383 lines
12 KiB
Rust
383 lines
12 KiB
Rust
use std::fmt;
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use std::ops::{Index, Range};
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use crate::algorithms::DiffHook;
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/// An enum representing a diffing algorithm.
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#[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord, Debug)]
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pub enum Algorithm {
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/// Picks the myers algorithm from [`crate::algorithms::myers`]
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Myers,
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/// Picks the patience algorithm from [`crate::algorithms::patience`]
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Patience,
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}
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impl Default for Algorithm {
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/// Returns the default algorithm ([`Algorithm::Myers`]).
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fn default() -> Algorithm {
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Algorithm::Myers
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}
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}
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/// The tag of a change.
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#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy, Ord, PartialOrd)]
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pub enum ChangeTag {
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/// The change indicates equality (not a change)
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Equal,
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/// The change indicates deleted text.
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Delete,
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/// The change indicates inserted text.
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Insert,
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}
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impl fmt::Display for ChangeTag {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(
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f,
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"{}",
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match &self {
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ChangeTag::Equal => ' ',
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ChangeTag::Delete => '-',
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ChangeTag::Insert => '+',
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}
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)
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}
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}
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/// Represents the expanded [`DiffOp`] change.
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///
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/// This type is returned from [`DiffOp::iter_changes`] and
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/// [`TextDiff::iter_changes`](crate::text::TextDiff::iter_changes).
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///
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/// It exists so that it's more convenient to work with textual differences as
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/// the underlying [`DiffOp`] encodes a group of changes.
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///
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/// This type has additional methods that are only available for types
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/// implementing [`DiffableStr`](crate::text::DiffableStr).
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#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy, Ord, PartialOrd)]
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pub struct Change<'s, T: ?Sized> {
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pub(crate) tag: ChangeTag,
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pub(crate) old_index: Option<usize>,
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pub(crate) new_index: Option<usize>,
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pub(crate) value: &'s T,
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}
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/// These methods are available for all change types.
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impl<'s, T: ?Sized> Change<'s, T> {
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/// Returns the change tag.
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pub fn tag(&self) -> ChangeTag {
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self.tag
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}
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/// Returns the old index if available.
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pub fn old_index(&self) -> Option<usize> {
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self.old_index
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}
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/// Returns the new index if available.
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pub fn new_index(&self) -> Option<usize> {
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self.new_index
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}
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/// Returns the underlying changed value.
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///
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/// Depending on the type of the underlying [`crate::text::DiffableStr`]
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/// this value is more or less useful. If you always want to have a utf-8
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/// string it's best to use the [`Change::as_str`] and
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/// [`Change::to_string_lossy`] methods.
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pub fn value(&self) -> &'s T {
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self.value
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}
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}
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/// Utility enum to capture a diff operation.
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///
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/// This is used by [`Capture`](crate::algorithms::Capture).
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#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
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pub enum DiffOp {
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/// A segment is equal (see [`DiffHook::equal`])
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Equal {
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/// The starting index in the old sequence.
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old_index: usize,
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/// The starting index in the new sequence.
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new_index: usize,
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/// The length of the segment.
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len: usize,
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},
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/// A segment was deleted (see [`DiffHook::delete`])
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Delete {
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/// The starting index in the old sequence.
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old_index: usize,
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/// The length of the old segment.
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old_len: usize,
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/// The starting index in the new sequence.
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new_index: usize,
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},
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/// A segment was inserted (see [`DiffHook::insert`])
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Insert {
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/// The starting index in the old sequence.
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old_index: usize,
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/// The starting index in the new sequence.
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new_index: usize,
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/// The length of the new segment.
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new_len: usize,
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},
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/// A segment was replaced (see [`DiffHook::replace`])
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Replace {
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/// The starting index in the old sequence.
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old_index: usize,
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/// The length of the old segment.
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old_len: usize,
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/// The starting index in the new sequence.
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new_index: usize,
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/// The length of the new segment.
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new_len: usize,
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},
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}
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/// The tag of a diff operation.
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#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy, Ord, PartialOrd)]
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pub enum DiffTag {
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/// The diff op encodes an equal segment.
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Equal,
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/// The diff op encodes a deleted segment.
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Delete,
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/// The diff op encodes an inserted segment.
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Insert,
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/// The diff op encodes a replaced segment.
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Replace,
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}
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impl DiffOp {
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/// Returns the tag of the operation.
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pub fn tag(self) -> DiffTag {
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self.as_tag_tuple().0
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}
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/// Returns the old range.
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pub fn old_range(&self) -> Range<usize> {
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self.as_tag_tuple().1
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}
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/// Returns the new range.
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pub fn new_range(&self) -> Range<usize> {
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self.as_tag_tuple().2
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}
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/// Transform the op into a tuple of diff tag and ranges.
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///
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/// This is useful when operating on slices. The returned format is
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/// `(tag, i1..i2, j1..j2)`:
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///
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/// * `Replace`: `a[i1..i2]` should be replaced by `b[j1..j2]`
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/// * `Delete`: `a[i1..i2]` should be deleted (`j1 == j2` in this case).
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/// * `Insert`: `b[j1..j2]` should be inserted at `a[i1..i2]` (`i1 == i2` in this case).
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/// * `Equal`: `a[i1..i2]` is equal to `b[j1..j2]`.
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pub fn as_tag_tuple(&self) -> (DiffTag, Range<usize>, Range<usize>) {
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match *self {
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DiffOp::Equal {
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old_index,
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new_index,
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len,
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} => (
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DiffTag::Equal,
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old_index..old_index + len,
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new_index..new_index + len,
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),
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DiffOp::Delete {
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old_index,
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new_index,
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old_len,
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} => (
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DiffTag::Delete,
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old_index..old_index + old_len,
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new_index..new_index,
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),
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DiffOp::Insert {
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old_index,
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new_index,
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new_len,
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} => (
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DiffTag::Insert,
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old_index..old_index,
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new_index..new_index + new_len,
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),
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DiffOp::Replace {
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old_index,
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old_len,
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new_index,
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new_len,
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} => (
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DiffTag::Replace,
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old_index..old_index + old_len,
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new_index..new_index + new_len,
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),
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}
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}
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/// Apply this operation to a diff hook.
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pub fn apply_to_hook<D: DiffHook>(&self, d: &mut D) -> Result<(), D::Error> {
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match *self {
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DiffOp::Equal {
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old_index,
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new_index,
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len,
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} => d.equal(old_index, new_index, len),
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DiffOp::Delete {
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old_index,
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old_len,
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new_index,
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} => d.delete(old_index, old_len, new_index),
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DiffOp::Insert {
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old_index,
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new_index,
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new_len,
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} => d.insert(old_index, new_index, new_len),
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DiffOp::Replace {
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old_index,
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old_len,
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new_index,
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new_len,
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} => d.replace(old_index, old_len, new_index, new_len),
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}
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}
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/// Iterates over all changes encoded in the diff op against old and new
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/// sequences.
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///
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/// `old` and `new` are two indexable objects like the types you pass to
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/// the diffing algorithm functions.
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pub fn iter_changes<'x, 'lookup, Old, New, T>(
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&self,
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old: &'lookup Old,
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new: &'lookup New,
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) -> impl Iterator<Item = Change<'x, T>> + 'lookup
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where
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Old: Index<usize, Output = &'x T> + ?Sized,
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New: Index<usize, Output = &'x T> + ?Sized,
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T: 'x + ?Sized,
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'x: 'lookup,
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{
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let (tag, old_range, new_range) = self.as_tag_tuple();
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let mut old_index = old_range.start;
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let mut new_index = new_range.start;
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let mut old_i = old_range.start;
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let mut new_i = new_range.start;
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std::iter::from_fn(move || match tag {
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DiffTag::Equal => {
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if old_i < old_range.end {
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let value = old[old_i];
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old_i += 1;
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old_index += 1;
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new_index += 1;
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Some(Change {
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tag: ChangeTag::Equal,
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old_index: Some(old_index - 1),
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new_index: Some(new_index - 1),
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value,
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})
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} else {
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None
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}
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}
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DiffTag::Delete => {
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if old_i < old_range.end {
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let value = old[old_i];
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old_i += 1;
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old_index += 1;
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Some(Change {
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tag: ChangeTag::Delete,
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old_index: Some(old_index - 1),
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new_index: None,
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value,
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})
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} else {
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None
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}
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}
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DiffTag::Insert => {
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if new_i < new_range.end {
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let value = new[new_i];
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new_i += 1;
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new_index += 1;
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Some(Change {
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tag: ChangeTag::Insert,
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old_index: None,
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new_index: Some(new_index - 1),
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value,
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})
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} else {
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None
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}
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}
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DiffTag::Replace => {
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if old_i < old_range.end {
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let value = old[old_i];
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old_i += 1;
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old_index += 1;
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Some(Change {
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tag: ChangeTag::Delete,
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old_index: Some(old_index - 1),
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new_index: None,
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value,
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})
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} else if new_i < new_range.end {
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let value = new[new_i];
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new_i += 1;
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new_index += 1;
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Some(Change {
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tag: ChangeTag::Insert,
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old_index: None,
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new_index: Some(new_index - 1),
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value,
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})
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} else {
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None
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}
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}
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})
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}
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}
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#[cfg(feature = "text")]
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mod text_additions {
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use super::*;
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use crate::text::DiffableStr;
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use std::borrow::Cow;
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/// The text interface can produce changes over [`DiffableStr`] implementing
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/// values. As those are generic interfaces for different types of strings
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/// utility methods to make working with standard rust strings more enjoyable.
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impl<'s, T: DiffableStr + ?Sized> Change<'s, T> {
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/// Returns the value as string if it is utf-8.
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pub fn as_str(&self) -> Option<&'s str> {
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T::as_str(self.value)
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}
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/// Returns the value (lossy) decoded as utf-8 string.
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pub fn to_string_lossy(&self) -> Cow<'s, str> {
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T::to_string_lossy(self.value)
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}
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/// Returns `true` if this change does not end in a newline and must be
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/// followed up by one if line based diffs are used.
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///
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/// The [`std::fmt::Display`] implementation of [`Change`] will automatically
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/// insert a newline after the value if this is true.
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pub fn missing_newline(&self) -> bool {
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!T::ends_with_newline(self.value)
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}
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}
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impl<'s, T: DiffableStr + ?Sized> fmt::Display for Change<'s, T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(
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f,
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"{}{}",
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self.to_string_lossy(),
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if self.missing_newline() { "\n" } else { "" }
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)
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}
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}
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}
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