# lib.rs.html -- source
Source to the Rust file `/home/travis/.cargo/registry/src/github.com-1ecc6299db9ec823/memory_units-0.3.0/src/lib.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Crate for safe conversion between units of memory.

    #![deny(missing_docs)]
    #![no_std]

    use core::mem;
    use core::ops;

    macro_rules! impl_byte_size {
        ( $name:ident , $byte_size:expr ) => {
            impl ByteSize for $name {
                #[inline]
                fn byte_size() -> Bytes {
                    Bytes($byte_size)
                }
            }
        }
    }

    macro_rules! impl_from_bytes {
        ( $name:ident ) => {
            impl From<$name> for Bytes {
                #[inline]
                fn from(x: $name) -> Bytes {
                    Bytes(x.0 * $name::byte_size().0)
                }
            }
        }
    }

    macro_rules! impl_ops {
        ( $name:ident ) => {
            impl<T: Into<Bytes>> RoundUpTo<$name> for T {
                fn round_up_to(self) -> $name {
                    let bytes: Bytes = self.into();
                    $name(round_up_to(bytes.0, $name::byte_size().0))
                }
            }

            impl<T: Into<Self>> ops::Add<T> for $name {
                type Output = Self;

                #[inline]
                fn add(self, rhs: T) -> Self {
                    $name(self.0 + rhs.into().0)
                }
            }

            impl<T: Into<Self>> ops::Sub<T> for $name {
                type Output = Self;

                #[inline]
                fn sub(self, rhs: T) -> Self {
                    $name(self.0 - rhs.into().0)
                }
            }

            impl<T: Into<Self>> ops::Mul<T> for $name {
                type Output = Self;

                #[inline]
                fn mul(self, rhs: T) -> Self {
                    $name(self.0 * rhs.into().0)
                }
            }

            impl<T: Into<Self>> ops::Div<T> for $name {
                type Output = Self;

                #[inline]
                fn div(self, rhs: T) -> Self {
                    $name(self.0 / rhs.into().0)
                }
            }
        }
    }

    macro_rules! define_newtype {
        (
            $( #[$attr:meta] )*
            newtype $name:ident = $t:ty;
        ) => {
            $( #[$attr] )*
            pub struct $name(pub $t);
        }
    }

    macro_rules! define_unit {
        (
            $( #[$attr:meta] )*
            newtype $name:ident is bytes = $byte_size:expr;
        ) => {
            define_newtype! {
                $( #[$attr] )*
                #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
                newtype $name = usize;
            }
            impl_byte_size!($name, $byte_size);
            impl_from_bytes!($name);
            impl_ops!($name);
        }
    }

    /// Returns the size of a type in [`Bytes`].
    ///
    /// # Example
    ///
    /// ```rust
    /// # use memory_units::*;
    /// #[repr(C)]
    /// struct Hello {
    ///     a: u32,
    ///     b: u32,
    /// }
    ///
    /// assert_eq!(size_of::<Hello>(), Bytes(4 + 4));
    /// ```
    ///
    /// [`Bytes`]: struct.Bytes.html
    #[inline]
    pub fn size_of<T>() -> Bytes {
        Bytes(mem::size_of::<T>())
    }

    /// A trait defining round up conversion between various memory units.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use memory_units::*;
    /// // `bytes` contains the size of 1 memory page in bytes.
    /// let mut bytes: Bytes = Pages(1).into();
    ///
    /// // Adding 1 to `bytes` makes it larger than the single page.
    /// bytes.0 += 1;
    /// let pages: Pages = bytes.round_up_to();
    /// assert_eq!(pages, Pages(2));
    /// ```
    pub trait RoundUpTo<T> {
        /// Returns minimum number of `T` to fit amount of space occupied by `self`.
        fn round_up_to(self) -> T;
    }

    #[inline]
    pub(crate) fn round_up_to(n: usize, divisor: usize) -> usize {
        (n + divisor - 1) / divisor
    }

    /// A trait defining the size, in bytes, of one unit of `Self`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use memory_units::*;
    /// println!("The size of one word in bytes is {}.", Words::byte_size().0);
    /// ```
    pub trait ByteSize {
        /// The size, in bytes, of a single unit of `Self`.
        fn byte_size() -> Bytes;
    }

    define_newtype! {
        /// Memory size specified in bytes.
        #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
        newtype Bytes = usize;
    }
    impl_byte_size!(Bytes, 1);
    impl_ops!(Bytes);

    pub mod wasm32 {
        //! WebAssembly-specific sizes and units.

        use super::*;
        use core::ops;

        define_unit! {
            /// Memory size specified in `wasm32` words.
            newtype Words is bytes = 4;
        }

        define_unit! {
            /// Memory size specified in WebAssembly [memory pages][memory page].
            ///
            /// [memory page]: https://en.wikipedia.org/wiki/Page_(computer_memory)
            newtype Pages is bytes = 65536;
        }
    }

    #[cfg(target_arch = "wasm32")]
    pub mod target {
        //! Sizes and units for the current compilation target.

        pub use wasm32::*;
    }

    #[cfg(not(target_arch = "wasm32"))]
    pub mod target {
        //! Sizes and units for the current compilation target.

        use super::*;
        use core::mem;
        use core::ops;

        define_unit! {
            /// Memory size specified in words.
            newtype Words is bytes = mem::size_of::<usize>();
        }

        define_unit! {
            /// Memory size specified in [memory pages][memory page].
            ///
            /// [memory page]: https://en.wikipedia.org/wiki/Page_(computer_memory)
            newtype Pages is bytes = 4096;
        }
    }

    pub use target::*;

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