Added lexer tests

Common/modules/File.h

@@ -0,0 +1,102 @@
+#pragma once
+
+#include <filesystem>
+#include <fstream>
+
+namespace LXC::Util
+{
+    // Error returned when Util::ReadFile runs into errors //
+    struct FileReadError final
+    {
+        // Different reasons why the error can occur //
+        enum Reason
+        {
+            FileNotFound,
+            PermissionDenied,
+            NotAFile
+        };
+
+        // Constructor to pass arguments to the struct //
+        FileReadError(const std::filesystem::path& _path, Reason _reason)
+            : path(_path), reason(_reason)
+        {}
+
+        // Error information //
+        const std::filesystem::path path;
+        const Reason reason;
+
+        // Turns the error into a c-string //
+        inline static const char* const ReasonStr(Reason reason)
+        {
+            static const char* reasons[] =
+            {
+                "File cannot be found",
+                "File reading permissions are denied",
+                "Not a file"
+            };
+
+            return reasons[reason];
+        }
+    };
+
+    // Util function to read a file as quick as possible with error handling //
+    inline ReturnVal<std::string, FileReadError> ReadFile(const std::filesystem::path& filepath)
+    {
+        // Checks the file exists //
+        if (!std::filesystem::exists(filepath))
+            return FunctionFail<FileReadError>(std::filesystem::absolute(filepath), FileReadError::FileNotFound);
+
+        // Checks it is a regular file //
+        if (!std::filesystem::is_regular_file(filepath))
+            return FunctionFail<FileReadError>(std::filesystem::absolute(filepath), FileReadError::NotAFile);
+
+        // Checks it can open the file //
+        std::ifstream file(filepath, std::ios::binary | std::ios::ate);
+        if (!file)
+            return FunctionFail<FileReadError>(std::filesystem::absolute(filepath), FileReadError::PermissionDenied);
+
+        // Copies the file to the output string //
+        const std::streamsize len = file.tellg();
+        file.seekg(0, std::ios::beg);
+
+        std::string contents(len, '\0');
+        file.read(&contents[0], len);
+
+        return contents;
+    }
+
+    // Struct to hold a position within a file //
+    struct FileLocation
+    {
+        unsigned short col;
+        unsigned short line;
+    };
+
+    // Finds the location of a given index within a file //
+    inline bool GetFileLocationAtIndex(FileLocation& location, const std::string& file, uint32_t index)
+    {
+        // Resets location //
+        location.line = 1;
+        location.col = 1;
+
+        // Returns false if outside the bounds //
+        if (index < 0 || index > file.length())
+            return false;
+
+        // Finds the location //
+        uint32_t localIndex = 0;
+        while (localIndex != index)
+        {
+            if (file[localIndex] == '\n')
+            {
+                location.line += 1;
+                location.col = 0;
+            }
+
+            location.col++;
+            localIndex++;
+        }
+
+        return true;
+    }
+}