zip: Simplify encoding config; add empty header matching

Author: mholt

zip.go

@@ -12,18 +12,12 @@ import (
 	"strings"
 
 	szip "github.com/STARRY-S/zip"
+	"golang.org/x/text/encoding"
 
 	"github.com/dsnet/compress/bzip2"
 	"github.com/klauspost/compress/zip"
 	"github.com/klauspost/compress/zstd"
 	"github.com/ulikunitz/xz"
-	"golang.org/x/text/encoding"
-	"golang.org/x/text/encoding/charmap"
-	"golang.org/x/text/encoding/japanese"
-	"golang.org/x/text/encoding/korean"
-	"golang.org/x/text/encoding/simplifiedchinese"
-	"golang.org/x/text/encoding/traditionalchinese"
-	"golang.org/x/text/encoding/unicode"
 )
 
 func init() {
@@ -80,7 +74,7 @@ type Zip struct {
 	// For files in zip archives that do not have UTF-8
 	// encoded filenames and comments, specify the character
 	// encoding here.
-	TextEncoding string
+	TextEncoding encoding.Encoding
 }
 
 func (z Zip) Extension() string { return ".zip" }
@@ -94,11 +88,16 @@ func (z Zip) Match(_ context.Context, filename string, stream io.Reader) (MatchR
 	}
 
 	// match file header
-	buf, err := readAtMost(stream, len(zipHeader))
-	if err != nil {
-		return mr, err
+	for _, hdr := range zipHeaders {
+		buf, err := readAtMost(stream, len(hdr))
+		if err != nil {
+			return mr, err
+		}
+		if bytes.Equal(buf, hdr) {
+			mr.ByStream = true
+			break
+		}
 	}
-	mr.ByStream = bytes.Equal(buf, zipHeader)
 
 	return mr, nil
 }
@@ -255,13 +254,14 @@ func (z Zip) Extract(ctx context.Context, sourceArchive io.Reader, handleFile Fi
 // It is a no-op if the text is already UTF-8 encoded or if z.TextEncoding
 // is not specified.
 func (z Zip) decodeText(hdr *zip.FileHeader) {
-	if hdr.NonUTF8 && z.TextEncoding != "" {
-		filename, err := decodeText(hdr.Name, z.TextEncoding)
+	if hdr.NonUTF8 && z.TextEncoding != nil {
+		dec := z.TextEncoding.NewDecoder()
+		filename, err := dec.String(hdr.Name)
 		if err == nil {
 			hdr.Name = filename
 		}
 		if hdr.Comment != "" {
-			comment, err := decodeText(hdr.Comment, z.TextEncoding)
+			comment, err := dec.String(hdr.Comment)
 			if err == nil {
 				hdr.Comment = comment
 			}
@@ -384,58 +384,11 @@ var compressedFormats = map[string]struct{}{
 	".zipx": {},
 }
 
-var encodings = map[string]encoding.Encoding{
-	"ibm866":            charmap.CodePage866,
-	"iso8859_2":         charmap.ISO8859_2,
-	"iso8859_3":         charmap.ISO8859_3,
-	"iso8859_4":         charmap.ISO8859_4,
-	"iso8859_5":         charmap.ISO8859_5,
-	"iso8859_6":         charmap.ISO8859_6,
-	"iso8859_7":         charmap.ISO8859_7,
-	"iso8859_8":         charmap.ISO8859_8,
-	"iso8859_8I":        charmap.ISO8859_8I,
-	"iso8859_10":        charmap.ISO8859_10,
-	"iso8859_13":        charmap.ISO8859_13,
-	"iso8859_14":        charmap.ISO8859_14,
-	"iso8859_15":        charmap.ISO8859_15,
-	"iso8859_16":        charmap.ISO8859_16,
-	"koi8r":             charmap.KOI8R,
-	"koi8u":             charmap.KOI8U,
-	"macintosh":         charmap.Macintosh,
-	"windows874":        charmap.Windows874,
-	"windows1250":       charmap.Windows1250,
-	"windows1251":       charmap.Windows1251,
-	"windows1252":       charmap.Windows1252,
-	"windows1253":       charmap.Windows1253,
-	"windows1254":       charmap.Windows1254,
-	"windows1255":       charmap.Windows1255,
-	"windows1256":       charmap.Windows1256,
-	"windows1257":       charmap.Windows1257,
-	"windows1258":       charmap.Windows1258,
-	"macintoshcyrillic": charmap.MacintoshCyrillic,
-	"gbk":               simplifiedchinese.GBK,
-	"gb18030":           simplifiedchinese.GB18030,
-	"big5":              traditionalchinese.Big5,
-	"eucjp":             japanese.EUCJP,
-	"iso2022jp":         japanese.ISO2022JP,
-	"shiftjis":          japanese.ShiftJIS,
-	"euckr":             korean.EUCKR,
-	"utf16be":           unicode.UTF16(unicode.BigEndian, unicode.IgnoreBOM),
-	"utf16le":           unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM),
+var zipHeaders = [][]byte{
+	[]byte("PK\x03\x04"), // normal
+	[]byte("PK\x05\x06"), // empty
 }
 
-// decodeText returns UTF-8 encoded text from the given charset.
-// Thanks to @zxdvd for contributing non-UTF-8 encoding logic in
-// #149, and to @pashifika for helping in #305.
-func decodeText(input, charset string) (string, error) {
-	if enc, ok := encodings[charset]; ok {
-		return enc.NewDecoder().String(input)
-	}
-	return "", fmt.Errorf("unrecognized charset %s", charset)
-}
-
-var zipHeader = []byte("PK\x03\x04") // NOTE: headers of empty zip files might end with 0x05,0x06 or 0x06,0x06 instead of 0x03,0x04
-
 // Interface guards
 var (
 	_ Archiver      = Zip{}