*: xattr can Update()

This is a gnarly patchset that has been mashed together.
It uncovered that some aspects of Check were never really working
correctly for `xattr` keywords, but also the `Update()` had been left
undone for a while.

This includes some API changes around the `Keyword` and `KeyVal` types.

Also I would like to update the signature for the `UpdateKeywordFunc` to
just accept a `KeyVal` as an argugment, rather than a keyword AND the
value. with this context there would be no need to guess on the value of
what's passed to the xattr update function of whether it needs or
already is base64 encoded.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

keywords.go

@@ -13,8 +13,30 @@ const DefaultVisFlags govis.VisFlag = govis.VisWhite | govis.VisOctal | govis.Vi
 
 // Keyword is the string name of a keyword, with some convenience functions for
 // determining whether it is a default or bsd standard keyword.
+// It first portion before the "="
 type Keyword string
 
+// Prefix is the portion of the keyword before a first "." (if present).
+//
+// Primarly for the xattr use-case, where the keyword `xattr.security.selinux` would have a Suffix of `security.selinux`.
+func (k Keyword) Prefix() Keyword {
+	if strings.Contains(string(k), ".") {
+		return Keyword(strings.SplitN(string(k), ".", 2)[0])
+	}
+	return k
+}
+
+// Suffix is the portion of the keyword after a first ".".
+// This is an option feature.
+//
+// Primarly for the xattr use-case, where the keyword `xattr.security.selinux` would have a Suffix of `security.selinux`.
+func (k Keyword) Suffix() string {
+	if strings.Contains(string(k), ".") {
+		return strings.SplitN(string(k), ".", 2)[1]
+	}
+	return string(k)
+}
+
 // Default returns whether this keyword is in the default set of keywords
 func (k Keyword) Default() bool {
 	return InKeywordSlice(k, DefaultKeywords)
@@ -93,24 +115,7 @@ func (kv KeyVal) Keyword() Keyword {
 	if !strings.Contains(string(kv), "=") {
 		return Keyword("")
 	}
-	chunks := strings.SplitN(strings.TrimSpace(string(kv)), "=", 2)[0]
-	if !strings.Contains(chunks, ".") {
-		return Keyword(chunks)
-	}
-	return Keyword(strings.SplitN(chunks, ".", 2)[0])
-}
-
-// KeywordSuffix is really only used for xattr, as the keyword is a prefix to
-// the xattr "namespace.key"
-func (kv KeyVal) KeywordSuffix() string {
-	if !strings.Contains(string(kv), "=") {
-		return ""
-	}
-	chunks := strings.SplitN(strings.TrimSpace(string(kv)), "=", 2)[0]
-	if !strings.Contains(chunks, ".") {
-		return ""
-	}
-	return strings.SplitN(chunks, ".", 2)[1]
+	return Keyword(strings.SplitN(strings.TrimSpace(string(kv)), "=", 2)[0])
 }
 
 // Value is the data/value portion of "keyword=value"
@@ -123,9 +128,6 @@ func (kv KeyVal) Value() string {
 
 // NewValue returns a new KeyVal with the newval
 func (kv KeyVal) NewValue(newval string) KeyVal {
-	if suff := kv.KeywordSuffix(); suff != "" {
-		return KeyVal(fmt.Sprintf("%s.%s=%s", kv.Keyword(), suff, newval))
-	}
 	return KeyVal(fmt.Sprintf("%s=%s", kv.Keyword(), newval))
 }
 
@@ -135,14 +137,23 @@ func (kv KeyVal) NewValue(newval string) KeyVal {
 // doing.
 func (kv KeyVal) Equal(b KeyVal) bool {
 	// TODO: Implement handling of tar_mtime.
-	return kv.Keyword() == b.Keyword() && kv.KeywordSuffix() == b.KeywordSuffix() && kv.Value() == b.Value()
+	return kv.Keyword() == b.Keyword() && kv.Value() == b.Value()
 }
 
-// keyvalSelector takes an array of KeyVal ("keyword=value") and filters out that only the set of keywords
+func keywordPrefixes(kvset []Keyword) []Keyword {
+	kvs := []Keyword{}
+	for _, kv := range kvset {
+		kvs = append(kvs, kv.Prefix())
+	}
+	return kvs
+}
+
+// keyvalSelector takes an array of KeyVal ("keyword=value") and filters out
+// that only the set of keywords
 func keyvalSelector(keyval []KeyVal, keyset []Keyword) []KeyVal {
 	retList := []KeyVal{}
 	for _, kv := range keyval {
-		if InKeywordSlice(kv.Keyword(), keyset) {
+		if InKeywordSlice(kv.Keyword().Prefix(), keywordPrefixes(keyset)) {
 			retList = append(retList, kv)
 		}
 	}
@@ -171,23 +182,23 @@ func keyValCopy(set []KeyVal) []KeyVal {
 
 // Has the "keyword" present in the list of KeyVal, and returns the
 // corresponding KeyVal, else an empty string.
-func Has(keyvals []KeyVal, keyword string) KeyVal {
+func Has(keyvals []KeyVal, keyword string) []KeyVal {
 	return HasKeyword(keyvals, Keyword(keyword))
 }
 
 // HasKeyword the "keyword" present in the list of KeyVal, and returns the
 // corresponding KeyVal, else an empty string.
-func HasKeyword(keyvals []KeyVal, keyword Keyword) KeyVal {
+// This match is done on the Prefix of the keyword only.
+func HasKeyword(keyvals []KeyVal, keyword Keyword) []KeyVal {
+	kvs := []KeyVal{}
 	for i := range keyvals {
-		if keyvals[i].Keyword() == keyword {
-			return keyvals[i]
+		if keyvals[i].Keyword().Prefix() == keyword.Prefix() {
+			kvs = append(kvs, keyvals[i])
 		}
 	}
-	return emptyKV
+	return kvs
 }
 
-var emptyKV = KeyVal("")
-
 // MergeSet takes the current setKeyVals, and then applies the entryKeyVals
 // such that the entry's values win. The union is returned.
 func MergeSet(setKeyVals, entryKeyVals []string) []KeyVal {
@@ -203,8 +214,11 @@ func MergeKeyValSet(setKeyVals, entryKeyVals []KeyVal) []KeyVal {
 	seenKeywords := []Keyword{}
 	for i := range retList {
 		word := retList[i].Keyword()
-		if ekv := HasKeyword(entryKeyVals, word); ekv != emptyKV {
-			retList[i] = ekv
+		for _, kv := range HasKeyword(entryKeyVals, word) {
+			// match on the keyword prefix and suffix here
+			if kv.Keyword() == word {
+				retList[i] = kv
+			}
 		}
 		seenKeywords = append(seenKeywords, word)
 	}