75 lines
1.9 KiB
Go
75 lines
1.9 KiB
Go
|
package compressutil
|
||
|
|
|
||
|
|
import (
|
||
|
|
"bytes"
|
||
|
|
"compress/lzw"
|
||
|
|
"fmt"
|
||
|
|
"io"
|
||
|
|
"log"
|
||
|
|
)
|
||
|
|
|
||
|
|
const (
|
||
|
|
CompressionCanaryJSON byte = 'Z'
|
||
|
|
)
|
||
|
|
|
||
|
|
func Compress(data []byte, canary byte) ([]byte, error) {
|
||
|
|
// Create a buffer and place the canary as its first byte
|
||
|
|
var buf bytes.Buffer
|
||
|
|
buf.Write([]byte{canary})
|
||
|
|
|
||
|
|
// Create writer to compress the JSON encoded bytes
|
||
|
|
writer := lzw.NewWriter(&buf, lzw.LSB, 8)
|
||
|
|
|
||
|
|
// Compress the JSON bytes
|
||
|
|
if _, err := writer.Write(data); err != nil {
|
||
|
|
return nil, fmt.Errorf("failed to compress JSON string; err: %v", err)
|
||
|
|
}
|
||
|
|
|
||
|
|
// Close the io.WriteCloser
|
||
|
|
if err := writer.Close(); err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
|
||
|
|
log.Printf("compressutil.Compress: len(compressedBytes): %d\n", len(buf.Bytes()))
|
||
|
|
|
||
|
|
// Return the compressed bytes with canary byte at the start
|
||
|
|
return buf.Bytes(), nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func Decompress(data []byte, canary byte) ([]byte, bool, error) {
|
||
|
|
if data == nil || len(data) < 2 {
|
||
|
|
return nil, false, fmt.Errorf("'data' being decompressed is invalid")
|
||
|
|
}
|
||
|
|
|
||
|
|
// Read the first byte
|
||
|
|
bytesReader := bytes.NewReader(data)
|
||
|
|
firstByte, err := bytesReader.ReadByte()
|
||
|
|
if err != nil {
|
||
|
|
return nil, false, fmt.Errorf("failed to read the first byte from the input")
|
||
|
|
}
|
||
|
|
|
||
|
|
// If the first byte doesn't match the canaryByte, it means that the
|
||
|
|
// content was not compressed in the first place. Try JSON decoding it.
|
||
|
|
if canary != firstByte {
|
||
|
|
return nil, true, nil
|
||
|
|
} else {
|
||
|
|
// If the first byte matches the canaryByte, remove the canary
|
||
|
|
// byte and try to decompress the data before JSON decoding it.
|
||
|
|
data = data[1:]
|
||
|
|
}
|
||
|
|
|
||
|
|
// Create a reader to read the compressed data
|
||
|
|
reader := lzw.NewReader(bytes.NewReader(data), lzw.LSB, 8)
|
||
|
|
|
||
|
|
// Close the io.ReadCloser
|
||
|
|
defer reader.Close()
|
||
|
|
|
||
|
|
// Read all the compressed data into a buffer
|
||
|
|
var jsonBuf bytes.Buffer
|
||
|
|
if _, err := io.Copy(&jsonBuf, reader); err != nil {
|
||
|
|
return nil, false, err
|
||
|
|
}
|
||
|
|
|
||
|
|
return jsonBuf.Bytes(), false, nil
|
||
|
|
}
|