81 lines
2.1 KiB
Go
81 lines
2.1 KiB
Go
package digest
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import (
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"crypto/sha256"
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"fmt"
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"hash"
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"github.com/jlhawn/go-crypto" // For ResumableHash
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_ "github.com/jlhawn/go-crypto/sha256" // For Resumable SHA256
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_ "github.com/jlhawn/go-crypto/sha512" // For Resumable SHA384, SHA512
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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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// 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 struct {
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alg string
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crypto.ResumableHash
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}
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var resumableHashAlgs = map[string]crypto.Hash{
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"sha256": crypto.SHA256,
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"sha384": crypto.SHA384,
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"sha512": crypto.SHA512,
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}
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// NewResumableDigester creates a new ResumableDigester with the given hashing
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// algorithm.
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func NewResumableDigester(alg string) (ResumableDigester, error) {
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hash, supported := resumableHashAlgs[alg]
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if !supported {
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return ResumableDigester{}, fmt.Errorf("unsupported resumable hash algorithm: %s", alg)
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}
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return ResumableDigester{
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alg: alg,
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ResumableHash: hash.New(),
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}, nil
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}
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// NewCanonicalResumableDigester creates a ResumableDigester using the default
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// digest algorithm.
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func NewCanonicalResumableDigester() ResumableDigester {
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return ResumableDigester{
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alg: "sha256",
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ResumableHash: crypto.SHA256.New(),
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}
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}
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// Digest returns the current digest for this resumable digester.
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func (d ResumableDigester) Digest() Digest {
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return NewDigest(d.alg, d.ResumableHash)
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}
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