item.go

// Copyright © SurrealDB Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package vtree

import (
	"github.com/surrealdb/tlist"
)

// Item represents a collection of versions and values, stored
// in order of version number.
type Item struct {
	pntr *tlist.List
}

func newItem() *Item {
	return &Item{
		pntr: tlist.New(),
	}
}

// Put inserts a value with the specified version number. It
// returns the previous value, or nil if it does not exist.
func (i *Item) Put(ver uint64, val []byte) []byte {
	if v := i.pntr.Put(ver, val); v != nil {
		return v.Val()
	}
	return nil
}

// Get selects a value with the specified version number, or
// the nearest latest value prior to the specified version.
// If '0' is specified for the version, then the latest item
// will be returned.
func (i *Item) Get(ver uint64) []byte {
	if v := i.pntr.Get(ver, tlist.Upto); v != nil {
		return v.Val()
	}
	return nil
}

// Del deletes a value with the specified version number, or
// the nearest latest value prior to the specified version.
func (i *Item) Del(ver uint64) []byte {
	if v := i.pntr.Del(ver, tlist.Upto); v != nil {
		return v.Val()
	}
	return nil
}

// Min returns the value of the minium version in the list.
func (i *Item) Min() []byte {
	if v := i.pntr.Min(); v != nil {
		return v.Val()
	}
	return nil
}

// Max returns the value of the maximum version in the list.
func (i *Item) Max() []byte {
	if v := i.pntr.Max(); v != nil {
		return v.Val()
	}
	return nil
}

// Seek searches for a value prior to the specified version
// number, and returns its version and value. If math.MinInt64
// is specified for the version, then the first item will be
// returned, and if math.MaxInt64 is used then the latest item
// will be returned.
func (i *Item) Seek(ver uint64) (uint64, []byte) {
	if v := i.pntr.Get(ver, tlist.Upto); v != nil {
		return v.Ver(), v.Val()
	}
	return 0, nil
}

// Walk iterates through all of the versions and values in the
// list, in order of version, starting at the first version.
func (i *Item) Walk(fn func(ver uint64, val []byte) bool) {
	i.pntr.Walk(func(i *tlist.Item) bool {
		return fn(i.Ver(), i.Val())
	})
}