2018-06-20 07:06:27 -05:00
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// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package intervals
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import (
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"bytes"
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"fmt"
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"strconv"
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"sync"
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)
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// Intervals store a list of intervals. Its purpose is to provide
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// methods to add new intervals and retrieve missing intervals that
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// need to be added.
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// It may be used in synchronization of streaming data to persist
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// retrieved data ranges between sessions.
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type Intervals struct {
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start uint64
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ranges [][2]uint64
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mu sync.RWMutex
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}
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// New creates a new instance of Intervals.
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// Start argument limits the lower bound of intervals.
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// No range bellow start bound will be added by Add method or
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// returned by Next method. This limit may be used for
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// tracking "live" synchronization, where the sync session
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// starts from a specific value, and if "live" sync intervals
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// need to be merged with historical ones, it can be safely done.
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func NewIntervals(start uint64) *Intervals {
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return &Intervals{
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start: start,
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}
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}
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// Add adds a new range to intervals. Range start and end are values
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// are both inclusive.
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func (i *Intervals) Add(start, end uint64) {
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i.mu.Lock()
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defer i.mu.Unlock()
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i.add(start, end)
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}
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func (i *Intervals) add(start, end uint64) {
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if start < i.start {
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start = i.start
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}
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if end < i.start {
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return
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}
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minStartJ := -1
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maxEndJ := -1
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j := 0
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for ; j < len(i.ranges); j++ {
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if minStartJ < 0 {
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if (start <= i.ranges[j][0] && end+1 >= i.ranges[j][0]) || (start <= i.ranges[j][1]+1 && end+1 >= i.ranges[j][1]) {
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if i.ranges[j][0] < start {
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start = i.ranges[j][0]
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}
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minStartJ = j
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}
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}
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if (start <= i.ranges[j][1] && end+1 >= i.ranges[j][1]) || (start <= i.ranges[j][0] && end+1 >= i.ranges[j][0]) {
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if i.ranges[j][1] > end {
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end = i.ranges[j][1]
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}
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maxEndJ = j
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}
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if end+1 <= i.ranges[j][0] {
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break
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}
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}
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if minStartJ < 0 && maxEndJ < 0 {
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i.ranges = append(i.ranges[:j], append([][2]uint64{{start, end}}, i.ranges[j:]...)...)
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return
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}
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if minStartJ >= 0 {
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i.ranges[minStartJ][0] = start
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}
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if maxEndJ >= 0 {
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i.ranges[maxEndJ][1] = end
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}
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if minStartJ >= 0 && maxEndJ >= 0 && minStartJ != maxEndJ {
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i.ranges[maxEndJ][0] = start
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i.ranges = append(i.ranges[:minStartJ], i.ranges[maxEndJ:]...)
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}
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}
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2018-08-27 03:49:29 -05:00
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// Merge adds all the intervals from the m Interval to current one.
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2018-06-20 07:06:27 -05:00
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func (i *Intervals) Merge(m *Intervals) {
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m.mu.RLock()
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defer m.mu.RUnlock()
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i.mu.Lock()
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defer i.mu.Unlock()
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for _, r := range m.ranges {
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i.add(r[0], r[1])
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}
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}
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// Next returns the first range interval that is not fulfilled. Returned
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// start and end values are both inclusive, meaning that the whole range
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// including start and end need to be added in order to full the gap
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// in intervals.
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// Returned value for end is 0 if the next interval is after the whole
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// range that is stored in Intervals. Zero end value represents no limit
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// on the next interval length.
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func (i *Intervals) Next() (start, end uint64) {
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i.mu.RLock()
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defer i.mu.RUnlock()
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l := len(i.ranges)
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if l == 0 {
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return i.start, 0
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}
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if i.ranges[0][0] != i.start {
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return i.start, i.ranges[0][0] - 1
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}
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if l == 1 {
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return i.ranges[0][1] + 1, 0
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}
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return i.ranges[0][1] + 1, i.ranges[1][0] - 1
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}
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// Last returns the value that is at the end of the last interval.
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func (i *Intervals) Last() (end uint64) {
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i.mu.RLock()
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defer i.mu.RUnlock()
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l := len(i.ranges)
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if l == 0 {
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return 0
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}
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return i.ranges[l-1][1]
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}
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// String returns a descriptive representation of range intervals
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// in [] notation, as a list of two element vectors.
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func (i *Intervals) String() string {
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return fmt.Sprint(i.ranges)
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}
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// MarshalBinary encodes Intervals parameters into a semicolon separated list.
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// The first element in the list is base36-encoded start value. The following
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// elements are two base36-encoded value ranges separated by comma.
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func (i *Intervals) MarshalBinary() (data []byte, err error) {
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d := make([][]byte, len(i.ranges)+1)
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d[0] = []byte(strconv.FormatUint(i.start, 36))
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for j := range i.ranges {
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r := i.ranges[j]
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d[j+1] = []byte(strconv.FormatUint(r[0], 36) + "," + strconv.FormatUint(r[1], 36))
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}
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return bytes.Join(d, []byte(";")), nil
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}
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// UnmarshalBinary decodes data according to the Intervals.MarshalBinary format.
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func (i *Intervals) UnmarshalBinary(data []byte) (err error) {
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d := bytes.Split(data, []byte(";"))
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l := len(d)
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if l == 0 {
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return nil
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}
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if l >= 1 {
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i.start, err = strconv.ParseUint(string(d[0]), 36, 64)
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if err != nil {
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return err
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}
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}
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if l == 1 {
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return nil
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}
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i.ranges = make([][2]uint64, 0, l-1)
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for j := 1; j < l; j++ {
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r := bytes.SplitN(d[j], []byte(","), 2)
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if len(r) < 2 {
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return fmt.Errorf("range %d has less then 2 elements", j)
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}
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start, err := strconv.ParseUint(string(r[0]), 36, 64)
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if err != nil {
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return fmt.Errorf("parsing the first element in range %d: %v", j, err)
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}
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end, err := strconv.ParseUint(string(r[1]), 36, 64)
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if err != nil {
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return fmt.Errorf("parsing the second element in range %d: %v", j, err)
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}
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i.ranges = append(i.ranges, [2]uint64{start, end})
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}
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return nil
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}
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