Initial QSfera import

Server/vendor/github.com/shurcooL/httpfs/union/union.go

@@ -0,0 +1,106 @@
+// Package union offers a simple http.FileSystem that can unify multiple filesystems at various mount points.
+package union
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+)
+
+// New creates an union filesystem with the provided mapping of mount points to filesystems.
+//
+// Each mount point must be of form "/mydir". It must start with a '/', and contain a single directory name.
+func New(mapping map[string]http.FileSystem) http.FileSystem {
+	u := &unionFS{
+		ns: make(map[string]http.FileSystem),
+		root: &dirInfo{
+			name: "/",
+		},
+	}
+	for mountPoint, fs := range mapping {
+		u.bind(mountPoint, fs)
+	}
+	return u
+}
+
+type unionFS struct {
+	ns   map[string]http.FileSystem // Key is mount point, e.g., "/mydir".
+	root *dirInfo
+}
+
+// bind mounts fs at mountPoint.
+// mountPoint must be of form "/mydir". It must start with a '/', and contain a single directory name.
+func (u *unionFS) bind(mountPoint string, fs http.FileSystem) {
+	u.ns[mountPoint] = fs
+	u.root.entries = append(u.root.entries, &dirInfo{
+		name: mountPoint[1:],
+	})
+}
+
+// Open opens the named file.
+func (u *unionFS) Open(path string) (http.File, error) {
+	// TODO: Maybe clean path?
+	if path == "/" {
+		return &dir{
+			dirInfo: u.root,
+		}, nil
+	}
+	for prefix, fs := range u.ns {
+		if path == prefix || strings.HasPrefix(path, prefix+"/") {
+			innerPath := path[len(prefix):]
+			if innerPath == "" {
+				innerPath = "/"
+			}
+			return fs.Open(innerPath)
+		}
+	}
+	return nil, &os.PathError{Op: "open", Path: path, Err: os.ErrNotExist}
+}
+
+// dirInfo is a static definition of a directory.
+type dirInfo struct {
+	name    string
+	entries []os.FileInfo
+}
+
+func (d *dirInfo) Read([]byte) (int, error) {
+	return 0, fmt.Errorf("cannot Read from directory %s", d.name)
+}
+func (d *dirInfo) Close() error               { return nil }
+func (d *dirInfo) Stat() (os.FileInfo, error) { return d, nil }
+
+func (d *dirInfo) Name() string       { return d.name }
+func (d *dirInfo) Size() int64        { return 0 }
+func (d *dirInfo) Mode() os.FileMode  { return 0755 | os.ModeDir }
+func (d *dirInfo) ModTime() time.Time { return time.Time{} } // Actual mod time is not computed because it's expensive and rarely needed.
+func (d *dirInfo) IsDir() bool        { return true }
+func (d *dirInfo) Sys() interface{}   { return nil }
+
+// dir is an opened dir instance.
+type dir struct {
+	*dirInfo
+	pos int // Position within entries for Seek and Readdir.
+}
+
+func (d *dir) Seek(offset int64, whence int) (int64, error) {
+	if offset == 0 && whence == io.SeekStart {
+		d.pos = 0
+		return 0, nil
+	}
+	return 0, fmt.Errorf("unsupported Seek in directory %s", d.dirInfo.name)
+}
+
+func (d *dir) Readdir(count int) ([]os.FileInfo, error) {
+	if d.pos >= len(d.dirInfo.entries) && count > 0 {
+		return nil, io.EOF
+	}
+	if count <= 0 || count > len(d.dirInfo.entries)-d.pos {
+		count = len(d.dirInfo.entries) - d.pos
+	}
+	e := d.dirInfo.entries[d.pos : d.pos+count]
+	d.pos += count
+	return e, nil
+}