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// Copyright (C) MongoDB, Inc. 2017-present.
//
// 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
package driver
import (
"bytes"
"compress/zlib"
"fmt"
"io"
"sync"
"github.com/golang/snappy"
"github.com/klauspost/compress/zstd"
"go.mongodb.org/mongo-driver/x/mongo/driver/wiremessage"
)
// CompressionOpts holds settings for how to compress a payload
type CompressionOpts struct {
Compressor wiremessage.CompressorID
ZlibLevel int
ZstdLevel int
UncompressedSize int32
}
var zstdEncoders sync.Map // map[zstd.EncoderLevel]*zstd.Encoder
func getZstdEncoder(level zstd.EncoderLevel) (*zstd.Encoder, error) {
if v, ok := zstdEncoders.Load(level); ok {
return v.(*zstd.Encoder), nil
}
encoder, err := zstd.NewWriter(nil, zstd.WithEncoderLevel(level))
if err != nil {
return nil, err
}
zstdEncoders.Store(level, encoder)
return encoder, nil
}
var zlibEncoders sync.Map // map[int /*level*/]*zlibEncoder
func getZlibEncoder(level int) (*zlibEncoder, error) {
if v, ok := zlibEncoders.Load(level); ok {
return v.(*zlibEncoder), nil
}
writer, err := zlib.NewWriterLevel(nil, level)
if err != nil {
return nil, err
}
encoder := &zlibEncoder{writer: writer, buf: new(bytes.Buffer)}
zlibEncoders.Store(level, encoder)
return encoder, nil
}
type zlibEncoder struct {
mu sync.Mutex
writer *zlib.Writer
buf *bytes.Buffer
}
func (e *zlibEncoder) Encode(dst, src []byte) ([]byte, error) {
e.mu.Lock()
defer e.mu.Unlock()
e.buf.Reset()
e.writer.Reset(e.buf)
_, err := e.writer.Write(src)
if err != nil {
return nil, err
}
err = e.writer.Close()
if err != nil {
return nil, err
}
dst = append(dst[:0], e.buf.Bytes()...)
return dst, nil
}
// CompressPayload takes a byte slice and compresses it according to the options passed
func CompressPayload(in []byte, opts CompressionOpts) ([]byte, error) {
switch opts.Compressor {
case wiremessage.CompressorNoOp:
return in, nil
case wiremessage.CompressorSnappy:
return snappy.Encode(nil, in), nil
case wiremessage.CompressorZLib:
encoder, err := getZlibEncoder(opts.ZlibLevel)
if err != nil {
return nil, err
}
return encoder.Encode(nil, in)
case wiremessage.CompressorZstd:
encoder, err := getZstdEncoder(zstd.EncoderLevelFromZstd(opts.ZstdLevel))
if err != nil {
return nil, err
}
return encoder.EncodeAll(in, nil), nil
default:
return nil, fmt.Errorf("unknown compressor ID %v", opts.Compressor)
}
}
// DecompressPayload takes a byte slice that has been compressed and undoes it according to the options passed
func DecompressPayload(in []byte, opts CompressionOpts) (uncompressed []byte, err error) {
switch opts.Compressor {
case wiremessage.CompressorNoOp:
return in, nil
case wiremessage.CompressorSnappy:
l, err := snappy.DecodedLen(in)
if err != nil {
return nil, fmt.Errorf("decoding compressed length %w", err)
} else if int32(l) != opts.UncompressedSize {
return nil, fmt.Errorf("unexpected decompression size, expected %v but got %v", opts.UncompressedSize, l)
}
uncompressed = make([]byte, opts.UncompressedSize)
return snappy.Decode(uncompressed, in)
case wiremessage.CompressorZLib:
r, err := zlib.NewReader(bytes.NewReader(in))
if err != nil {
return nil, err
}
defer func() {
err = r.Close()
}()
uncompressed = make([]byte, opts.UncompressedSize)
_, err = io.ReadFull(r, uncompressed)
if err != nil {
return nil, err
}
return uncompressed, nil
case wiremessage.CompressorZstd:
r, err := zstd.NewReader(bytes.NewBuffer(in))
if err != nil {
return nil, err
}
defer r.Close()
uncompressed = make([]byte, opts.UncompressedSize)
_, err = io.ReadFull(r, uncompressed)
if err != nil {
return nil, err
}
return uncompressed, nil
default:
return nil, fmt.Errorf("unknown compressor ID %v", opts.Compressor)
}
}
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