen_s(&file, path.c_str(), mode);
+#else
+    errno = 0;
+    static_assert(std::is_same_v<std::filesystem::path::value_type, char>);
+    file = fopen(path.c_str(), mode);
+    err = errno;
+#endif
+
+    if (!file) {
+        ThrowForError(err);
+    }
+
+    return file;
+}
+
+static FILE* OpenCore(const char* path, const MODE_TYPE* mode) {
+    return OpenCore(reinterpret_cast<const char8_t*>(path), mode);
+}
+
+FileStream::FileStream() noexcept : file(nullptr) {
+}
+
+FileStream::FileStream(void* file) : file(file) {
+    if (!file) {
+        CRASH("Invalid file handle");
+    }
+}
+
+FileStream::FileStream(FileStream&& other) noexcept {
+    file = other.file;
+    other.file = nullptr;
+}
+
+FileStream::~FileStream() {
+    if (file)
+        fclose(static_cast<FILE*>(file));
+}
+
+FileStream FileStream::OpenRead(const char* utf8Path) {
+    return FileStream(OpenCore(utf8Path, MODE("rb")));
+}
+
+FileStream FileStream::Create(const char* utf8Path) {
+    return FileStream(OpenCore(utf8Path, MODE("wb")));
+}
+
+std::vector<u8> FileStream::ReadFull() {
+    const auto fileHandle = ThrowIfNotOpen(*this);
+
+    std::vector<u8> result;
+
+    const auto startPos = ftell(fileHandle);
+    if (startPos == -1) {
+        ThrowForError(errno);
+    }
+
+    auto seekRes = fseek(fileHandle, 0, SEEK_END);
+    if (seekRes != 0) {
+        ThrowForError(errno);
+    }
+
+    const auto endPos = ftell(fileHandle);
+    if (endPos == -1) {
+        ThrowForError(errno);
+    }
+
+    seekRes = fseek(fileHandle, startPos, SEEK_SET);
+    if (seekRes != 0) {
+        ThrowForError(errno);
+    }
+
+    result.resize(endPos - startPos);
+
+    if (result.empty()) {
+        return result;
+    }
+
+    auto ret = fread(result.data(), 1, result.size(), fileHandle);
+    if (ret < result.size()) {
+        int err = errno;
+        // Error or EOF
+        if (feof(fileHandle)) {
+            result.resize(ret);
+        } else {
+            ThrowForError(err);
+        }
+    }
+
+    return result;
+}
+
+std::vector<u8> FileStream::ReadAllBytes(const char* utf8Path) {
+    auto handle = OpenRead(utf8Path);
+    return std::move(handle.ReadFull());
+}
+
+void FileStream::Write(const char* data, size_t dataLen) {
+    FILE* fileHandle = ThrowIfNotOpen(*this);
+
+    const auto ret = fwrite(data, 1, dataLen, fileHandle);
+    if (ret < dataLen) {
+        ThrowForError(errno);
+    }
+}
+
+void FileStream::WriteAllText(const char* utf8Path, const std::string_view text) {
+    auto handle = Create(utf8Path);
+    handle.Write(text.data(), text.size());
+}