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correct GetPartialString (#2887)

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This commit is contained in:
Mark Thom
2025-04-16 22:20:31 -07:00
committed by Mark Thom
parent e563fd8e4f
commit 4c46f0e54d
4 changed files with 184 additions and 107 deletions
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113
src/machine/heap.rs
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@@ -135,69 +135,72 @@ pub(crate) enum PStrSegmentCmpResult {
}
pub(crate) fn compare_pstr_slices(slice1: &[u8], slice2: &[u8]) -> PStrSegmentCmpResult {
use std::cmp::Ordering;
debug_assert!(!slice1.is_empty() && !slice2.is_empty());
let find_tail = |slice| unsafe { scan_slice_to_str(slice).tail_idx };
let calculate_result = |pos| {
use std::cmp::Ordering;
if slice1.get(pos).cloned().unwrap_or(0) == 0 {
// subtract 1 from pos to offset the increment of scan_slice_to_str if the
// string is "\0\".
let tail1_idx = find_tail(&slice1[pos..]);
let offset_pos_1 = (ALIGN - slice1.as_ptr().align_offset(ALIGN)) % ALIGN;
if slice2.get(pos).cloned().unwrap_or(0) == 0 {
let tail2_idx = find_tail(&slice2[pos..]);
let offset_pos_2 = (ALIGN - slice2.as_ptr().align_offset(ALIGN)) % ALIGN;
PStrSegmentCmpResult::Continue(
PStrContinuable::TailIndex(tail1_idx + cell_index!(pos + offset_pos_1)),
PStrContinuable::TailIndex(tail2_idx + cell_index!(pos + offset_pos_2)),
)
} else {
PStrSegmentCmpResult::Continue(
PStrContinuable::TailIndex(tail1_idx + cell_index!(pos)),
PStrContinuable::PStrOffset(pos),
)
}
} else if slice2.get(pos).cloned().unwrap_or(0) == 0 {
let tail2_idx = find_tail(&slice2[pos..]);
let offset_pos_2 = (ALIGN - slice2.as_ptr().align_offset(ALIGN)) % ALIGN;
PStrSegmentCmpResult::Continue(
PStrContinuable::PStrOffset(pos),
PStrContinuable::TailIndex(tail2_idx + cell_index!(pos + offset_pos_2)),
)
} else {
// Compute 7-byte chunks with the mismatching character at pos in the middle of
// each. This way, the character of which the byte at pos is a part will be
// validated and reached eventually by the utf8_chunks() iterator.
let slice1_range = pos.saturating_sub(3)..(pos + 4).min(slice1.len());
let slice2_range = pos.saturating_sub(3)..(pos + 4).min(slice2.len());
let chars1_iter = slice1[slice1_range].utf8_chunks();
let chars2_iter = slice2[slice2_range].utf8_chunks();
for (chunk1, chunk2) in chars1_iter.zip(chars2_iter) {
let result = chunk1.valid().cmp(chunk2.valid());
if result == Ordering::Greater {
return PStrSegmentCmpResult::Greater;
} else if result == Ordering::Less {
return PStrSegmentCmpResult::Less;
}
}
unreachable!()
}
};
match slice1
.iter()
.zip(slice2.iter())
.position(|(b1, b2)| b1 != b2 || *b1 == 0 || *b2 == 0)
{
Some(pos) => {
if slice1[pos] == 0 {
// subtract 1 from pos to offset the increment of scan_slice_to_str if the
// string is "\0\".
let tail1_idx = find_tail(&slice1[pos..]);
if slice2[pos] == 0 {
let tail2_idx = find_tail(&slice2[pos..]);
PStrSegmentCmpResult::Continue(
PStrContinuable::TailIndex(tail1_idx + cell_index!(pos)),
PStrContinuable::TailIndex(tail2_idx + cell_index!(pos)),
)
} else {
PStrSegmentCmpResult::Continue(
PStrContinuable::TailIndex(tail1_idx + cell_index!(pos)),
PStrContinuable::PStrOffset(pos),
)
}
} else if slice2[pos] == 0 {
let tail2_idx = find_tail(&slice2[pos..]);
PStrSegmentCmpResult::Continue(
PStrContinuable::PStrOffset(pos),
PStrContinuable::TailIndex(tail2_idx + cell_index!(pos)),
)
} else {
// Compute 7-byte chunks with the mismatching character at pos in the middle of
// each. This way, the character of which the byte at pos is a part will be
// validated and reached eventually by the utf8_chunks() iterator.
let slice1_range = pos.saturating_sub(3)..(pos + 4).min(slice1.len());
let slice2_range = pos.saturating_sub(3)..(pos + 4).min(slice2.len());
let chars1_iter = slice1[slice1_range].utf8_chunks();
let chars2_iter = slice2[slice2_range].utf8_chunks();
for (chunk1, chunk2) in chars1_iter.zip(chars2_iter) {
let result = chunk1.valid().cmp(chunk2.valid());
if result == Ordering::Greater {
return PStrSegmentCmpResult::Greater;
} else if result == Ordering::Less {
return PStrSegmentCmpResult::Less;
}
}
unreachable!()
}
}
None => {
unreachable!()
}
Some(pos) => calculate_result(pos),
None => calculate_result(slice1.len().min(slice2.len())),
}
}