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use crate::{Buf, Bytes};
use core::cmp;
/// A `Buf` adapter which limits the bytes read from an underlying buffer.
///
/// This struct is generally created by calling `take()` on `Buf`. See
/// documentation of [`take()`](trait.Buf.html#method.take) for more details.
#[derive(Debug)]
pub struct Take<T> {
inner: T,
limit: usize,
}
pub fn new<T>(inner: T, limit: usize) -> Take<T> {
Take { inner, limit }
}
impl<T> Take<T> {
/// Consumes this `Take`, returning the underlying value.
///
/// # Examples
///
/// ```rust
/// use bytes::{Buf, BufMut};
///
/// let mut buf = b"hello world".take(2);
/// let mut dst = vec![];
///
/// dst.put(&mut buf);
/// assert_eq!(*dst, b"he"[..]);
///
/// let mut buf = buf.into_inner();
///
/// dst.clear();
/// dst.put(&mut buf);
/// assert_eq!(*dst, b"llo world"[..]);
/// ```
pub fn into_inner(self) -> T {
self.inner
}
/// Gets a reference to the underlying `Buf`.
///
/// It is inadvisable to directly read from the underlying `Buf`.
///
/// # Examples
///
/// ```rust
/// use bytes::Buf;
///
/// let buf = b"hello world".take(2);
///
/// assert_eq!(11, buf.get_ref().remaining());
/// ```
pub fn get_ref(&self) -> &T {
&self.inner
}
/// Gets a mutable reference to the underlying `Buf`.
///
/// It is inadvisable to directly read from the underlying `Buf`.
///
/// # Examples
///
/// ```rust
/// use bytes::{Buf, BufMut};
///
/// let mut buf = b"hello world".take(2);
/// let mut dst = vec![];
///
/// buf.get_mut().advance(2);
///
/// dst.put(&mut buf);
/// assert_eq!(*dst, b"ll"[..]);
/// ```
pub fn get_mut(&mut self) -> &mut T {
&mut self.inner
}
/// Returns the maximum number of bytes that can be read.
///
/// # Note
///
/// If the inner `Buf` has fewer bytes than indicated by this method then
/// that is the actual number of available bytes.
///
/// # Examples
///
/// ```rust
/// use bytes::Buf;
///
/// let mut buf = b"hello world".take(2);
///
/// assert_eq!(2, buf.limit());
/// assert_eq!(b'h', buf.get_u8());
/// assert_eq!(1, buf.limit());
/// ```
pub fn limit(&self) -> usize {
self.limit
}
/// Sets the maximum number of bytes that can be read.
///
/// # Note
///
/// If the inner `Buf` has fewer bytes than `lim` then that is the actual
/// number of available bytes.
///
/// # Examples
///
/// ```rust
/// use bytes::{Buf, BufMut};
///
/// let mut buf = b"hello world".take(2);
/// let mut dst = vec![];
///
/// dst.put(&mut buf);
/// assert_eq!(*dst, b"he"[..]);
///
/// dst.clear();
///
/// buf.set_limit(3);
/// dst.put(&mut buf);
/// assert_eq!(*dst, b"llo"[..]);
/// ```
pub fn set_limit(&mut self, lim: usize) {
self.limit = lim
}
}
impl<T: Buf> Buf for Take<T> {
fn remaining(&self) -> usize {
cmp::min(self.inner.remaining(), self.limit)
}
fn chunk(&self) -> &[u8] {
let bytes = self.inner.chunk();
&bytes[..cmp::min(bytes.len(), self.limit)]
}
fn advance(&mut self, cnt: usize) {
assert!(cnt <= self.limit);
self.inner.advance(cnt);
self.limit -= cnt;
}
fn copy_to_bytes(&mut self, len: usize) -> Bytes {
assert!(len <= self.remaining(), "`len` greater than remaining");
let r = self.inner.copy_to_bytes(len);
self.limit -= len;
r
}
}