package needle import ( "fmt" "io" "github.com/klauspost/crc32" "github.com/chrislusf/seaweedfs/weed/util" ) var table = crc32.MakeTable(crc32.Castagnoli) type CRC uint32 func NewCRC(b []byte) CRC { return CRC(0).Update(b) } func (c CRC) Update(b []byte) CRC { return CRC(crc32.Update(uint32(c), table, b)) } func (c CRC) Value() uint32 { return uint32(c>>15|c<<17) + 0xa282ead8 } func (n *Needle) Etag() string { bits := make([]byte, 4) util.Uint32toBytes(bits, uint32(n.Checksum)) return fmt.Sprintf("%x", bits) } func NewCRCwriter(w io.Writer) *CRCwriter { return &CRCwriter{ crc: CRC(0), w: w, } } type CRCwriter struct { crc CRC w io.Writer } func (c *CRCwriter) Write(p []byte) (n int, err error) { n, err = c.w.Write(p) // with each write ... c.crc = c.crc.Update(p) return } func (c *CRCwriter) Sum() uint32 { return c.crc.Value() } // final hash