allocIndex

    fn allocIndex(f: *FuzzSingleThreadedAllocator, memory: []u8, alignment: Alignment) usize {
        @disableInstrumentation();

        const allocs_slice = f.allocs.slice();
        const i = mem.findScalar([*]u8, allocs_slice.items(.ptr), memory.ptr) orelse panic(
            "invalid SafeAllocator free of {f}",
            .{FormatMemory{ .memory = memory, .alignment = alignment }},
        );
        const expected_len = allocs_slice.items(.len)[i];
        const expected_align = allocs_slice.items(.alignment)[i];
        if (memory.len != expected_len or allocs_slice.items(.alignment)[i] != expected_align) {
            panic("SafeAllocator free {f} mismatches alloc {f}", .{
                FormatMemory{ .memory = memory, .alignment = alignment },
                FormatMemory{ .memory = memory.ptr[0..expected_len], .alignment = expected_align },
            });
        }
        return i;
    }