[#1523] local_object_storage: Move blobovnicza tree to a separate package

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/local_object_storage/blobstor/compression/compress.go

@@ -0,0 +1,102 @@
+package compression
+
+import (
+	"bytes"
+	"strings"
+
+	"github.com/klauspost/compress/zstd"
+	objectSDK "github.com/nspcc-dev/neofs-sdk-go/object"
+)
+
+// CConfig represents common compression-related configuration.
+type CConfig 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 *CConfig) 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 *CConfig) 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 *CConfig) 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 *CConfig) Compress(data []byte) []byte {
+	if c.Enabled {
+		return c.encoder.EncodeAll(data, make([]byte, 0, len(data)))
+	}
+	return data
+}
+
+// Close closes encoder and decoder, returns any error occured.
+func (c *CConfig) Close() error {
+	var err error
+	if c.encoder != nil {
+		err = c.encoder.Close()
+	}
+	if c.decoder != nil {
+		c.decoder.Close()
+	}
+	return err
+}