1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155

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
    }
}