verify: starts of a checking function

tar/verify/headers.go

@@ -1,23 +1,100 @@
 package verify
 
-import "time"
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
 
 // PosixHeader is the structure from a POSIX tar header, to be marshalled from
 // the tar stream, and available for on-disk comparison and verification
 type PosixHeader struct {
-	Name     string    `json:"name,omitempty"`
-	Mode     uint32    `json:"mode,omitempty"`
-	UID      uint32    `json:"uid,omitempty"`
-	GID      uint32    `json:"gid,omitempty"`
-	Size     int       `json:"size,omitempty"`
-	Mtime    time.Time `json:"mtime,omitempty"`
-	Checksum []byte    `json:"chksum,omitempty"`
-	LinkName string    `json:"linkname,omitempty"`
-	Magic    []byte    `json:"magic,omitempty"`
-	Version  string    `json:"version,omitempty"`
-	Uname    string    `json:"uname,omitempty"`
-	Gname    string    `json:"gname,omitempty"`
-	DevMajor int       `json:"devmajor,omitempty"`
-	DevMinor int       `json:"devminor,omitempty"`
-	Prefix   string    `json:"prefix,omitempty"`
+	Name     string      `json:"name,omitempty"`
+	Mode     os.FileMode `json:"mode,omitempty"`
+	UID      uint32      `json:"uid,omitempty"`
+	GID      uint32      `json:"gid,omitempty"`
+	Size     int64       `json:"size,omitempty"`
+	Mtime    time.Time   `json:"mtime,omitempty"`
+	Checksum []byte      `json:"chksum,omitempty"`
+	LinkName string      `json:"linkname,omitempty"`
+	Magic    []byte      `json:"magic,omitempty"`
+	Version  string      `json:"version,omitempty"`
+	Uname    string      `json:"uname,omitempty"`
+	Gname    string      `json:"gname,omitempty"`
+	DevMajor int         `json:"devmajor,omitempty"`
+	DevMinor int         `json:"devminor,omitempty"`
+	Prefix   string      `json:"prefix,omitempty"`
+}
+
+type PaxHeader struct {
+	Atime  time.Time
+	Ctime  time.Time
+	Xattrs map[string]string
+}
+
+type Header struct {
+	// maybe I do not want these grouped like this. Maybe this should be an interface instead.
+	Posix PosixHeader
+	Pax   PaxHeader
+}
+
+// Size returns file size (implements Sizer)
+func (hdr Header) Size() int64 {
+	return int64(hdr.Posix.Size)
+}
+
+// ModTime returns file mtime (implements ModTimer)
+func (hdr Header) ModTime() time.Time {
+	return hdr.Posix.Mtime
+}
+
+// Mode returns file mode (implements Moder)
+func (hdr Header) Mode() os.FileMode {
+	return hdr.Posix.Mode
+}
+
+func (hdr Header) LinkName() string {
+	return hdr.Posix.LinkName
+}
+
+// HeaderFromFile takes a relative root and the filename of the file to collect
+// information on.
+func HeaderFromFile(rel, filename string) (*Header, error) {
+	absRel, err := filepath.Abs(rel)
+	if err != nil {
+		return nil, err
+	}
+	if strings.HasPrefix(filename, "/") {
+		var err error
+		filename, err = filepath.Abs(filename)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	stat, err := os.Lstat(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	name := filename
+	if strings.HasPrefix(filename, absRel) {
+		name = strings.TrimPrefix(filename, absRel)
+	}
+
+	hdr := Header{
+		Posix: PosixHeader{
+			Name:  name,
+			Size:  stat.Size(),
+			Mode:  stat.Mode(),
+			Mtime: stat.ModTime(),
+		},
+	}
+	if stat.Mode()&os.ModeSymlink != 0 {
+		l, _ := os.Readlink(filename) // if this errors, the empty string is OK
+		hdr.Posix.LinkName = l
+	}
+
+	return &hdr, nil
 }