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Diffstat (limited to 'kube2msb/src/vendor/github.com/docker/distribution/digest/digester.go')
-rw-r--r-- | kube2msb/src/vendor/github.com/docker/distribution/digest/digester.go | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/kube2msb/src/vendor/github.com/docker/distribution/digest/digester.go b/kube2msb/src/vendor/github.com/docker/distribution/digest/digester.go new file mode 100644 index 0000000..f3105a4 --- /dev/null +++ b/kube2msb/src/vendor/github.com/docker/distribution/digest/digester.go @@ -0,0 +1,155 @@ +package digest + +import ( + "crypto" + "fmt" + "hash" + "io" +) + +// Algorithm identifies and implementation of a digester by an identifier. +// Note the that this defines both the hash algorithm used and the string +// encoding. +type Algorithm string + +// supported digest types +const ( + SHA256 Algorithm = "sha256" // sha256 with hex encoding + SHA384 Algorithm = "sha384" // sha384 with hex encoding + SHA512 Algorithm = "sha512" // sha512 with hex encoding + + // Canonical is the primary digest algorithm used with the distribution + // project. Other digests may be used but this one is the primary storage + // digest. + Canonical = SHA256 +) + +var ( + // TODO(stevvooe): Follow the pattern of the standard crypto package for + // registration of digests. Effectively, we are a registerable set and + // common symbol access. + + // algorithms maps values to hash.Hash implementations. Other algorithms + // may be available but they cannot be calculated by the digest package. + algorithms = map[Algorithm]crypto.Hash{ + SHA256: crypto.SHA256, + SHA384: crypto.SHA384, + SHA512: crypto.SHA512, + } +) + +// Available returns true if the digest type is available for use. If this +// returns false, New and Hash will return nil. +func (a Algorithm) Available() bool { + h, ok := algorithms[a] + if !ok { + return false + } + + // check availability of the hash, as well + return h.Available() +} + +func (a Algorithm) String() string { + return string(a) +} + +// Size returns number of bytes returned by the hash. +func (a Algorithm) Size() int { + h, ok := algorithms[a] + if !ok { + return 0 + } + return h.Size() +} + +// Set implemented to allow use of Algorithm as a command line flag. +func (a *Algorithm) Set(value string) error { + if value == "" { + *a = Canonical + } else { + // just do a type conversion, support is queried with Available. + *a = Algorithm(value) + } + + return nil +} + +// New returns a new digester for the specified algorithm. If the algorithm +// does not have a digester implementation, nil will be returned. This can be +// checked by calling Available before calling New. +func (a Algorithm) New() Digester { + return &digester{ + alg: a, + hash: a.Hash(), + } +} + +// Hash returns a new hash as used by the algorithm. If not available, the +// method will panic. Check Algorithm.Available() before calling. +func (a Algorithm) Hash() hash.Hash { + if !a.Available() { + // NOTE(stevvooe): A missing hash is usually a programming error that + // must be resolved at compile time. We don't import in the digest + // package to allow users to choose their hash implementation (such as + // when using stevvooe/resumable or a hardware accelerated package). + // + // Applications that may want to resolve the hash at runtime should + // call Algorithm.Available before call Algorithm.Hash(). + panic(fmt.Sprintf("%v not available (make sure it is imported)", a)) + } + + return algorithms[a].New() +} + +// FromReader returns the digest of the reader using the algorithm. +func (a Algorithm) FromReader(rd io.Reader) (Digest, error) { + digester := a.New() + + if _, err := io.Copy(digester.Hash(), rd); err != nil { + return "", err + } + + return digester.Digest(), nil +} + +// FromBytes digests the input and returns a Digest. +func (a Algorithm) FromBytes(p []byte) Digest { + digester := a.New() + + if _, err := digester.Hash().Write(p); err != nil { + // Writes to a Hash should never fail. None of the existing + // hash implementations in the stdlib or hashes vendored + // here can return errors from Write. Having a panic in this + // condition instead of having FromBytes return an error value + // avoids unnecessary error handling paths in all callers. + panic("write to hash function returned error: " + err.Error()) + } + + return digester.Digest() +} + +// TODO(stevvooe): Allow resolution of verifiers using the digest type and +// this registration system. + +// Digester calculates the digest of written data. Writes should go directly +// to the return value of Hash, while calling Digest will return the current +// value of the digest. +type Digester interface { + Hash() hash.Hash // provides direct access to underlying hash instance. + Digest() Digest +} + +// digester provides a simple digester definition that embeds a hasher. +type digester struct { + alg Algorithm + hash hash.Hash +} + +func (d *digester) Hash() hash.Hash { + return d.hash +} + +func (d *digester) Digest() Digest { + return NewDigest(d.alg, d.hash) +} |