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//! [Fragment] struct and implementation for dealing with fragments of source code.
use super::SourceRef;
use derive_more::Display;
use std::{ops::Range, str::Chars, sync::Arc};
#[cfg(doc)]
use crate::source_tracking::source::Source;
/// A fragment of source code.
///
/// This can be part of (or all of) a [Source].
#[derive(Clone, Debug, Display)]
#[display("{}", "self.as_str()")]
pub struct Fragment {
/// The [Source] that this fragment is in.
pub source: SourceRef,
/// Fragments are represented using byte ranges in the [Source] referenced by [Fragment::source].
///
/// This [Fragment] is considered invalid if this range is out of order or either end of it is not
/// on a char boundary in source according to [str::is_char_boundary].
pub range: Range<usize>,
}
impl Fragment {
/// Check that this [Fragment] is valid, and references a real existing (though possibly empty) part of
/// the [Fragment::source].
pub fn is_valid(&self) -> bool {
// Get a string reference to the whole source.
let source_as_str: &str = self.source.source().as_ref();
// Check validity.
self.range.end >= self.range.start
&& source_as_str.is_char_boundary(self.range.start)
&& source_as_str.is_char_boundary(self.range.end)
}
/// Get the [str] represented by this [Fragment].
///
/// # Panics
/// - This will [panic] in the unlikely event that [Fragment::range] is out of bounds or lands between char
/// boundaries for [Fragment::source].
pub fn as_str(&self) -> &str {
&self.source.source().as_str()[self.range.clone()]
}
/// Get the length (in bytes) of this [Fragment].
/// Does not check this [Fragment] for validity.
pub const fn len(&self) -> usize {
self.range.end.saturating_sub(self.range.start)
}
/// Check if this fragment has a [`Fragment::len`] `== 0`.
/// Does not check this [Fragment] for validity.
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
/// Check if this fragment is empty at the end of it's source.
///
/// Uses [debug_assert] to check for validity.
pub fn is_empty_at_end_of_source(&self) -> bool {
debug_assert!(self.is_valid());
self.source.source().as_str().len() <= self.range.start
}
/// Return true if this [Fragment] entirely contains another [Fragment] and they're from the same [Source] by
/// [Source::id].
///
/// If `other` is empty, it can still be considered to be contained in this [Fragment] if its
/// [Fragment::range] is entirely within `self`'s [Fragment::range] (basically whether the location of the empty
/// fragment is in this one).
pub fn contains(&self, other: &Self) -> bool {
self.source.id == other.source.id
&& self.range.start <= other.range.start
&& self.range.end >= other.range.end
}
/// Get the number of bytes between the beginning of `origin` and the beginning of `self`.
///
/// # Panics:
/// - Panics if `self` is not a [Fragment] within `origin` according to [`Fragment::contains`].
pub fn offset_from(&self, origin: &Self) -> usize {
if !origin.contains(self) {
panic!("This fragment must be contained in the original fragment");
}
self.range.start - origin.range.start
}
/// Get a [Chars] [Iterator] over the [char]acters in this [Fragment].
pub fn chars(&self) -> Chars<'_> {
self.as_str().chars()
}
/// Get a sub-fragment of this fragment (see [Fragment::contains]) with the whitespace at either end trimmed off.
/// This will return the fragment unchanged if it is empty.
///
/// This calls [Fragment::trim_start] and then [Fragment::trim_end] internally and should match the behavior of
/// [str::trim].
///
/// If this returns an empty [Fragment] it will be at the end of the parent [Fragment].
pub fn trimmed(self) -> Self {
self.trim_start().trim_end()
}
/// Get a sub-fragment of this fragment (see [Fragment::contains]) with the whitespace trimmed off the end.
/// This will return it unchanged if empty.
///
/// See [str::trim_end] for exact behaviors.
pub fn trim_end(mut self) -> Self {
// Get the string representation of this fragment.
let original_str: &str = self.as_str();
// Trim it.
let trimmed_str: &str = original_str.trim_end();
// Calculate the new end of the range.
let new_end: usize = self.range.start + trimmed_str.len();
// Update self.
self.range = self.range.start..new_end;
// Return the updated self.
self
}
/// Get a sub-fragment of this fragment (see [Fragment::contains]) with the whitespace trimmed off the start.
/// This will return it unchanged if empty.
///
/// See [str::trim_start] for exact behaviors.
pub fn trim_start(mut self) -> Self {
// Get the string representation of this fragment.
let original_str: &str = self.as_str();
// Trim it.
let trimmed_str: &str = original_str.trim_start();
// Calculate the new start of the range.
let new_start: usize = self.range.end - trimmed_str.len();
// Update self.
self.range = new_start..self.range.end;
// Return the updated self.
self
}
/// Split this [Fragment] into two sub-[Fragment]s, the left containing the first `bytes_from_start`
/// bytes, and the right containing the rest.
///
/// # Panics
/// - This will panic if the provided `bytes_from_start` does not land on a unicode character boundary or is larger
/// than the length of this fragment according to [str::is_char_boundary].
pub fn split_at(&self, bytes_from_start: usize) -> (Self, Self) {
// Check boundaries.
if !self.as_str().is_char_boundary(bytes_from_start) {
panic!("Cannot split in the middle of a unicode character");
}
self.split_at_unchecked(bytes_from_start)
}
/// This is the same as [Fragment::split_at] except it does not check that the created fragments are valid or
/// that either can call [Fragment::as_str] without panicking.
/// Use with caution.
///
/// Note that this is not technically `unsafe`, since all bugs that may emerge from abuse/misuse here are logic
/// bugs (not memory or concurrency bugs).
pub fn split_at_unchecked(&self, bytes_from_start: usize) -> (Self, Self) {
// Calculate ranges.
let left_range: Range<usize> = self.range.start..(self.range.start + bytes_from_start);
let right_range: Range<usize> = (self.range.start + bytes_from_start)..self.range.end;
// Construct fragments.
(
Fragment {
source: self.source.clone(),
range: left_range,
},
Fragment {
source: self.source.clone(),
range: right_range,
},
)
}
/// Move the start of this [Fragment] forward by a given number of bytes.
///
/// # Panics
/// - Panics if the advancing by `bytes` would create an invalid [Fragment].
pub fn advance_by(&mut self, bytes: usize) {
// Bounds check.
if !self.as_str().is_char_boundary(bytes) {
panic!("Advancing by {bytes} bytes would create an invalid fragment.");
}
self.advance_by_unchecked(bytes);
}
/// This is the same as [Fragment::advance_by] except without the bounds checking. Use carefully or the updated
/// [Fragment] will be invalid.
#[inline]
pub fn advance_by_unchecked(&mut self, bytes: usize) {
self.range.start += bytes;
}
/// Retain up to `bytes` bytes of this [Fragment].
///
/// # Panics
/// - Panics if the updated [Fragment] would be invalid.
pub fn retain(&mut self, bytes: usize) {
// Bounds check.
if !self.as_str().is_char_boundary(bytes) {
panic!("Retaining to {bytes} bytes would create an invalid fragment.");
}
self.retain_unchecked(bytes);
}
/// This is the same as [Fragment::retain] except without the bounds checking. Use carefully or the updated
/// [Fragment] will be invalid.
#[inline]
pub fn retain_unchecked(&mut self, bytes: usize) {
self.range.end = self.range.start + bytes;
}
/// Get a [Range] of line indices (0-indexed, see [Source::get_line]) that this fragment overlaps.
pub fn line_indices(&self) -> Range<usize> {
let start_line_index: usize = self.source.line_index(self.range.start);
// Subtract one when doing the end because if this fragment ends at the end of a line, we don't want to include
// the next line (obo -- range is exclusive).
let ending_line_index: usize = self.source.line_index(self.range.end - 1);
// Return the range.
start_line_index..ending_line_index
}
/// Get the line number (not index) that this line starts on.
///
/// This re-calculates [Fragment::line_indices], which may be expensive on very large files, so use with care.
pub fn starts_on_line(&self) -> usize {
self.line_indices().start + 1
}
/// Get the number of bytes between the start of the line that this [Fragment] starts on and the start of this
/// [Fragment]
pub fn starting_col_index(&self) -> usize {
let line_start_index = Arc::clone(&self.source)
.get_line(self.line_indices().start)
.range
.start;
self.range.start - line_start_index
}
/// Compute the "cover" over two [Fragment]s -- that is, the [Fragment] containing both of them and all the source
/// code in between.
///
/// # Panics
/// - If the [Fragment]s are from different sources.
pub fn cover(lhs: Fragment, rhs: Fragment) -> Fragment {
use std::cmp;
assert_eq!(lhs.source.id, rhs.source.id, "fragments must be from same source");
Fragment {
source: lhs.source,
range: cmp::min(lhs.range.start, rhs.range.start)
..cmp::max(lhs.range.end, rhs.range.end),
}
}
}
impl PartialEq for Fragment {
/// Fragment equality is based on referencing the same [Source] using [Arc::ptr_eq] and having the same
/// [Fragment::range].
fn eq(&self, other: &Self) -> bool {
self.source.id == other.source.id && self.range == other.range
}
}
impl Eq for Fragment {}
#[cfg(test)]
mod tests {
use super::Fragment;
use crate::source_tracking::{filename::FileName, source::Source};
use std::sync::Arc;
/// Utility function to create a one-off fragment over a static string.
fn from_static(s: &'static str) -> Fragment {
let source = Source::new_from_static_str(FileName::None, s);
let arc = Arc::new(source);
Fragment {
range: 0..arc.source().as_ref().len(),
source: arc,
}
}
#[test]
fn test_split_single() {
let a = from_static("+");
let (left, right) = a.split_at(1);
assert_eq!(left.as_str(), "+");
assert_eq!(right.as_str(), "");
}
#[test]
fn test_offset_from() {
let a = from_static("abcde");
let (b, c) = a.split_at(2);
assert_eq!(b.offset_from(&a), 0);
assert_eq!(c.offset_from(&a), 2);
}
#[test]
#[should_panic]
fn test_offset_panics() {
let a = from_static("abc");
let b = from_static("def");
a.offset_from(&b);
}
#[test]
fn test_trimmed_is_contained() {
let a = from_static(" aa aa ");
let b = a.clone().trimmed();
assert!(a.contains(&b));
assert_eq!(b.len(), 5);
}
#[test]
fn trimmed_empty() {
let empty = from_static("");
assert_eq!(empty.clone().trimmed(), empty);
}
#[test]
fn trimmed_whitespace() {
let w = from_static(" ");
assert!(w.clone().trimmed().is_empty());
}
}