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 //! #[macro_use] 28 //! extern crate memoffset; 29 //! 30 //! #[repr(C, packed)] 31 //! struct HelpMeIAmTrappedInAStructFactory { 32 //! help_me_before_they_: [u8; 15], 33 //! a: u32 34 //! } 35 //! 36 //! fn main() { 37 //! assert_eq!(offset_of!(HelpMeIAmTrappedInAStructFactory, a), 15); 38 //! assert_eq!(span_of!(HelpMeIAmTrappedInAStructFactory, a), 15..19); 39 //! assert_eq!(span_of!(HelpMeIAmTrappedInAStructFactory, help_me_before_they_ .. a), 0..15); 40 //! } 41 //! ``` 42 //! 43 //! This functionality can be useful, for example, for checksum calculations: 44 //! 45 //! ```ignore 46 //! #[repr(C, packed)] 47 //! struct Message { 48 //! header: MessageHeader, 49 //! fragment_index: u32, 50 //! fragment_count: u32, 51 //! payload: [u8; 1024], 52 //! checksum: u16 53 //! } 54 //! 55 //! let checksum_range = &raw[span_of!(Message, header..checksum)]; 56 //! let checksum = crc16(checksum_range); 57 //! ``` 58 59 // ANDROID: include standard library to build as a dylib 60 //#![no_std] 61 #![cfg_attr( 62 feature = "unstable_const", 63 feature( 64 ptr_offset_from, 65 const_fn, 66 const_ptr_offset_from, 67 const_maybe_uninit_as_ptr, 68 const_raw_ptr_deref, 69 ) 70 )] 71 72 #[macro_use] 73 #[cfg(doctests)] 74 #[cfg(doctest)] 75 extern crate doc_comment; 76 #[cfg(doctests)] 77 #[cfg(doctest)] 78 doctest!("../README.md"); 79 80 /// Hiden module for things the macros need to access. 81 #[doc(hidden)] 82 pub mod __priv { 83 #[doc(hidden)] 84 pub use std::mem; // ANDROID: use std instead of core, since we're not building with no-std. 85 #[doc(hidden)] 86 pub use std::ptr; // ANDROID: use std instead of core, since we're not building with no-std. 87 88 /// Use type inference to obtain the size of the pointee (without actually using the pointer). 89 #[doc(hidden)] size_of_pointee<T>(_ptr: *const T) -> usize90 pub fn size_of_pointee<T>(_ptr: *const T) -> usize { 91 mem::size_of::<T>() 92 } 93 } 94 95 #[macro_use] 96 mod raw_field; 97 #[macro_use] 98 mod offset_of; 99 #[macro_use] 100 mod span_of; 101