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)] 68 extern crate doc_comment; 69 #[cfg(doctests)] 70 #[cfg(doctest)] 71 doctest!("../README.md"); 72 73 /// Hidden module for things the macros need to access. 74 #[doc(hidden)] 75 pub 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)] size_of_pointee<T>(_ptr: *const T) -> usize83 pub fn size_of_pointee<T>(_ptr: *const T) -> usize { 84 mem::size_of::<T>() 85 } 86 } 87 88 #[macro_use] 89 mod raw_field; 90 #[macro_use] 91 mod offset_of; 92 #[macro_use] 93 mod span_of; 94