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//! Shared utilities used by both float and integer formatting.
#![doc(hidden)]
#![unstable(
feature = "numfmt",
reason = "internal routines only exposed for testing",
issue = "none"
)]
/// Formatted parts.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Part<'a> {
/// Given number of zero digits.
Zero(usize),
/// A literal number up to 5 digits.
Num(u16),
/// A verbatim copy of given bytes.
Copy(&'a [u8]),
}
impl<'a> Part<'a> {
/// Returns the exact byte length of given part.
pub fn len(&self) -> usize {
match *self {
Part::Zero(nzeroes) => nzeroes,
Part::Num(v) => v.checked_ilog10().unwrap_or_default() as usize + 1,
Part::Copy(buf) => buf.len(),
}
}
/// Writes a part into the supplied buffer.
/// Returns the number of written bytes, or `None` if the buffer is not enough.
/// (It may still leave partially written bytes in the buffer; do not rely on that.)
pub fn write(&self, out: &mut [u8]) -> Option<usize> {
let len = self.len();
if out.len() >= len {
match *self {
Part::Zero(nzeroes) => {
for c in &mut out[..nzeroes] {
*c = b'0';
}
}
Part::Num(mut v) => {
for c in out[..len].iter_mut().rev() {
*c = b'0' + (v % 10) as u8;
v /= 10;
}
}
Part::Copy(buf) => {
out[..buf.len()].copy_from_slice(buf);
}
}
Some(len)
} else {
None
}
}
}
/// Formatted result containing one or more parts.
/// This can be written to the byte buffer or converted to the allocated string.
#[allow(missing_debug_implementations)]
#[derive(Clone)]
pub struct Formatted<'a> {
/// A byte slice representing a sign, either `""`, `"-"` or `"+"`.
pub sign: &'static str,
/// Formatted parts to be rendered after a sign and optional zero padding.
pub parts: &'a [Part<'a>],
}
impl<'a> Formatted<'a> {
/// Returns the exact byte length of combined formatted result.
pub fn len(&self) -> usize {
self.sign.len() + self.parts.iter().map(|part| part.len()).sum::<usize>()
}
/// Writes all formatted parts into the supplied buffer.
/// Returns the number of written bytes, or `None` if the buffer is not enough.
/// (It may still leave partially written bytes in the buffer; do not rely on that.)
pub fn write(&self, out: &mut [u8]) -> Option<usize> {
out.get_mut(..self.sign.len())?.copy_from_slice(self.sign.as_bytes());
let mut written = self.sign.len();
for part in self.parts {
let len = part.write(&mut out[written..])?;
written += len;
}
Some(written)
}
}
|
