Update ring_buffer.go

[yshngg]

The read tail is len-1 values back from the read head.

[peterbourgon]

tailidx := headidx - rb.len + 1

Is the read tail (i.e. tailidx) not len+1 values back from the read head (i.e. headidx)?

[yshngg]

Hi @peterbourgon , thank you for responding!

Oh, sorry, I misunderstood "back from". I think you meant "back relative to the read direction".

[yshngg]

Sorry to bother you again — I think I'm getting confused once more. 😂

This seems to be a comment error.

tailidx := headidx - rb.len + 1
// is equivalent to
tailidx := headidx - (rb.len - 1)

So the read tail is rb.len-1 values back from the read head.

Example:

- Partially filled buffer (e.g., len=3, cap=5):
  Buffer: [1, 2, 3, _, _]
  headidx: 2 (value 3)
  tailidx: 0 (value 1)
  The read tail is 2 values back from the read head.

- Fully filled buffer (e.g., len=5, cap=5):
  Buffer: [1, 2, 3, 4, 5]
  headidx: 4 (value 5)
  tailidx: 0 (value 1)
  The read tail is 4 values back from the read head.

[peterbourgon]

You're right, the comment should read len-1, and the expr should be tailidx := headidx - (rb.len - 1). Please do make those changes in the PR, and sorry for the back-and-forth.

[yshngg]

@peterbourgon , review please. 🙏

[peterbourgon]

Thanks!