// Copyright Mozilla Foundation. See the COPYRIGHT

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

//

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

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

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

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

// except according to those terms.

// It's assumed that in due course Rust will have explicit SIMD but will not

// be good at run-time selection of SIMD vs. no-SIMD. In such a future,

// x86_64 will always use SSE2 and 32-bit x86 will use SSE2 when compiled with

// a Mozilla-shipped rustc. SIMD support and especially detection on ARM is a

// mess. Under the circumstances, it seems to make sense to optimize the ALU

// case for ARMv7 rather than x86. Annoyingly, I was unable to get useful

// numbers of the actual ARMv7 CPU I have access to, because (thermal?)

// throttling kept interfering. Since Raspberry Pi 3 (ARMv8 core but running

// ARMv7 code) produced reproducible performance numbers, that's the ARM

// computer that this code ended up being optimized for in the ALU case.

// Less popular CPU architectures simply get the approach that was chosen based

// on Raspberry Pi 3 measurements. The UTF-16 and UTF-8 ALU cases take

// different approaches based on benchmarking on Raspberry Pi 3.

#[cfg(all(

    feature = "simd-accel",

    any(

        target_feature = "sse2",

        all(target_endian = "little", target_arch = "aarch64"),

        all(target_endian = "little", target_feature = "neon")

    )

))]

use crate::simd_funcs::*;

cfg_if! {

    if #[cfg(feature = "simd-accel")] {

        #[allow(unused_imports)]

        use ::core::intrinsics::unlikely;

        #[allow(unused_imports)]

        use ::core::intrinsics::likely;

    } else {

        #[allow(dead_code)]

        #[inline(always)]

        fn unlikely(b: bool) -> bool {

            b

        }

        #[allow(dead_code)]

        #[inline(always)]

        fn likely(b: bool) -> bool {

            b

        }

    }

}

// Safety invariants for masks: data & mask = 0 for valid ASCII or basic latin utf-16

// `as` truncates, so works on 32-bit, too.

#[allow(dead_code)]

pub const ASCII_MASK: usize = 0x8080_8080_8080_8080u64 as usize;

// `as` truncates, so works on 32-bit, too.

#[allow(dead_code)]

pub const BASIC_LATIN_MASK: usize = 0xFF80_FF80_FF80_FF80u64 as usize;

#[allow(unused_macros)]

macro_rules! ascii_naive {

    ($name:ident, $src_unit:ty, $dst_unit:ty) => {

        /// Safety: src and dst must have len_unit elements and be aligned

        /// Safety-usable invariant: will return Some() when it fails

        /// to convert. The first value will be a u8 that is > 127.

        #[inline(always)]

        pub unsafe fn $name(

            src: *const $src_unit,

            dst: *mut $dst_unit,

            len: usize,

        ) -> Option<($src_unit, usize)> {

            // Yes, manually omitting the bound check here matters

            // a lot for perf.

            for i in 0..len {

                // Safety: len invariant used here

                let code_unit = *(src.add(i));

                // Safety: Upholds safety-usable invariant here

                if code_unit > 127 {

                    return Some((code_unit, i));

                }

                // Safety: len invariant used here

                *(dst.add(i)) = code_unit as $dst_unit;

            }

            return None;

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_alu {

    ($name:ident,

     // safety invariant: src/dst MUST be u8

     $src_unit:ty,

     $dst_unit:ty,

     // Safety invariant: stride_fn must consume and produce two usizes, and return the index of the first non-ascii when it fails

     $stride_fn:ident) => {

        /// Safety: src and dst must have len elements, src is valid for read, dst is valid for

        /// write

        /// Safety-usable invariant: will return Some() when it fails

        /// to convert. The first value will be a u8 that is > 127.

        #[cfg_attr(feature = "cargo-clippy", allow(never_loop, cast_ptr_alignment))]

        #[inline(always)]

        pub unsafe fn $name(

            src: *const $src_unit,

            dst: *mut $dst_unit,

            len: usize,

        ) -> Option<($src_unit, usize)> {

            let mut offset = 0usize;

            // This loop is only broken out of as a `goto` forward

            loop {

                // Safety: until_alignment becomes the number of bytes we need to munch until we are aligned to usize

                let mut until_alignment = {

                    // Check if the other unit aligns if we move the narrower unit

                    // to alignment.

                    //               if ::core::mem::size_of::<$src_unit>() == ::core::mem::size_of::<$dst_unit>() {

                    // ascii_to_ascii

                    let src_alignment = (src as usize) & ALU_ALIGNMENT_MASK;

                    let dst_alignment = (dst as usize) & ALU_ALIGNMENT_MASK;

                    if src_alignment != dst_alignment {

                        // Safety: bails early and ends up in the naïve branch where usize-alignment doesn't matter

                        break;

                    }

                    (ALU_ALIGNMENT - src_alignment) & ALU_ALIGNMENT_MASK

                    //               } else if ::core::mem::size_of::<$src_unit>() < ::core::mem::size_of::<$dst_unit>() {

                    // ascii_to_basic_latin

                    //                   let src_until_alignment = (ALIGNMENT - ((src as usize) & ALIGNMENT_MASK)) & ALIGNMENT_MASK;

                    //                   if (dst.add(src_until_alignment) as usize) & ALIGNMENT_MASK != 0 {

                    //                       break;

                    //                   }

                    //                   src_until_alignment

                    //               } else {

                    // basic_latin_to_ascii

                    //                   let dst_until_alignment = (ALIGNMENT - ((dst as usize) & ALIGNMENT_MASK)) & ALIGNMENT_MASK;

                    //                   if (src.add(dst_until_alignment) as usize) & ALIGNMENT_MASK != 0 {

                    //                       break;

                    //                   }

                    //                   dst_until_alignment

                    //               }

                };

                if until_alignment + ALU_STRIDE_SIZE <= len {

                    // Moving pointers to alignment seems to be a pessimization on

                    // x86_64 for operations that have UTF-16 as the internal

                    // Unicode representation. However, since it seems to be a win

                    // on ARM (tested ARMv7 code running on ARMv8 [rpi3]), except

                    // mixed results when encoding from UTF-16 and since x86 and

                    // x86_64 should be using SSE2 in due course, keeping the move

                    // to alignment here. It would be good to test on more ARM CPUs

                    // and on real MIPS and POWER hardware.

                    //

                    // Safety: This is the naïve code once again, for `until_alignment` bytes

                    while until_alignment != 0 {

                        let code_unit = *(src.add(offset));

                        if code_unit > 127 {

                            // Safety: Upholds safety-usable invariant here

                            return Some((code_unit, offset));

                        }

                        *(dst.add(offset)) = code_unit as $dst_unit;

                        // Safety: offset is the number of bytes copied so far

                        offset += 1;

                        until_alignment -= 1;

                    }

                    let len_minus_stride = len - ALU_STRIDE_SIZE;

                    loop {

                        // Safety: num_ascii is known to be a byte index of a non-ascii byte due to stride_fn's invariant

                        if let Some(num_ascii) = $stride_fn(

                            // Safety: These are known to be valid and aligned since we have at

                            // least ALU_STRIDE_SIZE data in these buffers, and offset is the

                            // number of elements copied so far, which according to the

                            // until_alignment calculation above will cause both src and dst to be

                            // aligned to usize after this add

                            src.add(offset) as *const usize,

                            dst.add(offset) as *mut usize,

                        ) {

                            offset += num_ascii;

                            // Safety: Upholds safety-usable invariant here by indexing into non-ascii byte

                            return Some((*(src.add(offset)), offset));

                        }

                        // Safety: offset continues to be the number of bytes copied so far, and

                        // maintains usize alignment for the next loop iteration

                        offset += ALU_STRIDE_SIZE;

                        // Safety: This is `offset > len - stride. This loop will continue as long as

                        // `offset <= len - stride`, which means there are `stride` bytes to still be read.

                        if offset > len_minus_stride {

                            break;

                        }

                    }

                }

                break;

            }

            // Safety: This is the naïve code, same as ascii_naive, and has no requirements

            // other than src/dst being valid for the the right lens

            while offset < len {

                // Safety: len invariant used here

                let code_unit = *(src.add(offset));

                if code_unit > 127 {

                    // Safety: Upholds safety-usable invariant here

                    return Some((code_unit, offset));

                }

                // Safety: len invariant used here

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

            None

        }

    };

}

#[allow(unused_macros)]

macro_rules! basic_latin_alu {

    ($name:ident,

    // safety invariant: use u8 for src/dest for ascii, and u16 for basic_latin

     $src_unit:ty,

     $dst_unit:ty,

    // safety invariant: stride function must munch ALU_STRIDE_SIZE*size(src_unit) bytes off of src and

    // write ALU_STRIDE_SIZE*size(dst_unit) bytes to dst

     $stride_fn:ident) => {

        /// Safety: src and dst must have len elements, src is valid for read, dst is valid for

        /// write

        /// Safety-usable invariant: will return Some() when it fails

        /// to convert. The first value will be a u8 that is > 127.

        #[cfg_attr(

            feature = "cargo-clippy",

            allow(never_loop, cast_ptr_alignment, cast_lossless)

        )]

        #[inline(always)]

        pub unsafe fn $name(

            src: *const $src_unit,

            dst: *mut $dst_unit,

            len: usize,

        ) -> Option<($src_unit, usize)> {

            let mut offset = 0usize;

            // This loop is only broken out of as a `goto` forward

            loop {

                // Safety: until_alignment becomes the number of bytes we need to munch from src/dest until we are aligned to usize

                // We ensure basic-latin has the same alignment as ascii, starting with ascii since it is smaller.

                let mut until_alignment = {

                    // Check if the other unit aligns if we move the narrower unit

                    // to alignment.

                    //               if ::core::mem::size_of::<$src_unit>() == ::core::mem::size_of::<$dst_unit>() {

                    // ascii_to_ascii

                    //                   let src_alignment = (src as usize) & ALIGNMENT_MASK;

                    //                   let dst_alignment = (dst as usize) & ALIGNMENT_MASK;

                    //                   if src_alignment != dst_alignment {

                    //                       break;

                    //                   }

                    //                   (ALIGNMENT - src_alignment) & ALIGNMENT_MASK

                    //               } else

                    if ::core::mem::size_of::<$src_unit>() < ::core::mem::size_of::<$dst_unit>() {

                        // ascii_to_basic_latin

                        let src_until_alignment = (ALU_ALIGNMENT

                            - ((src as usize) & ALU_ALIGNMENT_MASK))

                            & ALU_ALIGNMENT_MASK;

                        if (dst.wrapping_add(src_until_alignment) as usize) & ALU_ALIGNMENT_MASK

                            != 0

                        {

                            break;

                        }

                        src_until_alignment

                    } else {

                        // basic_latin_to_ascii

                        let dst_until_alignment = (ALU_ALIGNMENT

                            - ((dst as usize) & ALU_ALIGNMENT_MASK))

                            & ALU_ALIGNMENT_MASK;

                        if (src.wrapping_add(dst_until_alignment) as usize) & ALU_ALIGNMENT_MASK

                            != 0

                        {

                            break;

                        }

                        dst_until_alignment

                    }

                };

                if until_alignment + ALU_STRIDE_SIZE <= len {

                    // Moving pointers to alignment seems to be a pessimization on

                    // x86_64 for operations that have UTF-16 as the internal

                    // Unicode representation. However, since it seems to be a win

                    // on ARM (tested ARMv7 code running on ARMv8 [rpi3]), except

                    // mixed results when encoding from UTF-16 and since x86 and

                    // x86_64 should be using SSE2 in due course, keeping the move

                    // to alignment here. It would be good to test on more ARM CPUs

                    // and on real MIPS and POWER hardware.

                    //

                    // Safety: This is the naïve code once again, for `until_alignment` bytes

                    while until_alignment != 0 {

                        let code_unit = *(src.add(offset));

                        if code_unit > 127 {

                            // Safety: Upholds safety-usable invariant here

                            return Some((code_unit, offset));

                        }

                        *(dst.add(offset)) = code_unit as $dst_unit;

                        // Safety: offset is the number of bytes copied so far

                        offset += 1;

                        until_alignment -= 1;

                    }

                    let len_minus_stride = len - ALU_STRIDE_SIZE;

                    loop {

                        if !$stride_fn(

                            // Safety: These are known to be valid and aligned since we have at

                            // least ALU_STRIDE_SIZE data in these buffers, and offset is the

                            // number of elements copied so far, which according to the

                            // until_alignment calculation above will cause both src and dst to be

                            // aligned to usize after this add

                            src.add(offset) as *const usize,

                            dst.add(offset) as *mut usize,

                        ) {

                            break;

                        }

                        // Safety: offset continues to be the number of bytes copied so far, and

                        // maintains usize alignment for the next loop iteration

                        offset += ALU_STRIDE_SIZE;

                        // Safety: This is `offset > len - stride. This loop will continue as long as

                        // `offset <= len - stride`, which means there are `stride` bytes to still be read.

                        if offset > len_minus_stride {

                            break;

                        }

                    }

                }

                break;

            }

            // Safety: This is the naïve code once again, for leftover bytes

            while offset < len {

                // Safety: len invariant used here

                let code_unit = *(src.add(offset));

                if code_unit > 127 {

                    // Safety: Upholds safety-usable invariant here

                    return Some((code_unit, offset));

                }

                // Safety: len invariant used here

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

            None

        }

Unexecuted instantiation: encoding_rs::ascii::ascii_to_basic_latin

Unexecuted instantiation: encoding_rs::ascii::basic_latin_to_ascii

    };

}

#[allow(unused_macros)]

macro_rules! latin1_alu {

    // safety invariant: stride function must munch ALU_STRIDE_SIZE*size(src_unit) bytes off of src and

    // write ALU_STRIDE_SIZE*size(dst_unit) bytes to dst

    ($name:ident, $src_unit:ty, $dst_unit:ty, $stride_fn:ident) => {

        /// Safety: src and dst must have len elements, src is valid for read, dst is valid for

        /// write

        #[cfg_attr(

            feature = "cargo-clippy",

            allow(never_loop, cast_ptr_alignment, cast_lossless)

        )]

        #[inline(always)]

        pub unsafe fn $name(src: *const $src_unit, dst: *mut $dst_unit, len: usize) {

            let mut offset = 0usize;

            // This loop is only broken out of as a `goto` forward

            loop {

                // Safety: until_alignment becomes the number of bytes we need to munch from src/dest until we are aligned to usize

                // We ensure the UTF-16 side has the same alignment as the Latin-1 side, starting with Latin-1 since it is smaller.

                let mut until_alignment = {

                    if ::core::mem::size_of::<$src_unit>() < ::core::mem::size_of::<$dst_unit>() {

                        // unpack

                        let src_until_alignment = (ALU_ALIGNMENT

                            - ((src as usize) & ALU_ALIGNMENT_MASK))

                            & ALU_ALIGNMENT_MASK;

                        if (dst.wrapping_add(src_until_alignment) as usize) & ALU_ALIGNMENT_MASK

                            != 0

                        {

                            break;

                        }

                        src_until_alignment

                    } else {

                        // pack

                        let dst_until_alignment = (ALU_ALIGNMENT

                            - ((dst as usize) & ALU_ALIGNMENT_MASK))

                            & ALU_ALIGNMENT_MASK;

                        if (src.wrapping_add(dst_until_alignment) as usize) & ALU_ALIGNMENT_MASK

                            != 0

                        {

                            break;

                        }

                        dst_until_alignment

                    }

                };

                if until_alignment + ALU_STRIDE_SIZE <= len {

                    // Safety: This is the naïve code once again, for `until_alignment` bytes

                    while until_alignment != 0 {

                        let code_unit = *(src.add(offset));

                        *(dst.add(offset)) = code_unit as $dst_unit;

                        // Safety: offset is the number of bytes copied so far

                        offset += 1;

                        until_alignment -= 1;

                    }

                    let len_minus_stride = len - ALU_STRIDE_SIZE;

                    loop {

                        $stride_fn(

                            // Safety: These are known to be valid and aligned since we have at

                            // least ALU_STRIDE_SIZE data in these buffers, and offset is the

                            // number of elements copied so far, which according to the

                            // until_alignment calculation above will cause both src and dst to be

                            // aligned to usize after this add

                            src.add(offset) as *const usize,

                            dst.add(offset) as *mut usize,

                        );

                        // Safety: offset continues to be the number of bytes copied so far, and

                        // maintains usize alignment for the next loop iteration

                        offset += ALU_STRIDE_SIZE;

                        // Safety: This is `offset > len - stride. This loop will continue as long as

                        // `offset <= len - stride`, which means there are `stride` bytes to still be read.

                        if offset > len_minus_stride {

                            break;

                        }

                    }

                }

                break;

            }

            // Safety: This is the naïve code once again, for leftover bytes

            while offset < len {

                // Safety: len invariant used here

                let code_unit = *(src.add(offset));

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

        }

Unexecuted instantiation: encoding_rs::ascii::pack_latin1

Unexecuted instantiation: encoding_rs::ascii::unpack_latin1

    };

}

#[allow(unused_macros)]

macro_rules! ascii_simd_check_align {

    (

        $name:ident,

        $src_unit:ty,

        $dst_unit:ty,

        // Safety: This function must require aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_both_aligned:ident,

        // Safety: This function must require aligned/unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_src_aligned:ident,

        // Safety: This function must require unaligned/aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_dst_aligned:ident,

        // Safety: This function must require unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_neither_aligned:ident

    ) => {

        /// Safety: src/dst must be valid for reads/writes of `len` elements of their units.

        ///

        /// Safety-usable invariant: will return Some() when it encounters non-ASCII, with the first element in the Some being

        /// guaranteed to be non-ASCII (> 127), and the second being the offset where it is found

        #[inline(always)]

        pub unsafe fn $name(

            src: *const $src_unit,

            dst: *mut $dst_unit,

            len: usize,

        ) -> Option<($src_unit, usize)> {

            let mut offset = 0usize;

            // Safety: if this check succeeds we're valid for reading/writing at least `SIMD_STRIDE_SIZE` elements.

            if SIMD_STRIDE_SIZE <= len {

                let len_minus_stride = len - SIMD_STRIDE_SIZE;

                // XXX Should we first process one stride unconditionally as unaligned to

                // avoid the cost of the branchiness below if the first stride fails anyway?

                // XXX Should we just use unaligned SSE2 access unconditionally? It seems that

                // on Haswell, it would make sense to just use unaligned and not bother

                // checking. Need to benchmark older architectures before deciding.

                let dst_masked = (dst as usize) & SIMD_ALIGNMENT_MASK;

                // Safety: checking whether src is aligned

                if ((src as usize) & SIMD_ALIGNMENT_MASK) == 0 {

                    // Safety: Checking whether dst is aligned

                    if dst_masked == 0 {

                        loop {

                            // Safety: We're valid to read/write SIMD_STRIDE_SIZE elements and have the appropriate alignments

                            if !$stride_both_aligned(src.add(offset), dst.add(offset)) {

                                break;

                            }

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE` which means we always have at least `SIMD_STRIDE_SIZE` elements to munch next time.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    } else {

                        loop {

                            // Safety: We're valid to read/write SIMD_STRIDE_SIZE elements and have the appropriate alignments

                            if !$stride_src_aligned(src.add(offset), dst.add(offset)) {

                                break;

                            }

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE` which means we always have at least `SIMD_STRIDE_SIZE` elements to munch next time.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    }

                } else {

                    if dst_masked == 0 {

                        loop {

                            // Safety: We're valid to read/write SIMD_STRIDE_SIZE elements and have the appropriate alignments

                            if !$stride_dst_aligned(src.add(offset), dst.add(offset)) {

                                break;

                            }

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE` which means we always have at least `SIMD_STRIDE_SIZE` elements to munch next time.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    } else {

                        loop {

                            // Safety: We're valid to read/write SIMD_STRIDE_SIZE elements and have the appropriate alignments

                            if !$stride_neither_aligned(src.add(offset), dst.add(offset)) {

                                break;

                            }

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE` which means we always have at least `SIMD_STRIDE_SIZE` elements to munch next time.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    }

                }

            }

            while offset < len {

                // Safety: uses len invariant here and below

                let code_unit = *(src.add(offset));

                if code_unit > 127 {

                    // Safety: upholds safety-usable invariant

                    return Some((code_unit, offset));

                }

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

            None

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_simd_check_align_unrolled {

    (

        $name:ident,

        $src_unit:ty,

        $dst_unit:ty,

        // Safety: This function must require aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_both_aligned:ident,

        // Safety: This function must require aligned/unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_src_aligned:ident,

        // Safety: This function must require unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_neither_aligned:ident,

        // Safety: This function must require aligned src/dest that are valid for reading/writing 2*SIMD_STRIDE_SIZE src_unit/dst_unit

        $double_stride_both_aligned:ident,

        // Safety: This function must require aligned/unaligned src/dest that are valid for reading/writing 2*SIMD_STRIDE_SIZE src_unit/dst_unit

        $double_stride_src_aligned:ident

    ) => {

        /// Safety: src/dst must be valid for reads/writes of `len` elements of their units.

        ///

        /// Safety-usable invariant: will return Some() when it encounters non-ASCII, with the first element in the Some being

        /// guaranteed to be non-ASCII (> 127), and the second being the offset where it is found        #[inline(always)]

        pub unsafe fn $name(

            src: *const $src_unit,

            dst: *mut $dst_unit,

            len: usize,

        ) -> Option<($src_unit, usize)> {

            let unit_size = ::core::mem::size_of::<$src_unit>();

            let mut offset = 0usize;

            // This loop is only broken out of as a goto forward without

            // actually looping

            'outer: loop {

                // Safety: if this check succeeds we're valid for reading/writing at least `SIMD_STRIDE_SIZE` elements.

                if SIMD_STRIDE_SIZE <= len {

                    // First, process one unaligned

                    // Safety: this is safe to call since we're valid for this read/write

                    if !$stride_neither_aligned(src, dst) {

                        break 'outer;

                    }

                    offset = SIMD_STRIDE_SIZE;

                    // We have now seen 16 ASCII bytes. Let's guess that

                    // there will be enough more to justify more expense

                    // in the case of non-ASCII.

                    // Use aligned reads for the sake of old microachitectures.

                    //

                    // Safety: this correctly calculates the number of src_units that need to be read before the remaining list is aligned.

                    // This is less that SIMD_ALIGNMENT, which is also SIMD_STRIDE_SIZE (as documented)

                    let until_alignment = ((SIMD_ALIGNMENT

                        - ((src.add(offset) as usize) & SIMD_ALIGNMENT_MASK))

                        & SIMD_ALIGNMENT_MASK)

                        / unit_size;

                    // Safety: This addition won't overflow, because even in the 32-bit PAE case the

                    // address space holds enough code that the slice length can't be that

                    // close to address space size.

                    // offset now equals SIMD_STRIDE_SIZE, hence times 3 below.

                    //

                    // Safety: if this check succeeds we're valid for reading/writing at least `2 * SIMD_STRIDE_SIZE` elements plus `until_alignment`.

                    // The extra SIMD_STRIDE_SIZE in the condition is because `offset` is already `SIMD_STRIDE_SIZE`.

                    if until_alignment + (SIMD_STRIDE_SIZE * 3) <= len {

                        if until_alignment != 0 {

                            // Safety: this is safe to call since we're valid for this read/write (and more), and don't care about alignment

                            // This will copy over bytes that get decoded twice since it's not incrementing `offset` by SIMD_STRIDE_SIZE. This is fine.

                            if !$stride_neither_aligned(src.add(offset), dst.add(offset)) {

                                break;

                            }

                            offset += until_alignment;

                        }

                        // Safety: At this point we're valid for reading/writing 2*SIMD_STRIDE_SIZE elements

                        // Safety: Now `offset` is aligned for `src`

                        let len_minus_stride_times_two = len - (SIMD_STRIDE_SIZE * 2);

                        // Safety: This is whether dst is aligned

                        let dst_masked = (dst.add(offset) as usize) & SIMD_ALIGNMENT_MASK;

                        if dst_masked == 0 {

                            loop {

                                // Safety: both are aligned, we can call the aligned function. We're valid for reading/writing double stride from the initial condition

                                // and the loop break condition below

                                if let Some(advance) =

                                    $double_stride_both_aligned(src.add(offset), dst.add(offset))

                                {

                                    offset += advance;

                                    let code_unit = *(src.add(offset));

                                    // Safety: uses safety-usable invariant on ascii_to_ascii_simd_double_stride to return

                                    // guaranteed non-ascii

                                    return Some((code_unit, offset));

                                }

                                offset += SIMD_STRIDE_SIZE * 2;

                                // Safety: This is `offset > len - 2 * SIMD_STRIDE_SIZE` which means we always have at least `2 * SIMD_STRIDE_SIZE` elements to munch next time.

                                if offset > len_minus_stride_times_two {

                                    break;

                                }

                            }

                            // Safety: We're valid for reading/writing one more, and can still assume alignment

                            if offset + SIMD_STRIDE_SIZE <= len {

                                if !$stride_both_aligned(src.add(offset), dst.add(offset)) {

                                    break 'outer;

                                }

                                offset += SIMD_STRIDE_SIZE;

                            }

                        } else {

                            loop {

                                // Safety: only src is aligned here. We're valid for reading/writing double stride from the initial condition

                                // and the loop break condition below

                                if let Some(advance) =

                                    $double_stride_src_aligned(src.add(offset), dst.add(offset))

                                {

                                    offset += advance;

                                    let code_unit = *(src.add(offset));

                                    // Safety: uses safety-usable invariant on ascii_to_ascii_simd_double_stride to return

                                    // guaranteed non-ascii

                                    return Some((code_unit, offset));

                                }

                                offset += SIMD_STRIDE_SIZE * 2;

                                // Safety: This is `offset > len - 2 * SIMD_STRIDE_SIZE` which means we always have at least `2 * SIMD_STRIDE_SIZE` elements to munch next time.

                                if offset > len_minus_stride_times_two {

                                    break;

                                }

                            }

                            // Safety: We're valid for reading/writing one more, and can still assume alignment

                            if offset + SIMD_STRIDE_SIZE <= len {

                                if !$stride_src_aligned(src.add(offset), dst.add(offset)) {

                                    break 'outer;

                                }

                                offset += SIMD_STRIDE_SIZE;

                            }

                        }

                    } else {

                        // At most two iterations, so unroll

                        if offset + SIMD_STRIDE_SIZE <= len {

                            // Safety: The check above ensures we're allowed to read/write this, and we don't use alignment

                            if !$stride_neither_aligned(src.add(offset), dst.add(offset)) {

                                break;

                            }

                            offset += SIMD_STRIDE_SIZE;

                            if offset + SIMD_STRIDE_SIZE <= len {

                                // Safety: The check above ensures we're allowed to read/write this, and we don't use alignment

                                if !$stride_neither_aligned(src.add(offset), dst.add(offset)) {

                                    break;

                                }

                                offset += SIMD_STRIDE_SIZE;

                            }

                        }

                    }

                }

                break 'outer;

            }

            while offset < len {

                // Safety: relies straightforwardly on the `len` invariant

                let code_unit = *(src.add(offset));

                if code_unit > 127 {

                    // Safety-usable invariant upheld here

                    return Some((code_unit, offset));

                }

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

            None

        }

    };

}

#[allow(unused_macros)]

macro_rules! latin1_simd_check_align {

    (

        $name:ident,

        $src_unit:ty,

        $dst_unit:ty,

        // Safety: This function must require aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_both_aligned:ident,

        // Safety: This function must require aligned/unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_src_aligned:ident,

        // Safety: This function must require unaligned/aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_dst_aligned:ident,

        // Safety: This function must require unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_neither_aligned:ident

    ) => {

        /// Safety: src/dst must be valid for reads/writes of `len` elements of their units.

        #[inline(always)]

        pub unsafe fn $name(src: *const $src_unit, dst: *mut $dst_unit, len: usize) {

            let mut offset = 0usize;

            // Safety: if this check succeeds we're valid for reading/writing at least `SIMD_STRIDE_SIZE` elements.

            if SIMD_STRIDE_SIZE <= len {

                let len_minus_stride = len - SIMD_STRIDE_SIZE;

                // Whether dst is aligned

                let dst_masked = (dst as usize) & SIMD_ALIGNMENT_MASK;

                // Whether src is aligned

                if ((src as usize) & SIMD_ALIGNMENT_MASK) == 0 {

                    if dst_masked == 0 {

                        loop {

                            // Safety: Both were aligned, we can use the aligned function

                            $stride_both_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE`, which means in the next iteration we're valid for

                            // reading/writing at least SIMD_STRIDE_SIZE elements.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    } else {

                        loop {

                            // Safety: src was aligned, dst was not

                            $stride_src_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE`, which means in the next iteration we're valid for

                            // reading/writing at least SIMD_STRIDE_SIZE elements.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    }

                } else {

                    if dst_masked == 0 {

                        loop {

                            // Safety: src was aligned, dst was not

                            $stride_dst_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE`, which means in the next iteration we're valid for

                            // reading/writing at least SIMD_STRIDE_SIZE elements.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    } else {

                        loop {

                            // Safety: Neither were aligned

                            $stride_neither_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - SIMD_STRIDE_SIZE`, which means in the next iteration we're valid for

                            // reading/writing at least SIMD_STRIDE_SIZE elements.

                            if offset > len_minus_stride {

                                break;

                            }

                        }

                    }

                }

            }

            while offset < len {

                // Safety: relies straightforwardly on the `len` invariant

                let code_unit = *(src.add(offset));

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

        }

    };

}

#[allow(unused_macros)]

macro_rules! latin1_simd_check_align_unrolled {

    (

        $name:ident,

        $src_unit:ty,

        $dst_unit:ty,

        // Safety: This function must require aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_both_aligned:ident,

        // Safety: This function must require aligned/unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_src_aligned:ident,

        // Safety: This function must require unaligned/aligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_dst_aligned:ident,

        // Safety: This function must require unaligned src/dest that are valid for reading/writing SIMD_STRIDE_SIZE src_unit/dst_unit

        $stride_neither_aligned:ident

    ) => {

        /// Safety: src/dst must be valid for reads/writes of `len` elements of their units.

        #[inline(always)]

        pub unsafe fn $name(src: *const $src_unit, dst: *mut $dst_unit, len: usize) {

            let unit_size = ::core::mem::size_of::<$src_unit>();

            let mut offset = 0usize;

            // Safety: if this check succeeds we're valid for reading/writing at least `SIMD_STRIDE_SIZE` elements.

            if SIMD_STRIDE_SIZE <= len {

                // Safety: this correctly calculates the number of src_units that need to be read before the remaining list is aligned.

                // This is by definition less than SIMD_STRIDE_SIZE.

                let mut until_alignment = ((SIMD_STRIDE_SIZE

                    - ((src as usize) & SIMD_ALIGNMENT_MASK))

                    & SIMD_ALIGNMENT_MASK)

                    / unit_size;

                while until_alignment != 0 {

                    // Safety: This is a straightforward copy, since until_alignment is < SIMD_STRIDE_SIZE < len, this is in-bounds

                    *(dst.add(offset)) = *(src.add(offset)) as $dst_unit;

                    offset += 1;

                    until_alignment -= 1;

                }

                // Safety: here offset will be `until_alignment`, i.e. enough to align `src`.

                let len_minus_stride = len - SIMD_STRIDE_SIZE;

                // Safety: if this check succeeds we're valid for reading/writing at least `2 * SIMD_STRIDE_SIZE` elements.

                if offset + SIMD_STRIDE_SIZE * 2 <= len {

                    let len_minus_stride_times_two = len_minus_stride - SIMD_STRIDE_SIZE;

                    // Safety: at this point src is known to be aligned at offset, dst is not.

                    if (dst.add(offset) as usize) & SIMD_ALIGNMENT_MASK == 0 {

                        loop {

                            // Safety: We checked alignment of dst above, we can use the alignment functions. We're allowed to read/write 2*SIMD_STRIDE_SIZE elements, which we do.

                            $stride_both_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            $stride_both_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - 2 * SIMD_STRIDE_SIZE` which means we always have at least `2 * SIMD_STRIDE_SIZE` elements to munch next time.

                            if offset > len_minus_stride_times_two {

                                break;

                            }

                        }

                    } else {

                        loop {

                            // Safety: we ensured alignment of src already.

                            $stride_src_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            $stride_src_aligned(src.add(offset), dst.add(offset));

                            offset += SIMD_STRIDE_SIZE;

                            // Safety: This is `offset > len - 2 * SIMD_STRIDE_SIZE` which means we always have at least `2 * SIMD_STRIDE_SIZE` elements to munch next time.

                            if offset > len_minus_stride_times_two {

                                break;

                            }

                        }

                    }

                }

                // Safety: This is `offset > len - SIMD_STRIDE_SIZE` which means we are valid to munch SIMD_STRIDE_SIZE more elements, which we do

                if offset < len_minus_stride {

                    $stride_src_aligned(src.add(offset), dst.add(offset));

                    offset += SIMD_STRIDE_SIZE;

                }

            }

            while offset < len {

                // Safety: uses len invariant here and below

                let code_unit = *(src.add(offset));

                // On x86_64, this loop autovectorizes but in the pack

                // case there are instructions whose purpose is to make sure

                // each u16 in the vector is truncated before packing. However,

                // since we don't care about saturating behavior of SSE2 packing

                // when the input isn't Latin1, those instructions are useless.

                // Unfortunately, using the `assume` intrinsic to lie to the

                // optimizer doesn't make LLVM omit the trunctation that we

                // don't need. Possibly this loop could be manually optimized

                // to do the sort of thing that LLVM does but without the

                // ANDing the read vectors of u16 with a constant that discards

                // the high half of each u16. As far as I can tell, the

                // optimization assumes that doing a SIMD read past the end of

                // the array is OK.

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_simd_unalign {

    // Safety: stride_neither_aligned must be a function that requires src/dest be valid for unaligned reads/writes for SIMD_STRIDE_SIZE elements of type src_unit/dest_unit

    ($name:ident, $src_unit:ty, $dst_unit:ty, $stride_neither_aligned:ident) => {

        /// Safety: src and dst must be valid for reads/writes of len elements of type src_unit/dst_unit

        ///

        /// Safety-usable invariant: will return Some() when it encounters non-ASCII, with the first element in the Some being

        /// guaranteed to be non-ASCII (> 127), and the second being the offset where it is found

        #[inline(always)]

        pub unsafe fn $name(

            src: *const $src_unit,

            dst: *mut $dst_unit,

            len: usize,

        ) -> Option<($src_unit, usize)> {

            let mut offset = 0usize;

            // Safety: if this check succeeds we're valid for reading/writing at least `stride` elements.

            if SIMD_STRIDE_SIZE <= len {

                let len_minus_stride = len - SIMD_STRIDE_SIZE;

                loop {

                    // Safety: We know we're valid for `stride` reads/writes, so we can call this function. We don't need alignment.

                    if !$stride_neither_aligned(src.add(offset), dst.add(offset)) {

                        break;

                    }

                    offset += SIMD_STRIDE_SIZE;

                    // This is `offset > len - stride` which means we always have at least `stride` elements to munch next time.

                    if offset > len_minus_stride {

                        break;

                    }

                }

            }

            while offset < len {

                // Safety: Uses len invariant here and below

                let code_unit = *(src.add(offset));

                if code_unit > 127 {

                    // Safety-usable invariant upheld here

                    return Some((code_unit, offset));

                }

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

            None

        }

    };

}

#[allow(unused_macros)]

macro_rules! latin1_simd_unalign {

    // Safety: stride_neither_aligned must be a function that requires src/dest be valid for unaligned reads/writes for SIMD_STRIDE_SIZE elements of type src_unit/dest_unit

    ($name:ident, $src_unit:ty, $dst_unit:ty, $stride_neither_aligned:ident) => {

        /// Safety: src and dst must be valid for unaligned reads/writes of len elements of type src_unit/dst_unit

        #[inline(always)]

        pub unsafe fn $name(src: *const $src_unit, dst: *mut $dst_unit, len: usize) {

            let mut offset = 0usize;

            // Safety: if this check succeeds we're valid for reading/writing at least `stride` elements.

            if SIMD_STRIDE_SIZE <= len {

                let len_minus_stride = len - SIMD_STRIDE_SIZE;

                loop {

                    // Safety: We know we're valid for `stride` reads/writes, so we can call this function. We don't need alignment.

                    $stride_neither_aligned(src.add(offset), dst.add(offset));

                    offset += SIMD_STRIDE_SIZE;

                    // This is `offset > len - stride` which means we always have at least `stride` elements to munch next time.

                    if offset > len_minus_stride {

                        break;

                    }

                }

            }

            while offset < len {

                // Safety: Uses len invariant here

                let code_unit = *(src.add(offset));

                *(dst.add(offset)) = code_unit as $dst_unit;

                offset += 1;

            }

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_to_ascii_simd_stride {

    // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions)

    ($name:ident, $load:ident, $store:ident) => {

        /// Safety: src and dst must be valid for 16 bytes of read/write according to

        /// the $load/$store fn, which may allow for unaligned reads/writes or require

        /// alignment to either 16x8 or u8x16.

        #[inline(always)]

        pub unsafe fn $name(src: *const u8, dst: *mut u8) -> bool {

            let simd = $load(src);

            if !simd_is_ascii(simd) {

                return false;

            }

            $store(dst, simd);

            true

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_to_ascii_simd_double_stride {

    // Safety: store must be valid for 32 bytes of write, which may be unaligned (candidates: `store(8|16)_(aligned|unaligned)`)

    ($name:ident, $store:ident) => {

        /// Safety: src must be valid for 32 bytes of aligned u8x16 read

        /// dst must be valid for 32 bytes of unaligned write according to

        /// the $store fn, which may allow for unaligned writes or require

        /// alignment to either 16x8 or u8x16.

        ///

        /// Safety-usable invariant: Returns Some(index) if the element at `index` is invalid ASCII

        #[inline(always)]

        pub unsafe fn $name(src: *const u8, dst: *mut u8) -> Option<usize> {

            let first = load16_aligned(src);

            let second = load16_aligned(src.add(SIMD_STRIDE_SIZE));

            $store(dst, first);

            if unlikely(!simd_is_ascii(first | second)) {

                // Safety: mask_ascii produces a mask of all the high bits.

                let mask_first = mask_ascii(first);

                if mask_first != 0 {

                    // Safety: on little endian systems this will be the number of ascii bytes

                    // before the first non-ascii, i.e. valid for indexing src

                    // TODO SAFETY: What about big-endian systems?

                    return Some(mask_first.trailing_zeros() as usize);

                }

                $store(dst.add(SIMD_STRIDE_SIZE), second);

                let mask_second = mask_ascii(second);

                // Safety: on little endian systems this will be the number of ascii bytes

                // before the first non-ascii, i.e. valid for indexing src

                return Some(SIMD_STRIDE_SIZE + mask_second.trailing_zeros() as usize);

            }

            $store(dst.add(SIMD_STRIDE_SIZE), second);

            None

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_to_basic_latin_simd_stride {

    // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions)

    ($name:ident, $load:ident, $store:ident) => {

        /// Safety: src and dst must be valid for 16/32 bytes of read/write according to

        /// the $load/$store fn, which may allow for unaligned reads/writes or require

        /// alignment to either 16x8 or u8x16.

        #[inline(always)]

        pub unsafe fn $name(src: *const u8, dst: *mut u16) -> bool {

            let simd = $load(src);

            if !simd_is_ascii(simd) {

                return false;

            }

            let (first, second) = simd_unpack(simd);

            $store(dst, first);

            $store(dst.add(8), second);

            true

        }

    };

}

#[allow(unused_macros)]

macro_rules! ascii_to_basic_latin_simd_double_stride {

    // Safety: store must be valid for 16 bytes of write, which may be unaligned

    ($name:ident, $store:ident) => {

        /// Safety: src must be valid for 2*SIMD_STRIDE_SIZE bytes of aligned reads,

        /// aligned to either 16x8 or u8x16.

        /// dst must be valid for 2*SIMD_STRIDE_SIZE bytes of aligned or unaligned reads

        #[inline(always)]

        pub unsafe fn $name(src: *const u8, dst: *mut u16) -> Option<usize> {

            let first = load16_aligned(src);

            let second = load16_aligned(src.add(SIMD_STRIDE_SIZE));

            let (a, b) = simd_unpack(first);

            $store(dst, a);

            // Safety: divide by 2 since it's a u16 pointer

            $store(dst.add(SIMD_STRIDE_SIZE / 2), b);

            if unlikely(!simd_is_ascii(first | second)) {

                let mask_first = mask_ascii(first);

                if mask_first != 0 {

                    return Some(mask_first.trailing_zeros() as usize);

                }

                let (c, d) = simd_unpack(second);

                $store(dst.add(SIMD_STRIDE_SIZE), c);

                $store(dst.add(SIMD_STRIDE_SIZE + (SIMD_STRIDE_SIZE / 2)), d);

                let mask_second = mask_ascii(second);

                return Some(SIMD_STRIDE_SIZE + mask_second.trailing_zeros() as usize);

            }

            let (c, d) = simd_unpack(second);

            $store(dst.add(SIMD_STRIDE_SIZE), c);

            $store(dst.add(SIMD_STRIDE_SIZE + (SIMD_STRIDE_SIZE / 2)), d);

            None

        }

    };

}

#[allow(unused_macros)]

macro_rules! unpack_simd_stride {

    // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions)

    ($name:ident, $load:ident, $store:ident) => {

        /// Safety: src and dst must be valid for 16 bytes of read/write according to

        /// the $load/$store fn, which may allow for unaligned reads/writes or require

        /// alignment to either 16x8 or u8x16.

        #[inline(always)]

        pub unsafe fn $name(src: *const u8, dst: *mut u16) {

            let simd = $load(src);

            let (first, second) = simd_unpack(simd);

            $store(dst, first);

            $store(dst.add(8), second);

        }

    };

}

#[allow(unused_macros)]

macro_rules! basic_latin_to_ascii_simd_stride {

    // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions)