// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT

// file at the top-level directory of this distribution and at

// http://rust-lang.org/COPYRIGHT.

//

// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or

// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license

// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your

// option. This file may not be copied, modified, or distributed

// except according to those terms.

//! Big Integer Types for Rust

//!

//! * A [`BigUint`] is unsigned and represented as a vector of digits.

//! * A [`BigInt`] is signed and is a combination of [`BigUint`] and [`Sign`].

//!

//! Common numerical operations are overloaded, so we can treat them

//! the same way we treat other numbers.

//!

//! ## Example

//!

//! ```rust

//! # fn main() {

//! use num_bigint::BigUint;

//! use num_traits::One;

//!

//! // Calculate large fibonacci numbers.

//! fn fib(n: usize) -> BigUint {

//!     let mut f0 = BigUint::ZERO;

//!     let mut f1 = BigUint::one();

//!     for _ in 0..n {

//!         let f2 = f0 + &f1;

//!         f0 = f1;

//!         f1 = f2;

//!     }

//!     f0

//! }

//!

//! // This is a very large number.

//! println!("fib(1000) = {}", fib(1000));

//! # }

//! ```

//!

//! It's easy to generate large random numbers:

//!

//! ```rust,ignore

//! use num_bigint::{ToBigInt, RandBigInt};

//!

//! let mut rng = rand::thread_rng();

//! let a = rng.gen_bigint(1000);

//!

//! let low = -10000.to_bigint().unwrap();

//! let high = 10000.to_bigint().unwrap();

//! let b = rng.gen_bigint_range(&low, &high);

//!

//! // Probably an even larger number.

//! println!("{}", a * b);

//! ```

//!

//! See the "Features" section for instructions for enabling random number generation.

//!

//! ## Features

//!

//! The `std` crate feature is enabled by default, which enables [`std::error::Error`]

//! implementations and some internal use of floating point approximations. This can be disabled by

//! depending on `num-bigint` with `default-features = false`. Either way, the `alloc` crate is

//! always required for heap allocation of the `BigInt`/`BigUint` digits.

//!

//! ### Random Generation

//!

//! `num-bigint` supports the generation of random big integers when the `rand`

//! feature is enabled. To enable it include rand as

//!

//! ```toml

//! rand = "0.8"

//! num-bigint = { version = "0.4", features = ["rand"] }

//! ```

//!

//! Note that you must use the version of `rand` that `num-bigint` is compatible

//! with: `0.8`.

//!

//! ### Arbitrary Big Integers

//!

//! `num-bigint` supports `arbitrary` and `quickcheck` features to implement

//! [`arbitrary::Arbitrary`] and [`quickcheck::Arbitrary`], respectively, for both `BigInt` and

//! `BigUint`. These are useful for fuzzing and other forms of randomized testing.

//!

//! ### Serialization

//!

//! The `serde` feature adds implementations of [`Serialize`][serde::Serialize] and

//! [`Deserialize`][serde::Deserialize] for both `BigInt` and `BigUint`. Their serialized data is

//! generated portably, regardless of platform differences like the internal digit size.

//!

//!

//! ## Compatibility

//!

//! The `num-bigint` crate is tested for rustc 1.60 and greater.

#![cfg_attr(docsrs, feature(doc_cfg))]

#![doc(html_root_url = "https://docs.rs/num-bigint/0.4")]

#![warn(rust_2018_idioms)]

#![no_std]

#[macro_use]

extern crate alloc;

#[cfg(feature = "std")]

extern crate std;

use core::fmt;

#[macro_use]

mod macros;

mod bigint;

mod bigrand;

mod biguint;

#[cfg(target_pointer_width = "32")]

type UsizePromotion = u32;

#[cfg(target_pointer_width = "64")]

type UsizePromotion = u64;

#[cfg(target_pointer_width = "32")]

type IsizePromotion = i32;

#[cfg(target_pointer_width = "64")]

type IsizePromotion = i64;

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

pub struct ParseBigIntError {

    kind: BigIntErrorKind,

}

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

enum BigIntErrorKind {

    Empty,

    InvalidDigit,

}

impl ParseBigIntError {

    fn __description(&self) -> &str {

        use crate::BigIntErrorKind::*;

        match self.kind {

            Empty => "cannot parse integer from empty string",

            InvalidDigit => "invalid digit found in string",

        }

    }

    fn empty() -> Self {

        ParseBigIntError {

            kind: BigIntErrorKind::Empty,

        }

    }

    fn invalid() -> Self {

        ParseBigIntError {

            kind: BigIntErrorKind::InvalidDigit,

        }

    }

}

impl fmt::Display for ParseBigIntError {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        self.__description().fmt(f)

    }

}

#[cfg(feature = "std")]

#[cfg_attr(docsrs, doc(cfg(feature = "std")))]

impl std::error::Error for ParseBigIntError {

    fn description(&self) -> &str {

        self.__description()

    }

}

/// The error type returned when a checked conversion regarding big integer fails.

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

pub struct TryFromBigIntError<T> {

    original: T,

}

impl<T> TryFromBigIntError<T> {

    fn new(original: T) -> Self {

        TryFromBigIntError { original }

    }

    fn __description(&self) -> &str {

        "out of range conversion regarding big integer attempted"

    }

    /// Extract the original value, if available. The value will be available

    /// if the type before conversion was either [`BigInt`] or [`BigUint`].

    pub fn into_original(self) -> T {

        self.original

    }

}

#[cfg(feature = "std")]

#[cfg_attr(docsrs, doc(cfg(feature = "std")))]

impl<T> std::error::Error for TryFromBigIntError<T>

where

    T: fmt::Debug,

{

    fn description(&self) -> &str {

        self.__description()

    }

}

impl<T> fmt::Display for TryFromBigIntError<T> {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        self.__description().fmt(f)

    }

}

pub use crate::biguint::BigUint;

pub use crate::biguint::ToBigUint;

pub use crate::biguint::U32Digits;

pub use crate::biguint::U64Digits;

pub use crate::bigint::BigInt;

pub use crate::bigint::Sign;

pub use crate::bigint::ToBigInt;

#[cfg(feature = "rand")]

#[cfg_attr(docsrs, doc(cfg(feature = "rand")))]

pub use crate::bigrand::{RandBigInt, RandomBits, UniformBigInt, UniformBigUint};

mod big_digit {

    // A [`BigDigit`] is a [`BigUint`]'s composing element.

    cfg_digit!(

        pub(crate) type BigDigit = u32;

        pub(crate) type BigDigit = u64;

    );

    // A [`DoubleBigDigit`] is the internal type used to do the computations.  Its

    // size is the double of the size of [`BigDigit`].

    cfg_digit!(

        pub(crate) type DoubleBigDigit = u64;

        pub(crate) type DoubleBigDigit = u128;

    );

    pub(crate) const BITS: u8 = BigDigit::BITS as u8;

    pub(crate) const HALF_BITS: u8 = BITS / 2;

    pub(crate) const HALF: BigDigit = (1 << HALF_BITS) - 1;

    pub(crate) const MAX: BigDigit = BigDigit::MAX;

    const LO_MASK: DoubleBigDigit = MAX as DoubleBigDigit;

    #[inline]

    fn get_hi(n: DoubleBigDigit) -> BigDigit {

        (n >> BITS) as BigDigit

    }

    #[inline]

    fn get_lo(n: DoubleBigDigit) -> BigDigit {

        (n & LO_MASK) as BigDigit

    }

    /// Split one [`DoubleBigDigit`] into two [`BigDigit`]s.

    #[inline]

    pub(crate) fn from_doublebigdigit(n: DoubleBigDigit) -> (BigDigit, BigDigit) {

        (get_hi(n), get_lo(n))

    }

    /// Join two [`BigDigit`]s into one [`DoubleBigDigit`].

    #[inline]

    pub(crate) fn to_doublebigdigit(hi: BigDigit, lo: BigDigit) -> DoubleBigDigit {

        DoubleBigDigit::from(lo) | (DoubleBigDigit::from(hi) << BITS)

    }

}