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|
use std::cell::Cell;
use std::fmt;
/// Format all iterator elements lazily, separated by `sep`.
///
/// The format value can only be formatted once, after that the iterator is
/// exhausted.
///
/// See [`.format_with()`](crate::Itertools::format_with) for more information.
pub struct FormatWith<'a, I, F> {
sep: &'a str,
/// FormatWith uses interior mutability because Display::fmt takes &self.
inner: Cell<Option<(I, F)>>,
}
/// Format all iterator elements lazily, separated by `sep`.
///
/// The format value can only be formatted once, after that the iterator is
/// exhausted.
///
/// See [`.format()`](crate::Itertools::format)
/// for more information.
pub struct Format<'a, I> {
sep: &'a str,
/// Format uses interior mutability because Display::fmt takes &self.
inner: Cell<Option<I>>,
}
pub fn new_format<I, F>(iter: I, separator: &str, f: F) -> FormatWith<'_, I, F>
where
I: Iterator,
F: FnMut(I::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result,
{
FormatWith {
sep: separator,
inner: Cell::new(Some((iter, f))),
}
}
pub fn new_format_default<I>(iter: I, separator: &str) -> Format<'_, I>
where
I: Iterator,
{
Format {
sep: separator,
inner: Cell::new(Some(iter)),
}
}
impl<'a, I, F> fmt::Display for FormatWith<'a, I, F>
where
I: Iterator,
F: FnMut(I::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let (mut iter, mut format) = match self.inner.take() {
Some(t) => t,
None => panic!("FormatWith: was already formatted once"),
};
if let Some(fst) = iter.next() {
format(fst, &mut |disp: &dyn fmt::Display| disp.fmt(f))?;
iter.try_for_each(|elt| {
if !self.sep.is_empty() {
f.write_str(self.sep)?;
}
format(elt, &mut |disp: &dyn fmt::Display| disp.fmt(f))
})?;
}
Ok(())
}
}
impl<'a, I> Format<'a, I>
where
I: Iterator,
{
fn format(
&self,
f: &mut fmt::Formatter,
cb: fn(&I::Item, &mut fmt::Formatter) -> fmt::Result,
) -> fmt::Result {
let mut iter = match self.inner.take() {
Some(t) => t,
None => panic!("Format: was already formatted once"),
};
if let Some(fst) = iter.next() {
cb(&fst, f)?;
iter.try_for_each(|elt| {
if !self.sep.is_empty() {
f.write_str(self.sep)?;
}
cb(&elt, f)
})?;
}
Ok(())
}
}
macro_rules! impl_format {
($($fmt_trait:ident)*) => {
$(
impl<'a, I> fmt::$fmt_trait for Format<'a, I>
where I: Iterator,
I::Item: fmt::$fmt_trait,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self.format(f, fmt::$fmt_trait::fmt)
}
}
)*
}
}
impl_format! {Display Debug UpperExp LowerExp UpperHex LowerHex Octal Binary Pointer}
impl<'a, I, F> Clone for FormatWith<'a, I, F>
where
(I, F): Clone,
{
fn clone(&self) -> Self {
struct PutBackOnDrop<'r, 'a, I, F> {
into: &'r FormatWith<'a, I, F>,
inner: Option<(I, F)>,
}
// This ensures we preserve the state of the original `FormatWith` if `Clone` panics
impl<'r, 'a, I, F> Drop for PutBackOnDrop<'r, 'a, I, F> {
fn drop(&mut self) {
self.into.inner.set(self.inner.take())
}
}
let pbod = PutBackOnDrop {
inner: self.inner.take(),
into: self,
};
Self {
inner: Cell::new(pbod.inner.clone()),
sep: self.sep,
}
}
}
impl<'a, I> Clone for Format<'a, I>
where
I: Clone,
{
fn clone(&self) -> Self {
struct PutBackOnDrop<'r, 'a, I> {
into: &'r Format<'a, I>,
inner: Option<I>,
}
// This ensures we preserve the state of the original `FormatWith` if `Clone` panics
impl<'r, 'a, I> Drop for PutBackOnDrop<'r, 'a, I> {
fn drop(&mut self) {
self.into.inner.set(self.inner.take())
}
}
let pbod = PutBackOnDrop {
inner: self.inner.take(),
into: self,
};
Self {
inner: Cell::new(pbod.inner.clone()),
sep: self.sep,
}
}
}
|
