Add exception support to numem

source/numem/mem/exception.d

@@ -0,0 +1,92 @@
+/**
+    Numem Exception support
+*/
+module numem.mem.exception;
+import numem.mem.string;
+import numem.mem;
+import core.stdc.stdio;
+
+@nogc:
+
+/**
+    An exception which can be thrown from numem
+*/
+class NuException : Exception {
+nothrow @nogc:
+private:
+    nstring _msg;
+
+public:
+
+    ~this() {
+        // Debug build printing
+        debug printf("Exception freed! (msg=%s)\n", _msg.toCString());
+
+        nogc_delete(_msg);
+
+        // Free next-in-chain
+        Throwable t = this.next();
+        nogc_delete(t);
+    }
+
+    /**
+        Constructs a nogc exception
+    */
+    this(nstring msg, Throwable nextInChain, string file = __FILE__, size_t line = __LINE__) {
+        this._msg = msg;
+        super(this._msg.toDString(), nextInChain, file, line);
+    }
+
+    /**
+        Constructs a nogc exception
+    */
+    this(nstring msg, string file = __FILE__, size_t line = __LINE__) {
+        this(msg, null, file, line);
+    }
+
+    /**
+        Returns the error message
+    */
+    override
+    @__future const(char)[] message() const @safe nothrow {
+        return this.msg;
+    }
+
+    /**
+        Helper function to free this exception
+    */
+    void free() {
+        NuException ex = this;
+        nogc_delete(ex);
+    }
+}
+
+/**
+    Enforces the truthiness of a nstring
+*/
+void enforce(T)(T in_, nstring err) {
+    if (!in_) {
+        throw nogc_new!NuException(err);
+    }
+}
+
+/**
+    Enforces the truthiness of a nstring
+*/
+void enforce(T)(T in_, lazy NuException t) {
+    if (!in_) {
+        throw t;
+    }
+}
+
+@("Test catching exceptions")
+unittest {
+    auto str = nstring("Ooops!");
+    try {
+        enforce(false, str);
+    } catch(NuException ex) {
+        assert(ex.message() == str.toDString());
+
+        ex.free();
+    }
+}