/
indexblock.go
147 lines (130 loc) · 3.54 KB
/
indexblock.go
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// Copyright 2018 Google Inc.
//
// 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 sst
import (
"bytes"
"encoding/binary"
"io"
)
// TODO: there's a lot of duplication with datablock. Worth trying to merge?
type indexBlockBuilder struct {
buf *bytes.Buffer
prefixEncoder *prefixEncoder
bhBuffer *bytes.Buffer
}
func newIndexBlockBuilder() *indexBlockBuilder {
return &indexBlockBuilder{
buf: new(bytes.Buffer),
bhBuffer: new(bytes.Buffer),
prefixEncoder: newPrefixEncoder(16),
}
}
func (b *indexBlockBuilder) Append(key string, bh blockHandle) error {
b.bhBuffer.Reset()
bh.EncodeTo(b.bhBuffer)
if err := b.prefixEncoder.EncodeInto(b.buf, []byte(key), uint32(b.buf.Len())); err != nil {
return err
}
if err := writeUvarInt64(b.buf, uint64(b.bhBuffer.Len())); err != nil {
return err
}
if _, err := b.buf.Write(b.bhBuffer.Bytes()); err != nil {
return err
}
return nil
}
func (b *indexBlockBuilder) Finish() ([]byte, error) {
if err := b.prefixEncoder.WriteRestarts(b.buf); err != nil {
return nil, err
}
return b.buf.Bytes(), nil
}
type indexBlock struct {
r *bytes.Reader
restarts []int
}
func newIndexBlock(d []byte) *indexBlock {
nRestarts := int(binary.LittleEndian.Uint32(d[len(d)-4:]))
restarts := make([]int, 0, nRestarts)
restartOffset := len(d) - 4 - 4*nRestarts
for o := restartOffset; o < len(d)-4; o += 4 {
restarts = append(restarts, int(binary.LittleEndian.Uint32(d[o:o+4])))
}
return &indexBlock{
r: bytes.NewReader(d[:restartOffset]),
restarts: restarts,
}
}
func (b *indexBlock) Find(key string) (blockHandle, error) {
var bh blockHandle
kb := make([]byte, 0, MaxSstKeySize)
i, j := 0, len(b.restarts)-1
for i < j {
// lean right when there's two elements
h := int(uint(i+j+1) >> 1)
if _, err := b.r.Seek(int64(b.restarts[h]), io.SeekStart); err != nil {
return bh, err
}
eKey, err := prefixDecodeFrom(b.r, nil, kb)
if err != nil {
return bh, err
}
readKey := string(eKey)
if readKey < key {
i = h
} else {
j = h - 1
}
}
if _, err := b.r.Seek(int64(b.restarts[i]), io.SeekStart); err != nil {
return bh, err
}
var lastKey []byte
for b.r.Len() > 0 {
eKey, err := prefixDecodeFrom(b.r, lastKey, kb)
lastKey = eKey
readKey := string(eKey)
valueLen, err := binary.ReadUvarint(b.r)
if err != nil {
return bh, err
}
if key <= readKey {
bh, err = newBlockHandle(b.r)
return bh, err
}
if _, err = b.r.Seek(int64(valueLen), io.SeekCurrent); err != nil {
return bh, err
}
}
return bh, ErrNotFound
}
// Blocks returns the list of data blocks in this index.
func (b *indexBlock) Blocks() ([]blockHandle, error) {
var lastKey []byte
kb := make([]byte, 0, MaxSstKeySize)
var blocks []blockHandle
for b.r.Len() > 0 {
eKey, err := prefixDecodeFrom(b.r, lastKey, kb)
lastKey = eKey
if _, err := binary.ReadUvarint(b.r); err != nil {
return nil, err
}
bh, err := newBlockHandle(b.r)
if err != nil {
return nil, err
}
blocks = append(blocks, bh)
}
return blocks, nil
}