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124 lines
3.1 KiB
124 lines
3.1 KiB
// Copyright (c) 2017 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package zap
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import (
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"bytes"
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"encoding/binary"
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"io"
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"github.com/Smerity/govarint"
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)
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type chunkedIntCoder struct {
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final []byte
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maxDocNum uint64
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chunkSize uint64
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chunkBuf bytes.Buffer
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encoder *govarint.Base128Encoder
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chunkLens []uint64
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currChunk uint64
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buf []byte
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}
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// newChunkedIntCoder returns a new chunk int coder which packs data into
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// chunks based on the provided chunkSize and supports up to the specified
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// maxDocNum
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func newChunkedIntCoder(chunkSize uint64, maxDocNum uint64) *chunkedIntCoder {
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total := maxDocNum/chunkSize + 1
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rv := &chunkedIntCoder{
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chunkSize: chunkSize,
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maxDocNum: maxDocNum,
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chunkLens: make([]uint64, total),
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final: make([]byte, 0, 64),
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}
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rv.encoder = govarint.NewU64Base128Encoder(&rv.chunkBuf)
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return rv
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}
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// Reset lets you reuse this chunked int coder. buffers are reset and reused
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// from previous use. you cannot change the chunk size or max doc num.
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func (c *chunkedIntCoder) Reset() {
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c.final = c.final[:0]
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c.chunkBuf.Reset()
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c.currChunk = 0
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for i := range c.chunkLens {
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c.chunkLens[i] = 0
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}
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}
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// Add encodes the provided integers into the correct chunk for the provided
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// doc num. You MUST call Add() with increasing docNums.
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func (c *chunkedIntCoder) Add(docNum uint64, vals ...uint64) error {
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chunk := docNum / c.chunkSize
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if chunk != c.currChunk {
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// starting a new chunk
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if c.encoder != nil {
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// close out last
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c.Close()
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c.chunkBuf.Reset()
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}
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c.currChunk = chunk
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}
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for _, val := range vals {
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_, err := c.encoder.PutU64(val)
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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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return nil
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}
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// Close indicates you are done calling Add() this allows the final chunk
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// to be encoded.
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func (c *chunkedIntCoder) Close() {
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c.encoder.Close()
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encodingBytes := c.chunkBuf.Bytes()
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c.chunkLens[c.currChunk] = uint64(len(encodingBytes))
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c.final = append(c.final, encodingBytes...)
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}
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// Write commits all the encoded chunked integers to the provided writer.
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func (c *chunkedIntCoder) Write(w io.Writer) (int, error) {
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bufNeeded := binary.MaxVarintLen64 * (1 + len(c.chunkLens))
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if len(c.buf) < bufNeeded {
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c.buf = make([]byte, bufNeeded)
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}
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buf := c.buf
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// write out the number of chunks & each chunkLen
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n := binary.PutUvarint(buf, uint64(len(c.chunkLens)))
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for _, chunkLen := range c.chunkLens {
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n += binary.PutUvarint(buf[n:], uint64(chunkLen))
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}
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tw, err := w.Write(buf[:n])
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if err != nil {
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return tw, err
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}
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// write out the data
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nw, err := w.Write(c.final)
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tw += nw
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if err != nil {
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return tw, err
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}
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return tw, nil
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}
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