// NewInflater creates a new io.ReadCloser that satisfies reads by decompressing data read from r.
// The implementation buffers input and may read more data than necessary from r.
// It is the caller's responsibility to call Close on the ReadCloser when done.
func NewInflater(r io.Reader) (io.ReadCloser, os.Error) {
z := new(reader)
if fr, ok := r.(flate.Reader); ok {
z.r = fr
} else {
z.r = bufio.NewReader(r)
}
_, err := io.ReadFull(z.r, z.scratch[0:2])
if err != nil {
return nil, err
}
h := uint(z.scratch[0])<<8 | uint(z.scratch[1])
if (z.scratch[0]&0x0f != zlibDeflate) || (h%31 != 0) {
return nil, HeaderError
}
if z.scratch[1]&0x20 != 0 {
// BUG(nigeltao): The zlib package does not implement the FDICT flag.
return nil, UnsupportedError
}
z.digest = adler32.New()
z.inflater = flate.NewInflater(z.r)
return z, nil
}
func (z *Inflater) readHeader(save bool) os.Error {
_, err := io.ReadFull(z.r, z.buf[0:10])
if err != nil {
return err
}
if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate {
return HeaderError
}
z.flg = z.buf[3]
if save {
z.Mtime = get4(z.buf[4:8])
// z.buf[8] is xfl, ignored
z.OS = z.buf[9]
}
z.digest.Reset()
z.digest.Write(z.buf[0:10])
if z.flg&flagExtra != 0 {
n, err := z.read2()
if err != nil {
return err
}
data := make([]byte, n)
if _, err = io.ReadFull(z.r, data); err != nil {
return err
}
if save {
z.Extra = data
}
}
var s string
if z.flg&flagName != 0 {
if s, err = z.readString(); err != nil {
return err
}
if save {
z.Name = s
}
}
if z.flg&flagComment != 0 {
if s, err = z.readString(); err != nil {
return err
}
if save {
z.Comment = s
}
}
if z.flg&flagHdrCrc != 0 {
n, err := z.read2()
if err != nil {
return err
}
sum := z.digest.Sum32() & 0xFFFF
if n != sum {
return HeaderError
}
}
z.digest.Reset()
z.inflater = flate.NewInflater(z.r)
return nil
}