Generic pool & handle implementation for Zig. Based on Andre Weissflog's "Handles Are The Better Pointers".
Exposing API resources using pools and handles is a common way to avoid exposing implementation details to calling code and providing some insulation against stale references in data structures maintained by the caller.
When the caller is provided a handle instead of an opaque pointer, the API implementation is free to move resources around, replace them, and even discard them.
Pool(index_bits: u8, cycle_bits: u8, TResource: type, TColumns: type) Handle(index_bits: u8, cycle_bits: u8, TResource: type)The generic Pool type has configurable bit distribution for the Handle's index/cycle fields, and supports multiple columns of data to be indexed by a handle, using std.MultiArrayList to store all of the pool data in a single memory allocation. The TResource parameter ensures the pool and handle types can be distinct types even when other parameters are the same.
Example build.zig:
pub fn build(b: *std.Build) void { const exe = b.addExecutable(.{ ... }); const zpool = b.dependency("zpool", .{}); exe.root_module.addImport("zpool", zpool.module("root")); }Now in your code you may import and use zpool:
const Pool = @import("zpool").Pool; const ImagePtr = graphics.Image; const ImageInfo = graphics.ImageInfo; pub const ImagePool = Pool(16, 16, ImagePtr, struct { ptr: ImagePtr, info: ImageInfo, }); pub const ImageHandle = ImagePool.Handle;var imagePool = ImagePool.initMaxCapacity(allocator); defer pool.deinit();pub fn acquireImage(info: ImageInfo) !ImageHandle { const handle : ImageHandle = try imagePool.add(.{ .ptr = graphics.createImage(info), .info = info, }); return handle; } pub fn drawImage(handle: ImageHandle) !void { // get the stored ImagePtr const ptr : ImagePtr = try imagePool.getColumn(handle, .ptr); graphics.drawImage(ptr); } pub fn resizeImage(handle: ImageHandle, width: u16, height: u16) !void { // get a pointer to the stored ImageInfo const info : *ImageInfo = try imagePool.getColumnPtr(handle, .info); const old_width = info.width; const old_height = info.height; const old_pixels = // allocate memory to store old pixels // get the stored ImagePtr const ptr = try imagePool.getColumn(handle, .ptr); graphics.readPixels(ptr, old_pixels); const new_pixels = // allocate memory to store new pixels super_eagle.resizeImage( old_width, old_height, old_pixels, new_width, new_height, new_pixels); graphics.writePixels(ptr, new_width, new_height, new_pixels); // update the stored ImageInfo info.width = new_width; info.height = new_height; } 
