bitpacking 0.5.1

use super::{BitPacker, UnsafeBitPacker};

#[cfg(target_arch = "x86_64")]
use Available;

const BLOCK_LEN: usize = 32 * 4;


#[cfg(any(target_arch="x86_64"))]
mod sse3 {

    use super::BLOCK_LEN;
    use Available;

    use std::arch::x86_64::__m128i as DataType;
    use std::arch::x86_64::_mm_set1_epi32 as set1;
    use std::arch::x86_64::_mm_srli_epi32 as right_shift_32;
    use std::arch::x86_64::_mm_slli_epi32 as left_shift_32;
    use std::arch::x86_64::_mm_or_si128 as op_or;
    use std::arch::x86_64::_mm_and_si128 as op_and;
    use std::arch::x86_64::_mm_lddqu_si128 as load_unaligned;
    use std::arch::x86_64::_mm_storeu_si128 as store_unaligned;
    use std::arch::x86_64::{_mm_add_epi32,  _mm_shuffle_epi32, _mm_srli_si128, _mm_sub_epi32, _mm_slli_si128, _mm_cvtsi128_si32};

    #[allow(non_snake_case)]
    unsafe fn or_collapse_to_u32(accumulator: DataType) -> u32 {
        let a__b__c__d_ = accumulator;
        let ______a__b_ = _mm_srli_si128(a__b__c__d_, 8);
        let a__b__ca_db = op_or(a__b__c__d_, ______a__b_);
        let ___a__b__ca = _mm_srli_si128(a__b__ca_db, 4);
        let _______cadb = op_or(a__b__ca_db, ___a__b__ca);
        _mm_cvtsi128_si32(_______cadb) as u32
    }

    #[target_feature(enable="sse3")]
    unsafe fn compute_delta(curr: DataType, prev: DataType) -> DataType {
        _mm_sub_epi32(curr,
                      op_or(_mm_slli_si128(curr, 4),
                            _mm_srli_si128(prev, 12))
        )
    }

    #[target_feature(enable="sse3")]
    #[allow(non_snake_case)]
    unsafe fn integrate_delta(prev: DataType, delta: DataType) -> DataType {
        let offset = _mm_shuffle_epi32(prev, 0xff);
        let a__b__c__d_ = delta;
        let ______a__b_ = _mm_slli_si128(delta, 8);
        let a__b__ca_db = _mm_add_epi32(______a__b_, a__b__c__d_);
        let ___a__b__ca = _mm_slli_si128(a__b__ca_db, 4);
        let a_ab_abc_abcd: DataType = _mm_add_epi32(___a__b__ca, a__b__ca_db);
        _mm_add_epi32(offset, a_ab_abc_abcd)
    }

    declare_bitpacker!(target_feature(enable="sse3"));

    impl Available for UnsafeBitPackerImpl {
        fn available() -> bool {
            is_x86_feature_detected!("sse3")
        }
    }
}

mod scalar {

    use super::BLOCK_LEN;
    use Available;

    type DataType = [u32; 4];


    fn set1(el: i32) -> DataType {
        [el as u32; 4]
    }

    fn right_shift_32(el: DataType, shift: i32) -> DataType {
        [el[0] >> shift,
         el[1] >> shift,
         el[2] >> shift,
         el[3] >> shift]
    }

    fn left_shift_32(el: DataType, shift: i32) -> DataType {
        [el[0] << shift,
         el[1] << shift,
         el[2] << shift,
         el[3] << shift]
    }

    fn op_or(left: DataType, right: DataType) -> DataType {
        [left[0] | right[0],
         left[1] | right[1],
         left[2] | right[2],
         left[3] | right[3]]
    }

    fn op_and(left: DataType, right: DataType) -> DataType {
        [left[0] & right[0],
         left[1] & right[1],
         left[2] & right[2],
         left[3] & right[3]]
    }

    unsafe fn load_unaligned(addr: *const DataType) -> DataType {
        *addr
    }

    unsafe fn store_unaligned(addr: *mut DataType, data: DataType) {
        *addr = data;
    }

    fn or_collapse_to_u32(accumulator: DataType) -> u32 {
        (accumulator[0] | accumulator[1]) | (accumulator[2] | accumulator[3])
    }

    fn compute_delta(curr: DataType, prev: DataType) -> DataType {
        [
            curr[0].wrapping_sub(prev[3]),
            curr[1].wrapping_sub(curr[0]),
            curr[2].wrapping_sub(curr[1]),
            curr[3].wrapping_sub(curr[2]),
        ]
    }

    fn integrate_delta(offset: DataType, delta: DataType) -> DataType {
        let el0 = offset[3].wrapping_add(delta[0]);
        let el1 = el0.wrapping_add(delta[1]);
        let el2 = el1.wrapping_add(delta[2]);
        let el3 = el2.wrapping_add(delta[3]);
        [el0, el1, el2, el3]
    }


    // The `cfg(any(debug, not(debug)))` is here to put an attribute that has no effect.
    //
    // For other bitpacker, we enable specific CPU instruction set, but for the
    // scalar bitpacker none is required.
    declare_bitpacker!(cfg(any(debug, not(debug))) );

    impl Available for UnsafeBitPackerImpl {
        fn available() -> bool {
            true
        }
    }
}

enum InstructionSet {
    #[cfg(target_arch = "x86_64")]
    SSE3,
    Scalar
}


/// `BitPacker4x` packs integers in groups of 4. This gives an opportunity
/// to leverage `SSE3` instructions to encode and decode the stream.
///
/// One block must contain `128 integers`.
pub struct BitPacker4x(InstructionSet);

impl BitPacker for BitPacker4x {

    const BLOCK_LEN: usize = BLOCK_LEN;


    /// Returns the best available implementation for the current CPU.
    fn new() -> Self {
        #[cfg(target_arch = "x86_64")]
        {
            if sse3::UnsafeBitPackerImpl::available() {
                return BitPacker4x(InstructionSet::SSE3);
            }
        }
        BitPacker4x(InstructionSet::Scalar)
    }

    fn compress(&self, decompressed: &[u32], compressed: &mut [u8], num_bits: u8) -> usize {
        unsafe {
            match self.0 {
                #[cfg(target_arch = "x86_64")]
                InstructionSet::SSE3 =>
                    sse3::UnsafeBitPackerImpl::compress(decompressed, compressed, num_bits),
                InstructionSet::Scalar =>
                    scalar::UnsafeBitPackerImpl::compress(decompressed, compressed, num_bits)
            }
        }
    }

    fn compress_sorted(&self, initial: u32, decompressed: &[u32], compressed: &mut [u8], num_bits: u8) -> usize {
        unsafe {
            match self.0 {
                #[cfg(target_arch = "x86_64")]
                InstructionSet::SSE3 =>
                    sse3::UnsafeBitPackerImpl::compress_sorted(initial, decompressed, compressed, num_bits),
                InstructionSet::Scalar =>
                    scalar::UnsafeBitPackerImpl::compress_sorted(initial, decompressed, compressed, num_bits)
            }
        }
    }

    fn decompress(&self, compressed: &[u8], decompressed: &mut [u32], num_bits: u8) -> usize {
        unsafe {
            match self.0 {
                #[cfg(target_arch = "x86_64")]
                InstructionSet::SSE3 =>
                    sse3::UnsafeBitPackerImpl::decompress(compressed, decompressed, num_bits),
                InstructionSet::Scalar =>
                    scalar::UnsafeBitPackerImpl::decompress(compressed, decompressed, num_bits),
            }
        }
    }

    fn decompress_sorted(&self, initial: u32, compressed: &[u8], decompressed: &mut [u32], num_bits: u8) -> usize {
        unsafe {
            match self.0 {
                #[cfg(target_arch = "x86_64")]
                InstructionSet::SSE3 =>
                    sse3::UnsafeBitPackerImpl::decompress_sorted(initial, compressed, decompressed, num_bits),
                InstructionSet::Scalar =>
                    scalar::UnsafeBitPackerImpl::decompress_sorted(initial, compressed, decompressed, num_bits)
            }
        }
    }

    fn num_bits(&self, decompressed: &[u32]) -> u8 {
        unsafe {
            match self.0 {
                #[cfg(target_arch = "x86_64")]
                InstructionSet::SSE3 =>
                    sse3::UnsafeBitPackerImpl::num_bits(decompressed),
                InstructionSet::Scalar =>
                    scalar::UnsafeBitPackerImpl::num_bits(decompressed)
            }
        }
    }

    fn num_bits_sorted(&self, initial: u32, decompressed: &[u32]) -> u8 {
        unsafe {
            match self.0 {
                #[cfg(target_arch = "x86_64")]
                InstructionSet::SSE3 =>
                    sse3::UnsafeBitPackerImpl::num_bits_sorted(initial, decompressed),
                InstructionSet::Scalar =>
                    scalar::UnsafeBitPackerImpl::num_bits_sorted(initial, decompressed)
            }
        }
    }
}

#[cfg(target_arch = "x86_64")]
#[cfg(test)]
mod tests {
    use Available;
    use super::{scalar, sse3};
    use tests::test_util_compatible;
    use super::BLOCK_LEN;

    #[test]
    fn test_compatible() {
        if sse3::UnsafeBitPackerImpl::available() {
            test_util_compatible::<scalar::UnsafeBitPackerImpl, sse3::UnsafeBitPackerImpl>(BLOCK_LEN);
        }
    }
}