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
156
157
158
159
160
161
162
163
164
165
#![allow(unknown_lints, unexpected_cfgs)]
#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
#![doc(test(
    no_crate_inject,
    attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
))]
#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]

//! Provides abstractions for working with bytes.
//!
//! The `bytes` crate provides an efficient byte buffer structure
//! ([`Bytes`]) and traits for working with buffer
//! implementations ([`Buf`], [`BufMut`]).
//!
//! # `Bytes`
//!
//! `Bytes` is an efficient container for storing and operating on contiguous
//! slices of memory. It is intended for use primarily in networking code, but
//! could have applications elsewhere as well.
//!
//! `Bytes` values facilitate zero-copy network programming by allowing multiple
//! `Bytes` objects to point to the same underlying memory. This is managed by
//! using a reference count to track when the memory is no longer needed and can
//! be freed.
//!
//! A `Bytes` handle can be created directly from an existing byte store (such as `&[u8]`
//! or `Vec<u8>`), but usually a `BytesMut` is used first and written to. For
//! example:
//!
//! ```rust
//! use bytes::{BytesMut, BufMut};
//!
//! let mut buf = BytesMut::with_capacity(1024);
//! buf.put(&b"hello world"[..]);
//! buf.put_u16(1234);
//!
//! let a = buf.split();
//! assert_eq!(a, b"hello world\x04\xD2"[..]);
//!
//! buf.put(&b"goodbye world"[..]);
//!
//! let b = buf.split();
//! assert_eq!(b, b"goodbye world"[..]);
//!
//! assert_eq!(buf.capacity(), 998);
//! ```
//!
//! In the above example, only a single buffer of 1024 is allocated. The handles
//! `a` and `b` will share the underlying buffer and maintain indices tracking
//! the view into the buffer represented by the handle.
//!
//! See the [struct docs](`Bytes`) for more details.
//!
//! # `Buf`, `BufMut`
//!
//! These two traits provide read and write access to buffers. The underlying
//! storage may or may not be in contiguous memory. For example, `Bytes` is a
//! buffer that guarantees contiguous memory, but a [rope] stores the bytes in
//! disjoint chunks. `Buf` and `BufMut` maintain cursors tracking the current
//! position in the underlying byte storage. When bytes are read or written, the
//! cursor is advanced.
//!
//! [rope]: https://en.wikipedia.org/wiki/Rope_(data_structure)
//!
//! ## Relation with `Read` and `Write`
//!
//! At first glance, it may seem that `Buf` and `BufMut` overlap in
//! functionality with [`std::io::Read`] and [`std::io::Write`]. However, they
//! serve different purposes. A buffer is the value that is provided as an
//! argument to `Read::read` and `Write::write`. `Read` and `Write` may then
//! perform a syscall, which has the potential of failing. Operations on `Buf`
//! and `BufMut` are infallible.

extern crate alloc;

#[cfg(feature = "std")]
extern crate std;

pub mod buf;
pub use crate::buf::{Buf, BufMut};

mod bytes;
mod bytes_mut;
mod fmt;
mod loom;
pub use crate::bytes::Bytes;
pub use crate::bytes_mut::BytesMut;

// Optional Serde support
#[cfg(feature = "serde")]
mod serde;

#[inline(never)]
#[cold]
fn abort() -> ! {
    #[cfg(feature = "std")]
    {
        std::process::abort();
    }

    #[cfg(not(feature = "std"))]
    {
        struct Abort;
        impl Drop for Abort {
            fn drop(&mut self) {
                panic!();
            }
        }
        let _a = Abort;
        panic!("abort");
    }
}

#[inline(always)]
#[cfg(feature = "std")]
fn saturating_sub_usize_u64(a: usize, b: u64) -> usize {
    use core::convert::TryFrom;
    match usize::try_from(b) {
        Ok(b) => a.saturating_sub(b),
        Err(_) => 0,
    }
}

#[inline(always)]
#[cfg(feature = "std")]
fn min_u64_usize(a: u64, b: usize) -> usize {
    use core::convert::TryFrom;
    match usize::try_from(a) {
        Ok(a) => usize::min(a, b),
        Err(_) => b,
    }
}

/// Panic with a nice error message.
#[cold]
fn panic_advance(idx: usize, len: usize) -> ! {
    panic!(
        "advance out of bounds: the len is {} but advancing by {}",
        len, idx
    );
}

#[cold]
fn panic_does_not_fit(size: usize, nbytes: usize) -> ! {
    panic!(
        "size too large: the integer type can fit {} bytes, but nbytes is {}",
        size, nbytes
    );
}

/// Precondition: dst >= original
///
/// The following line is equivalent to:
///
/// ```rust,ignore
/// self.ptr.as_ptr().offset_from(ptr) as usize;
/// ```
///
/// But due to min rust is 1.39 and it is only stabilized
/// in 1.47, we cannot use it.
#[inline]
fn offset_from(dst: *const u8, original: *const u8) -> usize {
    dst as usize - original as usize
}