[#1715] blobstor: Allow to specify custom compression level

Change-Id: I140c39b9dceaaeb58767061b131777af22242b19
Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/blobstor/compression/compress.go

@@ -4,15 +4,26 @@ import (
 	"bytes"
 	"strings"
 
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/assert"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	"github.com/klauspost/compress"
 	"github.com/klauspost/compress/zstd"
 )
 
+type Level string
+
+const (
+	LevelDefault      Level = ""
+	LevelOptimal      Level = "optimal"
+	LevelFastest      Level = "fastest"
+	LevelSmallestSize Level = "smallest_size"
+)
+
 // Config represents common compression-related configuration.
 type Config struct {
 	Enabled                    bool
 	UncompressableContentTypes []string
+	Level                      Level
 
 	UseCompressEstimation       bool
 	CompressEstimationThreshold float64
@@ -30,7 +41,7 @@ func (c *Config) Init() error {
 	var err error
 
 	if c.Enabled {
-		c.encoder, err = zstd.NewWriter(nil)
+		c.encoder, err = zstd.NewWriter(nil, zstd.WithEncoderLevel(c.compressionLevel()))
 		if err != nil {
 			return err
 		}
@@ -116,3 +127,24 @@ func (c *Config) Close() error {
 	}
 	return err
 }
+
+func (c *Config) HasValidCompressionLevel() bool {
+	return c.Level == LevelDefault ||
+		c.Level == LevelOptimal ||
+		c.Level == LevelFastest ||
+		c.Level == LevelSmallestSize
+}
+
+func (c *Config) compressionLevel() zstd.EncoderLevel {
+	switch c.Level {
+	case LevelDefault, LevelOptimal:
+		return zstd.SpeedDefault
+	case LevelFastest:
+		return zstd.SpeedFastest
+	case LevelSmallestSize:
+		return zstd.SpeedBestCompression
+	default:
+		assert.Fail("unknown compression level", string(c.Level))
+		return zstd.SpeedDefault
+	}
+}