consul: Filter keys, refactor to interface

consul/filter.go

@@ -5,35 +5,85 @@ import (
 	"github.com/hashicorp/consul/consul/structs"
 )
 
-func FilterDirEnt(acl acl.ACL, ent structs.DirEntries) structs.DirEntries {
-	// Remove any keys blocked by ACLs
-	removed := 0
-	for i := 0; i < len(ent); i++ {
-		if !acl.KeyRead(ent[i].Key) {
-			ent[i] = nil
-			removed++
-		}
-	}
+type dirEntFilter struct {
+	acl acl.ACL
+	ent structs.DirEntries
+}
 
+func (d *dirEntFilter) Len() int {
+	return len(d.ent)
+}
+func (d *dirEntFilter) Filter(i int) bool {
+	return !d.acl.KeyRead(d.ent[i].Key)
+}
+func (d *dirEntFilter) Move(dst, src, span int) {
+	copy(d.ent[dst:dst+span], d.ent[src:src+span])
+}
+
+// FilterDirEnt is used to filter a list of directory entries
+// by applying an ACL policy
+func FilterDirEnt(acl acl.ACL, ent structs.DirEntries) structs.DirEntries {
+	df := dirEntFilter{acl: acl, ent: ent}
+	return ent[:FilterEntries(&df)]
+}
+
+type keyFilter struct {
+	acl  acl.ACL
+	keys []string
+}
+
+func (k *keyFilter) Len() int {
+	return len(k.keys)
+}
+func (k *keyFilter) Filter(i int) bool {
+	return !k.acl.KeyRead(k.keys[i])
+}
+
+func (k *keyFilter) Move(dst, src, span int) {
+	copy(k.keys[dst:dst+span], k.keys[src:src+span])
+}
+
+// FilterKeys is used to filter a list of keys by
+// applying an ACL policy
+func FilterKeys(acl acl.ACL, keys []string) []string {
+	kf := keyFilter{acl: acl, keys: keys}
+	return keys[:FilterEntries(&kf)]
+}
+
+// Filter interfae is used with FilterEntries to do an
+// in-place filter of a slice.
+type Filter interface {
+	Len() int
+	Filter(int) bool
+	Move(dst, src, span int)
+}
+
+// FilterEntries is used to do an inplace filter of
+// a slice. This has cost proportional to the list length.
+func FilterEntries(f Filter) int {
 	// Compact the list
 	dst := 0
 	src := 0
-	n := len(ent) - removed
+	n := f.Len()
 	for dst < n {
-		for ent[src] == nil && src < n {
+		for src < n && f.Filter(src) {
 			src++
 		}
+		if src == n {
+			break
+		}
 		end := src + 1
-		for ent[end] != nil && end < n {
+		for end < n && !f.Filter(end) {
 			end++
 		}
 		span := end - src
-		copy(ent[dst:dst+span], ent[src:src+span])
-		dst += span
-		src += span
+		if span > 0 {
+			f.Move(dst, src, span)
+			dst += span
+			src += span
+		}
 	}
 
-	// Trim the entries
-	ent = ent[:n]
-	return ent
+	// Return the size of the slice
+	return dst
 }

consul/filter_test.go

@@ -49,6 +49,37 @@ func TestFilterDirEnt(t *testing.T) {
 	}
 }
 
+func TestKeys(t *testing.T) {
+	policy, _ := acl.Parse(testFilterRules)
+	aclR, _ := acl.New(acl.DenyAll(), policy)
+
+	type tcase struct {
+		in  []string
+		out []string
+	}
+	cases := []tcase{
+		tcase{
+			in:  []string{"foo/test", "foo/priv/nope", "foo/other", "zoo"},
+			out: []string{"foo/test", "foo/other"},
+		},
+		tcase{
+			in:  []string{"abe", "lincoln"},
+			out: nil,
+		},
+		tcase{
+			in:  []string{"abe", "foo/1", "foo/2", "foo/3", "nope"},
+			out: []string{"foo/1", "foo/2", "foo/3"},
+		},
+	}
+
+	for _, tc := range cases {
+		out := FilterKeys(aclR, tc.in)
+		if !reflect.DeepEqual(out, tc.out) {
+			t.Fatalf("bad: %#v %#v", out, tc.out)
+		}
+	}
+}
+
 var testFilterRules = `
 key "" {
 	policy = "deny"