use unicode_width::UnicodeWidthChar;
use super::*;
#[cfg(test)]
mod tests;
/// Finds all newlines, multi-byte characters, and non-narrow characters in a
/// SourceFile.
///
/// This function will use an SSE2 enhanced implementation if hardware support
/// is detected at runtime.
pub fn analyze_source_file(
src: &str,
source_file_start_pos: BytePos)
-> (Vec<BytePos>, Vec<MultiByteChar>, Vec<NonNarrowChar>)
{
let mut lines = vec![source_file_start_pos];
let mut multi_byte_chars = vec![];
let mut non_narrow_chars = vec![];
// Calls the right implementation, depending on hardware support available.
analyze_source_file_dispatch(src,
source_file_start_pos,
&mut lines,
&mut multi_byte_chars,
&mut non_narrow_chars);
// The code above optimistically registers a new line *after* each \n
// it encounters. If that point is already outside the source_file, remove
// it again.
if let Some(&last_line_start) = lines.last() {
let source_file_end = source_file_start_pos + BytePos::from_usize(src.len());
assert!(source_file_end >= last_line_start);
if last_line_start == source_file_end {
lines.pop();
}
}
(lines, multi_byte_chars, non_narrow_chars)
}
cfg_if::cfg_if! {
if #[cfg(all(any(target_arch = "x86", target_arch = "x86_64")))] {
fn analyze_source_file_dispatch(src: &str,
source_file_start_pos: BytePos,
lines: &mut Vec<BytePos>,
multi_byte_chars: &mut Vec<MultiByteChar>,
non_narrow_chars: &mut Vec<NonNarrowChar>) {
if is_x86_feature_detected!("sse2") {
unsafe {
analyze_source_file_sse2(src,
source_file_start_pos,
lines,
multi_byte_chars,
non_narrow_chars);
}
} else {
analyze_source_file_generic(src,
src.len(),
source_file_start_pos,
lines,
multi_byte_chars,
non_narrow_chars);
}
}
/// Checks 16 byte chunks of text at a time. If the chunk contains
/// something other than printable ASCII characters and newlines, the
/// function falls back to the generic implementation. Otherwise it uses
/// SSE2 intrinsics to quickly find all newlines.
#[target_feature(enable = "sse2")]
unsafe fn analyze_source_file_sse2(src: &str,
output_offset: BytePos,
lines: &mut Vec<BytePos>,
multi_byte_chars: &mut Vec<MultiByteChar>,
non_narrow_chars: &mut Vec<NonNarrowChar>) {
#[cfg(target_arch = "x86")]
use std::arch::x86::*;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::*;
const CHUNK_SIZE: usize = 16;
let src_bytes = src.as_bytes();
let chunk_count = src.len() / CHUNK_SIZE;
// This variable keeps track of where we should start decoding a
// chunk. If a multi-byte character spans across chunk boundaries,
// we need to skip that part in the next chunk because we already
// handled it.
let mut intra_chunk_offset = 0;
for chunk_index in 0 .. chunk_count {
let ptr = src_bytes.as_ptr() as *const __m128i;
// We don't know if the pointer is aligned to 16 bytes, so we
// use `loadu`, which supports unaligned loading.
let chunk = _mm_loadu_si128(ptr.offset(chunk_index as isize));
// For character in the chunk, see if its byte value is < 0, which
// indicates that it's part of a UTF-8 char.
let multibyte_test = _mm_cmplt_epi8(chunk, _mm_set1_epi8(0));
// Create a bit mask from the comparison results.
let multibyte_mask = _mm_movemask_epi8(multibyte_test);
// If the bit mask is all zero, we only have ASCII chars here:
if multibyte_mask == 0 {
assert!(intra_chunk_offset == 0);
// Check if there are any control characters in the chunk. All
// control characters that we can encounter at this point have a
// byte value less than 32 or ...
let control_char_test0 = _mm_cmplt_epi8(chunk, _mm_set1_epi8(32));
let control_char_mask0 = _mm_movemask_epi8(control_char_test0);
// ... it's the ASCII 'DEL' character with a value of 127.
let control_char_test1 = _mm_cmpeq_epi8(chunk, _mm_set1_epi8(127));
let control_char_mask1 = _mm_movemask_epi8(control_char_test1);
let control_char_mask = control_char_mask0 | control_char_mask1;
if control_char_mask != 0 {
// Check for newlines in the chunk
let newlines_test = _mm_cmpeq_epi8(chunk, _mm_set1_epi8(b'\n' as i8));
let newlines_mask = _mm_movemask_epi8(newlines_test);
if control_char_mask == newlines_mask {
// All control characters are newlines, record them
let mut newlines_mask = 0xFFFF0000 | newlines_mask as u32;
let output_offset = output_offset +
BytePos::from_usize(chunk_index * CHUNK_SIZE + 1);
loop {
let index = newlines_mask.trailing_zeros();
if index >= CHUNK_SIZE as u32 {
// We have arrived at the end of the chunk.
break
}
lines.push(BytePos(index) + output_offset);
// Clear the bit, so we can find the next one.
newlines_mask &= (!1) << index;
}
// We are done for this chunk. All control characters were
// newlines and we took care of those.
continue
} else {
// Some of the control characters are not newlines,
// fall through to the slow path below.
}
} else {
// No control characters, nothing to record for this chunk
continue
}
}
// The slow path.
// There are control chars in here, fallback to generic decoding.
let scan_start = chunk_index * CHUNK_SIZE + intra_chunk_offset;
intra_chunk_offset = analyze_source_file_generic(
&src[scan_start .. ],
CHUNK_SIZE - intra_chunk_offset,
BytePos::from_usize(scan_start) + output_offset,
lines,
multi_byte_chars,
non_narrow_chars
);
}
// There might still be a tail left to analyze
let tail_start = chunk_count * CHUNK_SIZE + intra_chunk_offset;
if tail_start < src.len() {
analyze_source_file_generic(&src[tail_start as usize ..],
src.len() - tail_start,
output_offset + BytePos::from_usize(tail_start),
lines,
multi_byte_chars,
non_narrow_chars);
}
}
} else {
// The target (or compiler version) does not support SSE2 ...
fn analyze_source_file_dispatch(src: &str,
source_file_start_pos: BytePos,
lines: &mut Vec<BytePos>,
multi_byte_chars: &mut Vec<MultiByteChar>,
non_narrow_chars: &mut Vec<NonNarrowChar>) {
analyze_source_file_generic(src,
src.len(),
source_file_start_pos,
lines,
multi_byte_chars,
non_narrow_chars);
}
}
}
// `scan_len` determines the number of bytes in `src` to scan. Note that the
// function can read past `scan_len` if a multi-byte character start within the
// range but extends past it. The overflow is returned by the function.
fn analyze_source_file_generic(src: &str,
scan_len: usize,
output_offset: BytePos,
lines: &mut Vec<BytePos>,
multi_byte_chars: &mut Vec<MultiByteChar>,
non_narrow_chars: &mut Vec<NonNarrowChar>)
-> usize
{
assert!(src.len() >= scan_len);
let mut i = 0;
let src_bytes = src.as_bytes();
while i < scan_len {
let byte = unsafe {
// We verified that i < scan_len <= src.len()
*src_bytes.get_unchecked(i as usize)
};
// How much to advance in order to get to the next UTF-8 char in the
// string.
let mut char_len = 1;
if byte < 32 {
// This is an ASCII control character, it could be one of the cases
// that are interesting to us.
let pos = BytePos::from_usize(i) + output_offset;
match byte {
b'\n' => {
lines.push(pos + BytePos(1));
}
b'\t' => {
non_narrow_chars.push(NonNarrowChar::Tab(pos));
}
_ => {
non_narrow_chars.push(NonNarrowChar::ZeroWidth(pos));
}
}
} else if byte >= 127 {
// The slow path:
// This is either ASCII control character "DEL" or the beginning of
// a multibyte char. Just decode to `char`.
let c = (&src[i..]).chars().next().unwrap();
char_len = c.len_utf8();
let pos = BytePos::from_usize(i) + output_offset;
if char_len > 1 {
assert!(char_len >=2 && char_len <= 4);
let mbc = MultiByteChar {
pos,
bytes: char_len as u8,
};
multi_byte_chars.push(mbc);
}
// Assume control characters are zero width.
// FIXME: How can we decide between `width` and `width_cjk`?
let char_width = UnicodeWidthChar::width(c).unwrap_or(0);
if char_width != 1 {
non_narrow_chars.push(NonNarrowChar::new(pos, char_width));
}
}
i += char_len;
}
i - scan_len
}