//! UEFI Base Environment

//!

//! This module defines the base environment for UEFI development. It provides types and macros as

//! declared in the UEFI specification, as well as de-facto standard additions provided by the

//! reference implementation by Intel.

//!

//! # Target Configuration

//!

//! Wherever possible, native rust types are used to represent their UEFI counter-parts. However,

//! this means the ABI depends on the implementation of said rust types. Hence, native rust types

//! are only used where rust supports a stable ABI of said types, and their ABI matches the ABI

//! defined by the UEFI specification.

//!

//! Nevertheless, even if the ABI of a specific type is marked stable, this does not imply that it

//! is the same across architectures. For instance, rust's `u64` type has the same binary

//! representation as the `UINT64` type in UEFI. But this does not imply that it has the same

//! binary representation on `x86_64` and on `ppc64be`. As a result of this, the compilation of

//! this module is tied to the target-configuration you passed to the rust compiler. Wherever

//! possible and reasonable, any architecture differences are abstracted, though. This means that

//! in most cases you can use this module even though your target-configuration might not match

//! the native UEFI target-configuration.

//!

//! The recommend way to compile your code, is to use the native target-configuration for UEFI.

//! These configurations are not necessarily included in the upstream rust compiler. Hence, you

//! might have to craft one yourself. For all systems that we can test on, we make sure to push

//! the target configuration into upstream rust-lang.

//!

//! However, there are situations where you want to access UEFI data from a non-native host. For

//! instance, a UEFI boot loader might store data in boot variables, formatted according to types

//! declared in the UEFI specification. An OS booted thereafter might want to access these

//! variables, but it might be compiled with a different target-configuration than the UEFI

//! environment that it was booted from. A similar situation occurs when you call UEFI runtime

//! functions from your OS. In all those cases, you should very likely be able to use this module

//! to interact with UEFI as well. This is, because most bits of the target-configuration of UEFI

//! and your OS very likely match. In fact, to figure out whether this is safe, you need to make

//! sure that the rust ABI would match in both target-configurations. If it is, all other details

//! are handled within this module just fine.

//!

//! In case of doubt, contact us!

//!

//! # Core Primitives

//!

//! Several of the UEFI primitives are represented by native Rust. These have no type aliases or

//! other definitions here, but you are recommended to use native rust directly. These include:

//!

//!  * `NULL`, `void *`: Void pointers have a native rust implementation in

//!                      [`c_void`](core::ffi::c_void). `NULL` is represented through

//!                      [`null`](core::ptr::null) and [`is_null()`](core::ptr) for

//!                      all pointer types.

//!  * `uint8_t`..`uint64_t`,

//!    `int8_t`..`int64_t`: Fixed-size integers are represented by their native rust equivalents

//!                         (`u8`..`u64`, `i8`..`i64`).

//!

//!  * `UINTN`, `INTN`: Native-sized (or instruction-width sized) integers are represented by

//!                     their native rust equivalents (`usize`, `isize`).

//!

//! # UEFI Details

//!

//! The UEFI Specification describes its target environments in detail. Each supported

//! architecture has a separate section with details on calling conventions, CPU setup, and more.

//! You are highly recommended to conduct the UEFI Specification for details on the programming

//! environment. Following a summary of key parts relevant to rust developers:

//!

//!  * Similar to rust, integers are either fixed-size, or native size. This maps nicely to the

//!    native rust types. The common `long`, `int`, `short` types known from ISO-C are not used.

//!    Whenever you refer to memory (either pointing to it, or remember the size of a memory

//!    block), the native size integers should be your tool of choice.

//!

//!  * Even though the CPU might run in any endianness, all stored data is little-endian. That

//!    means, if you encounter integers split into byte-arrays (e.g.,

//!    `CEfiDevicePathProtocol.length`), you must assume it is little-endian encoded. But if you

//!    encounter native integers, you must assume they are encoded in native endianness.

//!    For now the UEFI specification only defines little-endian architectures, hence this did not

//!    pop up as actual issue. Future extensions might change this, though.

//!

//!  * The Microsoft calling-convention is used. That is, all external calls to UEFI functions

//!    follow a calling convention that is very similar to that used on Microsoft Windows. All

//!    such ABI functions must be marked with the right calling-convention. The UEFI Specification

//!    defines some additional common rules for all its APIs, though. You will most likely not see

//!    any of these mentioned in the individual API documentions. So here is a short reminder:

//!

//!     * Pointers must reference physical-memory locations (no I/O mappings, no

//!       virtual addresses, etc.). Once ExitBootServices() was called, and the

//!       virtual address mapping was set, you must provide virtual-memory

//!       locations instead.

//!     * Pointers must be correctly aligned.

//!     * NULL is disallowed, unless explicitly mentioned otherwise.

//!     * Data referenced by pointers is undefined on error-return from a

//!       function.

//!     * You must not pass data larger than native-size (sizeof(CEfiUSize)) on

//!       the stack. You must pass them by reference.

//!

//!  * Stack size is at least 128KiB and 16-byte aligned. All stack space might be marked

//!    non-executable! Once ExitBootServices() was called, you must guarantee at least 4KiB of

//!    stack space, 16-byte aligned for all runtime services you call.

//!    Details might differ depending on architectures. But the numbers here should serve as

//!    ball-park figures.

// Target Architecture

//

// The UEFI Specification explicitly lists all supported target architectures. While external

// implementors are free to port UEFI to other targets, we need information on the target

// architecture to successfully compile for it. This includes calling-conventions, register

// layouts, endianness, and more. Most of these details are hidden in the rust-target-declaration.

// However, some details are still left to the actual rust code.

//

// This initial check just makes sure the compilation is halted with a suitable error message if

// the target architecture is not supported.

//

// We try to minimize conditional compilations as much as possible. A simple search for

// `target_arch` should reveal all uses throughout the code-base. If you add your target to this

// error-check, you must adjust all other uses as well.

//

// Similarly, UEFI only defines configurations for little-endian architectures so far. Several

// bits of the specification are thus unclear how they would be applied on big-endian systems. We

// therefore mark it as unsupported. If you override this, you are on your own.

#[cfg(not(any(

    target_arch = "arm",

    target_arch = "aarch64",

    target_arch = "x86",

    target_arch = "x86_64"

)))]

compile_error!("The target architecture is not supported.");

#[cfg(not(any(target_endian = "little")))]

compile_error!("The target endianness is not supported.");

// eficall_abi!()

//

// This macro is the architecture-dependent implementation of eficall!(). See the documentation of

// the eficall!() macro for a description.

#[cfg(target_arch = "arm")]

#[macro_export]

#[doc(hidden)]

macro_rules! eficall_abi {

    (($($prefix:tt)*),($($suffix:tt)*)) => { $($prefix)* extern "aapcs" $($suffix)* };

}

// XXX: Rust does not define aapcs64, yet. Once it does, we should switch to it, rather than

//      referring to the system default.

#[cfg(target_arch = "aarch64")]

#[macro_export]

#[doc(hidden)]

macro_rules! eficall_abi {

    (($($prefix:tt)*),($($suffix:tt)*)) => { $($prefix)* extern "C" $($suffix)* };

}

#[cfg(target_arch = "x86")]

#[macro_export]

#[doc(hidden)]

macro_rules! eficall_abi {

    (($($prefix:tt)*),($($suffix:tt)*)) => { $($prefix)* extern "cdecl" $($suffix)* };

}

#[cfg(target_arch = "x86_64")]

#[macro_export]

#[doc(hidden)]

macro_rules! eficall_abi {

    (($($prefix:tt)*),($($suffix:tt)*)) => { $($prefix)* extern "win64" $($suffix)* };

}

#[cfg(not(any(

    target_arch = "arm",

    target_arch = "aarch64",

    target_arch = "x86",

    target_arch = "x86_64"

)))]

#[macro_export]

#[doc(hidden)]

macro_rules! eficall_abi {

    (($($prefix:tt)*),($($suffix:tt)*)) => { $($prefix)* extern "C" $($suffix)* };

}

/// Annotate function with UEFI calling convention

///

/// This macro takes a function-declaration as argument and produces the same function-declaration

/// but annotated with the correct calling convention. Since the default `extern "C"` annotation

/// depends on your compiler defaults, we cannot use it. Instead, this macro selects the default

/// for your target platform.

///

/// Ideally, the macro would expand to `extern "<abi>"` so you would be able to write:

///

/// ```ignore

/// // THIS DOES NOT WORK!

/// pub fn eficall!{} foobar() {

///     // ...

/// }

/// ```

///

/// However, macros are evaluated too late for this to work. Instead, the entire construct must be

/// wrapped in a macro, which then expands to the same construct but with `extern "<abi>"`

/// inserted at the correct place:

///

/// ```

/// use r_efi::{eficall, eficall_abi};

///

/// eficall!{pub fn foobar() {

///     // ...

/// }}

///

/// type FooBar = eficall!{fn(u8) -> (u8)};

/// ```

///

/// The `eficall!{}` macro takes either a function-type or function-definition as argument. It

/// inserts `extern "<abi>"` after the function qualifiers, but before the `fn` keyword.

///

/// # Internals

///

/// The `eficall!{}` macro tries to parse the function header so it can insert `extern "<abi>"` at

/// the right place. If, for whatever reason, this does not work with a particular syntax, you can

/// use the internal `eficall_abi!{}` macro. This macro takes two token-streams as input and

/// evaluates to the concatenation of both token-streams, but separated by the selected ABI.

///

/// For instance, the following 3 type definitions are equivalent, assuming the selected ABI

/// is "C":

///

/// ```

/// use r_efi::{eficall, eficall_abi};

///

/// type FooBar1 = unsafe extern "C" fn(u8) -> (u8);

/// type FooBar2 = eficall!{unsafe fn(u8) -> (u8)};

/// type FooBar3 = eficall_abi!{(unsafe), (fn(u8) -> (u8))};

/// ```

///

/// # Calling Conventions

///

/// The UEFI specification defines the calling convention for each platform individually. It

/// usually refers to other standards for details, but adds some restrictions on top. As of this

/// writing, it mentions:

///

///  * aarch32 / arm: The `aapcs` calling-convention is used. It is native to aarch32 and described

///                   in a document called

///                   "Procedure Call Standard for the ARM Architecture". It is openly distributed

///                   by ARM and widely known under the keyword `aapcs`.

///  * aarch64: The `aapcs64` calling-convention is used. It is native to aarch64 and described in

///             a document called

///             "Procedure Call Standard for the ARM 64-bit Architecture (AArch64)". It is openly

///             distributed by ARM and widely known under the keyword `aapcs64`.

///  * ia-64: The "P64 C Calling Convention" as described in the

///           "Itanium Software Conventions and Runtime Architecture Guide". It is also

///           standardized in the "Intel Itanium SAL Specification".

///  * RISC-V: The "Standard RISC-V C Calling Convention" is used. The UEFI specification

///            describes it in detail, but also refers to the official RISC-V resources for

///            detailed information.

///  * x86 / ia-32: The `cdecl` C calling convention is used. Originated in the C Language and

///                 originally tightly coupled to C specifics. Unclear whether a formal

///                 specification exists (does anyone know?). Most compilers support it under the

///                 `cdecl` keyword, and in nearly all situations it is the default on x86.

///  * x86_64 / amd64 / x64: The `win64` calling-convention is used. It is similar to the `sysv64`

///                          convention that is used on most non-windows x86_64 systems, but not

///                          exactly the same. Microsoft provides open documentation on it. See

///                          MSDN "x64 Software Conventions -> Calling Conventions".

///                          The UEFI Specification does not directly refer to `win64`, but

///                          contains a full specification of the calling convention itself.

///

/// Note that in most cases the UEFI Specification adds several more restrictions on top of the

/// common calling-conventions. These restrictions usually do not affect how the compiler will lay

/// out the function calls. Instead, it usually only restricts the set of APIs that are allowed in

/// UEFI. Therefore, most compilers already support the calling conventions used on UEFI.

///

/// # Variadics

///

/// For some reason, the rust compiler allows variadics only in combination with the `"C"` calling

/// convention, even if the selected calling-convention matches what `"C"` would select on the

/// target platform. Hence, you will very likely be unable to use variadics with this macro.

/// Luckily, all of the UEFI functions that use variadics are wrappers around more low-level

/// accessors, so they are not necessarily required.

#[macro_export]

macro_rules! eficall {

    // Muncher

    //

    // The `@munch()` rules are internal and should not be invoked directly. We walk through the

    // input, moving one token after the other from the suffix into the prefix until we find the

    // position where to insert `extern "<abi>"`. This muncher never drops any tokens, hence we

    // can safely match invalid statements just fine, as the compiler will later print proper

    // diagnostics when parsing the macro output.

    // Once done, we invoke the `eficall_abi!{}` macro, which simply inserts the correct ABI.

    (@munch(($($prefix:tt)*),(pub $($suffix:tt)*))) => { eficall!{@munch(($($prefix)* pub),($($suffix)*))} };

    (@munch(($($prefix:tt)*),(unsafe $($suffix:tt)*))) => { eficall!{@munch(($($prefix)* unsafe),($($suffix)*))} };

    (@munch(($($prefix:tt)*),($($suffix:tt)*))) => { eficall_abi!{($($prefix)*),($($suffix)*)} };

    // Entry Point

    //

    // This captures the entire argument and invokes its own TT-muncher, but splits the input into

    // prefix and suffix, so the TT-muncher can walk through it. Note that initially everything is

    // in the suffix and the prefix is empty.

    ($($arg:tt)*) => { eficall!{@munch((),($($arg)*))} };

}

/// Boolean Type

///

/// This boolean type works very similar to the rust primitive type of [`bool`]. However, the rust

/// primitive type has no stable ABI, hence we provide this type to represent booleans on the FFI

/// interface.

///

/// UEFI defines booleans to be 1-byte integers, which can only have the values of `0` or `1`.

/// However, in practice anything non-zero is considered `true` by nearly all UEFI systems. Hence,

/// this type implements a boolean over `u8` and maps `0` to `false`, everything else to `true`.

///

/// The binary representation of this type is ABI. That is, you are allowed to transmute from and

/// to `u8`. Furthermore, this type never modifies its binary representation. If it was

/// initialized as, or transmuted from, a specific integer value, this value will be retained.

/// However, on the rust side you will never see the integer value. It instead behaves truly as a

/// boolean. If you need access to the integer value, you have to transmute it back to `u8`.

#[repr(C)]

#[derive(Copy, Clone, Debug, Eq)]

pub struct Boolean(u8);

/// Single-byte Character Type

///

/// The `Char8` type represents single-byte characters. UEFI defines them to be ASCII compatible,

/// using the ISO-Latin-1 character set.

pub type Char8 = u8;

/// Dual-byte Character Type

///

/// The `Char16` type represents dual-byte characters. UEFI defines them to be UCS-2 encoded.

pub type Char16 = u16;

/// Status Codes

///

/// UEFI uses the `Status` type to represent all kinds of status codes. This includes return codes

/// from functions, but also complex state of different devices and drivers. It is a simple

/// `usize`, but wrapped in a rust-type to allow us to implement helpers on this type. Depending

/// on the context, different state is stored in it. Note that it is always binary compatible to a

/// usize!

#[repr(C)]

#[derive(Copy, Clone, Debug, PartialEq, Eq)]

pub struct Status(usize);

/// Object Handles

///

/// Handles represent access to an opaque object. Handles are untyped by default, but get a

/// meaning when you combine them with an interface. Internally, they are simple void pointers. It

/// is the UEFI driver model that applies meaning to them.

pub type Handle = *mut core::ffi::c_void;

/// Event Objects

///

/// Event objects represent hooks into the main-loop of a UEFI environment. They allow to register

/// callbacks, to be invoked when a specific event happens. In most cases you use events to

/// register timer-based callbacks, as well as chaining events together. Internally, they are

/// simple void pointers. It is the UEFI task management that applies meaning to them.

pub type Event = *mut core::ffi::c_void;

/// Logical Block Addresses

///

/// The LBA type is used to denote logical block addresses of block devices. It is a simple 64-bit

/// integer, that is used to denote addresses when working with block devices.

pub type Lba = u64;

/// Thread Priority Levels

///

/// The process model of UEFI systems is highly simplified. Priority levels are used to order

/// execution of pending tasks. The TPL type denotes a priority level of a specific task. The

/// higher the number, the higher the priority. It is a simple integer type, but its range is

/// usually highly restricted. The UEFI task management provides constants and accessors for TPLs.

pub type Tpl = usize;

/// Physical Memory Address

///

/// A simple 64bit integer containing a physical memory address.

pub type PhysicalAddress = u64;

/// Virtual Memory Address

///

/// A simple 64bit integer containing a virtual memory address.

pub type VirtualAddress = u64;

/// Application Entry Point

///

/// This type defines the entry-point of UEFI applications. It is ABI and cannot be changed.

/// Whenever you load UEFI images, the entry-point is called with this signature.

///

/// In most cases the UEFI image (or application) is unloaded when control returns from the entry

/// point. In case of UEFI drivers, they can request to stay loaded until an explicit unload.

///

/// The system table is provided as mutable pointer. This is, because there is no guarantee that

/// timer interrupts do not modify the table. Furthermore, exiting boot services causes several

/// modifications on that table. And lastly, the system table lives longer than the function

/// invocation, if invoked as an UEFI driver.

/// In most cases it is perfectly fine to cast the pointer to a real rust reference. However, this

/// should be an explicit decision by the caller.

pub type ImageEntryPoint = fn(Handle, *mut crate::system::SystemTable) -> Status;

/// Globally Unique Identifiers

///

/// The `Guid` type represents globally unique identifiers as defined by RFC-4122 (i.e., only the

/// `10x` variant is used), with the caveat that LE is used instead of BE. The type must be 64-bit

/// aligned.

///

/// Note that only the binary representation of Guids is stable. You are highly recommended to

/// interpret Guids as 128bit integers.

///

/// UEFI uses the Microsoft-style Guid format. Hence, a lot of documentation and code refers to

/// these Guids. If you thusly cannot treat Guids as 128-bit integers, this Guid type allows you

/// to access the individual fields of the Microsoft-style Guid. A reminder of the Guid encoding:

///

/// ```text

///    0                   1                   2                   3

///    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

///   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

///   |                          time_low                             |

///   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

///   |       time_mid                |         time_hi_and_version   |

///   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

///   |clk_seq_hi_res |  clk_seq_low  |         node (0-1)            |

///   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

///   |                         node (2-5)                            |

///   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

/// ```

///

/// The individual fields are encoded as little-endian. Accessors are provided for the Guid

/// structure allowing access to these fields in native endian byte order.

#[repr(C, align(8))]

#[derive(Copy, Clone, Debug, PartialEq, Eq)]

pub struct Guid {

    time_low: [u8; 4],

    time_mid: [u8; 2],

    time_hi_and_version: [u8; 2],

    clk_seq_hi_res: u8,

    clk_seq_low: u8,

    node: [u8; 6],

}

/// Network MAC Address

///

/// This type encapsulates a single networking media access control address

/// (MAC). It is a simple 32 bytes buffer with no special alignment. Note that

/// no comparison function are defined by default, since trailing bytes of the

/// address might be random.

///

/// The interpretation of the content differs depending on the protocol it is

/// used with. See each documentation for details. In most cases this contains

/// an Ethernet address.

#[repr(C)]

#[derive(Copy, Clone, Debug)]

pub struct MacAddress {

    pub addr: [u8; 32],

}

/// IPv4 Address

///

/// Binary representation of an IPv4 address. It is encoded in network byte

/// order (i.e., big endian). Note that no special alignment restrictions are

/// defined by the standard specification.

#[repr(C)]

#[derive(Copy, Clone, Debug, PartialEq, Eq)]

pub struct Ipv4Address {

    pub addr: [u8; 4],

}

/// IPv6 Address

///

/// Binary representation of an IPv6 address, encoded in network byte order

/// (i.e., big endian). Similar to the IPv4 address, no special alignment

/// restrictions are defined by the standard specification.

#[repr(C)]

#[derive(Copy, Clone, Debug, PartialEq, Eq)]

pub struct Ipv6Address {

    pub addr: [u8; 16],

}

/// IP Address

///

/// A union type over the different IP addresses available. Alignment is always

/// fixed to 4-bytes. Note that trailing bytes might be random, so no

/// comparison functions are derived.

#[repr(C, align(4))]

#[derive(Copy, Clone)]

pub union IpAddress {

    pub addr: [u32; 4],

    pub v4: Ipv4Address,

    pub v6: Ipv6Address,

}

impl Boolean {

    /// Literal False

    ///

    /// This constant represents the `false` value of the `Boolean` type.

    pub const FALSE: Boolean = Boolean(0u8);

    /// Literal True

    ///

    /// This constant represents the `true` value of the `Boolean` type.

    pub const TRUE: Boolean = Boolean(1u8);

}

impl From<u8> for Boolean {

    fn from(v: u8) -> Self {

        Boolean(v)

    }

}

impl From<bool> for Boolean {

    fn from(v: bool) -> Self {

        match v {

            false => Boolean::FALSE,

            true => Boolean::TRUE,

        }

    }

}

impl From<Boolean> for bool {

    fn from(v: Boolean) -> Self {

        match v.0 {

            0 => false,

            _ => true,

        }

    }

}

impl PartialEq for Boolean {

    fn eq(&self, other: &Boolean) -> bool {

        <bool as From<Boolean>>::from(*self) == (*other).into()

    }

}

impl PartialEq<bool> for Boolean {

    fn eq(&self, other: &bool) -> bool {

        *other == (*self).into()

    }

}

impl Status {

    const WIDTH: usize = 8usize * core::mem::size_of::<Status>();

    const MASK: usize = 0xc0 << (Status::WIDTH - 8);

    const ERROR_MASK: usize = 0x80 << (Status::WIDTH - 8);

    const WARNING_MASK: usize = 0x00 << (Status::WIDTH - 8);

    /// Success Code

    ///

    /// This code represents a successfull function invocation. Its value is guaranteed to be 0.

    /// However, note that warnings are considered success as well, so this is not the only code

    /// that can be returned by UEFI functions on success. However, in nearly all situations

    /// warnings are not allowed, so the effective result will be SUCCESS.

    pub const SUCCESS: Status = Status::from_usize(0);

    // List of predefined error codes

    pub const LOAD_ERROR: Status = Status::from_usize(1 | Status::ERROR_MASK);

    pub const INVALID_PARAMETER: Status = Status::from_usize(2 | Status::ERROR_MASK);

    pub const UNSUPPORTED: Status = Status::from_usize(3 | Status::ERROR_MASK);

    pub const BAD_BUFFER_SIZE: Status = Status::from_usize(4 | Status::ERROR_MASK);

    pub const BUFFER_TOO_SMALL: Status = Status::from_usize(5 | Status::ERROR_MASK);

    pub const NOT_READY: Status = Status::from_usize(6 | Status::ERROR_MASK);

    pub const DEVICE_ERROR: Status = Status::from_usize(7 | Status::ERROR_MASK);

    pub const WRITE_PROTECTED: Status = Status::from_usize(8 | Status::ERROR_MASK);

    pub const OUT_OF_RESOURCES: Status = Status::from_usize(9 | Status::ERROR_MASK);

    pub const VOLUME_CORRUPTED: Status = Status::from_usize(10 | Status::ERROR_MASK);

    pub const VOLUME_FULL: Status = Status::from_usize(11 | Status::ERROR_MASK);

    pub const NO_MEDIA: Status = Status::from_usize(12 | Status::ERROR_MASK);

    pub const MEDIA_CHANGED: Status = Status::from_usize(13 | Status::ERROR_MASK);

    pub const NOT_FOUND: Status = Status::from_usize(14 | Status::ERROR_MASK);

    pub const ACCESS_DENIED: Status = Status::from_usize(15 | Status::ERROR_MASK);

    pub const NO_RESPONSE: Status = Status::from_usize(16 | Status::ERROR_MASK);

    pub const NO_MAPPING: Status = Status::from_usize(17 | Status::ERROR_MASK);

    pub const TIMEOUT: Status = Status::from_usize(18 | Status::ERROR_MASK);

    pub const NOT_STARTED: Status = Status::from_usize(19 | Status::ERROR_MASK);

    pub const ALREADY_STARTED: Status = Status::from_usize(20 | Status::ERROR_MASK);

    pub const ABORTED: Status = Status::from_usize(21 | Status::ERROR_MASK);

    pub const ICMP_ERROR: Status = Status::from_usize(22 | Status::ERROR_MASK);

    pub const TFTP_ERROR: Status = Status::from_usize(23 | Status::ERROR_MASK);

    pub const PROTOCOL_ERROR: Status = Status::from_usize(24 | Status::ERROR_MASK);

    pub const INCOMPATIBLE_VERSION: Status = Status::from_usize(25 | Status::ERROR_MASK);

    pub const SECURITY_VIOLATION: Status = Status::from_usize(26 | Status::ERROR_MASK);

    pub const CRC_ERROR: Status = Status::from_usize(27 | Status::ERROR_MASK);

    pub const END_OF_MEDIA: Status = Status::from_usize(28 | Status::ERROR_MASK);

    pub const END_OF_FILE: Status = Status::from_usize(31 | Status::ERROR_MASK);

    pub const INVALID_LANGUAGE: Status = Status::from_usize(32 | Status::ERROR_MASK);

    pub const COMPROMISED_DATA: Status = Status::from_usize(33 | Status::ERROR_MASK);

    pub const IP_ADDRESS_CONFLICT: Status = Status::from_usize(34 | Status::ERROR_MASK);

    pub const HTTP_ERROR: Status = Status::from_usize(35 | Status::ERROR_MASK);

    // List of predefined warning codes

    pub const WARN_UNKNOWN_GLYPH: Status = Status::from_usize(1 | Status::WARNING_MASK);

    pub const WARN_DELETE_FAILURE: Status = Status::from_usize(2 | Status::WARNING_MASK);

    pub const WARN_WRITE_FAILURE: Status = Status::from_usize(3 | Status::WARNING_MASK);

    pub const WARN_BUFFER_TOO_SMALL: Status = Status::from_usize(4 | Status::WARNING_MASK);

    pub const WARN_STALE_DATA: Status = Status::from_usize(5 | Status::WARNING_MASK);

    pub const WARN_FILE_SYSTEM: Status = Status::from_usize(6 | Status::WARNING_MASK);

    pub const WARN_RESET_REQUIRED: Status = Status::from_usize(7 | Status::WARNING_MASK);

    /// Create Status Code from Integer

    ///

    /// This takes the literal value of a status code and turns it into a `Status` object. Note

    /// that we want it as `const fn` so we cannot use `core::convert::From`.

    pub const fn from_usize(v: usize) -> Status {

        Status(v)

    }

    /// Return Underlying Integer Representation

    ///

    /// This takes the `Status` object and returns the underlying integer representation as

    /// defined by the UEFI specification.

    pub const fn as_usize(&self) -> usize {

        self.0

    }

    fn value(&self) -> usize {

        self.0

    }

    fn mask(&self) -> usize {

        self.value() & Status::MASK

    }

    /// Check whether this is an error

    ///

    /// This returns true if the given status code is considered an error. Errors mean the

    /// operation did not succeed, nor produce any valuable output. Output parameters must be

    /// considered invalid if an error was returned. That is, its content is not well defined.

    pub fn is_error(&self) -> bool {

        self.mask() == Status::ERROR_MASK

    }

    /// Check whether this is a warning

    ///

    /// This returns true if the given status code is considered a warning. Warnings are to be

    /// treated as success, but might indicate data loss or other device errors. However, if an

    /// operation returns with a warning code, it must be considered successfull, and the output

    /// parameters are valid.

    pub fn is_warning(&self) -> bool {

        self.value() != 0 && self.mask() == Status::WARNING_MASK

    }

}

impl From<Status> for Result<Status, Status> {

    fn from(status: Status) -> Self {

        if status.is_error() {

            Err(status)

        } else {

            Ok(status)

        }

    }

}

impl Guid {

    const fn u32_to_bytes_le(num: u32) -> [u8; 4] {

        [

            num as u8,

            (num >> 8) as u8,

            (num >> 16) as u8,

            (num >> 24) as u8,

        ]

    }

    const fn u32_from_bytes_le(bytes: &[u8; 4]) -> u32 {

        (bytes[0] as u32)

            | ((bytes[1] as u32) << 8)

            | ((bytes[2] as u32) << 16)

            | ((bytes[3] as u32) << 24)

    }

    const fn u16_to_bytes_le(num: u16) -> [u8; 2] {

        [num as u8, (num >> 8) as u8]

    }

    const fn u16_from_bytes_le(bytes: &[u8; 2]) -> u16 {

        (bytes[0] as u16) | ((bytes[1] as u16) << 8)

    }

    /// Initialize a Guid from its individual fields

    ///

    /// This function initializes a Guid object given the individual fields as specified in the

    /// UEFI specification. That is, if you simply copy the literals from the specification into

    /// your code, this function will correctly initialize the Guid object.

    ///

    /// In other words, this takes the individual fields in native endian and converts them to the

    /// correct endianness for a UEFI Guid.

    pub const fn from_fields(

        time_low: u32,

        time_mid: u16,

        time_hi_and_version: u16,

        clk_seq_hi_res: u8,

        clk_seq_low: u8,

        node: &[u8; 6],

    ) -> Guid {

        Guid {

            time_low: Self::u32_to_bytes_le(time_low),

            time_mid: Self::u16_to_bytes_le(time_mid),

            time_hi_and_version: Self::u16_to_bytes_le(time_hi_and_version),

            clk_seq_hi_res: clk_seq_hi_res,

            clk_seq_low: clk_seq_low,

            node: *node,

        }

    }

    /// Access a Guid as individual fields

    ///

    /// This decomposes a Guid back into the individual fields as given in the specification. The

    /// individual fields are returned in native-endianness.

    pub const fn as_fields(&self) -> (u32, u16, u16, u8, u8, &[u8; 6]) {

        (

            Self::u32_from_bytes_le(&self.time_low),

            Self::u16_from_bytes_le(&self.time_mid),

            Self::u16_from_bytes_le(&self.time_hi_and_version),

            self.clk_seq_hi_res,

            self.clk_seq_low,

            &self.node,

        )

    }

    /// Access a Guid as raw byte array

    ///

    /// This provides access to a Guid through a byte array. It is a simple re-interpretation of

    /// the Guid value as a 128-bit byte array. No conversion is performed. This is a simple cast.

    pub fn as_bytes(&self) -> &[u8; 16] {

        unsafe { core::mem::transmute::<&Guid, &[u8; 16]>(self) }

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use std::mem::{align_of, size_of};

    // Verify Type Size and Alignemnt

    //

    // Since UEFI defines explicitly the ABI of their types, we can verify that our implementation

    // is correct by checking the size and alignment of the ABI types matches what the spec

    // mandates.

    #[test]

    fn type_size_and_alignment() {

        //

        // Booleans

        //

        assert_eq!(size_of::<Boolean>(), 1);

        assert_eq!(align_of::<Boolean>(), 1);

        //

        // Char8 / Char16

        //

        assert_eq!(size_of::<Char8>(), 1);

        assert_eq!(align_of::<Char8>(), 1);

        assert_eq!(size_of::<Char16>(), 2);

        assert_eq!(align_of::<Char16>(), 2);

        assert_eq!(size_of::<Char8>(), size_of::<u8>());

        assert_eq!(align_of::<Char8>(), align_of::<u8>());

        assert_eq!(size_of::<Char16>(), size_of::<u16>());

        assert_eq!(align_of::<Char16>(), align_of::<u16>());

        //

        // Status

        //

        assert_eq!(size_of::<Status>(), size_of::<usize>());

        assert_eq!(align_of::<Status>(), align_of::<usize>());

        //

        // Handles / Events

        //

        assert_eq!(size_of::<Handle>(), size_of::<usize>());

        assert_eq!(align_of::<Handle>(), align_of::<usize>());

        assert_eq!(size_of::<Event>(), size_of::<usize>());

        assert_eq!(align_of::<Event>(), align_of::<usize>());

        assert_eq!(size_of::<Handle>(), size_of::<*mut ()>());

        assert_eq!(align_of::<Handle>(), align_of::<*mut ()>());

        assert_eq!(size_of::<Event>(), size_of::<*mut ()>());

        assert_eq!(align_of::<Event>(), align_of::<*mut ()>());

        //

        // Lba / Tpl

        //

        assert_eq!(size_of::<Lba>(), size_of::<u64>());

        assert_eq!(align_of::<Lba>(), align_of::<u64>());

        assert_eq!(size_of::<Tpl>(), size_of::<usize>());

        assert_eq!(align_of::<Tpl>(), align_of::<usize>());

        //

        // PhysicalAddress / VirtualAddress

        //

        assert_eq!(size_of::<PhysicalAddress>(), size_of::<u64>());

        assert_eq!(align_of::<PhysicalAddress>(), align_of::<u64>());

        assert_eq!(size_of::<VirtualAddress>(), size_of::<u64>());

        assert_eq!(align_of::<VirtualAddress>(), align_of::<u64>());

        //

        // ImageEntryPoint

        //

        assert_eq!(size_of::<ImageEntryPoint>(), size_of::<fn()>());

        assert_eq!(align_of::<ImageEntryPoint>(), align_of::<fn()>());

        //

        // Guid

        //

        assert_eq!(size_of::<Guid>(), 16);

        assert_eq!(align_of::<Guid>(), 8);

        //

        // Networking Types

        //

        assert_eq!(size_of::<MacAddress>(), 32);

        assert_eq!(align_of::<MacAddress>(), 1);

        assert_eq!(size_of::<Ipv4Address>(), 4);

        assert_eq!(align_of::<Ipv4Address>(), 1);

        assert_eq!(size_of::<Ipv6Address>(), 16);

        assert_eq!(align_of::<Ipv6Address>(), 1);

        assert_eq!(size_of::<IpAddress>(), 16);

        assert_eq!(align_of::<IpAddress>(), 4);

    }

    #[test]

    fn eficall() {

        //

        // Make sure the eficall!{} macro can deal with all kinds of function callbacks.

        //

        let _: eficall! {fn()};

        let _: eficall! {unsafe fn()};

        let _: eficall! {fn(i32)};

        let _: eficall! {fn(i32) -> i32};

        let _: eficall! {fn(i32, i32) -> (i32, i32)};

        eficall! {fn _unused00() {}}

        eficall! {unsafe fn _unused01() {}}

        eficall! {pub unsafe fn _unused02() {}}

    }

    // Verify Boolean ABI

    //

    // Even though booleans are strictly 1-bit, and thus 0 or 1, in practice all UEFI systems

    // treat it more like C does, and a boolean formatted as `u8` now allows any value other than

    // 0 to represent `true`. Make sure we support the same.

    #[test]

    fn booleans() {

        // Verify PartialEq works.

        assert_ne!(Boolean::FALSE, Boolean::TRUE);

        // Verify Boolean<->bool conversion and comparison works.

        assert_eq!(Boolean::FALSE, false);

        assert_eq!(Boolean::TRUE, true);

        // Iterate all possible values for `u8` and verify 0 behaves as `false`, and everything

        // else behaves as `true`. We verify both, the natural constructor through `From`, as well

        // as a transmute.

        for i in 0u8..=255u8 {

            let v1: Boolean = i.into();

            let v2: Boolean = unsafe { std::mem::transmute::<u8, Boolean>(i) };

            assert_eq!(v1, v2);

            assert_eq!(v1, v1);

            assert_eq!(v2, v2);

            match i {

                0 => {

                    assert_eq!(v1, Boolean::FALSE);

                    assert_eq!(v1, false);

                    assert_eq!(v2, Boolean::FALSE);

                    assert_eq!(v2, false);

                    assert_ne!(v1, Boolean::TRUE);

                    assert_ne!(v1, true);

                    assert_ne!(v2, Boolean::TRUE);

                    assert_ne!(v2, true);

                }

                _ => {

                    assert_eq!(v1, Boolean::TRUE);

                    assert_eq!(v1, true);

                    assert_eq!(v2, Boolean::TRUE);

                    assert_eq!(v2, true);

                    assert_ne!(v1, Boolean::FALSE);

                    assert_ne!(v1, false);

                    assert_ne!(v2, Boolean::FALSE);

                    assert_ne!(v2, false);

                }

            }

        }

    }

}