Nu:Mem is a package for D which implements various nogc memory managment tools, allowing classes, strings, and more to be handled safely in nogc mode. This library is still a work in progress, but is intended to be used within Inochi2D's nogc rewrite to allow the library to have good ergonomics, while allowing more seamless integration with other programming languages.

     

Roadmap

This is a incomplete and unordered roadmap of features I want to add and have added

• Utilities for managing D classes with no gc
  • nogc_new (nogc new alternative)
  • nogc_delete (nogc destroy alternative)
• Smart (ref-counted) pointers.
  • shared_ptr (strong reference)
  • weak_ptr (weak, borrowed reference)
  • unique_ptr (strong, single-owner reference)
• C++ style vector struct
• C++ style string struct
• C++ style map
• C++ style set
• nogc compatible exceptions (must derive from NuException)
• Safe nogc streams**
  • FileStream*
  • MemoryStream*
  • NetworkStream
• Endianness utilities
• Support for minimal D runtime
  • tinyd-rt**
• File handling**
  • Check if file exists
  • Iterate directories
  • Cross platform path handling
• Networking
  • Sockets
  • IP utilities
• Character encoding handling
  • UTF-8
  • UTF-16
  • UTF-32
  • Unicode
    • Codepoints
    • Grapheme handling
    • Character classification
  • Allow plugging more handlers in?
• String formatting (compatible with phobos syntax?)

*: Implemented but untested.
**: Partially implemented.

Using numem

Numem allows you to instantiate classes without the GC, it's highly recommended that you mark all functions in classes as @nogc to avoid GC conflicts.

Using nogc_new you can instantiate types on the heap, and nogc_delete can destruct and free types.

import numem.all;

class MyClass {
@nogc:
    void doSomething() {
        import core.stdc.stdio : printf;
        printf("Hello, world!\n");
    }
}

void main() {
    MyClass klass = nogc_new!MyClass();
    klass.doSomething();

    nogc_delete(klass);
}

All features of classes are available without the GC, such as subclassing and interfaces.

Smart Pointers

Numem features smart pointers, which allows you to reference instantiated types.
If a smart pointer is placed on the heap then it will be freed automatically on the exit of the scope.

import numem.all;

class MyClass {
@nogc:
    void doSomething() {
        import core.stdc.stdio : printf;
        printf("Hello, world!\n");
    }
}

void func() {
    // Will instantiate a shared_ptr on the stack, referencing MyClass.
    shared_ptr!MyClass klass = shared_new!MyClass();

    // alias this is used, so you can call members of the contained
    // type directly.
    klass.doSomething();
}

void main() {
    // After this call klass should be freed automatically.
    func();
}

Smart pointers are split in to 3 categories:

• unique_ptr - This smart pointer is the only owner of a piece of memory.
  Assining the smart pointer will move the owner between unique_ptrs

• shared_ptr - This smart pointer can be copied and have multiple owners.
  Once all owners are freed, the content of the shared_ptr will also be freed.

• weak_ptr - This smart pointer is created via the borrow() function of unique_ptr and shared_ptr.
  Weak pointers do not own the memory they reference, but nontheless keep track of the state of the state of the parent pointer.
  Weak pointers get() function will return null if the owners of the memory have freed it.

C++-style Vectors and Maps

Numem includes vector, map and set types, which are alternatives to D dynamic arrays, associative arrays and sets.
Each of these types are split in to their base type and a weak counterpart. The "strong" containers will free elements on removal, and the weak counterparts will not.

The nstring type is a UTF-8 container for text, which uses vector as a backing store. nstring will automatically create null terminators when the string is modified. The functions toCString() and toDString() does not make copies of the string, but just returns a pointer to its start, or a slice of it (excluding the null terminator).
This allows nstring to have excellent C interop at minimal performance cost.

Tracing leaks

You can build numem with the --debug=trace flag to trace creation and destruction of types via stdout.

Using with no C runtime available

This library is still a work in progress and some edge cases are not handled yet.
You can pass NoC as a version parameter to let numem know to not rely on the C stdlib.

Note

Some parts of the library will pretend GC'ed types are no-gc, as such you should be careful about mixing GCed code in.