930 lines
16 KiB
Go
930 lines
16 KiB
Go
// Copyright 2014 The b Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package b
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import (
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"fmt"
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"io"
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"sync"
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)
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const (
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kx = 32 //TODO benchmark tune this number if using custom key/value type(s).
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kd = 32 //TODO benchmark tune this number if using custom key/value type(s).
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)
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func init() {
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if kd < 1 {
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panic(fmt.Errorf("kd %d: out of range", kd))
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}
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if kx < 2 {
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panic(fmt.Errorf("kx %d: out of range", kx))
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}
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}
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var (
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btDPool = sync.Pool{New: func() interface{} { return &d{} }}
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btEPool = btEpool{sync.Pool{New: func() interface{} { return &Enumerator{} }}}
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btTPool = btTpool{sync.Pool{New: func() interface{} { return &Tree{} }}}
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btXPool = sync.Pool{New: func() interface{} { return &x{} }}
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)
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type btTpool struct{ sync.Pool }
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func (p *btTpool) get(cmp Cmp) *Tree {
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x := p.Get().(*Tree)
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x.cmp = cmp
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return x
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}
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type btEpool struct{ sync.Pool }
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func (p *btEpool) get(err error, hit bool, i int, k int, q *d, t *Tree, ver int64) *Enumerator {
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x := p.Get().(*Enumerator)
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x.err, x.hit, x.i, x.k, x.q, x.t, x.ver = err, hit, i, k, q, t, ver
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return x
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}
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type (
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// Cmp compares a and b. Return value is:
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//
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// < 0 if a < b
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// 0 if a == b
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// > 0 if a > b
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//
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Cmp func(a, b int) int
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d struct { // data page
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c int
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d [2*kd + 1]de
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n *d
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p *d
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}
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de struct { // d element
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k int
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v int
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}
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// Enumerator captures the state of enumerating a tree. It is returned
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// from the Seek* methods. The enumerator is aware of any mutations
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// made to the tree in the process of enumerating it and automatically
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// resumes the enumeration at the proper key, if possible.
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//
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// However, once an Enumerator returns io.EOF to signal "no more
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// items", it does no more attempt to "resync" on tree mutation(s). In
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// other words, io.EOF from an Enumaretor is "sticky" (idempotent).
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Enumerator struct {
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err error
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hit bool
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i int
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k int
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q *d
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t *Tree
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ver int64
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}
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// Tree is a B+tree.
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Tree struct {
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c int
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cmp Cmp
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first *d
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last *d
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r interface{}
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ver int64
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}
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xe struct { // x element
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ch interface{}
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k int
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}
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x struct { // index page
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c int
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x [2*kx + 2]xe
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}
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)
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var ( // R/O zero values
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zd d
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zde de
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ze Enumerator
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zk int
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zt Tree
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zx x
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zxe xe
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)
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func clr(q interface{}) {
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switch x := q.(type) {
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case *x:
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for i := 0; i <= x.c; i++ { // Ch0 Sep0 ... Chn-1 Sepn-1 Chn
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clr(x.x[i].ch)
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}
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*x = zx
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btXPool.Put(x)
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case *d:
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*x = zd
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btDPool.Put(x)
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}
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}
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// -------------------------------------------------------------------------- x
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func newX(ch0 interface{}) *x {
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r := btXPool.Get().(*x)
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r.x[0].ch = ch0
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return r
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}
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func (q *x) extract(i int) {
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q.c--
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if i < q.c {
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copy(q.x[i:], q.x[i+1:q.c+1])
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q.x[q.c].ch = q.x[q.c+1].ch
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q.x[q.c].k = zk // GC
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q.x[q.c+1] = zxe // GC
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}
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}
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func (q *x) insert(i int, k int, ch interface{}) *x {
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c := q.c
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if i < c {
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q.x[c+1].ch = q.x[c].ch
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copy(q.x[i+2:], q.x[i+1:c])
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q.x[i+1].k = q.x[i].k
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}
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c++
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q.c = c
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q.x[i].k = k
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q.x[i+1].ch = ch
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return q
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}
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func (q *x) siblings(i int) (l, r *d) {
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if i >= 0 {
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if i > 0 {
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l = q.x[i-1].ch.(*d)
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}
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if i < q.c {
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r = q.x[i+1].ch.(*d)
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}
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}
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return
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}
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// -------------------------------------------------------------------------- d
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func (l *d) mvL(r *d, c int) {
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copy(l.d[l.c:], r.d[:c])
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copy(r.d[:], r.d[c:r.c])
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l.c += c
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r.c -= c
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}
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func (l *d) mvR(r *d, c int) {
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copy(r.d[c:], r.d[:r.c])
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copy(r.d[:c], l.d[l.c-c:])
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r.c += c
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l.c -= c
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}
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// ----------------------------------------------------------------------- Tree
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// TreeNew returns a newly created, empty Tree. The compare function is used
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// for key collation.
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func TreeNew(cmp Cmp) *Tree {
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return btTPool.get(cmp)
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}
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// Clear removes all K/V pairs from the tree.
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func (t *Tree) Clear() {
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if t.r == nil {
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return
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}
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clr(t.r)
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t.c, t.first, t.last, t.r = 0, nil, nil, nil
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t.ver++
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}
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// Close performs Clear and recycles t to a pool for possible later reuse. No
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// references to t should exist or such references must not be used afterwards.
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func (t *Tree) Close() {
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t.Clear()
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*t = zt
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btTPool.Put(t)
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}
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func (t *Tree) cat(p *x, q, r *d, pi int) {
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t.ver++
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q.mvL(r, r.c)
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if r.n != nil {
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r.n.p = q
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} else {
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t.last = q
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}
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q.n = r.n
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*r = zd
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btDPool.Put(r)
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if p.c > 1 {
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p.extract(pi)
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p.x[pi].ch = q
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return
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}
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switch x := t.r.(type) {
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case *x:
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*x = zx
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btXPool.Put(x)
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case *d:
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*x = zd
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btDPool.Put(x)
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}
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t.r = q
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}
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func (t *Tree) catX(p, q, r *x, pi int) {
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t.ver++
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q.x[q.c].k = p.x[pi].k
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copy(q.x[q.c+1:], r.x[:r.c])
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q.c += r.c + 1
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q.x[q.c].ch = r.x[r.c].ch
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*r = zx
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btXPool.Put(r)
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if p.c > 1 {
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p.c--
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pc := p.c
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if pi < pc {
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p.x[pi].k = p.x[pi+1].k
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copy(p.x[pi+1:], p.x[pi+2:pc+1])
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p.x[pc].ch = p.x[pc+1].ch
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p.x[pc].k = zk // GC
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p.x[pc+1].ch = nil // GC
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}
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return
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}
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switch x := t.r.(type) {
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case *x:
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*x = zx
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btXPool.Put(x)
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case *d:
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*x = zd
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btDPool.Put(x)
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}
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t.r = q
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}
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// Delete removes the k's KV pair, if it exists, in which case Delete returns
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// true.
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func (t *Tree) Delete(k int) (ok bool) {
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pi := -1
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var p *x
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q := t.r
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if q == nil {
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return false
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}
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for {
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var i int
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i, ok = t.find(q, k)
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if ok {
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switch x := q.(type) {
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case *x:
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if x.c < kx && q != t.r {
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x, i = t.underflowX(p, x, pi, i)
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}
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pi = i + 1
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p = x
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q = x.x[pi].ch
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ok = false
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continue
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case *d:
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t.extract(x, i)
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if x.c >= kd {
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return true
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}
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if q != t.r {
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t.underflow(p, x, pi)
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} else if t.c == 0 {
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t.Clear()
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}
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return true
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}
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}
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switch x := q.(type) {
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case *x:
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if x.c < kx && q != t.r {
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x, i = t.underflowX(p, x, pi, i)
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}
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pi = i
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p = x
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q = x.x[i].ch
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case *d:
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return false
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}
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}
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}
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func (t *Tree) extract(q *d, i int) { // (r int) {
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t.ver++
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//r = q.d[i].v // prepared for Extract
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q.c--
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if i < q.c {
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copy(q.d[i:], q.d[i+1:q.c+1])
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}
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q.d[q.c] = zde // GC
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t.c--
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return
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}
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func (t *Tree) find(q interface{}, k int) (i int, ok bool) {
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var mk int
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l := 0
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switch x := q.(type) {
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case *x:
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h := x.c - 1
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for l <= h {
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m := (l + h) >> 1
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mk = x.x[m].k
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switch cmp := t.cmp(k, mk); {
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case cmp > 0:
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l = m + 1
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case cmp == 0:
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return m, true
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default:
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h = m - 1
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}
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}
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case *d:
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h := x.c - 1
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for l <= h {
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m := (l + h) >> 1
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mk = x.d[m].k
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switch cmp := t.cmp(k, mk); {
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case cmp > 0:
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l = m + 1
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case cmp == 0:
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return m, true
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default:
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h = m - 1
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}
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}
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}
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return l, false
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}
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// First returns the first item of the tree in the key collating order, or
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// (zero-value, zero-value) if the tree is empty.
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func (t *Tree) First() (k int, v int) {
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if q := t.first; q != nil {
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q := &q.d[0]
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k, v = q.k, q.v
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}
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return
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}
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// Get returns the value associated with k and true if it exists. Otherwise Get
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// returns (zero-value, false).
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func (t *Tree) Get(k int) (v int, ok bool) {
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q := t.r
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if q == nil {
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return
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}
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for {
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var i int
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if i, ok = t.find(q, k); ok {
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switch x := q.(type) {
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case *x:
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q = x.x[i+1].ch
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continue
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case *d:
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return x.d[i].v, true
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}
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}
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switch x := q.(type) {
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case *x:
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q = x.x[i].ch
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default:
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return
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}
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}
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}
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func (t *Tree) insert(q *d, i int, k int, v int) *d {
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t.ver++
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c := q.c
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if i < c {
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copy(q.d[i+1:], q.d[i:c])
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}
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c++
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q.c = c
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q.d[i].k, q.d[i].v = k, v
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t.c++
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return q
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}
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// Last returns the last item of the tree in the key collating order, or
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// (zero-value, zero-value) if the tree is empty.
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func (t *Tree) Last() (k int, v int) {
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if q := t.last; q != nil {
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q := &q.d[q.c-1]
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k, v = q.k, q.v
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}
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return
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}
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// Len returns the number of items in the tree.
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func (t *Tree) Len() int {
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return t.c
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}
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func (t *Tree) overflow(p *x, q *d, pi, i int, k int, v int) {
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t.ver++
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l, r := p.siblings(pi)
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if l != nil && l.c < 2*kd {
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l.mvL(q, 1)
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t.insert(q, i-1, k, v)
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p.x[pi-1].k = q.d[0].k
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return
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}
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if r != nil && r.c < 2*kd {
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if i < 2*kd {
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q.mvR(r, 1)
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t.insert(q, i, k, v)
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p.x[pi].k = r.d[0].k
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return
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}
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t.insert(r, 0, k, v)
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p.x[pi].k = k
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return
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}
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t.split(p, q, pi, i, k, v)
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}
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// Seek returns an Enumerator positioned on a an item such that k >= item's
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// key. ok reports if k == item.key The Enumerator's position is possibly
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// after the last item in the tree.
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func (t *Tree) Seek(k int) (e *Enumerator, ok bool) {
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q := t.r
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if q == nil {
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e = btEPool.get(nil, false, 0, k, nil, t, t.ver)
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return
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}
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for {
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var i int
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if i, ok = t.find(q, k); ok {
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switch x := q.(type) {
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case *x:
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q = x.x[i+1].ch
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continue
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case *d:
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return btEPool.get(nil, ok, i, k, x, t, t.ver), true
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}
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}
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switch x := q.(type) {
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case *x:
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q = x.x[i].ch
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case *d:
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return btEPool.get(nil, ok, i, k, x, t, t.ver), false
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}
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}
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}
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// SeekFirst returns an enumerator positioned on the first KV pair in the tree,
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// if any. For an empty tree, err == io.EOF is returned and e will be nil.
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func (t *Tree) SeekFirst() (e *Enumerator, err error) {
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q := t.first
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if q == nil {
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return nil, io.EOF
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}
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return btEPool.get(nil, true, 0, q.d[0].k, q, t, t.ver), nil
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}
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// SeekLast returns an enumerator positioned on the last KV pair in the tree,
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// if any. For an empty tree, err == io.EOF is returned and e will be nil.
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func (t *Tree) SeekLast() (e *Enumerator, err error) {
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q := t.last
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if q == nil {
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return nil, io.EOF
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}
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return btEPool.get(nil, true, q.c-1, q.d[q.c-1].k, q, t, t.ver), nil
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}
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// Set sets the value associated with k.
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func (t *Tree) Set(k int, v int) {
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//dbg("--- PRE Set(%v, %v)\n%s", k, v, t.dump())
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//defer func() {
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// dbg("--- POST\n%s\n====\n", t.dump())
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//}()
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pi := -1
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var p *x
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q := t.r
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if q == nil {
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z := t.insert(btDPool.Get().(*d), 0, k, v)
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t.r, t.first, t.last = z, z, z
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return
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}
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for {
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i, ok := t.find(q, k)
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if ok {
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switch x := q.(type) {
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case *x:
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if x.c > 2*kx {
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x, i = t.splitX(p, x, pi, i)
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}
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pi = i + 1
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p = x
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q = x.x[i+1].ch
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continue
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case *d:
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x.d[i].v = v
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}
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return
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}
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switch x := q.(type) {
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case *x:
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if x.c > 2*kx {
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x, i = t.splitX(p, x, pi, i)
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|
}
|
|
pi = i
|
|
p = x
|
|
q = x.x[i].ch
|
|
case *d:
|
|
switch {
|
|
case x.c < 2*kd:
|
|
t.insert(x, i, k, v)
|
|
default:
|
|
t.overflow(p, x, pi, i, k, v)
|
|
}
|
|
return
|
|
}
|
|
}
|
|
}
|
|
|
|
// Put combines Get and Set in a more efficient way where the tree is walked
|
|
// only once. The upd(ater) receives (old-value, true) if a KV pair for k
|
|
// exists or (zero-value, false) otherwise. It can then return a (new-value,
|
|
// true) to create or overwrite the existing value in the KV pair, or
|
|
// (whatever, false) if it decides not to create or not to update the value of
|
|
// the KV pair.
|
|
//
|
|
// tree.Set(k, v) call conceptually equals calling
|
|
//
|
|
// tree.Put(k, func(int, bool){ return v, true })
|
|
//
|
|
// modulo the differing return values.
|
|
func (t *Tree) Put(k int, upd func(oldV int, exists bool) (newV int, write bool)) (oldV int, written bool) {
|
|
pi := -1
|
|
var p *x
|
|
q := t.r
|
|
var newV int
|
|
if q == nil {
|
|
// new KV pair in empty tree
|
|
newV, written = upd(newV, false)
|
|
if !written {
|
|
return
|
|
}
|
|
|
|
z := t.insert(btDPool.Get().(*d), 0, k, newV)
|
|
t.r, t.first, t.last = z, z, z
|
|
return
|
|
}
|
|
|
|
for {
|
|
i, ok := t.find(q, k)
|
|
if ok {
|
|
switch x := q.(type) {
|
|
case *x:
|
|
if x.c > 2*kx {
|
|
x, i = t.splitX(p, x, pi, i)
|
|
}
|
|
pi = i + 1
|
|
p = x
|
|
q = x.x[i+1].ch
|
|
continue
|
|
case *d:
|
|
oldV = x.d[i].v
|
|
newV, written = upd(oldV, true)
|
|
if !written {
|
|
return
|
|
}
|
|
|
|
x.d[i].v = newV
|
|
}
|
|
return
|
|
}
|
|
|
|
switch x := q.(type) {
|
|
case *x:
|
|
if x.c > 2*kx {
|
|
x, i = t.splitX(p, x, pi, i)
|
|
}
|
|
pi = i
|
|
p = x
|
|
q = x.x[i].ch
|
|
case *d: // new KV pair
|
|
newV, written = upd(newV, false)
|
|
if !written {
|
|
return
|
|
}
|
|
|
|
switch {
|
|
case x.c < 2*kd:
|
|
t.insert(x, i, k, newV)
|
|
default:
|
|
t.overflow(p, x, pi, i, k, newV)
|
|
}
|
|
return
|
|
}
|
|
}
|
|
}
|
|
|
|
func (t *Tree) split(p *x, q *d, pi, i int, k int, v int) {
|
|
t.ver++
|
|
r := btDPool.Get().(*d)
|
|
if q.n != nil {
|
|
r.n = q.n
|
|
r.n.p = r
|
|
} else {
|
|
t.last = r
|
|
}
|
|
q.n = r
|
|
r.p = q
|
|
|
|
copy(r.d[:], q.d[kd:2*kd])
|
|
for i := range q.d[kd:] {
|
|
q.d[kd+i] = zde
|
|
}
|
|
q.c = kd
|
|
r.c = kd
|
|
var done bool
|
|
if i > kd {
|
|
done = true
|
|
t.insert(r, i-kd, k, v)
|
|
}
|
|
if pi >= 0 {
|
|
p.insert(pi, r.d[0].k, r)
|
|
} else {
|
|
t.r = newX(q).insert(0, r.d[0].k, r)
|
|
}
|
|
if done {
|
|
return
|
|
}
|
|
|
|
t.insert(q, i, k, v)
|
|
}
|
|
|
|
func (t *Tree) splitX(p *x, q *x, pi int, i int) (*x, int) {
|
|
t.ver++
|
|
r := btXPool.Get().(*x)
|
|
copy(r.x[:], q.x[kx+1:])
|
|
q.c = kx
|
|
r.c = kx
|
|
if pi >= 0 {
|
|
p.insert(pi, q.x[kx].k, r)
|
|
q.x[kx].k = zk
|
|
for i := range q.x[kx+1:] {
|
|
q.x[kx+i+1] = zxe
|
|
}
|
|
|
|
switch {
|
|
case i < kx:
|
|
return q, i
|
|
case i == kx:
|
|
return p, pi
|
|
default: // i > kx
|
|
return r, i - kx - 1
|
|
}
|
|
}
|
|
|
|
nr := newX(q).insert(0, q.x[kx].k, r)
|
|
t.r = nr
|
|
q.x[kx].k = zk
|
|
for i := range q.x[kx+1:] {
|
|
q.x[kx+i+1] = zxe
|
|
}
|
|
|
|
switch {
|
|
case i < kx:
|
|
return q, i
|
|
case i == kx:
|
|
return nr, 0
|
|
default: // i > kx
|
|
return r, i - kx - 1
|
|
}
|
|
}
|
|
|
|
func (t *Tree) underflow(p *x, q *d, pi int) {
|
|
t.ver++
|
|
l, r := p.siblings(pi)
|
|
|
|
if l != nil && l.c+q.c >= 2*kd {
|
|
l.mvR(q, 1)
|
|
p.x[pi-1].k = q.d[0].k
|
|
return
|
|
}
|
|
|
|
if r != nil && q.c+r.c >= 2*kd {
|
|
q.mvL(r, 1)
|
|
p.x[pi].k = r.d[0].k
|
|
r.d[r.c] = zde // GC
|
|
return
|
|
}
|
|
|
|
if l != nil {
|
|
t.cat(p, l, q, pi-1)
|
|
return
|
|
}
|
|
|
|
t.cat(p, q, r, pi)
|
|
}
|
|
|
|
func (t *Tree) underflowX(p *x, q *x, pi int, i int) (*x, int) {
|
|
t.ver++
|
|
var l, r *x
|
|
|
|
if pi >= 0 {
|
|
if pi > 0 {
|
|
l = p.x[pi-1].ch.(*x)
|
|
}
|
|
if pi < p.c {
|
|
r = p.x[pi+1].ch.(*x)
|
|
}
|
|
}
|
|
|
|
if l != nil && l.c > kx {
|
|
q.x[q.c+1].ch = q.x[q.c].ch
|
|
copy(q.x[1:], q.x[:q.c])
|
|
q.x[0].ch = l.x[l.c].ch
|
|
q.x[0].k = p.x[pi-1].k
|
|
q.c++
|
|
i++
|
|
l.c--
|
|
p.x[pi-1].k = l.x[l.c].k
|
|
return q, i
|
|
}
|
|
|
|
if r != nil && r.c > kx {
|
|
q.x[q.c].k = p.x[pi].k
|
|
q.c++
|
|
q.x[q.c].ch = r.x[0].ch
|
|
p.x[pi].k = r.x[0].k
|
|
copy(r.x[:], r.x[1:r.c])
|
|
r.c--
|
|
rc := r.c
|
|
r.x[rc].ch = r.x[rc+1].ch
|
|
r.x[rc].k = zk
|
|
r.x[rc+1].ch = nil
|
|
return q, i
|
|
}
|
|
|
|
if l != nil {
|
|
i += l.c + 1
|
|
t.catX(p, l, q, pi-1)
|
|
q = l
|
|
return q, i
|
|
}
|
|
|
|
t.catX(p, q, r, pi)
|
|
return q, i
|
|
}
|
|
|
|
// ----------------------------------------------------------------- Enumerator
|
|
|
|
// Close recycles e to a pool for possible later reuse. No references to e
|
|
// should exist or such references must not be used afterwards.
|
|
func (e *Enumerator) Close() {
|
|
*e = ze
|
|
btEPool.Put(e)
|
|
}
|
|
|
|
// Next returns the currently enumerated item, if it exists and moves to the
|
|
// next item in the key collation order. If there is no item to return, err ==
|
|
// io.EOF is returned.
|
|
func (e *Enumerator) Next() (k int, v int, err error) {
|
|
if err = e.err; err != nil {
|
|
return
|
|
}
|
|
|
|
if e.ver != e.t.ver {
|
|
f, hit := e.t.Seek(e.k)
|
|
if !e.hit && hit {
|
|
if err = f.next(); err != nil {
|
|
return
|
|
}
|
|
}
|
|
|
|
*e = *f
|
|
f.Close()
|
|
}
|
|
if e.q == nil {
|
|
e.err, err = io.EOF, io.EOF
|
|
return
|
|
}
|
|
|
|
if e.i >= e.q.c {
|
|
if err = e.next(); err != nil {
|
|
return
|
|
}
|
|
}
|
|
|
|
i := e.q.d[e.i]
|
|
k, v = i.k, i.v
|
|
e.k, e.hit = k, false
|
|
e.next()
|
|
return
|
|
}
|
|
|
|
func (e *Enumerator) next() error {
|
|
if e.q == nil {
|
|
e.err = io.EOF
|
|
return io.EOF
|
|
}
|
|
|
|
switch {
|
|
case e.i < e.q.c-1:
|
|
e.i++
|
|
default:
|
|
if e.q, e.i = e.q.n, 0; e.q == nil {
|
|
e.err = io.EOF
|
|
}
|
|
}
|
|
return e.err
|
|
}
|
|
|
|
// Prev returns the currently enumerated item, if it exists and moves to the
|
|
// previous item in the key collation order. If there is no item to return, err
|
|
// == io.EOF is returned.
|
|
func (e *Enumerator) Prev() (k int, v int, err error) {
|
|
if err = e.err; err != nil {
|
|
return
|
|
}
|
|
|
|
if e.ver != e.t.ver {
|
|
f, hit := e.t.Seek(e.k)
|
|
if !e.hit && hit {
|
|
if err = f.prev(); err != nil {
|
|
return
|
|
}
|
|
}
|
|
|
|
*e = *f
|
|
f.Close()
|
|
}
|
|
if e.q == nil {
|
|
e.err, err = io.EOF, io.EOF
|
|
return
|
|
}
|
|
|
|
if e.i >= e.q.c {
|
|
if err = e.next(); err != nil {
|
|
return
|
|
}
|
|
}
|
|
|
|
i := e.q.d[e.i]
|
|
k, v = i.k, i.v
|
|
e.k, e.hit = k, false
|
|
e.prev()
|
|
return
|
|
}
|
|
|
|
func (e *Enumerator) prev() error {
|
|
if e.q == nil {
|
|
e.err = io.EOF
|
|
return io.EOF
|
|
}
|
|
|
|
switch {
|
|
case e.i > 0:
|
|
e.i--
|
|
default:
|
|
if e.q = e.q.p; e.q == nil {
|
|
e.err = io.EOF
|
|
break
|
|
}
|
|
|
|
e.i = e.q.c - 1
|
|
}
|
|
return e.err
|
|
}
|