/
tag_lzw.go
56 lines (51 loc) · 1.17 KB
/
tag_lzw.go
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package gofast
import "compress/lzw"
import "bytes"
import "io"
import "fmt"
import s "github.com/bnclabs/gosettings"
func makeLZW(t *Transport, _ s.Settings) (uint64, tagfn, tagfn) {
var wbuf bytes.Buffer
enc := func(in, out []byte) int {
if len(in) == 0 {
return 0
}
wbuf.Reset()
writer := lzw.NewWriter(&wbuf, lzw.LSB, 8 /*litWidth*/)
if _, err := writer.Write(in); err != nil {
panic(fmt.Errorf("error encoding lzw: %v", err))
}
writer.Close()
return copy(out, wbuf.Bytes())
}
dec := func(in, out []byte) int {
if len(in) == 0 {
return 0
}
reader := lzw.NewReader(bytes.NewReader(in), lzw.LSB, 8 /*litWidth*/)
n, err := readAll(reader, out)
if err != nil {
panic(fmt.Errorf("error decoding lzw: %v", err))
}
reader.Close()
return n
}
return tagLzw, enc, dec
}
func readAll(r io.Reader, out []byte) (n int, err error) {
c := 0
for err == nil {
// Per http://golang.org/pkg/io/#Reader, it is valid for Read to
// return EOF with non-zero number of bytes at the end of the
// input stream
c, err = r.Read(out[n:])
n += c
}
if err == io.EOF {
return n, nil
}
return n, err
}
func init() {
tagFactory["lzw"] = makeLZW
}