ringidx

Documentation

Overview

Package ringidx provides circular indexing logic for writing a given length of data into a fixed-sized buffer and wrapping around this buffer, overwriting the oldest data. No copying is required so it is highly efficient

Index

• type FIx
  • func (fi *FIx) Idx(i int) int
  • func (fi *FIx) IdxIsValid(i int) bool
  • func (fi *FIx) Shift(n int)
• type Idx
  • func (ri *Idx) Add(n int)
  • func (ri *Idx) Idx(i int) int
  • func (ri *Idx) IdxIsValid(i int) bool
  • func (ri *Idx) LastIdx() int
  • func (ri *Idx) Reset()
  • func (ri *Idx) Shift(n int)

Types

type FIx

type FIx struct {
	Zi  int `desc:"the zero index position -- where logical 0 is in physical buffer"`
	Len int `desc:"the length of the buffer -- wraps around at this modulus"`
}

FIx is a fixed-length ring index structure -- does not grow or shrink dynamically.

func (*FIx) Idx

func (fi *FIx) Idx(i int) int

Idx returns the physical index of the logical index i. i must be < Len.

func (*FIx) IdxIsValid

func (fi *FIx) IdxIsValid(i int) bool

IdxIsValid returns true if given index is valid: >= 0 and < Len

func (*FIx) Shift

func (fi *FIx) Shift(n int)

Shift moves the zero index up by n.

type Idx

type Idx struct {
	StIdx int `` /* 175-byte string literal not displayed */
	Len   int `desc:"the number of items stored starting at StIdx.  Capped at Max"`
	Max   int `desc:"the maximum number of items that can be stored in this ring"`
}

Idx is the ring index structure, maintaining starting index and length into a ring-buffer with maximum length Max. Max must be > 0 and Len <= Max. When adding new items would overflow Max, starting index is shifted over to overwrite the oldest items with the new ones. No moving is ever required -- just a fixed-length buffer of size Max.

func (*Idx) Add

func (ri *Idx) Add(n int)

Add adds given number of items to the ring (n <= Len. Shift is called for Len+n - Max extra items to make room.

func (*Idx) Idx

func (ri *Idx) Idx(i int) int

Idx returns the index of the i'th item starting from StIdx. i must be < Len.

func (*Idx) IdxIsValid

func (ri *Idx) IdxIsValid(i int) bool

IdxIsValid returns true if given index is valid: >= 0 and < Len

func (*Idx) LastIdx

func (ri *Idx) LastIdx() int

LastIdx returns the index of the last (most recently added) item in the ring. Only valid if Len > 0

func (*Idx) Reset

func (ri *Idx) Reset()

Reset initializes start index and length to 0

func (*Idx) Shift

func (ri *Idx) Shift(n int)

Shift moves the starting index up by n, and decrements the Len by n as well. This is called prior to adding new items if doing so would exceed Max length.