polars_io/csv/read/splitfields.rs
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#[cfg(not(feature = "simd"))]
mod inner {
/// An adapted version of std::iter::Split.
/// This exists solely because we cannot split the lines naively as
pub(crate) struct SplitFields<'a> {
v: &'a [u8],
separator: u8,
finished: bool,
quote_char: u8,
quoting: bool,
eol_char: u8,
}
impl<'a> SplitFields<'a> {
pub(crate) fn new(
slice: &'a [u8],
separator: u8,
quote_char: Option<u8>,
eol_char: u8,
) -> Self {
Self {
v: slice,
separator,
finished: false,
quote_char: quote_char.unwrap_or(b'"'),
quoting: quote_char.is_some(),
eol_char,
}
}
unsafe fn finish_eol(
&mut self,
need_escaping: bool,
idx: usize,
) -> Option<(&'a [u8], bool)> {
self.finished = true;
debug_assert!(idx <= self.v.len());
Some((self.v.get_unchecked(..idx), need_escaping))
}
fn finish(&mut self, need_escaping: bool) -> Option<(&'a [u8], bool)> {
self.finished = true;
Some((self.v, need_escaping))
}
fn eof_oel(&self, current_ch: u8) -> bool {
current_ch == self.separator || current_ch == self.eol_char
}
}
impl<'a> Iterator for SplitFields<'a> {
// the bool is used to indicate that it requires escaping
type Item = (&'a [u8], bool);
#[inline]
fn next(&mut self) -> Option<(&'a [u8], bool)> {
if self.finished {
return None;
} else if self.v.is_empty() {
return self.finish(false);
}
let mut needs_escaping = false;
// There can be strings with separators:
// "Street, City",
// SAFETY:
// we have checked bounds
let pos = if self.quoting && unsafe { *self.v.get_unchecked(0) } == self.quote_char {
needs_escaping = true;
// There can be pair of double-quotes within string.
// Each of the embedded double-quote characters must be represented
// by a pair of double-quote characters:
// e.g. 1997,Ford,E350,"Super, ""luxurious"" truck",20020
// denotes if we are in a string field, started with a quote
let mut in_field = false;
let mut idx = 0u32;
let mut current_idx = 0u32;
// micro optimizations
#[allow(clippy::explicit_counter_loop)]
for &c in self.v.iter() {
if c == self.quote_char {
// toggle between string field enclosure
// if we encounter a starting '"' -> in_field = true;
// if we encounter a closing '"' -> in_field = false;
in_field = !in_field;
}
if !in_field && self.eof_oel(c) {
if c == self.eol_char {
// SAFETY:
// we are in bounds
return unsafe {
self.finish_eol(needs_escaping, current_idx as usize)
};
}
idx = current_idx;
break;
}
current_idx += 1;
}
if idx == 0 {
return self.finish(needs_escaping);
}
idx as usize
} else {
match self.v.iter().position(|&c| self.eof_oel(c)) {
None => return self.finish(needs_escaping),
Some(idx) => unsafe {
// SAFETY:
// idx was just found
if *self.v.get_unchecked(idx) == self.eol_char {
return self.finish_eol(needs_escaping, idx);
} else {
idx
}
},
}
};
unsafe {
debug_assert!(pos <= self.v.len());
// SAFETY:
// we are in bounds
let ret = Some((self.v.get_unchecked(..pos), needs_escaping));
self.v = self.v.get_unchecked(pos + 1..);
ret
}
}
}
}
#[cfg(feature = "simd")]
mod inner {
use std::simd::prelude::*;
use polars_utils::clmul::prefix_xorsum_inclusive;
const SIMD_SIZE: usize = 64;
type SimdVec = u8x64;
/// An adapted version of std::iter::Split.
/// This exists solely because we cannot split the lines naively as
pub(crate) struct SplitFields<'a> {
pub v: &'a [u8],
separator: u8,
pub finished: bool,
quote_char: u8,
quoting: bool,
eol_char: u8,
simd_separator: SimdVec,
simd_eol_char: SimdVec,
simd_quote_char: SimdVec,
previous_valid_ends: u64,
}
impl<'a> SplitFields<'a> {
pub(crate) fn new(
slice: &'a [u8],
separator: u8,
quote_char: Option<u8>,
eol_char: u8,
) -> Self {
let simd_separator = SimdVec::splat(separator);
let simd_eol_char = SimdVec::splat(eol_char);
let quoting = quote_char.is_some();
let quote_char = quote_char.unwrap_or(b'"');
let simd_quote_char = SimdVec::splat(quote_char);
Self {
v: slice,
separator,
finished: false,
quote_char,
quoting,
eol_char,
simd_separator,
simd_eol_char,
simd_quote_char,
previous_valid_ends: 0,
}
}
unsafe fn finish_eol(
&mut self,
need_escaping: bool,
pos: usize,
) -> Option<(&'a [u8], bool)> {
self.finished = true;
debug_assert!(pos <= self.v.len());
Some((self.v.get_unchecked(..pos), need_escaping))
}
#[inline]
fn finish(&mut self, need_escaping: bool) -> Option<(&'a [u8], bool)> {
self.finished = true;
Some((self.v, need_escaping))
}
fn eof_oel(&self, current_ch: u8) -> bool {
current_ch == self.separator || current_ch == self.eol_char
}
}
impl<'a> Iterator for SplitFields<'a> {
// the bool is used to indicate that it requires escaping
type Item = (&'a [u8], bool);
#[inline]
fn next(&mut self) -> Option<(&'a [u8], bool)> {
// This must be before we check the cached value
if self.finished {
return None;
}
// Then check cached value as this is hot.
if self.previous_valid_ends != 0 {
let pos = self.previous_valid_ends.trailing_zeros() as usize;
self.previous_valid_ends >>= (pos + 1) as u64;
unsafe {
debug_assert!(pos < self.v.len());
// SAFETY:
// we are in bounds
let needs_escaping = self
.v
.first()
.map(|c| *c == self.quote_char && self.quoting)
.unwrap_or(false);
if *self.v.get_unchecked(pos) == self.eol_char {
return self.finish_eol(needs_escaping, pos);
}
let bytes = self.v.get_unchecked(..pos);
self.v = self.v.get_unchecked(pos + 1..);
let ret = Some((bytes, needs_escaping));
return ret;
}
}
if self.v.is_empty() {
return self.finish(false);
}
let mut needs_escaping = false;
// There can be strings with separators:
// "Street, City",
// SAFETY:
// we have checked bounds
let pos = if self.quoting && unsafe { *self.v.get_unchecked(0) } == self.quote_char {
let mut total_idx = 0;
needs_escaping = true;
let mut not_in_field_previous_iter = true;
loop {
let bytes = unsafe { self.v.get_unchecked(total_idx..) };
if bytes.len() > SIMD_SIZE {
let lane: [u8; SIMD_SIZE] = unsafe {
bytes
.get_unchecked(0..SIMD_SIZE)
.try_into()
.unwrap_unchecked()
};
let simd_bytes = SimdVec::from(lane);
let has_eol = simd_bytes.simd_eq(self.simd_eol_char);
let has_sep = simd_bytes.simd_eq(self.simd_separator);
let quote_mask = simd_bytes.simd_eq(self.simd_quote_char).to_bitmask();
let mut end_mask = (has_sep | has_eol).to_bitmask();
let mut not_in_quote_field = prefix_xorsum_inclusive(quote_mask);
if not_in_field_previous_iter {
not_in_quote_field = !not_in_quote_field;
}
not_in_field_previous_iter =
(not_in_quote_field & (1 << (SIMD_SIZE - 1))) > 0;
end_mask &= not_in_quote_field;
if end_mask != 0 {
let pos = end_mask.trailing_zeros() as usize;
total_idx += pos;
debug_assert!(
self.v[total_idx] == self.eol_char
|| self.v[total_idx] == self.separator
);
if pos == SIMD_SIZE - 1 {
self.previous_valid_ends = 0;
} else {
self.previous_valid_ends = end_mask >> (pos + 1) as u64;
}
break;
} else {
total_idx += SIMD_SIZE;
}
} else {
// There can be a pair of double-quotes within a string.
// Each of the embedded double-quote characters must be represented
// by a pair of double-quote characters:
// e.g. 1997,Ford,E350,"Super, ""luxurious"" truck",20020
// denotes if we are in a string field, started with a quote
let mut in_field = !not_in_field_previous_iter;
// usize::MAX is unset.
let mut idx = usize::MAX;
let mut current_idx = 0;
// micro optimizations
#[allow(clippy::explicit_counter_loop)]
for &c in bytes.iter() {
if c == self.quote_char {
// toggle between string field enclosure
// if we encounter a starting '"' -> in_field = true;
// if we encounter a closing '"' -> in_field = false;
in_field = !in_field;
}
if !in_field && self.eof_oel(c) {
if c == self.eol_char {
// SAFETY:
// we are in bounds
return unsafe {
self.finish_eol(needs_escaping, current_idx + total_idx)
};
}
idx = current_idx;
break;
}
current_idx += 1;
}
if idx == usize::MAX {
return self.finish(needs_escaping);
}
total_idx += idx;
debug_assert!(
self.v[total_idx] == self.eol_char
|| self.v[total_idx] == self.separator
);
break;
}
}
total_idx
} else {
let mut total_idx = 0;
loop {
let bytes = unsafe { self.v.get_unchecked(total_idx..) };
if bytes.len() > SIMD_SIZE {
let lane: [u8; SIMD_SIZE] = unsafe {
bytes
.get_unchecked(0..SIMD_SIZE)
.try_into()
.unwrap_unchecked()
};
let simd_bytes = SimdVec::from(lane);
let has_eol_char = simd_bytes.simd_eq(self.simd_eol_char);
let has_separator = simd_bytes.simd_eq(self.simd_separator);
let has_any_mask = (has_separator | has_eol_char).to_bitmask();
if has_any_mask != 0 {
total_idx += has_any_mask.trailing_zeros() as usize;
break;
} else {
total_idx += SIMD_SIZE;
}
} else {
match bytes.iter().position(|&c| self.eof_oel(c)) {
None => return self.finish(needs_escaping),
Some(idx) => {
total_idx += idx;
break;
},
}
}
}
unsafe {
if *self.v.get_unchecked(total_idx) == self.eol_char {
return self.finish_eol(needs_escaping, total_idx);
} else {
total_idx
}
}
};
unsafe {
debug_assert!(pos < self.v.len());
// SAFETY:
// we are in bounds
let ret = Some((self.v.get_unchecked(..pos), needs_escaping));
self.v = self.v.get_unchecked(pos + 1..);
ret
}
}
}
}
pub(crate) use inner::SplitFields;
#[cfg(test)]
mod test {
use super::SplitFields;
#[test]
fn test_splitfields() {
let input = "\"foo\",\"bar\"";
let mut fields = SplitFields::new(input.as_bytes(), b',', Some(b'"'), b'\n');
assert_eq!(fields.next(), Some(("\"foo\"".as_bytes(), true)));
assert_eq!(fields.next(), Some(("\"bar\"".as_bytes(), true)));
assert_eq!(fields.next(), None);
let input2 = "\"foo\n bar\";\"baz\";12345";
let mut fields2 = SplitFields::new(input2.as_bytes(), b';', Some(b'"'), b'\n');
assert_eq!(fields2.next(), Some(("\"foo\n bar\"".as_bytes(), true)));
assert_eq!(fields2.next(), Some(("\"baz\"".as_bytes(), true)));
assert_eq!(fields2.next(), Some(("12345".as_bytes(), false)));
assert_eq!(fields2.next(), None);
}
}