119 lines
2.9 KiB
Go
119 lines
2.9 KiB
Go
package compression
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import (
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"bytes"
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"strings"
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objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
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"github.com/klauspost/compress"
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"github.com/klauspost/compress/zstd"
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)
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// Config represents common compression-related configuration.
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type Config struct {
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Enabled bool
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UncompressableContentTypes []string
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UseCompressEstimation bool
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CompressEstimationThreshold float64
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encoder *zstd.Encoder
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decoder *zstd.Decoder
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}
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// zstdFrameMagic contains first 4 bytes of any compressed object
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// https://github.com/klauspost/compress/blob/master/zstd/framedec.go#L58 .
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var zstdFrameMagic = []byte{0x28, 0xb5, 0x2f, 0xfd}
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// Init initializes compression routines.
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func (c *Config) Init() error {
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var err error
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if c.Enabled {
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c.encoder, err = zstd.NewWriter(nil)
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if err != nil {
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return err
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}
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}
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c.decoder, err = zstd.NewReader(nil)
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return err
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}
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// NeedsCompression returns true if the object should be compressed.
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// For an object to be compressed 2 conditions must hold:
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// 1. Compression is enabled in settings.
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// 2. Object MIME Content-Type is allowed for compression.
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func (c *Config) NeedsCompression(obj *objectSDK.Object) bool {
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if !c.Enabled || len(c.UncompressableContentTypes) == 0 {
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return c.Enabled
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}
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for _, attr := range obj.Attributes() {
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if attr.Key() == objectSDK.AttributeContentType {
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for _, value := range c.UncompressableContentTypes {
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match := false
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switch {
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case len(value) > 0 && value[len(value)-1] == '*':
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match = strings.HasPrefix(attr.Value(), value[:len(value)-1])
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case len(value) > 0 && value[0] == '*':
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match = strings.HasSuffix(attr.Value(), value[1:])
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default:
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match = attr.Value() == value
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}
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if match {
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return false
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}
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}
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}
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}
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return c.Enabled
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}
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// Decompress decompresses data if it starts with the magic
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// and returns data untouched otherwise.
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func (c *Config) Decompress(data []byte) ([]byte, error) {
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if len(data) < 4 || !bytes.Equal(data[:4], zstdFrameMagic) {
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return data, nil
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}
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return c.decoder.DecodeAll(data, nil)
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}
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// Compress compresses data if compression is enabled
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// and returns data untouched otherwise.
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func (c *Config) Compress(data []byte) []byte {
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if c == nil || !c.Enabled {
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return data
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}
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if c.UseCompressEstimation {
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estimated := compress.Estimate(data)
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if estimated >= c.CompressEstimationThreshold {
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return c.compress(data)
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}
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return data
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}
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return c.compress(data)
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}
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func (c *Config) compress(data []byte) []byte {
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maxSize := c.encoder.MaxEncodedSize(len(data))
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compressed := c.encoder.EncodeAll(data, make([]byte, 0, maxSize))
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if len(data) < len(compressed) {
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return data
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}
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return compressed
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}
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// Close closes encoder and decoder, returns any error occurred.
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func (c *Config) Close() error {
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var err error
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if c.encoder != nil {
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err = c.encoder.Close()
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}
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if c.decoder != nil {
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c.decoder.Close()
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}
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return err
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}
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