vendor/memoffset-0.2.1/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 //! Some of the funcationality of the crate makes no sense when used along with structs that
  24 //! are not `#[repr(C, packed)]`, but it is up to the user to make sure that they are.
  25 //!
  26 //! ## Examples
  27 //! ```
  28 //! #[macro_use]
  29 //! extern crate memoffset;
  30 //!
  31 //! #[repr(C, packed)]
  32 //! struct HelpMeIAmTrappedInAStructFactory {
  33 //!     help_me_before_they_: [u8; 15],
  34 //!     a: u32
  35 //! }
  36 //!
  37 //! fn main() {
  38 //!     assert_eq!(offset_of!(HelpMeIAmTrappedInAStructFactory, a), 15);
  39 //!     assert_eq!(span_of!(HelpMeIAmTrappedInAStructFactory, a), 15..19);
  40 //!     assert_eq!(span_of!(HelpMeIAmTrappedInAStructFactory, help_me_before_they_[2] .. a), 2..15);
  41 //! }
  42 //! ```
  43 //!
  44 //! This functionality can be useful, for example, for checksum calculations:
  45 //!
  46 //! ```ignore
  47 //! #[repr(C, packed)]
  48 //! struct Message {
  49 //!     header: MessageHeader,
  50 //!     fragment_index: u32,
  51 //!     fragment_count: u32,
  52 //!     payload: [u8; 1024],
  53 //!     checksum: u16
  54 //! }
  55 //!
  56 //! let checksum_range = &raw[span_of!(Message, header..checksum)];
  57 //! let checksum = crc16(checksum_range);
  58 //! ```
  59
  60 #![no_std]
  61
  62 // This `use` statement enables the macros to use `$crate::mem`.
  63 // Doing this enables this crate to function under both std and no-std crates.
  64 #[doc(hidden)]
  65 pub use core::mem;
  66
  67 #[macro_use]
  68 mod offset_of;
  69 #[macro_use]
  70 mod span_of;