diff options
Diffstat (limited to 'third_party/rust/encoding_rs/src/ascii.rs')
| -rw-r--r-- | third_party/rust/encoding_rs/src/ascii.rs | 388 |
1 files changed, 382 insertions, 6 deletions
diff --git a/third_party/rust/encoding_rs/src/ascii.rs b/third_party/rust/encoding_rs/src/ascii.rs index 90644de7a4..80233f285e 100644 --- a/third_party/rust/encoding_rs/src/ascii.rs +++ b/third_party/rust/encoding_rs/src/ascii.rs @@ -51,6 +51,8 @@ cfg_if! { } } +// 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; @@ -62,6 +64,9 @@ 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, @@ -71,10 +76,13 @@ macro_rules! ascii_naive { // 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 $dst_unit; } return None; @@ -85,9 +93,15 @@ macro_rules! ascii_naive { #[allow(unused_macros)] macro_rules! ascii_alu { ($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( @@ -98,6 +112,7 @@ macro_rules! ascii_alu { 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. @@ -106,6 +121,7 @@ macro_rules! ascii_alu { 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 @@ -134,25 +150,40 @@ macro_rules! ascii_alu { // 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; } @@ -160,11 +191,17 @@ macro_rules! ascii_alu { } 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 $dst_unit; offset += 1; } @@ -176,9 +213,16 @@ macro_rules! ascii_alu { #[allow(unused_macros)] macro_rules! basic_latin_alu { ($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) @@ -192,6 +236,8 @@ macro_rules! basic_latin_alu { 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. @@ -237,24 +283,37 @@ macro_rules! basic_latin_alu { // 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; } @@ -262,11 +321,15 @@ macro_rules! basic_latin_alu { } 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 $dst_unit; offset += 1; } @@ -277,7 +340,11 @@ macro_rules! basic_latin_alu { #[allow(unused_macros)] macro_rules! latin1_alu { + // safety invariant: stride function must munch ALU_STRIDE_SIZE*size(src_unit) bytes off of src and + // write ALU_STRIDE_SIZE*size(dst_unit) bytes to dst ($name:ident, $src_unit:ty, $dst_unit:ty, $stride_fn:ident) => { + /// Safety: src and dst must have len elements, src is valid for read, dst is valid for + /// write #[cfg_attr( feature = "cargo-clippy", allow(never_loop, cast_ptr_alignment, cast_lossless) @@ -287,6 +354,8 @@ macro_rules! latin1_alu { let mut offset = 0usize; // This loop is only broken out of as a `goto` forward loop { + // Safety: until_alignment becomes the number of bytes we need to munch from src/dest until we are aligned to usize + // We ensure the UTF-16 side has the same alignment as the Latin-1 side, starting with Latin-1 since it is smaller. let mut until_alignment = { if ::core::mem::size_of::<$src_unit>() < ::core::mem::size_of::<$dst_unit>() { // unpack @@ -313,19 +382,30 @@ macro_rules! latin1_alu { } }; 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; } @@ -333,7 +413,9 @@ macro_rules! latin1_alu { } 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; @@ -348,11 +430,19 @@ 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 $src_unit, @@ -360,6 +450,7 @@ macro_rules! ascii_simd_check_align { len: usize, ) -> Option<($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 @@ -368,23 +459,29 @@ macro_rules! ascii_simd_check_align { // 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; } @@ -393,20 +490,24 @@ macro_rules! ascii_simd_check_align { } 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; } @@ -415,8 +516,10 @@ macro_rules! ascii_simd_check_align { } } 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; @@ -433,13 +536,21 @@ 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 ) => { - #[inline(always)] + /// 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 $dst_unit, @@ -450,8 +561,10 @@ macro_rules! ascii_simd_check_align_unrolled { // This loop is only broken out of as a goto forward without // actually looping 'outer: loop { + // Safety: if this check succeeds we're valid for reading/writing at least `SIMD_STRIDE_SIZE` elements. if SIMD_STRIDE_SIZE <= len { // First, process one unaligned + // Safety: this is safe to call since we're valid for this read/write if !$stride_neither_aligned(src, dst) { break 'outer; } @@ -461,37 +574,54 @@ macro_rules! ascii_simd_check_align_unrolled { // 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; - // This addition won't overflow, because even in the 32-bit PAE case the + // 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; @@ -500,18 +630,25 @@ macro_rules! ascii_simd_check_align_unrolled { } } 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; @@ -522,11 +659,13 @@ macro_rules! ascii_simd_check_align_unrolled { } 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; } @@ -538,8 +677,10 @@ macro_rules! ascii_simd_check_align_unrolled { 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; @@ -556,30 +697,45 @@ 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; } @@ -588,16 +744,22 @@ macro_rules! latin1_simd_check_align { } 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; } @@ -606,6 +768,7 @@ macro_rules! latin1_simd_check_align { } } 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; @@ -620,56 +783,74 @@ 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 { $stride_src_aligned(src.add(offset), dst.add(offset)); offset += SIMD_STRIDE_SIZE; } } while offset < len { + // Safety: uses len invariant here and below let code_unit = *(src.add(offset)); // On x86_64, this loop autovectorizes but in the pack // case there are instructions whose purpose is to make sure @@ -693,7 +874,12 @@ macro_rules! latin1_simd_check_align_unrolled { #[allow(unused_macros)] macro_rules! ascii_simd_unalign { + // Safety: stride_neither_aligned must be a function that requires src/dest be valid for unaligned reads/writes for SIMD_STRIDE_SIZE elements of type src_unit/dest_unit ($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 $src_unit, @@ -701,21 +887,26 @@ macro_rules! ascii_simd_unalign { len: usize, ) -> Option<($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 $dst_unit; @@ -728,21 +919,27 @@ macro_rules! ascii_simd_unalign { #[allow(unused_macros)] macro_rules! latin1_simd_unalign { + // Safety: stride_neither_aligned must be a function that requires src/dest be valid for unaligned reads/writes for SIMD_STRIDE_SIZE elements of type src_unit/dest_unit ($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 $dst_unit; offset += 1; @@ -753,7 +950,11 @@ macro_rules! latin1_simd_unalign { #[allow(unused_macros)] macro_rules! ascii_to_ascii_simd_stride { + // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions) ($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 = $load(src); @@ -768,19 +969,32 @@ macro_rules! ascii_to_ascii_simd_stride { #[allow(unused_macros)] macro_rules! ascii_to_ascii_simd_double_stride { + // Safety: store must be valid for 32 bytes of write, which may be unaligned (candidates: `store(8|16)_(aligned|unaligned)`) ($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); } $store(dst.add(SIMD_STRIDE_SIZE), second); @@ -791,7 +1005,11 @@ macro_rules! ascii_to_ascii_simd_double_stride { #[allow(unused_macros)] macro_rules! ascii_to_basic_latin_simd_stride { + // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions) ($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 = $load(src); @@ -808,13 +1026,18 @@ macro_rules! ascii_to_basic_latin_simd_stride { #[allow(unused_macros)] macro_rules! ascii_to_basic_latin_simd_double_stride { + // Safety: store must be valid for 16 bytes of write, which may be unaligned ($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 $store(dst.add(SIMD_STRIDE_SIZE / 2), b); if unlikely(!simd_is_ascii(first | second)) { let mask_first = mask_ascii(first); @@ -837,7 +1060,11 @@ macro_rules! ascii_to_basic_latin_simd_double_stride { #[allow(unused_macros)] macro_rules! unpack_simd_stride { + // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions) ($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 = $load(src); @@ -850,7 +1077,11 @@ macro_rules! unpack_simd_stride { #[allow(unused_macros)] macro_rules! basic_latin_to_ascii_simd_stride { + // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions) ($name:ident, $load:ident, $store:ident) => { + /// Safety: src and dst must be valid for 32/16 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 u16, dst: *mut u8) -> bool { let first = $load(src); @@ -867,7 +1098,11 @@ macro_rules! basic_latin_to_ascii_simd_stride { #[allow(unused_macros)] macro_rules! pack_simd_stride { + // Safety: load/store must be valid for 16 bytes of read/write, which may be unaligned. (candidates: `(load|store)(16|8)_(unaligned|aligned)` functions) ($name:ident, $load:ident, $store:ident) => { + /// Safety: src and dst must be valid for 32/16 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 u16, dst: *mut u8) { let first = $load(src); @@ -893,6 +1128,8 @@ cfg_if! { pub const ALU_ALIGNMENT_MASK: usize = 7; + // Safety for stride macros: We stick to the load8_aligned/etc family of functions. We consistently produce + // neither_unaligned variants using only unaligned inputs. ascii_to_ascii_simd_stride!(ascii_to_ascii_stride_neither_aligned, load16_unaligned, store16_unaligned); ascii_to_basic_latin_simd_stride!(ascii_to_basic_latin_stride_neither_aligned, load16_unaligned, store8_unaligned); @@ -901,6 +1138,8 @@ cfg_if! { basic_latin_to_ascii_simd_stride!(basic_latin_to_ascii_stride_neither_aligned, load8_unaligned, store16_unaligned); pack_simd_stride!(pack_stride_neither_aligned, load8_unaligned, store16_unaligned); + // Safety for conversion macros: We use the unalign macro with unalign functions above. All stride functions were produced + // by stride macros that universally munch a single SIMD_STRIDE_SIZE worth of elements. ascii_simd_unalign!(ascii_to_ascii, u8, u8, ascii_to_ascii_stride_neither_aligned); ascii_simd_unalign!(ascii_to_basic_latin, u8, u16, ascii_to_basic_latin_stride_neither_aligned); ascii_simd_unalign!(basic_latin_to_ascii, u16, u8, basic_latin_to_ascii_stride_neither_aligned); @@ -919,6 +1158,9 @@ cfg_if! { pub const SIMD_ALIGNMENT_MASK: usize = 15; + // Safety for stride macros: We stick to the load8_aligned/etc family of functions. We consistently name + // aligned/unaligned functions according to src/dst being aligned/unaligned + ascii_to_ascii_simd_stride!(ascii_to_ascii_stride_both_aligned, load16_aligned, store16_aligned); ascii_to_ascii_simd_stride!(ascii_to_ascii_stride_src_aligned, load16_aligned, store16_unaligned); ascii_to_ascii_simd_stride!(ascii_to_ascii_stride_dst_aligned, load16_unaligned, store16_aligned); @@ -944,6 +1186,9 @@ cfg_if! { pack_simd_stride!(pack_stride_dst_aligned, load8_unaligned, store16_aligned); pack_simd_stride!(pack_stride_neither_aligned, load8_unaligned, store16_unaligned); + // Safety for conversion macros: We use the correct pattern of both/src/dst/neither here. All stride functions were produced + // by stride macros that universally munch a single SIMD_STRIDE_SIZE worth of elements. + ascii_simd_check_align!(ascii_to_ascii, u8, u8, ascii_to_ascii_stride_both_aligned, ascii_to_ascii_stride_src_aligned, ascii_to_ascii_stride_dst_aligned, ascii_to_ascii_stride_neither_aligned); ascii_simd_check_align!(ascii_to_basic_latin, u8, u16, ascii_to_basic_latin_stride_both_aligned, ascii_to_basic_latin_stride_src_aligned, ascii_to_basic_latin_stride_dst_aligned, ascii_to_basic_latin_stride_neither_aligned); ascii_simd_check_align!(basic_latin_to_ascii, u16, u8, basic_latin_to_ascii_stride_both_aligned, basic_latin_to_ascii_stride_src_aligned, basic_latin_to_ascii_stride_dst_aligned, basic_latin_to_ascii_stride_neither_aligned); @@ -958,12 +1203,16 @@ cfg_if! { pub const SIMD_STRIDE_SIZE: usize = 16; + /// Safety-usable invariant: This should be identical to SIMD_STRIDE_SIZE (used by ascii_simd_check_align_unrolled) pub const SIMD_ALIGNMENT: usize = 16; pub const MAX_STRIDE_SIZE: usize = 16; pub const SIMD_ALIGNMENT_MASK: usize = 15; + // Safety for stride macros: We stick to the load8_aligned/etc family of functions. We consistently name + // aligned/unaligned functions according to src/dst being aligned/unaligned + ascii_to_ascii_simd_double_stride!(ascii_to_ascii_simd_double_stride_both_aligned, store16_aligned); ascii_to_ascii_simd_double_stride!(ascii_to_ascii_simd_double_stride_src_aligned, store16_unaligned); @@ -989,6 +1238,9 @@ cfg_if! { pack_simd_stride!(pack_stride_both_aligned, load8_aligned, store16_aligned); pack_simd_stride!(pack_stride_src_aligned, load8_aligned, store16_unaligned); + // Safety for conversion macros: We use the correct pattern of both/src/dst/neither/double_both/double_src here. All stride functions were produced + // by stride macros that universally munch a single SIMD_STRIDE_SIZE worth of elements. + ascii_simd_check_align_unrolled!(ascii_to_ascii, u8, u8, ascii_to_ascii_stride_both_aligned, ascii_to_ascii_stride_src_aligned, ascii_to_ascii_stride_neither_aligned, ascii_to_ascii_simd_double_stride_both_aligned, ascii_to_ascii_simd_double_stride_src_aligned); ascii_simd_check_align_unrolled!(ascii_to_basic_latin, u8, u16, ascii_to_basic_latin_stride_both_aligned, ascii_to_basic_latin_stride_src_aligned, ascii_to_basic_latin_stride_neither_aligned, ascii_to_basic_latin_simd_double_stride_both_aligned, ascii_to_basic_latin_simd_double_stride_src_aligned); @@ -998,14 +1250,21 @@ cfg_if! { } else if #[cfg(all(target_endian = "little", target_pointer_width = "64"))] { // Aligned ALU word, little-endian, 64-bit + /// Safety invariant: this is the amount of bytes consumed by + /// unpack_alu. This will be twice the pointer width, as it consumes two usizes. + /// This is also the number of bytes produced by pack_alu. + /// This is also the number of u16 code units produced/consumed by unpack_alu/pack_alu respectively. pub const ALU_STRIDE_SIZE: usize = 16; pub const MAX_STRIDE_SIZE: usize = 16; + // Safety invariant: this is the pointer width in bytes pub const ALU_ALIGNMENT: usize = 8; + // Safety invariant: this is a mask for getting the bits of a pointer not aligned to ALU_ALIGNMENT pub const ALU_ALIGNMENT_MASK: usize = 7; + /// Safety: dst must point to valid space for writing four `usize`s #[inline(always)] unsafe fn unpack_alu(word: usize, second_word: usize, dst: *mut usize) { let first = ((0x0000_0000_FF00_0000usize & word) << 24) | @@ -1024,12 +1283,14 @@ cfg_if! { ((0x00FF_0000_0000_0000usize & second_word) >> 16) | ((0x0000_FF00_0000_0000usize & second_word) >> 24) | ((0x0000_00FF_0000_0000usize & second_word) >> 32); + // Safety: fn invariant used here *dst = first; *(dst.add(1)) = second; *(dst.add(2)) = third; *(dst.add(3)) = fourth; } + /// Safety: dst must point to valid space for writing two `usize`s #[inline(always)] unsafe fn pack_alu(first: usize, second: usize, third: usize, fourth: usize, dst: *mut usize) { let word = ((0x00FF_0000_0000_0000usize & second) << 8) | @@ -1048,20 +1309,28 @@ cfg_if! { ((0x0000_00FF_0000_0000usize & third) >> 16) | ((0x0000_0000_00FF_0000usize & third) >> 8) | (0x0000_0000_0000_00FFusize & third); + // Safety: fn invariant used here *dst = word; *(dst.add(1)) = second_word; } } else if #[cfg(all(target_endian = "little", target_pointer_width = "32"))] { // Aligned ALU word, little-endian, 32-bit + /// Safety invariant: this is the amount of bytes consumed by + /// unpack_alu. This will be twice the pointer width, as it consumes two usizes. + /// This is also the number of bytes produced by pack_alu. + /// This is also the number of u16 code units produced/consumed by unpack_alu/pack_alu respectively. pub const ALU_STRIDE_SIZE: usize = 8; pub const MAX_STRIDE_SIZE: usize = 8; + // Safety invariant: this is the pointer width in bytes pub const ALU_ALIGNMENT: usize = 4; + // Safety invariant: this is a mask for getting the bits of a pointer not aligned to ALU_ALIGNMENT pub const ALU_ALIGNMENT_MASK: usize = 3; + /// Safety: dst must point to valid space for writing four `usize`s #[inline(always)] unsafe fn unpack_alu(word: usize, second_word: usize, dst: *mut usize) { let first = ((0x0000_FF00usize & word) << 8) | @@ -1072,12 +1341,14 @@ cfg_if! { (0x0000_00FFusize & second_word); let fourth = ((0xFF00_0000usize & second_word) >> 8) | ((0x00FF_0000usize & second_word) >> 16); + // Safety: fn invariant used here *dst = first; *(dst.add(1)) = second; *(dst.add(2)) = third; *(dst.add(3)) = fourth; } + /// Safety: dst must point to valid space for writing two `usize`s #[inline(always)] unsafe fn pack_alu(first: usize, second: usize, third: usize, fourth: usize, dst: *mut usize) { let word = ((0x00FF_0000usize & second) << 8) | @@ -1088,20 +1359,28 @@ cfg_if! { ((0x0000_00FFusize & fourth) << 16) | ((0x00FF_0000usize & third) >> 8) | (0x0000_00FFusize & third); + // Safety: fn invariant used here *dst = word; *(dst.add(1)) = second_word; } } else if #[cfg(all(target_endian = "big", target_pointer_width = "64"))] { // Aligned ALU word, big-endian, 64-bit + /// Safety invariant: this is the amount of bytes consumed by + /// unpack_alu. This will be twice the pointer width, as it consumes two usizes. + /// This is also the number of bytes produced by pack_alu. + /// This is also the number of u16 code units produced/consumed by unpack_alu/pack_alu respectively. pub const ALU_STRIDE_SIZE: usize = 16; pub const MAX_STRIDE_SIZE: usize = 16; + // Safety invariant: this is the pointer width in bytes pub const ALU_ALIGNMENT: usize = 8; + // Safety invariant: this is a mask for getting the bits of a pointer not aligned to ALU_ALIGNMENT pub const ALU_ALIGNMENT_MASK: usize = 7; + /// Safety: dst must point to valid space for writing four `usize`s #[inline(always)] unsafe fn unpack_alu(word: usize, second_word: usize, dst: *mut usize) { let first = ((0xFF00_0000_0000_0000usize & word) >> 8) | @@ -1120,12 +1399,14 @@ cfg_if! { ((0x0000_0000_00FF_0000usize & second_word) << 16) | ((0x0000_0000_0000_FF00usize & second_word) << 8) | (0x0000_0000_0000_00FFusize & second_word); + // Safety: fn invariant used here *dst = first; *(dst.add(1)) = second; *(dst.add(2)) = third; *(dst.add(3)) = fourth; } + /// Safety: dst must point to valid space for writing two `usize`s #[inline(always)] unsafe fn pack_alu(first: usize, second: usize, third: usize, fourth: usize, dst: *mut usize) { let word = ((0x00FF0000_00000000usize & first) << 8) | @@ -1144,20 +1425,28 @@ cfg_if! { ((0x000000FF_00000000usize & fourth) >> 16) | ((0x00000000_00FF0000usize & fourth) >> 8) | (0x00000000_000000FFusize & fourth); + // Safety: fn invariant used here *dst = word; *(dst.add(1)) = second_word; } } else if #[cfg(all(target_endian = "big", target_pointer_width = "32"))] { // Aligned ALU word, big-endian, 32-bit + /// Safety invariant: this is the amount of bytes consumed by + /// unpack_alu. This will be twice the pointer width, as it consumes two usizes. + /// This is also the number of bytes produced by pack_alu. + /// This is also the number of u16 code units produced/consumed by unpack_alu/pack_alu respectively. pub const ALU_STRIDE_SIZE: usize = 8; pub const MAX_STRIDE_SIZE: usize = 8; + // Safety invariant: this is the pointer width in bytes pub const ALU_ALIGNMENT: usize = 4; + // Safety invariant: this is a mask for getting the bits of a pointer not aligned to ALU_ALIGNMENT pub const ALU_ALIGNMENT_MASK: usize = 3; + /// Safety: dst must point to valid space for writing four `usize`s #[inline(always)] unsafe fn unpack_alu(word: usize, second_word: usize, dst: *mut usize) { let first = ((0xFF00_0000usize & word) >> 8) | @@ -1168,12 +1457,14 @@ cfg_if! { ((0x00FF_0000usize & second_word) >> 16); let fourth = ((0x0000_FF00usize & second_word) << 8) | (0x0000_00FFusize & second_word); + // Safety: fn invariant used here *dst = first; *(dst.add(1)) = second; *(dst.add(2)) = third; *(dst.add(3)) = fourth; } + /// Safety: dst must point to valid space for writing two `usize`s #[inline(always)] unsafe fn pack_alu(first: usize, second: usize, third: usize, fourth: usize, dst: *mut usize) { let word = ((0x00FF_0000usize & first) << 8) | @@ -1184,6 +1475,7 @@ cfg_if! { ((0x0000_00FFusize & third) << 16) | ((0x00FF_0000usize & fourth) >> 8) | (0x0000_00FFusize & fourth); + // Safety: fn invariant used here *dst = word; *(dst.add(1)) = second_word; } @@ -1195,6 +1487,8 @@ cfg_if! { } cfg_if! { + // Safety-usable invariant: this counts the zeroes from the "first byte" of utf-8 data packed into a usize + // with the target endianness if #[cfg(target_endian = "little")] { #[allow(dead_code)] #[inline(always)] @@ -1212,19 +1506,24 @@ cfg_if! { cfg_if! { if #[cfg(all(feature = "simd-accel", target_endian = "little", target_arch = "disabled"))] { + /// Safety-usable invariant: Will return the value and position of the first non-ASCII byte in the slice in a Some if found. + /// In other words, the first element of the Some is always `> 127` #[inline(always)] pub fn validate_ascii(slice: &[u8]) -> Option<(u8, usize)> { let src = slice.as_ptr(); let len = slice.len(); 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: src at offset is valid for a `SIMD_STRIDE_SIZE` read let simd = unsafe { load16_unaligned(src.add(offset)) }; if !simd_is_ascii(simd) { break; } offset += SIMD_STRIDE_SIZE; + // 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; } @@ -1233,6 +1532,7 @@ cfg_if! { while offset < len { let code_unit = slice[offset]; if code_unit > 127 { + // Safety: Safety-usable invariant upheld here return Some((code_unit, offset)); } offset += 1; @@ -1240,13 +1540,17 @@ cfg_if! { None } } else if #[cfg(all(feature = "simd-accel", target_feature = "sse2"))] { + /// 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 fn validate_ascii(slice: &[u8]) -> Option<(u8, usize)> { let src = slice.as_ptr(); let len = slice.len(); let mut offset = 0usize; + // Safety: if this check succeeds we're valid for reading at least `stride` elements. if SIMD_STRIDE_SIZE <= len { // First, process one unaligned vector + // Safety: src is valid for a `SIMD_STRIDE_SIZE` read let simd = unsafe { load16_unaligned(src) }; let mask = mask_ascii(simd); if mask != 0 { @@ -1255,18 +1559,26 @@ cfg_if! { return Some((non_ascii, offset)); } offset = SIMD_STRIDE_SIZE; + // Safety: Now that offset has changed we don't yet know how much it is valid for // 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 by definition less than SIMD_ALIGNMENT, which is defined to be equal to SIMD_STRIDE_SIZE. let until_alignment = unsafe { (SIMD_ALIGNMENT - ((src.add(offset) as usize) & SIMD_ALIGNMENT_MASK)) & SIMD_ALIGNMENT_MASK }; // 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 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 (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. let simd = unsafe { load16_unaligned(src.add(offset)) }; let mask = mask_ascii(simd); if mask != 0 { @@ -1276,53 +1588,78 @@ cfg_if! { } offset += until_alignment; } + // Safety: At this point we're valid for reading 2*SIMD_STRIDE_SIZE elements + // Safety: Now `offset` is aligned for `src` let len_minus_stride_times_two = len - (SIMD_STRIDE_SIZE * 2); loop { + // Safety: We were valid for this read, and were aligned. let first = unsafe { load16_aligned(src.add(offset)) }; let second = unsafe { load16_aligned(src.add(offset + SIMD_STRIDE_SIZE)) }; if !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? offset += mask_first.trailing_zeros() as usize; } else { 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 offset += SIMD_STRIDE_SIZE + mask_second.trailing_zeros() as usize; } + // Safety: We know this is non-ASCII, and can uphold the safety-usable invariant here let non_ascii = unsafe { *src.add(offset) }; + return Some((non_ascii, 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: if this check succeeds we're valid for reading at least `SIMD_STRIDE_SIZE` if offset + SIMD_STRIDE_SIZE <= len { - let simd = unsafe { load16_aligned(src.add(offset)) }; - let mask = mask_ascii(simd); + // Safety: We were valid for this read, and were aligned. + let simd = unsafe { load16_aligned(src.add(offset)) }; + // Safety: mask_ascii produces a mask of all the high bits. + let mask = mask_ascii(simd); if mask != 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 offset += mask.trailing_zeros() as usize; let non_ascii = unsafe { *src.add(offset) }; + // Safety: We know this is non-ASCII, and can uphold the safety-usable invariant here return Some((non_ascii, offset)); } offset += SIMD_STRIDE_SIZE; } } else { + // Safety: this is the unaligned branch // At most two iterations, so unroll + // Safety: if this check succeeds we're valid for reading at least `SIMD_STRIDE_SIZE` if offset + SIMD_STRIDE_SIZE <= len { + // Safety: We're valid for this read but must use an unaligned read let simd = unsafe { load16_unaligned(src.add(offset)) }; let mask = mask_ascii(simd); if mask != 0 { offset += mask.trailing_zeros() as usize; let non_ascii = unsafe { *src.add(offset) }; + // Safety-usable invariant upheld here (same as above) return Some((non_ascii, offset)); } offset += SIMD_STRIDE_SIZE; + // Safety: if this check succeeds we're valid for reading at least `SIMD_STRIDE_SIZE` if offset + SIMD_STRIDE_SIZE <= len { + // Safety: We're valid for this read but must use an unaligned read let simd = unsafe { load16_unaligned(src.add(offset)) }; let mask = mask_ascii(simd); if mask != 0 { offset += mask.trailing_zeros() as usize; let non_ascii = unsafe { *src.add(offset) }; + // Safety-usable invariant upheld here (same as above) return Some((non_ascii, offset)); } offset += SIMD_STRIDE_SIZE; @@ -1331,8 +1668,10 @@ cfg_if! { } } while offset < len { + // Safety: relies straightforwardly on the `len` invariant let code_unit = unsafe { *(src.add(offset)) }; if code_unit > 127 { + // Safety-usable invariant upheld here return Some((code_unit, offset)); } offset += 1; @@ -1340,31 +1679,40 @@ cfg_if! { None } } else { + // Safety-usable invariant: returns byte index of first non-ascii byte #[inline(always)] fn find_non_ascii(word: usize, second_word: usize) -> Option<usize> { let word_masked = word & ASCII_MASK; let second_masked = second_word & ASCII_MASK; if (word_masked | second_masked) == 0 { + // Both are ascii, invariant upheld return None; } if word_masked != 0 { let zeros = count_zeros(word_masked); - // `zeros` now contains 7 (for the seven bits of non-ASCII) + // `zeros` now contains 0 to 7 (for the seven bits of masked ASCII in little endian, + // or up to 7 bits of non-ASCII in big endian if the first byte is non-ASCII) // plus 8 times the number of ASCII in text order before the // non-ASCII byte in the little-endian case or 8 times the number of ASCII in // text order before the non-ASCII byte in the big-endian case. let num_ascii = (zeros >> 3) as usize; + // Safety-usable invariant upheld here return Some(num_ascii); } let zeros = count_zeros(second_masked); - // `zeros` now contains 7 (for the seven bits of non-ASCII) + // `zeros` now contains 0 to 7 (for the seven bits of masked ASCII in little endian, + // or up to 7 bits of non-ASCII in big endian if the first byte is non-ASCII) // plus 8 times the number of ASCII in text order before the // non-ASCII byte in the little-endian case or 8 times the number of ASCII in // text order before the non-ASCII byte in the big-endian case. let num_ascii = (zeros >> 3) as usize; + // Safety-usable invariant upheld here Some(ALU_ALIGNMENT + num_ascii) } + /// Safety: `src` must be valid for the reads of two `usize`s + /// + /// Safety-usable invariant: will return byte index of first non-ascii byte #[inline(always)] unsafe fn validate_ascii_stride(src: *const usize) -> Option<usize> { let word = *src; @@ -1372,6 +1720,8 @@ cfg_if! { find_non_ascii(word, second_word) } + /// 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 #[cfg_attr(feature = "cargo-clippy", allow(cast_ptr_alignment))] #[inline(always)] pub fn validate_ascii(slice: &[u8]) -> Option<(u8, usize)> { @@ -1379,23 +1729,30 @@ cfg_if! { let len = slice.len(); let mut offset = 0usize; let mut until_alignment = (ALU_ALIGNMENT - ((src as usize) & ALU_ALIGNMENT_MASK)) & ALU_ALIGNMENT_MASK; + // Safety: If this check fails we're valid to read `until_alignment + ALU_STRIDE_SIZE` elements if until_alignment + ALU_STRIDE_SIZE <= len { while until_alignment != 0 { let code_unit = slice[offset]; if code_unit > 127 { + // Safety-usable invairant upheld here return Some((code_unit, offset)); } offset += 1; until_alignment -= 1; } + // Safety: At this point we have read until_alignment elements and + // are valid for `ALU_STRIDE_SIZE` more. let len_minus_stride = len - ALU_STRIDE_SIZE; loop { + // Safety: we were valid for this read let ptr = unsafe { src.add(offset) as *const usize }; if let Some(num_ascii) = unsafe { validate_ascii_stride(ptr) } { offset += num_ascii; + // Safety-usable invairant upheld here using the invariant from validate_ascii_stride() return Some((unsafe { *(src.add(offset)) }, offset)); } offset += ALU_STRIDE_SIZE; + // Safety: This is `offset > ALU_STRIDE_SIZE` which means we always have at least `2 * ALU_STRIDE_SIZE` elements to munch next time. if offset > len_minus_stride { break; } @@ -1404,6 +1761,7 @@ cfg_if! { while offset < len { let code_unit = slice[offset]; if code_unit > 127 { + // Safety-usable invairant upheld here return Some((code_unit, offset)); } offset += 1; @@ -1428,36 +1786,47 @@ cfg_if! { pub const ALU_ALIGNMENT_MASK: usize = 3; } else { + // Safety: src points to two valid `usize`s, dst points to four valid `usize`s #[inline(always)] unsafe fn unpack_latin1_stride_alu(src: *const usize, dst: *mut usize) { + // Safety: src safety invariant used here let word = *src; let second_word = *(src.add(1)); + // Safety: dst safety invariant passed down unpack_alu(word, second_word, dst); } + // Safety: src points to four valid `usize`s, dst points to two valid `usize`s #[inline(always)] unsafe fn pack_latin1_stride_alu(src: *const usize, dst: *mut usize) { + // Safety: src safety invariant used here let first = *src; let second = *(src.add(1)); let third = *(src.add(2)); let fourth = *(src.add(3)); + // Safety: dst safety invariant passed down pack_alu(first, second, third, fourth, dst); } + // Safety: src points to two valid `usize`s, dst points to four valid `usize`s #[inline(always)] unsafe fn ascii_to_basic_latin_stride_alu(src: *const usize, dst: *mut usize) -> bool { + // Safety: src safety invariant used here let word = *src; let second_word = *(src.add(1)); // Check if the words contains non-ASCII if (word & ASCII_MASK) | (second_word & ASCII_MASK) != 0 { return false; } + // Safety: dst safety invariant passed down unpack_alu(word, second_word, dst); true } + // Safety: src points four valid `usize`s, dst points to two valid `usize`s #[inline(always)] unsafe fn basic_latin_to_ascii_stride_alu(src: *const usize, dst: *mut usize) -> bool { + // Safety: src safety invariant used here let first = *src; let second = *(src.add(1)); let third = *(src.add(2)); @@ -1465,16 +1834,22 @@ cfg_if! { if (first & BASIC_LATIN_MASK) | (second & BASIC_LATIN_MASK) | (third & BASIC_LATIN_MASK) | (fourth & BASIC_LATIN_MASK) != 0 { return false; } + // Safety: dst safety invariant passed down pack_alu(first, second, third, fourth, dst); true } + // Safety: src, dst both point to two valid `usize`s each + // Safety-usable invariant: Will return byte index of first non-ascii byte. #[inline(always)] unsafe fn ascii_to_ascii_stride(src: *const usize, dst: *mut usize) -> Option<usize> { + // Safety: src safety invariant used here let word = *src; let second_word = *(src.add(1)); + // Safety: src safety invariant used here *dst = word; *(dst.add(1)) = second_word; + // Relies on safety-usable invariant here find_non_ascii(word, second_word) } @@ -1482,6 +1857,7 @@ cfg_if! { basic_latin_alu!(basic_latin_to_ascii, u16, u8, basic_latin_to_ascii_stride_alu); latin1_alu!(unpack_latin1, u8, u16, unpack_latin1_stride_alu); latin1_alu!(pack_latin1, u16, u8, pack_latin1_stride_alu); + // Safety invariant upheld: ascii_to_ascii_stride will return byte index of first non-ascii if found ascii_alu!(ascii_to_ascii, u8, u8, ascii_to_ascii_stride); } } |