vendor/memoffset-0.6.5/src/lib.rs

   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     feature = "unstable_const",
  61     feature(const_ptr_offset_from, const_refs_to_cell)
  62 )]
  63
  64 #[macro_use]
  65 #[cfg(doctests)]
  66 #[cfg(doctest)]
  67 extern crate doc_comment;
  68 #[cfg(doctests)]
  69 #[cfg(doctest)]
  70 doctest!("../README.md");
  71
  72 /// Hidden module for things the macros need to access.
  73 #[doc(hidden)]
  74 pub mod __priv {
  75     #[doc(hidden)]
  76     pub use core::mem;
  77     #[doc(hidden)]
  78     pub use core::ptr;
  79
  80     /// Use type inference to obtain the size of the pointee (without actually using the pointer).
  81     #[doc(hidden)]
  82     pub fn size_of_pointee<T>(_ptr: *const T) -> usize {
  83         mem::size_of::<T>()
  84     }
  85 }
  86
  87 #[macro_use]
  88 mod raw_field;
  89 #[macro_use]
  90 mod offset_of;
  91 #[macro_use]
  92 mod span_of;