// Copyright 2012 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.

//! Operations and constants for `uint`

pub use self::inst::{
    div_ceil, div_round, div_floor, iterate,
    next_power_of_two
};

pub mod inst {
    use iter;
    use num::{Primitive, BitCount};
    use sys;

    pub type T = uint;
    #[allow(non_camel_case_types)]
    pub type T_SIGNED = int;

    #[cfg(target_arch = "x86")]
    #[cfg(target_arch = "arm")]
    #[cfg(target_arch = "mips")]
    pub static bits: uint = 32;

    #[cfg(target_arch = "x86_64")]
    pub static bits: uint = 64;

    impl Primitive for uint {
        #[cfg(target_word_size = "32")]
        #[inline(always)]
        fn bits() -> uint { 32 }

        #[cfg(target_word_size = "64")]
        #[inline(always)]
        fn bits() -> uint { 64 }

        #[inline(always)]
        fn bytes() -> uint { Primitive::bits::<uint>() / 8 }
    }

    #[cfg(target_word_size = "32")]
    #[inline(always)]
    impl BitCount for uint {
        /// Counts the number of bits set. Wraps LLVM's `ctpop` intrinsic.
        #[inline(always)]
        fn population_count(&self) -> uint { (*self as i32).population_count() as uint }

        /// Counts the number of leading zeros. Wraps LLVM's `ctlz` intrinsic.
        #[inline(always)]
        fn leading_zeros(&self) -> uint { (*self as i32).leading_zeros() as uint }

        /// Counts the number of trailing zeros. Wraps LLVM's `cttz` intrinsic.
        #[inline(always)]
        fn trailing_zeros(&self) -> uint { (*self as i32).trailing_zeros() as uint }
    }

    #[cfg(target_word_size = "64")]
    #[inline(always)]
    impl BitCount for uint {
        /// Counts the number of bits set. Wraps LLVM's `ctpop` intrinsic.
        #[inline(always)]
        fn population_count(&self) -> uint { (*self as i64).population_count() as uint }

        /// Counts the number of leading zeros. Wraps LLVM's `ctlz` intrinsic.
        #[inline(always)]
        fn leading_zeros(&self) -> uint { (*self as i64).leading_zeros() as uint }

        /// Counts the number of trailing zeros. Wraps LLVM's `cttz` intrinsic.
        #[inline(always)]
        fn trailing_zeros(&self) -> uint { (*self as i64).trailing_zeros() as uint }
    }

    ///
    /// Divide two numbers, return the result, rounded up.
    ///
    /// # Arguments
    ///
    /// * x - an integer
    /// * y - an integer distinct from 0u
    ///
    /// # Return value
    ///
    /// The smallest integer `q` such that `x/y <= q`.
    ///
    pub fn div_ceil(x: uint, y: uint) -> uint {
        let div = x / y;
        if x % y == 0u { div }
        else { div + 1u }
    }

    ///
    /// Divide two numbers, return the result, rounded to the closest integer.
    ///
    /// # Arguments
    ///
    /// * x - an integer
    /// * y - an integer distinct from 0u
    ///
    /// # Return value
    ///
    /// The integer `q` closest to `x/y`.
    ///
    pub fn div_round(x: uint, y: uint) -> uint {
        let div = x / y;
        if x % y * 2u  < y { div }
        else { div + 1u }
    }

    ///
    /// Divide two numbers, return the result, rounded down.
    ///
    /// Note: This is the same function as `div`.
    ///
    /// # Arguments
    ///
    /// * x - an integer
    /// * y - an integer distinct from 0u
    ///
    /// # Return value
    ///
    /// The smallest integer `q` such that `x/y <= q`. This
    /// is either `x/y` or `x/y + 1`.
    ///
    pub fn div_floor(x: uint, y: uint) -> uint { return x / y; }

    ///
    /// Iterate over the range [`lo`..`hi`), or stop when requested
    ///
    /// # Arguments
    ///
    /// * lo - The integer at which to start the loop (included)
    /// * hi - The integer at which to stop the loop (excluded)
    /// * it - A block to execute with each consecutive integer of the range.
    ///        Return `true` to continue, `false` to stop.
    ///
    /// # Return value
    ///
    /// `true` If execution proceeded correctly, `false` if it was interrupted,
    /// that is if `it` returned `false` at any point.
    ///
    pub fn iterate(lo: uint, hi: uint, it: &fn(uint) -> bool) -> bool {
        let mut i = lo;
        while i < hi {
            if (!it(i)) { return false; }
            i += 1u;
        }
        return true;
    }

    #[cfg(stage0)]
    impl iter::Times for uint {
        #[inline(always)]
        ///
        /// A convenience form for basic iteration. Given a uint `x`,
        /// `for x.times { ... }` executes the given block x times.
        ///
        /// Equivalent to `for uint::range(0, x) |_| { ... }`.
        ///
        /// Not defined on all integer types to permit unambiguous
        /// use with integer literals of inferred integer-type as
        /// the self-value (eg. `for 100.times { ... }`).
        ///
        fn times(&self, it: &fn() -> bool) {
            let mut i = *self;
            while i > 0 {
                if !it() { break }
                i -= 1;
            }
        }
    }

    #[cfg(not(stage0))]
    impl iter::Times for uint {
        #[inline(always)]
        ///
        /// A convenience form for basic iteration. Given a uint `x`,
        /// `for x.times { ... }` executes the given block x times.
        ///
        /// Equivalent to `for uint::range(0, x) |_| { ... }`.
        ///
        /// Not defined on all integer types to permit unambiguous
        /// use with integer literals of inferred integer-type as
        /// the self-value (eg. `for 100.times { ... }`).
        ///
        fn times(&self, it: &fn() -> bool) -> bool {
            let mut i = *self;
            while i > 0 {
                if !it() { return false; }
                i -= 1;
            }
            return true;
        }
    }

    /// Returns the smallest power of 2 greater than or equal to `n`
    #[inline(always)]
    pub fn next_power_of_two(n: uint) -> uint {
        let halfbits: uint = sys::size_of::<uint>() * 4u;
        let mut tmp: uint = n - 1u;
        let mut shift: uint = 1u;
        while shift <= halfbits { tmp |= tmp >> shift; shift <<= 1u; }
        return tmp + 1u;
    }

    #[test]
    fn test_next_power_of_two() {
        assert!((next_power_of_two(0u) == 0u));
        assert!((next_power_of_two(1u) == 1u));
        assert!((next_power_of_two(2u) == 2u));
        assert!((next_power_of_two(3u) == 4u));
        assert!((next_power_of_two(4u) == 4u));
        assert!((next_power_of_two(5u) == 8u));
        assert!((next_power_of_two(6u) == 8u));
        assert!((next_power_of_two(7u) == 8u));
        assert!((next_power_of_two(8u) == 8u));
        assert!((next_power_of_two(9u) == 16u));
        assert!((next_power_of_two(10u) == 16u));
        assert!((next_power_of_two(11u) == 16u));
        assert!((next_power_of_two(12u) == 16u));
        assert!((next_power_of_two(13u) == 16u));
        assert!((next_power_of_two(14u) == 16u));
        assert!((next_power_of_two(15u) == 16u));
        assert!((next_power_of_two(16u) == 16u));
        assert!((next_power_of_two(17u) == 32u));
        assert!((next_power_of_two(18u) == 32u));
        assert!((next_power_of_two(19u) == 32u));
        assert!((next_power_of_two(20u) == 32u));
        assert!((next_power_of_two(21u) == 32u));
        assert!((next_power_of_two(22u) == 32u));
        assert!((next_power_of_two(23u) == 32u));
        assert!((next_power_of_two(24u) == 32u));
        assert!((next_power_of_two(25u) == 32u));
        assert!((next_power_of_two(26u) == 32u));
        assert!((next_power_of_two(27u) == 32u));
        assert!((next_power_of_two(28u) == 32u));
        assert!((next_power_of_two(29u) == 32u));
        assert!((next_power_of_two(30u) == 32u));
        assert!((next_power_of_two(31u) == 32u));
        assert!((next_power_of_two(32u) == 32u));
        assert!((next_power_of_two(33u) == 64u));
        assert!((next_power_of_two(34u) == 64u));
        assert!((next_power_of_two(35u) == 64u));
        assert!((next_power_of_two(36u) == 64u));
        assert!((next_power_of_two(37u) == 64u));
        assert!((next_power_of_two(38u) == 64u));
        assert!((next_power_of_two(39u) == 64u));
    }

    #[test]
    fn test_overflows() {
        use uint;
        assert!((uint::max_value > 0u));
        assert!((uint::min_value <= 0u));
        assert!((uint::min_value + uint::max_value + 1u == 0u));
    }

    #[test]
    fn test_div() {
        assert!((div_floor(3u, 4u) == 0u));
        assert!((div_ceil(3u, 4u)  == 1u));
        assert!((div_round(3u, 4u) == 1u));
    }

    #[test]
    pub fn test_times() {
        use iter::Times;
        let ten = 10 as uint;
        let mut accum = 0;
        for ten.times { accum += 1; }
        assert!((accum == 10));
    }
}