55 lines
1.4 KiB
Go
55 lines
1.4 KiB
Go
package digest
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import (
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"crypto/sha256"
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"hash"
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)
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// Digester calculates the digest of written data. It is functionally
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// equivalent to hash.Hash but provides methods for returning the Digest type
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// rather than raw bytes.
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type Digester struct {
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alg string
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hash.Hash
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}
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// NewDigester create a new Digester with the given hashing algorithm and instance
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// of that algo's hasher.
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func NewDigester(alg string, h hash.Hash) Digester {
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return Digester{
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alg: alg,
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Hash: h,
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}
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}
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// NewCanonicalDigester is a convenience function to create a new Digester with
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// our default settings.
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func NewCanonicalDigester() Digester {
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return NewDigester("sha256", sha256.New())
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}
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// Digest returns the current digest for this digester.
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func (d *Digester) Digest() Digest {
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return NewDigest(d.alg, d.Hash)
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}
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// ResumableHash is the common interface implemented by all resumable hash
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// functions.
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type ResumableHash interface {
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// ResumableHash is a superset of hash.Hash
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hash.Hash
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// Len returns the number of bytes written to the Hash so far.
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Len() uint64
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// State returns a snapshot of the state of the Hash.
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State() ([]byte, error)
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// Restore resets the Hash to the given state.
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Restore(state []byte) error
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}
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// ResumableDigester is a digester that can export its internal state and be
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// restored from saved state.
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type ResumableDigester interface {
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ResumableHash
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Digest() Digest
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}
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