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53 lines
1.2 KiB
Go
53 lines
1.2 KiB
Go
// Copyright (c) 2011 The Grumble Authors
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// The use of this source code is goverened by a BSD-style
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// license that can be found in the LICENSE-file.
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package blobstore
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import (
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"bytes"
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"crypto/sha1"
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"encoding/hex"
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"errors"
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"hash"
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"io"
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)
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// blobReader is based on the principles of the checksumReader from the archive/zip
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// package of the Go standard library.
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// ErrHashMismatch is returned if a blobReader has read a file whose computed hash
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// did not match its key.
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var ErrHashMismatch = errors.New("hash mismatch")
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// blobReader reads a blob from disk, hashing all incoming data. On EOF, it checks
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// whether the read data matches the key.
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type blobReader struct {
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rc io.ReadCloser
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sum []byte
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hash hash.Hash
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}
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func newBlobReader(rc io.ReadCloser, key string) (br *blobReader, err error) {
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sum, err := hex.DecodeString(key)
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if err != nil {
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return
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}
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return &blobReader{rc, sum, sha1.New()}, nil
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}
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func (r *blobReader) Read(b []byte) (n int, err error) {
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n, err = r.rc.Read(b)
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r.hash.Write(b[:n])
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if err != io.EOF {
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return
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}
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if !bytes.Equal(r.sum, r.hash.Sum()) {
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err = ErrHashMismatch
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}
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return
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}
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func (r *blobReader) Close() error {
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return r.rc.Close()
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}
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