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use crate::{
body::SizeHint,
http::header::{CONTENT_LENGTH, HeaderMap},
};
use super::frame::headers;
pub(crate) trait BodySize {
/// Parse content-length from headers.
/// Returns `Err(())` if the header is present but malformed (RFC 7540 ยง8.1.2.6).
fn from_header(headers: &HeaderMap, is_end_stream: bool) -> Result<Self, ()>
where
Self: Sized;
/// Subtract `len` bytes received in a DATA frame.
/// Returns `Err(())` if this would underflow (overflow: more data than declared).
fn dec(&mut self, len: usize) -> Result<(), ()>;
/// Returns `Err` if remaining != 0 at END_STREAM (underflow: less data than declared).
fn ensure_zero(&self) -> Result<(), ()>;
}
impl BodySize for SizeHint {
fn from_header(headers: &HeaderMap, is_end_stream: bool) -> Result<Self, ()> {
if is_end_stream {
Ok(Self::None)
} else {
match headers.get(CONTENT_LENGTH) {
Some(v) => {
let s = v.to_str().map_err(|_| ())?;
let len = headers::parse_u64(s.as_bytes())?;
Ok(Self::Exact(len))
}
None => Ok(Self::Unknown),
}
}
}
/// Subtract `len` bytes received in a DATA frame.
/// Returns `Err(())` if this would underflow (overflow: more data than declared).
fn dec(&mut self, len: usize) -> Result<(), ()> {
match self {
Self::Unknown => Ok(()),
Self::None => Err(()),
Self::Exact(rem) => {
*rem = rem.checked_sub(len as u64).ok_or(())?;
Ok(())
}
}
}
/// Returns `Err` if remaining != 0 at END_STREAM (underflow: less data than declared).
fn ensure_zero(&self) -> Result<(), ()> {
match self {
Self::Unknown | Self::None | Self::Exact(0) => Ok(()),
Self::Exact(_) => Err(()),
}
}
}