// CompressionFormat checks to see if the data in the provided reader uses
// a supported compression format. If it does not, an UnsupportedErr is
// returned.
func CompressionFormat(r io.ReaderAt) (compress.Format, error) {
f, err := compress.GetFormat(r)
if err != nil {
return compress.Unknown, err
}
// see if the format is a supported on
switch f {
case compress.GZip:
return f, nil
case compress.BZip2: // only decompression is supported.
return f, nil
case compress.LZ4:
return f, nil
default:
return f, ErrUnsupported
}
}
// Decompress is the handler for decompression. The decompression format to use
// is determined by the magic bytes within the data. If no match is found, an
// ErrUnsupported is returned. Bytes read is returned along with any non io.EOF
// error that may have occurred. If the reader doesn't implement io.ReaderAt
// a panic will occur.
func Decompress(r io.Reader, w io.Writer) (int64, error) {
a, ok := r.(io.ReaderAt)
if !ok {
panic("io.Reader does not implement io.ReaderAt")
}
f, err := compress.GetFormat(a)
if err != nil {
return 0, err
}
switch f {
case compress.GZip:
return DecompressGZip(r, w)
case compress.BZip2:
return DecompressBZip2(r, w)
case compress.LZ4:
return DecompressLZ4(r, w)
default:
return 0, ErrUnsupported
}
}