forked from cayleygraph/cayley
/
decompressor.go
46 lines (42 loc) · 1.18 KB
/
decompressor.go
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// Copyright 2014 The Cayley Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package internal
import (
"bufio"
"bytes"
"compress/bzip2"
"compress/gzip"
"io"
)
const (
gzipMagic = "\x1f\x8b"
b2zipMagic = "BZh"
)
// Decompressor detects the file type of an io.Reader between
// bzip, gzip, or raw quad file.
func Decompressor(r io.Reader) (io.Reader, error) {
br := bufio.NewReader(r)
buf, err := br.Peek(3)
if err != nil {
return nil, err
}
switch {
case bytes.Compare(buf[:2], []byte(gzipMagic)) == 0:
return gzip.NewReader(br)
case bytes.Compare(buf[:3], []byte(b2zipMagic)) == 0:
return bzip2.NewReader(br), nil
default:
return br, nil
}
}