Merge pull request #78 from cpunion/fs-parent-sub

fs: add fs.Parent, fs.Sub

http/fs/fs.go

@@ -22,6 +22,7 @@ import (
 	"net/http"
 	"os"
 	"path"
+	"strings"
 	"time"
 )
 
@@ -258,3 +259,45 @@ func Root() http.FileSystem {
 }
 
 // -----------------------------------------------------------------------------------------
+
+type parentFS struct {
+	parentDir string
+	fs        http.FileSystem
+}
+
+func Parent(parentDir string, fs http.FileSystem) http.FileSystem {
+	parentDir = strings.TrimSuffix(parentDir, "/")
+	if !strings.HasPrefix(parentDir, "/") {
+		parentDir = "/" + parentDir
+	}
+	return &parentFS{parentDir, fs}
+}
+
+func (p *parentFS) Open(name string) (f http.File, err error) {
+	if !strings.HasPrefix(name, p.parentDir) {
+		return nil, os.ErrNotExist
+	}
+	path := name[len(p.parentDir):]
+	return p.fs.Open(path)
+}
+
+// -----------------------------------------------------------------------------------------
+
+type subFS struct {
+	subDir string
+	fs     http.FileSystem
+}
+
+func Sub(fs http.FileSystem, subDir string) http.FileSystem {
+	subDir = strings.TrimSuffix(subDir, "/")
+	if !strings.HasPrefix(subDir, "/") {
+		subDir = "/" + subDir
+	}
+	return &subFS{subDir, fs}
+}
+
+func (p *subFS) Open(name string) (f http.File, err error) {
+	return p.fs.Open(p.subDir + name)
+}
+
+// -----------------------------------------------------------------------------------------

http/fs/fs_test.go

@@ -0,0 +1,37 @@
+package fs
+
+import (
+	"os"
+	"testing"
+)
+
+func TestParentFS(t *testing.T) {
+	fs := FilesWithContent("a.txt", "a")
+	if _, err := fs.Open("/a.txt"); err != nil {
+		t.Fatal(err)
+	}
+
+	p := Parent("files", fs)
+	if _, err := p.Open("/files/a.txt"); err != nil {
+		t.Fatal(err)
+	}
+	_, err := p.Open("/a.txt")
+	if err == nil {
+		t.Fatal("expect error")
+	}
+	if !os.IsNotExist(err) {
+		t.Fatalf("expect os.IsNotExist(err) but got %v", err)
+	}
+}
+
+func TestSubFS(t *testing.T) {
+	fs := FilesWithContent("files/a.txt", "a")
+	if _, err := fs.Open("/files/a.txt"); err != nil {
+		t.Fatal(err)
+	}
+
+	s := Sub(fs, "files")
+	if _, err := s.Open("/a.txt"); err != nil {
+		t.Fatal(err)
+	}
+}