mirror of https://github.com/perkeep/perkeep.git
86 lines
2.2 KiB
Go
86 lines
2.2 KiB
Go
/*
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Copyright 2013 The Perkeep Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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// Package hashutil contains misc hashing functions lacking homes elsewhere.
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package hashutil // import "perkeep.org/internal/hashutil"
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import (
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"crypto/sha1"
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"crypto/sha256"
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"fmt"
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"hash"
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"io"
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"perkeep.org/pkg/blob"
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)
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// SHA256Prefix computes the SHA-256 digest of data and returns
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// its first twenty lowercase hex digits.
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func SHA256Prefix(data []byte) string {
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h := sha256.New()
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h.Write(data)
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return fmt.Sprintf("%x", h.Sum(nil))[:20]
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}
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// SHA1Prefix computes the SHA-1 digest of data and returns
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// its first twenty lowercase hex digits.
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func SHA1Prefix(data []byte) string {
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h := sha1.New()
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h.Write(data)
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return fmt.Sprintf("%x", h.Sum(nil))[:20]
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}
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// TrackDigestReader is an io.Reader wrapper which records the digest of what it reads.
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type TrackDigestReader struct {
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r io.Reader
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h hash.Hash
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// DoLegacySHA1 sets whether to also compute the legacy SHA-1 hash.
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DoLegacySHA1 bool
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s1 hash.Hash // optional legacy SHA-1 hash, for servers with old data
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}
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func NewTrackDigestReader(r io.Reader) *TrackDigestReader {
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return &TrackDigestReader{r: r}
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}
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// Hash returns the current hash sum.
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func (t *TrackDigestReader) Hash() hash.Hash {
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return t.h
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}
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// LegacySHA1Hash returns the current legacy SHA-1 hash sum.
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func (t *TrackDigestReader) LegacySHA1Hash() hash.Hash {
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return t.s1
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}
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func (t *TrackDigestReader) Read(p []byte) (n int, err error) {
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n, err = t.r.Read(p)
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if t.h == nil {
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// TODO(mpl): maybe let the constructor take a Hash, and then no need to depend on blob pkg.
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t.h = blob.NewHash()
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}
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t.h.Write(p[:n])
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if t.DoLegacySHA1 {
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if t.s1 == nil {
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t.s1 = sha1.New()
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}
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t.s1.Write(p[:n])
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}
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return n, err
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}
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