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Add BlobCompressor to compress blob and text fields on fly
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| package lz4 | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/binary" | ||
| "fmt" | ||
|
|
||
| "github.com/pierrec/lz4/v4" | ||
| ) | ||
|
|
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| type BlobCompressor struct { | ||
| prefix []byte | ||
| prefixPlusLen int | ||
| limit int | ||
| } | ||
|
|
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| var defaultPrefix = []byte{0x01, 0x11, 0x22, 0x33} | ||
|
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| func NewBlobCompressor(limit int) BlobCompressor { | ||
| return BlobCompressor{ | ||
| prefix: defaultPrefix, | ||
| prefixPlusLen: len(defaultPrefix) + 4, | ||
| limit: limit, | ||
| } | ||
| } | ||
|
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| func (c BlobCompressor) Compress(data []byte) ([]byte, error) { | ||
| if len(data) < c.limit { | ||
| return data, nil | ||
| } | ||
| buf := make([]byte, len(c.prefix)+lz4.CompressBlockBound(len(data)+4)) | ||
| copy(buf, c.prefix) | ||
|
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| var compressor lz4.Compressor | ||
|
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| n, err := compressor.CompressBlock(data, buf[c.prefixPlusLen:]) | ||
| // According to lz4.CompressBlock doc, it doesn't fail as long as the dst | ||
| // buffer length is at least lz4.CompressBlockBound(len(data))) bytes, but | ||
| // we check for error anyway just to be thorough. | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| binary.BigEndian.PutUint32(buf[len(c.prefix):], uint32(len(data))) | ||
|
|
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| return buf[:c.prefixPlusLen+n], nil | ||
| } | ||
|
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| func (c BlobCompressor) Decompress(data []byte) ([]byte, error) { | ||
| if !bytes.HasPrefix(data, c.prefix) { | ||
| return data, nil | ||
| } | ||
| if len(data) < 4+len(c.prefix) { | ||
| return nil, fmt.Errorf("compressed data should be >4, got=%d", len(data)) | ||
| } | ||
| uncompressedLength := binary.BigEndian.Uint32(data[len(c.prefix):]) | ||
| if uncompressedLength == 0 { | ||
| return nil, nil | ||
| } | ||
| buf := make([]byte, uncompressedLength) | ||
| n, err := lz4.UncompressBlock(data[c.prefixPlusLen:], buf) | ||
| return buf[:n], err | ||
| } |
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