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const std = @import("std");
/// A nullable allocator the same size as `std.mem.Allocator`.
pub const NullableAllocator = struct {
ptr: *anyopaque = undefined,
// Utilize the null pointer optimization on the vtable instead of
// the regular ptr because some allocator implementations might tag their
// `ptr` property.
vtable: ?*const std.mem.Allocator.VTable = null,
pub inline fn init(a: std.mem.Allocator) @This() {
return .{
.ptr = a.ptr,
.vtable = a.vtable,
};
}
pub inline fn isNull(this: @This()) bool {
return this.vtable == null;
}
pub inline fn get(this: @This()) ?std.mem.Allocator {
return if (this.vtable) |vt| std.mem.Allocator{ .ptr = this.ptr, .vtable = vt } else null;
}
};
comptime {
if (@sizeOf(NullableAllocator) != @sizeOf(std.mem.Allocator)) {
@compileError("Expected the sizes to be the same.");
}
}
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