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|
use std::fmt;
use std::ops::{Index, Range};
use crate::algorithms::utils::is_empty_range;
use crate::algorithms::DiffHook;
use crate::iter::ChangesIter;
/// An enum representing a diffing algorithm.
#[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord, Debug)]
#[cfg_attr(
feature = "serde",
derive(serde::Serialize, serde::Deserialize),
serde(rename_all = "snake_case")
)]
pub enum Algorithm {
/// Picks the myers algorithm from [`crate::algorithms::myers`]
Myers,
/// Picks the patience algorithm from [`crate::algorithms::patience`]
Patience,
/// Picks the LCS algorithm from [`crate::algorithms::lcs`]
Lcs,
}
impl Default for Algorithm {
/// Returns the default algorithm ([`Algorithm::Myers`]).
fn default() -> Algorithm {
Algorithm::Myers
}
}
/// The tag of a change.
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy, Ord, PartialOrd)]
#[cfg_attr(
feature = "serde",
derive(serde::Serialize, serde::Deserialize),
serde(rename_all = "snake_case")
)]
pub enum ChangeTag {
/// The change indicates equality (not a change)
Equal,
/// The change indicates deleted text.
Delete,
/// The change indicates inserted text.
Insert,
}
impl fmt::Display for ChangeTag {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(
f,
"{}",
match &self {
ChangeTag::Equal => ' ',
ChangeTag::Delete => '-',
ChangeTag::Insert => '+',
}
)
}
}
/// Represents the expanded [`DiffOp`] change.
///
/// This type is returned from [`DiffOp::iter_changes`] and
/// [`TextDiff::iter_changes`](crate::text::TextDiff::iter_changes).
///
/// It exists so that it's more convenient to work with textual differences as
/// the underlying [`DiffOp`] encodes a group of changes.
///
/// This type has additional methods that are only available for types
/// implementing [`DiffableStr`](crate::text::DiffableStr).
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy, Ord, PartialOrd)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
pub struct Change<T> {
pub(crate) tag: ChangeTag,
pub(crate) old_index: Option<usize>,
pub(crate) new_index: Option<usize>,
pub(crate) value: T,
}
/// These methods are available for all change types.
impl<T: Clone> Change<T> {
/// Returns the change tag.
pub fn tag(&self) -> ChangeTag {
self.tag
}
/// Returns the old index if available.
pub fn old_index(&self) -> Option<usize> {
self.old_index
}
/// Returns the new index if available.
pub fn new_index(&self) -> Option<usize> {
self.new_index
}
/// Returns the underlying changed value.
///
/// Depending on the type of the underlying [`crate::text::DiffableStr`]
/// this value is more or less useful. If you always want to have a utf-8
/// string it's best to use the [`Change::as_str`] and
/// [`Change::to_string_lossy`] methods.
pub fn value(&self) -> T {
self.value.clone()
}
/// Returns the underlying changed value as reference.
pub fn value_ref(&self) -> &T {
&self.value
}
/// Returns the underlying changed value as mutable reference.
pub fn value_mut(&mut self) -> &mut T {
&mut self.value
}
}
/// Utility enum to capture a diff operation.
///
/// This is used by [`Capture`](crate::algorithms::Capture).
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
#[cfg_attr(
feature = "serde",
derive(serde::Serialize, serde::Deserialize),
serde(rename_all = "snake_case", tag = "op")
)]
pub enum DiffOp {
/// A segment is equal (see [`DiffHook::equal`])
Equal {
/// The starting index in the old sequence.
old_index: usize,
/// The starting index in the new sequence.
new_index: usize,
/// The length of the segment.
len: usize,
},
/// A segment was deleted (see [`DiffHook::delete`])
Delete {
/// The starting index in the old sequence.
old_index: usize,
/// The length of the old segment.
old_len: usize,
/// The starting index in the new sequence.
new_index: usize,
},
/// A segment was inserted (see [`DiffHook::insert`])
Insert {
/// The starting index in the old sequence.
old_index: usize,
/// The starting index in the new sequence.
new_index: usize,
/// The length of the new segment.
new_len: usize,
},
/// A segment was replaced (see [`DiffHook::replace`])
Replace {
/// The starting index in the old sequence.
old_index: usize,
/// The length of the old segment.
old_len: usize,
/// The starting index in the new sequence.
new_index: usize,
/// The length of the new segment.
new_len: usize,
},
}
/// The tag of a diff operation.
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy, Ord, PartialOrd)]
#[cfg_attr(
feature = "serde",
derive(serde::Serialize, serde::Deserialize),
serde(rename_all = "snake_case")
)]
pub enum DiffTag {
/// The diff op encodes an equal segment.
Equal,
/// The diff op encodes a deleted segment.
Delete,
/// The diff op encodes an inserted segment.
Insert,
/// The diff op encodes a replaced segment.
Replace,
}
impl DiffOp {
/// Returns the tag of the operation.
pub fn tag(self) -> DiffTag {
self.as_tag_tuple().0
}
/// Returns the old range.
pub fn old_range(&self) -> Range<usize> {
self.as_tag_tuple().1
}
/// Returns the new range.
pub fn new_range(&self) -> Range<usize> {
self.as_tag_tuple().2
}
/// Transform the op into a tuple of diff tag and ranges.
///
/// This is useful when operating on slices. The returned format is
/// `(tag, i1..i2, j1..j2)`:
///
/// * `Replace`: `a[i1..i2]` should be replaced by `b[j1..j2]`
/// * `Delete`: `a[i1..i2]` should be deleted (`j1 == j2` in this case).
/// * `Insert`: `b[j1..j2]` should be inserted at `a[i1..i2]` (`i1 == i2` in this case).
/// * `Equal`: `a[i1..i2]` is equal to `b[j1..j2]`.
pub fn as_tag_tuple(&self) -> (DiffTag, Range<usize>, Range<usize>) {
match *self {
DiffOp::Equal {
old_index,
new_index,
len,
} => (
DiffTag::Equal,
old_index..old_index + len,
new_index..new_index + len,
),
DiffOp::Delete {
old_index,
new_index,
old_len,
} => (
DiffTag::Delete,
old_index..old_index + old_len,
new_index..new_index,
),
DiffOp::Insert {
old_index,
new_index,
new_len,
} => (
DiffTag::Insert,
old_index..old_index,
new_index..new_index + new_len,
),
DiffOp::Replace {
old_index,
old_len,
new_index,
new_len,
} => (
DiffTag::Replace,
old_index..old_index + old_len,
new_index..new_index + new_len,
),
}
}
/// Apply this operation to a diff hook.
pub fn apply_to_hook<D: DiffHook>(&self, d: &mut D) -> Result<(), D::Error> {
match *self {
DiffOp::Equal {
old_index,
new_index,
len,
} => d.equal(old_index, new_index, len),
DiffOp::Delete {
old_index,
old_len,
new_index,
} => d.delete(old_index, old_len, new_index),
DiffOp::Insert {
old_index,
new_index,
new_len,
} => d.insert(old_index, new_index, new_len),
DiffOp::Replace {
old_index,
old_len,
new_index,
new_len,
} => d.replace(old_index, old_len, new_index, new_len),
}
}
/// Iterates over all changes encoded in the diff op against old and new
/// sequences.
///
/// `old` and `new` are two indexable objects like the types you pass to
/// the diffing algorithm functions.
///
/// ```rust
/// use similar::{ChangeTag, Algorithm};
/// use similar::capture_diff_slices;
/// let old = vec!["foo", "bar", "baz"];
/// let new = vec!["foo", "bar", "blah"];
/// let ops = capture_diff_slices(Algorithm::Myers, &old, &new);
/// let changes: Vec<_> = ops
/// .iter()
/// .flat_map(|x| x.iter_changes(&old, &new))
/// .map(|x| (x.tag(), x.value()))
/// .collect();
/// assert_eq!(changes, vec![
/// (ChangeTag::Equal, "foo"),
/// (ChangeTag::Equal, "bar"),
/// (ChangeTag::Delete, "baz"),
/// (ChangeTag::Insert, "blah"),
/// ]);
/// ```
pub fn iter_changes<'lookup, Old, New, T>(
&self,
old: &'lookup Old,
new: &'lookup New,
) -> ChangesIter<'lookup, Old, New, T>
where
Old: Index<usize, Output = T> + ?Sized,
New: Index<usize, Output = T> + ?Sized,
{
ChangesIter::new(old, new, *self)
}
/// Given a diffop yields the changes it encodes against the given slices.
///
/// This is similar to [`DiffOp::iter_changes`] but instead of yielding the
/// individual changes it yields consequitive changed slices.
///
/// This will only ever yield a single tuple or two tuples in case a
/// [`DiffOp::Replace`] operation is passed.
///
/// ```rust
/// use similar::{ChangeTag, Algorithm};
/// use similar::capture_diff_slices;
/// let old = vec!["foo", "bar", "baz"];
/// let new = vec!["foo", "bar", "blah"];
/// let ops = capture_diff_slices(Algorithm::Myers, &old, &new);
/// let changes: Vec<_> = ops.iter().flat_map(|x| x.iter_slices(&old, &new)).collect();
/// assert_eq!(changes, vec![
/// (ChangeTag::Equal, &["foo", "bar"][..]),
/// (ChangeTag::Delete, &["baz"][..]),
/// (ChangeTag::Insert, &["blah"][..]),
/// ]);
/// ```
///
/// Due to lifetime restrictions it's currently impossible for the
/// returned slices to outlive the lookup.
pub fn iter_slices<'lookup, Old, New, T>(
&self,
old: &'lookup Old,
new: &'lookup New,
) -> impl Iterator<Item = (ChangeTag, &'lookup T)>
where
T: 'lookup + ?Sized,
Old: Index<Range<usize>, Output = T> + ?Sized,
New: Index<Range<usize>, Output = T> + ?Sized,
{
match *self {
DiffOp::Equal { old_index, len, .. } => {
Some((ChangeTag::Equal, &old[old_index..old_index + len]))
.into_iter()
.chain(None)
}
DiffOp::Insert {
new_index, new_len, ..
} => Some((ChangeTag::Insert, &new[new_index..new_index + new_len]))
.into_iter()
.chain(None),
DiffOp::Delete {
old_index, old_len, ..
} => Some((ChangeTag::Delete, &old[old_index..old_index + old_len]))
.into_iter()
.chain(None),
DiffOp::Replace {
old_index,
old_len,
new_index,
new_len,
} => Some((ChangeTag::Delete, &old[old_index..old_index + old_len]))
.into_iter()
.chain(Some((
ChangeTag::Insert,
&new[new_index..new_index + new_len],
))),
}
}
pub(crate) fn is_empty(&self) -> bool {
let (_, old, new) = self.as_tag_tuple();
is_empty_range(&old) && is_empty_range(&new)
}
pub(crate) fn shift_left(&mut self, adjust: usize) {
self.adjust((adjust, true), (0, false));
}
pub(crate) fn shift_right(&mut self, adjust: usize) {
self.adjust((adjust, false), (0, false));
}
pub(crate) fn grow_left(&mut self, adjust: usize) {
self.adjust((adjust, true), (adjust, false));
}
pub(crate) fn grow_right(&mut self, adjust: usize) {
self.adjust((0, false), (adjust, false));
}
pub(crate) fn shrink_left(&mut self, adjust: usize) {
self.adjust((0, false), (adjust, true));
}
pub(crate) fn shrink_right(&mut self, adjust: usize) {
self.adjust((adjust, false), (adjust, true));
}
fn adjust(&mut self, adjust_offset: (usize, bool), adjust_len: (usize, bool)) {
#[inline(always)]
fn modify(val: &mut usize, adj: (usize, bool)) {
if adj.1 {
*val -= adj.0;
} else {
*val += adj.0;
}
}
match self {
DiffOp::Equal {
old_index,
new_index,
len,
} => {
modify(old_index, adjust_offset);
modify(new_index, adjust_offset);
modify(len, adjust_len);
}
DiffOp::Delete {
old_index,
old_len,
new_index,
} => {
modify(old_index, adjust_offset);
modify(old_len, adjust_len);
modify(new_index, adjust_offset);
}
DiffOp::Insert {
old_index,
new_index,
new_len,
} => {
modify(old_index, adjust_offset);
modify(new_index, adjust_offset);
modify(new_len, adjust_len);
}
DiffOp::Replace {
old_index,
old_len,
new_index,
new_len,
} => {
modify(old_index, adjust_offset);
modify(old_len, adjust_len);
modify(new_index, adjust_offset);
modify(new_len, adjust_len);
}
}
}
}
#[cfg(feature = "text")]
mod text_additions {
use super::*;
use crate::text::DiffableStr;
use std::borrow::Cow;
/// The text interface can produce changes over [`DiffableStr`] implementing
/// values. As those are generic interfaces for different types of strings
/// utility methods to make working with standard rust strings more enjoyable.
impl<'s, T: DiffableStr + ?Sized> Change<&'s T> {
/// Returns the value as string if it is utf-8.
pub fn as_str(&self) -> Option<&'s str> {
T::as_str(self.value)
}
/// Returns the value (lossy) decoded as utf-8 string.
pub fn to_string_lossy(&self) -> Cow<'s, str> {
T::to_string_lossy(self.value)
}
/// Returns `true` if this change does not end in a newline and must be
/// followed up by one if line based diffs are used.
///
/// The [`std::fmt::Display`] implementation of [`Change`] will automatically
/// insert a newline after the value if this is true.
pub fn missing_newline(&self) -> bool {
!T::ends_with_newline(self.value)
}
}
impl<'s, T: DiffableStr + ?Sized> fmt::Display for Change<&'s T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(
f,
"{}{}",
self.to_string_lossy(),
if self.missing_newline() { "\n" } else { "" }
)
}
}
}
|