fix: len(buf) => cap(buf)

[BaiZe1998]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update
• Go Version Update
• Dependency Update

Description

len(buf) must equal to 0 for AvailableBuffer()

// AvailableBuffer returns an empty buffer with b.Available() capacity.
// This buffer is intended to be appended to and
// passed to an immediately succeeding [Writer.Write] call.
// The buffer is only valid until the next write operation on b.
func (b *Writer) AvailableBuffer() []byte {
	return b.buf[b.n:][:0]
}

i think the len(buf) may switch to cap(buf) ?

https://github.com/gorilla/websocket/blob/main/server.go#L208

buf := brw.Writer.AvailableBuffer()

var writeBuf []byte
if u.WriteBufferPool == nil && u.WriteBufferSize == 0 && len(buf) >= maxFrameHeaderSize+256 {
    // Reuse hijacked write buffer as connection buffer.
    writeBuf = buf
}

Related Tickets & Documents

• Related Issue #
• Closes #

Added/updated tests?

• Yes
• No, and this is why: please replace this line with details on why tests
  have not been included
• I need help with writing tests

Run verifications and test

• make verify is passing
• make test is passing

[FZambia]

Please note, it seems not enough because the code here will panic due to slice bounds out of range (try using conn.WriteMessage).

It seems that 8915bad introduced performance regression here because buffer is not really re-used now.

Also, the mentioned commit disabled test - 8915bad#diff-53170cac6baf0bf02f3aaa3994259ea4cffaaf2498e768fb7e03cf9f752af96cR124