frostfs-node/pkg/local_object_storage/blobstor/compression/compress.go
Evgenii Stratonikov a1b4ba9980 [#209] compression: Do not store uncompressible data
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
2023-05-03 16:28:29 +03:00

107 lines
2.6 KiB
Go

package compression
import (
"bytes"
"strings"
objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
"github.com/klauspost/compress/zstd"
)
// Config represents common compression-related configuration.
type Config struct {
Enabled bool
UncompressableContentTypes []string
encoder *zstd.Encoder
decoder *zstd.Decoder
}
// zstdFrameMagic contains first 4 bytes of any compressed object
// https://github.com/klauspost/compress/blob/master/zstd/framedec.go#L58 .
var zstdFrameMagic = []byte{0x28, 0xb5, 0x2f, 0xfd}
// Init initializes compression routines.
func (c *Config) Init() error {
var err error
if c.Enabled {
c.encoder, err = zstd.NewWriter(nil)
if err != nil {
return err
}
}
c.decoder, err = zstd.NewReader(nil)
if err != nil {
return err
}
return nil
}
// NeedsCompression returns true if the object should be compressed.
// For an object to be compressed 2 conditions must hold:
// 1. Compression is enabled in settings.
// 2. Object MIME Content-Type is allowed for compression.
func (c *Config) NeedsCompression(obj *objectSDK.Object) bool {
if !c.Enabled || len(c.UncompressableContentTypes) == 0 {
return c.Enabled
}
for _, attr := range obj.Attributes() {
if attr.Key() == objectSDK.AttributeContentType {
for _, value := range c.UncompressableContentTypes {
match := false
switch {
case len(value) > 0 && value[len(value)-1] == '*':
match = strings.HasPrefix(attr.Value(), value[:len(value)-1])
case len(value) > 0 && value[0] == '*':
match = strings.HasSuffix(attr.Value(), value[1:])
default:
match = attr.Value() == value
}
if match {
return false
}
}
}
}
return c.Enabled
}
// Decompress decompresses data if it starts with the magic
// and returns data untouched otherwise.
func (c *Config) Decompress(data []byte) ([]byte, error) {
if len(data) < 4 || !bytes.Equal(data[:4], zstdFrameMagic) {
return data, nil
}
return c.decoder.DecodeAll(data, nil)
}
// Compress compresses data if compression is enabled
// and returns data untouched otherwise.
func (c *Config) Compress(data []byte) []byte {
if c == nil || !c.Enabled {
return data
}
maxSize := c.encoder.MaxEncodedSize(len(data))
compressed := c.encoder.EncodeAll(data, make([]byte, 0, maxSize))
if len(data) < len(compressed) {
return data
}
return compressed
}
// Close closes encoder and decoder, returns any error occurred.
func (c *Config) Close() error {
var err error
if c.encoder != nil {
err = c.encoder.Close()
}
if c.decoder != nil {
c.decoder.Close()
}
return err
}