vendor/memoffset/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 //! #[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 #![no_std]
  60 #![cfg_attr(
  61     feature = "unstable_const",
  62     feature(
  63         ptr_offset_from,
  64         const_ptr_offset_from,
  65         const_transmute,
  66         const_raw_ptr_deref,
  67     )
  68 )]
  69 #![cfg_attr(feature = "unstable_raw", feature(raw_ref_macros))]
  70
  71 #[macro_use]
  72 #[cfg(doctests)]
  73 #[cfg(doctest)]
  74 extern crate doc_comment;
  75 #[cfg(doctests)]
  76 #[cfg(doctest)]
  77 doctest!("../README.md");
  78
  79 // This `use` statement enables the macros to use `$crate::mem`.
  80 // Doing this enables this crate to function under both std and no-std crates.
  81 #[doc(hidden)]
  82 pub use core::mem;
  83 #[doc(hidden)]
  84 pub use core::ptr;
  85
  86 #[macro_use]
  87 mod raw_field;
  88 #[macro_use]
  89 mod offset_of;
  90 #[macro_use]
  91 mod span_of;