文件列表:

LICENSE (16725, 2023-11-26)
build.zig (767, 2023-11-26)
build.zig.zon (178, 2023-11-26)
src/ (0, 2023-11-26)
src/memutils.zig (1740, 2023-11-26)
src/meta.zig (935, 2023-11-26)
src/rc.zig (4658, 2023-11-26)

# zig-memutils Memory utilities for the Zig programming language, including a reference counted pointer This repository contains a few usable patterns for memory management in Zig. ## Owner and Borrower Owners and Borrowers allow you to specify the ownership of data (usually a pointer or a structure with `deinit`). As in Zig there are no in language semantics to make this clear. For example the `std.StringHashMap` does not own its keys. In Owner-Borrower memory model would signatures of some functions look like this: ```zig // instead of fn put(self: *Self, key: []const u8, value: V) !void // this fn put(self: *Self, key: Borrower([]const u8), value: V) !void ``` To get most of the features of this model, one should always pair an `Owner` instance with its respective `deinit()` ```zig var owner: Owner(usize) = .{ .data = 0 }; defer owner.deinit(); some_fn_borrowing(owner.borrow()); some_fn_owning(owner.give()); // this is an error, as ownership was already transfered // some_fn_owning(owner.give()); ``` `Borrower` instances are only informative about the API, they do not themselves need to be deinitialized and do not perform any checks about their validity. ## Rc the reference counted pointer Rc allows to hold multiple references to a place in memory when there is no easy way to make sure that that memory isn't pointed to from anywhere else. It's a very standard datastructure in many programming languages. But this implementation provides a few interesting properties. Unless a slice is provided, one should pass the type that the memory location should have __not the pointer to that memory!__ ```zig var rc = Rc(usize).init(0, std.testing.allocator); defer rc.drop(); const raw_ptr: *usize = rc.get(); ``` If the type has a `fn deinit(*T)` or a `fn deinit(*T, std.mem.Allocator)` member function, the `Rc` will automatically call this function before destroying it's memory location. A custom deinit function can also be provided with `init_w_deinit_fn`, and must have the `*const fn (*T, std.mem.Allocator)` type signature. For a propper usage, `Rc` should never be "copy assigned", but that is currently unenforcable in Zig. ```zig var rc = Rc(usize).init(0, std.testing.allocator); defer rc.drop(); // never do this var rc2 = rc; // instead do this var rc3 = rc.borrow(); defer rc3.drop(); ``` ### Rc with a slice If one wishes to use `Rc` with a slice, the semantics are a bit different. The biggest difference is that `Rc` now expects the slice as it's argument instead of the item's type. ```zig var rc = Rc([]u8).init_dupe("string", std.testing.allocator); defer rc.drop(); var rc2 = Rc([]u8).init(6, std.testing.allocator); defer rc2.drop(); @memcpy(rc2.get(), "string"); ``` Otherwise `Rc` behaves the same. However slices usually provide a way to subslice, but simply doing `rc.get()[0..3]` would not increase the reference count. For this `Rc` implements `fn subslice(from, to)`. This does not copy memory, only creates a new `Rc` that still works with the same memory location, will potentially free the whole memory if no references to the memory exist, but returns a different slice when calling `get`. ```zig var rc = Rc([]u8).init_dupe("test", std.testing.allocator); defer rc.drop(); var rc2 = rc.subslice(0, 3); defer rc2.drop(); ``` ### Rc in multithreaded environments Rc can be also used in multithreaded environments in a way that does not introduce a cost in single threaded environments. To convert `Rc` into an multithreading friendly one, simply call `fn atomic()`. The type signature stays the same and all functions have the same behavior, but `borrow` and `drop` are now thread-safe. > Note that this operation can only be performed once. ```zig var rc = Rc(usize).init(0, std.testing.allocator); defer rc.drop(); rc.atomic(); // from now on, rc is thread-safe, even the previous borrows ```

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