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proposal: bufio: add (*reader).ResetWithSize to initialize as fields and use with Peek #61146

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Jorropo opened this issue Jul 2, 2023 · 1 comment
Open

proposal: bufio: add (*reader).ResetWithSize to initialize as fields and use with Peek #61146

Jorropo opened this issue Jul 2, 2023 · 1 comment
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@Jorropo
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Jorropo commented Jul 2, 2023 •
edited

I would like to embed the bufio as reader in my fields to avoid pointers to pointers, reduce allocations and memory used:

 type mything struct{
  someStuff thisIsSomeStuff
- reader *bufio.Reader
+ reader bufio.Reader
 }

This is doable by calling thing.reader.Reset(r) however I also need to use (*reader).Peek but I can't specify the size.
So instead I write: thing.reader = *bufio.NewReaderWithSize(r, maximumBlockSize) which feels wrong.

Proposal:

// ResetWithSize is like [Reset] but it will allocate a new buffer if the current buffer is smaller than required.
func (*Reader) ResetWithSize(r io.Reader, size int)

Potential implementation:

// ResetWithSize is like [Reset] but it will allocate a new buffer if the current buffer is smaller than required.
func (b *Reader) ResetWithSize(r io.Reader, size int) {
 if len(b.buf) < size {
  b.buf = make([]byte, size)
 }
 b.reset(r)
}
@gopherbot gopherbot added this to the Proposal milestone Jul 2, 2023
@bcmills
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bcmills commented Jul 5, 2023

It does seem strange that Reset allocates a new buffer but hard-codes defaultBufSize. 🤔

I wonder if it would be better to provide a more general Resize(size int) method, with the constraint that the new size must be less than or equal to the number of bytes already buffered (as reported by Buffered). It seems like that would work equally well for this use-case, and may address others as well.

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@bcmills @gopherbot @Jorropo