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gitea/vendor/github.com/blevesearch/zapx/v12/intcoder.go

203 lines
5.3 KiB

// Copyright (c) 2017 Couchbase, 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 zap
import (
"bytes"
"encoding/binary"
"io"
"math"
)
const termNotEncoded = math.MaxUint64
type chunkedIntCoder struct {
final []byte
chunkSize uint64
chunkBuf bytes.Buffer
chunkLens []uint64
currChunk uint64
buf []byte
}
// newChunkedIntCoder returns a new chunk int coder which packs data into
// chunks based on the provided chunkSize and supports up to the specified
// maxDocNum
func newChunkedIntCoder(chunkSize uint64, maxDocNum uint64) *chunkedIntCoder {
total := maxDocNum/chunkSize + 1
rv := &chunkedIntCoder{
chunkSize: chunkSize,
chunkLens: make([]uint64, total),
final: make([]byte, 0, 64),
}
return rv
}
// Reset lets you reuse this chunked int coder. buffers are reset and reused
// from previous use. you cannot change the chunk size or max doc num.
func (c *chunkedIntCoder) Reset() {
c.final = c.final[:0]
c.chunkBuf.Reset()
c.currChunk = 0
for i := range c.chunkLens {
c.chunkLens[i] = 0
}
}
// SetChunkSize changes the chunk size. It is only valid to do so
// with a new chunkedIntCoder, or immediately after calling Reset()
func (c *chunkedIntCoder) SetChunkSize(chunkSize uint64, maxDocNum uint64) {
total := int(maxDocNum/chunkSize + 1)
c.chunkSize = chunkSize
if cap(c.chunkLens) < total {
c.chunkLens = make([]uint64, total)
} else {
c.chunkLens = c.chunkLens[:total]
}
}
// Add encodes the provided integers into the correct chunk for the provided
// doc num. You MUST call Add() with increasing docNums.
func (c *chunkedIntCoder) Add(docNum uint64, vals ...uint64) error {
chunk := docNum / c.chunkSize
if chunk != c.currChunk {
// starting a new chunk
c.Close()
c.chunkBuf.Reset()
c.currChunk = chunk
}
if len(c.buf) < binary.MaxVarintLen64 {
c.buf = make([]byte, binary.MaxVarintLen64)
}
for _, val := range vals {
wb := binary.PutUvarint(c.buf, val)
_, err := c.chunkBuf.Write(c.buf[:wb])
if err != nil {
return err
}
}
return nil
}
func (c *chunkedIntCoder) AddBytes(docNum uint64, buf []byte) error {
chunk := docNum / c.chunkSize
if chunk != c.currChunk {
// starting a new chunk
c.Close()
c.chunkBuf.Reset()
c.currChunk = chunk
}
_, err := c.chunkBuf.Write(buf)
return err
}
// Close indicates you are done calling Add() this allows the final chunk
// to be encoded.
func (c *chunkedIntCoder) Close() {
encodingBytes := c.chunkBuf.Bytes()
c.chunkLens[c.currChunk] = uint64(len(encodingBytes))
c.final = append(c.final, encodingBytes...)
c.currChunk = uint64(cap(c.chunkLens)) // sentinel to detect double close
}
// Write commits all the encoded chunked integers to the provided writer.
func (c *chunkedIntCoder) Write(w io.Writer) (int, error) {
bufNeeded := binary.MaxVarintLen64 * (1 + len(c.chunkLens))
if len(c.buf) < bufNeeded {
c.buf = make([]byte, bufNeeded)
}
buf := c.buf
// convert the chunk lengths into chunk offsets
chunkOffsets := modifyLengthsToEndOffsets(c.chunkLens)
// write out the number of chunks & each chunk offsets
n := binary.PutUvarint(buf, uint64(len(chunkOffsets)))
for _, chunkOffset := range chunkOffsets {
n += binary.PutUvarint(buf[n:], chunkOffset)
}
tw, err := w.Write(buf[:n])
if err != nil {
return tw, err
}
// write out the data
nw, err := w.Write(c.final)
tw += nw
if err != nil {
return tw, err
}
return tw, nil
}
// writeAt commits all the encoded chunked integers to the provided writer
// and returns the starting offset, total bytes written and an error
func (c *chunkedIntCoder) writeAt(w io.Writer) (uint64, int, error) {
startOffset := uint64(termNotEncoded)
if len(c.final) <= 0 {
return startOffset, 0, nil
}
if chw := w.(*CountHashWriter); chw != nil {
startOffset = uint64(chw.Count())
}
tw, err := c.Write(w)
return startOffset, tw, err
}
func (c *chunkedIntCoder) FinalSize() int {
return len(c.final)
}
// modifyLengthsToEndOffsets converts the chunk length array
// to a chunk offset array. The readChunkBoundary
// will figure out the start and end of every chunk from
// these offsets. Starting offset of i'th index is stored
// in i-1'th position except for 0'th index and ending offset
// is stored at i'th index position.
// For 0'th element, starting position is always zero.
// eg:
// Lens -> 5 5 5 5 => 5 10 15 20
// Lens -> 0 5 0 5 => 0 5 5 10
// Lens -> 0 0 0 5 => 0 0 0 5
// Lens -> 5 0 0 0 => 5 5 5 5
// Lens -> 0 5 0 0 => 0 5 5 5
// Lens -> 0 0 5 0 => 0 0 5 5
func modifyLengthsToEndOffsets(lengths []uint64) []uint64 {
var runningOffset uint64
var index, i int
for i = 1; i <= len(lengths); i++ {
runningOffset += lengths[i-1]
lengths[index] = runningOffset
index++
}
return lengths
}
func readChunkBoundary(chunk int, offsets []uint64) (uint64, uint64) {
var start uint64
if chunk > 0 {
start = offsets[chunk-1]
}
return start, offsets[chunk]
}