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