Merge pull request #9 from the-maldridge/indexed

Add index generation for caches

.gitignore

@@ -1,2 +1,2 @@
-examples/*/*.cache
+examples/*/*.cache*
 vendor/

cache/cache.go

@@ -2,7 +2,10 @@
 package cache
 
 import (
+	"bytes"
+	"fmt"
 	"io"
+	"sort"
 )
 
 type ACL func(e Entry) bool
@@ -57,3 +60,34 @@ func (c *Cache) WriteTo(w io.Writer) (int64, error) {
 	}
 	return total, nil
 }
+
+// Index generates an index for the given cache on a particular
+// column.  This is required for caches beyond a libnss-cache defined
+// size in order for them to be read correctly.
+func (c *Cache) Index(col int) bytes.Buffer {
+	ordered := make([]string, len(c.entries))
+	mapped := make(map[string]Entry, len(c.entries))
+	for i := range c.entries {
+		key := c.entries[i].Column(col)
+		ordered[i] = key
+		mapped[key] = c.entries[i]
+	}
+
+	// libnss-cache depends on the indexes being ordered in order
+	// to accelerate the system with a binary search.
+	sort.Strings(ordered)
+
+	var b bytes.Buffer
+	var offset int64
+	for _, key := range ordered {
+		b.WriteString(key)
+		b.WriteByte(0)
+		fmt.Fprintf(&b, "%08d", offset)
+		for i := 0; i < 32-len(key)-1; i++ {
+			b.WriteByte(0)
+		}
+		b.WriteString("\n")
+		offset += int64(len(mapped[key].String())) + 1
+	}
+	return b
+}

cache/cache_test.go

@@ -101,3 +101,36 @@ func TestCache_WriteTo(t *testing.T) {
 	_, err := c.WriteTo(w)
 	assert.NotNil(t, err)
 }
+
+func TestCacheIndex(t *testing.T) {
+	c := NewCache()
+	c.Add(&PasswdEntry{
+		Name:   "foo",
+		Passwd: "x",
+		UID:    1000,
+		GID:    1000,
+		GECOS:  "Mr Foo",
+		Dir:    "/home/foo",
+		Shell:  "/bin/bash",
+	}, &PasswdEntry{
+		Name:   "admin",
+		Passwd: "x",
+		UID:    1002,
+		GID:    1000,
+		GECOS:  "Admin",
+		Dir:    "/home/admin",
+		Shell:  "/bin/bash",
+	}, &PasswdEntry{
+		Name:   "bar",
+		Passwd: "x",
+		UID:    1001,
+		GID:    1000,
+		GECOS:  "Mrs Bar",
+		Dir:    "/home/bar",
+		Shell:  "/bin/bash",
+	})
+
+	idx := c.Index(0)
+	expected := []byte{97, 100, 109, 105, 110, 0, 48, 48, 48, 48, 48, 48, 48, 48, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 98, 97, 114, 0, 48, 48, 48, 48, 48, 48, 52, 55, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 102, 111, 111, 0, 48, 48, 48, 48, 48, 48, 57, 50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10}
+	assert.Equal(t, expected, idx.Bytes())
+}

cache/entries.go

@@ -9,6 +9,8 @@ import (
 type Entry interface {
 	fmt.Stringer
 	io.WriterTo
+
+	Column(int) string
 }
 
 // PasswdEntry describes an entry of the /etc/passwd file
@@ -44,6 +46,19 @@ func (e *PasswdEntry) args() []interface{} {
 	}
 }
 
+// Column returns the information from the requested columns or an
+// empty string if no column is known.
+func (e *PasswdEntry) Column(col int) string {
+	switch col {
+	case 0:
+		return e.Name
+	case 2:
+		return fmt.Sprintf("%d", e.UID)
+	default:
+		return ""
+	}
+}
+
 func (e *PasswdEntry) String() string {
 	return fmt.Sprintf(e.format(), e.args()...)
 }
@@ -89,6 +104,17 @@ func (e *ShadowEntry) args() []interface{} {
 	}
 }
 
+// Column returns the information from the requested columns or an
+// empty string if no column is known.
+func (e *ShadowEntry) Column(col int) string {
+	switch col {
+	case 0:
+		return e.Name
+	default:
+		return ""
+	}
+}
+
 func (e *ShadowEntry) String() string {
 	return fmt.Sprintf(e.format(), e.args()...)
 }
@@ -124,6 +150,19 @@ func (e *GroupEntry) args() []interface{} {
 	}
 }
 
+// Column returns the information from the requested columns or an
+// empty string if no column is known.
+func (e *GroupEntry) Column(col int) string {
+	switch col {
+	case 0:
+		return e.Name
+	case 2:
+		return fmt.Sprintf("%d", e.GID)
+	default:
+		return ""
+	}
+}
+
 func (e *GroupEntry) String() string {
 	return fmt.Sprintf(e.format(), e.args()...)
 }

cache/entries_test.go

@@ -36,6 +36,21 @@ func TestPasswdEntry_WriteTo(t *testing.T) {
 	assert.Equal(t, expected, b.String())
 }
 
+func TestPasswdEntry_Column(t *testing.T) {
+	e := PasswdEntry{
+		Name:  "foo",
+		UID:   1000,
+		GID:   1000,
+		GECOS: "Mr Foo",
+		Dir:   "/home/foo",
+		Shell: "/usr/bin/bash",
+	}
+
+	assert.Equal(t, "foo", e.Column(0))
+	assert.Equal(t, "1000", e.Column(2))
+	assert.Equal(t, "", e.Column(1))
+}
+
 func TestShadowEntry_String(t *testing.T) {
 	e := ShadowEntry{
 		Name: "foo",
@@ -56,6 +71,14 @@ func TestShadowEntry_WriteTo(t *testing.T) {
 	assert.Equal(t, expected, b.String())
 }
 
+func TestShadowEntry_Column(t *testing.T) {
+	e := ShadowEntry{
+		Name: "foo",
+	}
+	assert.Equal(t, "foo", e.Column(0))
+	assert.Equal(t, "", e.Column(1))
+}
+
 func TestGroupEntry_String(t *testing.T) {
 	e := GroupEntry{
 		Name: "foo",
@@ -76,6 +99,16 @@ func TestGroupEntry_WriteTo(t *testing.T) {
 	assert.Equal(t, expected, b.String())
 }
 
+func TestGroupEntry_Column(t *testing.T) {
+	e := GroupEntry{
+		Name: "foo",
+		GID:  1000,
+	}
+	assert.Equal(t, "foo", e.Column(0))
+	assert.Equal(t, "1000", e.Column(2))
+	assert.Equal(t, "", e.Column(1))
+}
+
 func writerToError(i int64, e error) error {
 	return e
 }

nsscache.go

@@ -3,7 +3,7 @@ package nsscache
 
 import (
 	"fmt"
-	"path"
+	"path/filepath"
 
 	"os"
 
@@ -75,7 +75,8 @@ func defaultWriteOptions() WriteOptions {
 	}
 }
 
-// WriteFiles write the content of the cache structs into files that libnss-cache can read
+// WriteFiles write the content of the cache structs into files that
+// libnss-cache can read.
 func (cm *CacheMap) WriteFiles(options *WriteOptions) error {
 	wo := defaultWriteOptions()
 	if options != nil {
@@ -88,12 +89,32 @@ func (cm *CacheMap) WriteFiles(options *WriteOptions) error {
 	}
 
 	for _, name := range []string{"passwd", "shadow", "group"} {
-		filepath := path.Join(wo.Directory, fmt.Sprintf("%s.%s", name, wo.Extension))
+		fpath := filepath.Join(wo.Directory, fmt.Sprintf("%s.%s", name, wo.Extension))
 		mode := 0644
 		if name == "shadow" {
 			mode = 0000
 		}
-		if err := WriteAtomic(filepath, (*cm)[name], os.FileMode(mode)); err != nil {
+		if err := WriteAtomic(fpath, (*cm)[name], os.FileMode(mode)); err != nil {
+			return err
+		}
+	}
+
+	idxCfg := []struct {
+		cache  string
+		column int
+		supext string
+	}{
+		{"passwd", 0, "ixname"},
+		{"passwd", 2, "ixuid"},
+		{"group", 0, "ixname"},
+		{"group", 2, "ixgid"},
+		{"shadow", 0, "ixname"},
+	}
+
+	for _, idx := range idxCfg {
+		fpath := filepath.Join(wo.Directory, fmt.Sprintf("%s.%s.%s", idx.cache, wo.Extension, idx.supext))
+		idx := (*cm)[idx.cache].Index(idx.column)
+		if err := WriteAtomic(fpath, &idx, os.FileMode(0644)); err != nil {
 			return err
 		}
 	}

nsscache_test.go

@@ -164,8 +164,16 @@ func TestCacheMap_WriteFiles(t *testing.T) {
 
 	_, err = os.Stat(path.Join(dir, "passwd.cachetest"))
 	assert.Nil(t, err)
+	_, err = os.Stat(path.Join(dir, "passwd.cachetest.ixname"))
+	assert.Nil(t, err)
+	_, err = os.Stat(path.Join(dir, "passwd.cachetest.ixuid"))
+	assert.Nil(t, err)
 	_, err = os.Stat(path.Join(dir, "group.cachetest"))
 	assert.Nil(t, err)
+	_, err = os.Stat(path.Join(dir, "group.cachetest.ixname"))
+	assert.Nil(t, err)
+	_, err = os.Stat(path.Join(dir, "group.cachetest.ixgid"))
+	assert.Nil(t, err)
 	_, err = os.Stat(path.Join(dir, "shadow.cachetest"))
 	assert.Nil(t, err)