/
reader.go
219 lines (202 loc) · 4.61 KB
/
reader.go
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package kaito
import (
"compress/bzip2"
"compress/gzip"
"errors"
"io"
"os/exec"
"runtime"
"github.com/ulikunitz/xz"
)
type Reader struct {
io.Reader // Just delegate all Read operation to this Reader
}
func New(r io.Reader) io.Reader {
return NewWithOptions(r, 0)
}
func NewWithOptions(r io.Reader, o Options) io.Reader {
this := new(Reader)
this.Reader = newCodecDetectReader(this, r, o)
return this
}
// We need to read at most 6 bytes to detect gzip, bzip2 and xz format.
const maxHeaderLength = 6
type codecType int
const (
codecUndetermined = iota
codecGzip
codecBzip2
codecXz
)
var errUnknownCodec = errors.New("Unknown codec")
type codecDetectReader struct {
kaito *Reader // Pointer to KaitoReader
in io.Reader
opts Options
buf [maxHeaderLength]byte
len int // number of bytes read in buf
}
func newCodecDetectReader(k *Reader, r io.Reader, o Options) *codecDetectReader {
return &codecDetectReader{kaito: k, in: r, opts: o}
}
func (cdr *codecDetectReader) detect() (codecType, error) {
isEOF := false
n, err := cdr.in.Read(cdr.buf[cdr.len:])
if err != nil {
if err == io.EOF {
isEOF = true
} else {
return codecUndetermined, err
}
}
cdr.len += n
// ここから下は、ホントはDFAを書いたほうが効率がよい
if cdr.len >= 1 && cdr.buf[0] != 0x1F && cdr.buf[0] != 'B' && cdr.buf[0] != 0xFD {
return codecUndetermined, errUnknownCodec
}
if cdr.len >= 2 && cdr.buf[0] == 0x1F {
if cdr.buf[1] == 0x8B && !cdr.opts.IsDisableGzip() {
return codecGzip, nil
}
return codecUndetermined, errUnknownCodec
}
if cdr.len >= 3 && cdr.buf[0] == 'B' && !cdr.opts.IsDisableBzip2() {
if cdr.buf[1] == 'Z' && cdr.buf[2] == 'h' {
return codecBzip2, nil
}
return codecUndetermined, errUnknownCodec
}
if cdr.len >= 6 && cdr.buf[0] == 0xFD {
if cdr.buf[1] == '7' && cdr.buf[2] == 'z' && cdr.buf[3] == 'X' && cdr.buf[4] == 'Z' && cdr.buf[5] == 0x00 && !cdr.opts.IsDisableXz() {
return codecXz, nil
}
return codecUndetermined, errUnknownCodec
}
if isEOF || cdr.len >= maxHeaderLength {
return codecUndetermined, errUnknownCodec
}
return codecUndetermined, nil
}
func (cdr *codecDetectReader) Read(p []byte) (int, error) {
var codec codecType
var err error
for {
codec, err = cdr.detect() // Read header if it is not read yet
if codec != codecUndetermined {
break
}
if err != nil {
if err == errUnknownCodec {
err = nil // not error
break
}
return copy(p, cdr.buf[0:cdr.len]), err
}
}
switch codec {
case codecGzip:
err = cdr.initGzip()
case codecBzip2:
err = cdr.initBzip2()
case codecXz:
err = cdr.initXz()
default: // Here, codec == CODEC_UNDETERMINED, it is treated as plain text
r, w := io.Pipe()
go func() {
w.Write(cdr.buf[0:cdr.len])
io.Copy(w, cdr.in)
w.Close()
}()
cdr.kaito.Reader = r
}
if err != nil {
return copy(p, cdr.buf[0:cdr.len]), err
}
return cdr.kaito.Reader.Read(p)
}
func (cdr *codecDetectReader) initGzip() error {
if !cdr.opts.IsForceNative() {
err := cdr.initCmd("gzip", "-cd")
if err == nil {
return nil
}
// Fallback through Golang-native implementation.
}
r, w := io.Pipe()
go func() {
w.Write(cdr.buf[0:cdr.len])
io.Copy(w, cdr.in)
w.Close()
}()
unzipped, err := gzip.NewReader(r)
if err != nil {
return err
}
cdr.kaito.Reader = unzipped
return nil
}
func (cdr *codecDetectReader) initBzip2() error {
if !cdr.opts.IsForceNative() {
err := cdr.initCmd("bzip2", "-cd")
if err == nil {
return nil
}
// Fallback through Golang-native implementation.
}
r, w := io.Pipe()
go func() {
w.Write(cdr.buf[0:cdr.len])
io.Copy(w, cdr.in)
w.Close()
}()
cdr.kaito.Reader = bzip2.NewReader(r)
return nil
}
func (cdr *codecDetectReader) initXz() error {
if !cdr.opts.IsForceNative() {
err := cdr.initCmd("xz", "-cd")
if err == nil {
return nil
}
// Fallback through Golang-native implementation.
}
r, w := io.Pipe()
go func() {
w.Write(cdr.buf[0:cdr.len])
io.Copy(w, cdr.in)
w.Close()
}()
unxz, err := (xz.ReaderConfig{SingleStream: true}).NewReader(r)
if err != nil {
return nil
}
cdr.kaito.Reader = unxz
return nil
}
func (cdr *codecDetectReader) initCmd(c string, args ...string) (err error) {
cmd := exec.Command(c, args...)
stdin, err := cmd.StdinPipe()
if err != nil {
return err
}
stdout, err := cmd.StdoutPipe()
if err != nil {
return err
}
err = cmd.Start()
if err != nil {
return err
}
go func() {
stdin.Write(cdr.buf[0:cdr.len])
io.Copy(stdin, cdr.in)
stdin.Close()
}()
cdr.kaito.Reader = stdout
runtime.SetFinalizer(cdr.kaito, func(o interface{}) {
stdin.Close()
stdout.Close()
cmd.Wait()
})
return nil
}