1// Copyright (c) 2017 Gilad Naaman 2// 3// Permission is hereby granted, free of charge, to any person obtaining a copy 4// of this software and associated documentation files (the "Software"), to deal 5// in the Software without restriction, including without limitation the rights 6// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 7// copies of the Software, and to permit persons to whom the Software is 8// furnished to do so, subject to the following conditions: 9// 10// The above copyright notice and this permission notice shall be included in all 11// copies or substantial portions of the Software. 12// 13// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 14// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 15// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 16// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 17// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 18// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 19// SOFTWARE. 20 21//! A crate used for calculating offsets of struct members and their spans. 22//! 23//! This functionality currently can not be used in compile time code such as `const` or `const fn` definitions. 24//! 25//! ## Examples 26//! ``` 27//! use memoffset::{offset_of, span_of}; 28//! 29//! #[repr(C, packed)] 30//! struct HelpMeIAmTrappedInAStructFactory { 31//! help_me_before_they_: [u8; 15], 32//! a: u32 33//! } 34//! 35//! fn main() { 36//! assert_eq!(offset_of!(HelpMeIAmTrappedInAStructFactory, a), 15); 37//! assert_eq!(span_of!(HelpMeIAmTrappedInAStructFactory, a), 15..19); 38//! assert_eq!(span_of!(HelpMeIAmTrappedInAStructFactory, help_me_before_they_ .. a), 0..15); 39//! } 40//! ``` 41//! 42//! This functionality can be useful, for example, for checksum calculations: 43//! 44//! ```ignore 45//! #[repr(C, packed)] 46//! struct Message { 47//! header: MessageHeader, 48//! fragment_index: u32, 49//! fragment_count: u32, 50//! payload: [u8; 1024], 51//! checksum: u16 52//! } 53//! 54//! let checksum_range = &raw[span_of!(Message, header..checksum)]; 55//! let checksum = crc16(checksum_range); 56//! ``` 57 58#![no_std] 59#![cfg_attr( 60 all(feature = "unstable_const", not(stable_const)), 61 feature(const_ptr_offset_from) 62)] 63#![cfg_attr(feature = "unstable_const", feature(const_refs_to_cell))] 64 65#[macro_use] 66#[cfg(doctests)] 67#[cfg(doctest)] 68extern crate doc_comment; 69#[cfg(doctests)] 70#[cfg(doctest)] 71doctest!("../README.md"); 72 73/// Hidden module for things the macros need to access. 74#[doc(hidden)] 75pub mod __priv { 76 #[doc(hidden)] 77 pub use core::mem; 78 #[doc(hidden)] 79 pub use core::ptr; 80 81 /// Use type inference to obtain the size of the pointee (without actually using the pointer). 82 #[doc(hidden)] 83 pub fn size_of_pointee<T>(_ptr: *const T) -> usize { 84 mem::size_of::<T>() 85 } 86} 87 88#[macro_use] 89mod raw_field; 90#[macro_use] 91mod offset_of; 92#[macro_use] 93mod span_of; 94