109 lines
1.7 KiB
Go
109 lines
1.7 KiB
Go
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package index
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import (
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"encoding/binary"
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"errors"
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"io"
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)
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const pageSize = 2048
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var errPageFull = errors.New("page full")
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type pageCursor interface {
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Iterator
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append(v DocID) error
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}
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type page interface {
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cursor() pageCursor
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init(v DocID) error
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data() []byte
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}
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type pageDelta struct {
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b []byte
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}
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type pageType uint8
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const (
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pageTypeDelta pageType = iota
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)
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func newPageDelta(data []byte) *pageDelta {
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return &pageDelta{b: data}
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}
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func (p *pageDelta) init(v DocID) error {
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// Write first value.
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binary.PutUvarint(p.b, uint64(v))
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return nil
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}
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func (p *pageDelta) cursor() pageCursor {
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return &pageDeltaCursor{data: p.b}
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}
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func (p *pageDelta) data() []byte {
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return p.b
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}
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type pageDeltaCursor struct {
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data []byte
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pos int
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cur DocID
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}
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func (p *pageDeltaCursor) append(id DocID) error {
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// Run to the end.
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_, err := p.Next()
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for ; err == nil; _, err = p.Next() {
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// Consume.
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}
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if err != io.EOF {
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return err
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}
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if len(p.data)-p.pos < binary.MaxVarintLen64 {
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return errPageFull
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}
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if p.cur >= id {
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return errOutOfOrder
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}
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p.pos += binary.PutUvarint(p.data[p.pos:], uint64(id-p.cur))
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p.cur = id
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return nil
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}
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func (p *pageDeltaCursor) Close() error {
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return nil
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}
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func (p *pageDeltaCursor) Seek(min DocID) (v DocID, err error) {
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if min < p.cur {
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p.pos = 0
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}
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for v, err = p.Next(); err == nil && v < min; v, err = p.Next() {
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// Consume.
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}
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return p.cur, err
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}
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func (p *pageDeltaCursor) Next() (DocID, error) {
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var n int
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var dv uint64
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if p.pos == 0 {
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dv, n = binary.Uvarint(p.data)
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p.cur = DocID(dv)
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} else {
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dv, n = binary.Uvarint(p.data[p.pos:])
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if n <= 0 || dv == 0 {
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return 0, io.EOF
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}
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p.cur += DocID(dv)
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}
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p.pos += n
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return p.cur, nil
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}
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