With this if foo is a mutable slice, it is possible to do
foo.into_buf().put_u32_le(42);
Before this patch into_buf would create a Cursor<&'a [u8]> and it
would not be possible to write into it.
The intent of the license was to dual license MIT & Apache 2.0. However,
the messaging was copy / pasted from rust-lang.
Clarify the license as exclusively MIT.
Fixes#215
* Recycle space when reserving from Vec-backed Bytes
BytesMut::reserve, when called on a BytesMut instance which is backed by
a non-shared Vec<u8>, would previously just delegate to Vec::reserve
regardless of the current location in the buffer. If the Bytes is
actually the trailing component of a larger Vec, then the unused space
won't be recycled. In applications which continually move the pointer
forward to consume data as it comes in, this can cause the underlying
buffer to get extremely large.
This commit checks whether there's extra space at the start of the
backing Vec in this case, and reuses the unused space if possible
instead of allocating.
* Avoid excessive copying when reusing Vec space
Only reuse space in a Vec-backed Bytes when doing so would gain back
more than half of the current capacity. This avoids excessive copy
operations when a large buffer is almost (but not completely) full.
* Recycle space when reserving from Vec-backed Bytes
BytesMut::reserve, when called on a BytesMut instance which is backed by
a non-shared Vec<u8>, would previously just delegate to Vec::reserve
regardless of the current location in the buffer. If the Bytes is
actually the trailing component of a larger Vec, then the unused space
won't be recycled. In applications which continually move the pointer
forward to consume data as it comes in, this can cause the underlying
buffer to get extremely large.
This commit checks whether there's extra space at the start of the
backing Vec in this case, and reuses the unused space if possible
instead of allocating.
* Avoid excessive copying when reusing Vec space
Only reuse space in a Vec-backed Bytes when doing so would gain back
more than half of the current capacity. This avoids excessive copy
operations when a large buffer is almost (but not completely) full.
This patch fixes the `copy_to_slice` function, rectifying the logic.
However, the incorrect code does not result in incorrect behavior as the
only case `cnt != src.len()` is during the final iteration, and since
`src.len()` is greater than `cnt` in that case, `off` will be
incremented by too much, but this will still trigger the `off <
dst.len()` condition.
The only danger is `src.len()` could cause an overflow.
* make Buf and BufMut usable as trait objects
- All the `get_*` and `put_*` methods that take `T: ByteOrder` have
a `where Self: Sized` bound added, so that they are only usable from
sized types. It was impossible to make `Buf` or `BufMut` into trait
objects before, so this change doesn't break anyone.
- Add `get_n_be`/`get_n_le`/`put_n_be`/`put_n_le` methods that can be
used on trait objects.
- Deprecate the export of `ByteOrder` and methods generic on it.
* remove deprecated ByteOrder methods
Removes the `_be` suffix from all methods, implying that the default
people should use is network endian.
- All the `get_*` and `put_*` methods that take `T: ByteOrder` have
a `where Self: Sized` bound added, so that they are only usable from
sized types. It was impossible to make `Buf` or `BufMut` into trait
objects before, so this change doesn't break anyone.
- Add `get_n_be`/`get_n_le`/`put_n_be`/`put_n_le` methods that can be
used on trait objects.
- Deprecate the export of `ByteOrder` and methods generic on it.
Fixes#163
If `shallow_clone` is called with `&mut self`, and `Bytes` contains
`Vec`, then expensive CAS can be avoided, because no other thread
have references to this `Bytes` object.
Bench `split_off_and_drop` difference:
Before the diff:
```
test split_off_and_drop ... bench: 91,858 ns/iter (+/- 17,401)
```
With the diff:
```
test split_off_and_drop ... bench: 81,162 ns/iter (+/- 17,603)
```
* Compact Bytes original capacity representation
In order to avoid unnecessary allocations, a `Bytes` structure remembers
the capacity with which it was first created. When a reserve operation
is issued, this original capacity value is used to as a baseline for
reallocating new storage.
Previously, this original capacity value was stored in its raw form. In
other words, the original capacity `usize` was stored as is. In order to
reclaim some `Bytes` internal storage space for additional features,
this original capacity value is compressed from requiring 16 bits to 3.
To do this, instead of storing the exact original capacity. The original
capacity is rounded down to the nearest power of two. If the original
capacity is less than 1024, then it is rounded down to zero. This
roughly means that the original capacity is now stored as a table:
0 => 0
1 => 1k
2 => 2k
3 => 4k
4 => 8k
5 => 16k
6 => 32k
7 => 64k
For the purposes that the original capacity feature was introduced, this
is sufficient granularity.
* Provide `advance` on Bytes and BytesMut
This is the `advance` function that would be part of a `Buf`
implementation. However, `Bytes` and `BytesMut` cannot impl `Buf` until
the next breaking release.
The implementation uses the additional storage made available by the
previous commit to store the number of bytes that the view was advanced.
The `ptr` pointer will point to the start of the window, avoiding any
pointer arithmetic when dereferencing the `Bytes` handle.
* Inner: make uninitialized construction explicit
* Remove Inner2
* Remove unnecessary transmutes
* Use AtomicPtr::get_mut where possible
* Some minor tweaks
Carl Lerche