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Merge pull request #1307 from stevvooe/panic-on-unavailable

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digest: panic on unavailable hash algorithm
This commit is contained in:
Stephen Day 2015-12-29 18:47:02 -08:00
commit 0404e5a622
1 changed files with 11 additions and 3 deletions
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14
digest/digester.go
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@ -2,6 +2,7 @@ package digest
import (
"crypto"
"fmt"
"hash"
"io"
)
@ -84,11 +85,18 @@ func (a Algorithm) New() Digester {
}
}
// Hash returns a new hash as used by the algorithm. If not available, nil is
// returned. Make sure to check Available before calling.
// 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() {
return nil
// 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()