doc(error): document possible varsig encoding/decoding errors

error.go

@@ -0,0 +1,43 @@
+package varsig
+
+import "errors"
+
+// ErrMissingSignature is returned when a varsig v0 is parsed and does
+// not contain the expected signature bytes.  This is expected in some
+// intermediate cases, such as the UCAN v1 specification.
+var ErrMissingSignature = errors.New("missing signature expected in varsig v0")
+
+// ErrNotYetImplemented is returned when a function is currently under
+// construction.  For released versions of this library, this error should
+// never occur.
+var ErrNotYetImplemented = errors.New("not yet implemented")
+
+// ErrUnexpectedSignaturePresent is returned when a signature is present
+// in  a varsig >= v1.
+var ErrUnexpectedSignaturePresent = errors.New("unexpected signature present in varsig >= v1")
+
+// ErrUnexpectedSignatureSize is returned when the length of the decoded
+// signature doesn't match the expected signature length as defined by the
+// signing algorithm or sent via a Varsig field.
+var ErrUnexpectedSignatureSize = errors.New("unexpected signature size in varsig v0")
+
+// ErrUnknownHashAlgoritm is returned when an unexpected value is provided
+// while decoding the hashing algorithm.
+var ErrUnknownHashAlgorithm = errors.New("unknown hash algorithm")
+
+// ErrUnsupportedPayloadEncoding is returned when an unexpected value is
+// provided while decoding the payload encoding field.  The allowed values
+// for this field may vary based on the varsig version.
+var ErrUnsupportedPayloadEncoding = errors.New("unsupported payload encoding")
+
+// ErrUnknownSignAlgorith is returned when the Registry doesn't have a
+// parsing function for the decoded signing algorithm.
+var ErrUnknownSignAlgorithm = errors.New("unknown signing algorithm")
+
+// ErrUnsupportedVersion is returned when an unsupported varsig version
+// field is present.
+var ErrUnsupportedVersion = errors.New("unsupported version")
+
+// ErrBadPrefix is returned when the prefix field contains a value other
+// than 0x34 (encoded as a uvarint).
+var ErrBadPrefix = errors.New("varsig prefix not found")