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 == nil || !c.Enabled { return data } return c.encoder.EncodeAll(data, make([]byte, 0, len(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 }