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|
//! Reader type for consuming nested TLV records within a DER document.
use crate::{reader::Reader, Error, ErrorKind, Header, Length, Result};
/// Reader type used by [`Reader::read_nested`].
pub struct NestedReader<'i, R> {
/// Inner reader type.
inner: &'i mut R,
/// Nested input length.
input_len: Length,
/// Position within the nested input.
position: Length,
}
impl<'i, 'r, R: Reader<'r>> NestedReader<'i, R> {
/// Create a new nested reader which can read the given [`Length`].
pub(crate) fn new(inner: &'i mut R, len: Length) -> Result<Self> {
if len <= inner.remaining_len() {
Ok(Self {
inner,
input_len: len,
position: Length::ZERO,
})
} else {
Err(ErrorKind::Incomplete {
expected_len: (inner.offset() + len)?,
actual_len: (inner.offset() + inner.remaining_len())?,
}
.at(inner.offset()))
}
}
/// Move the position cursor the given length, returning an error if there
/// isn't enough remaining data in the nested input.
fn advance_position(&mut self, len: Length) -> Result<()> {
let new_position = (self.position + len)?;
if new_position <= self.input_len {
self.position = new_position;
Ok(())
} else {
Err(ErrorKind::Incomplete {
expected_len: (self.inner.offset() + len)?,
actual_len: (self.inner.offset() + self.remaining_len())?,
}
.at(self.inner.offset()))
}
}
}
impl<'i, 'r, R: Reader<'r>> Reader<'r> for NestedReader<'i, R> {
fn input_len(&self) -> Length {
self.input_len
}
fn peek_byte(&self) -> Option<u8> {
if self.is_finished() {
None
} else {
self.inner.peek_byte()
}
}
fn peek_header(&self) -> Result<Header> {
if self.is_finished() {
Err(Error::incomplete(self.offset()))
} else {
// TODO(tarcieri): handle peeking past nested length
self.inner.peek_header()
}
}
fn position(&self) -> Length {
self.position
}
fn read_slice(&mut self, len: Length) -> Result<&'r [u8]> {
self.advance_position(len)?;
self.inner.read_slice(len)
}
fn error(&mut self, kind: ErrorKind) -> Error {
self.inner.error(kind)
}
fn offset(&self) -> Length {
self.inner.offset()
}
fn read_into<'o>(&mut self, out: &'o mut [u8]) -> Result<&'o [u8]> {
self.advance_position(Length::try_from(out.len())?)?;
self.inner.read_into(out)
}
}
|
