archive: support using lzma (MR 25)

fixes: https://gitlab.com/postmarketOS/postmarketos-mkinitfs/-/issues/2

go.mod

@@ -5,5 +5,6 @@ go 1.16
 require (
 	github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e
 	github.com/klauspost/compress v1.15.12
+	github.com/ulikunitz/xz v0.5.10
 	golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c
 )

go.sum

@@ -2,5 +2,7 @@ github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e h1:hHg27A0RS
 github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e/go.mod h1:oDpT4efm8tSYHXV5tHSdRvBet/b/QzxZ+XyyPehvm3A=
 github.com/klauspost/compress v1.15.12 h1:YClS/PImqYbn+UILDnqxQCZ3RehC9N318SU3kElDUEM=
 github.com/klauspost/compress v1.15.12/go.mod h1:QPwzmACJjUTFsnSHH934V6woptycfrDDJnH7hvFVbGM=
+github.com/ulikunitz/xz v0.5.10 h1:t92gobL9l3HE202wg3rlk19F6X+JOxl9BBrCCMYEYd8=
+github.com/ulikunitz/xz v0.5.10/go.mod h1:nbz6k7qbPmH4IRqmfOplQw/tblSgqTqBwxkY0oWt/14=
 golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c h1:F1jZWGFhYfh0Ci55sIpILtKKK8p3i2/krTr0H1rg74I=
 golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

internal/archive/archive.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/cavaliercoder/go-cpio"
 	"github.com/klauspost/compress/zstd"
+	"github.com/ulikunitz/xz"
 	"gitlab.com/postmarketOS/postmarketos-mkinitfs/internal/filelist"
 	"gitlab.com/postmarketOS/postmarketos-mkinitfs/internal/osutil"
 )
@@ -26,6 +27,7 @@ type CompressFormat string
 
 const (
 	FormatGzip CompressFormat = "gzip"
+	FormatLzma CompressFormat = "lzma"
 	FormatZstd CompressFormat = "zstd"
 )
 
@@ -98,6 +100,9 @@ func ExtractFormatLevel(s string) (format CompressFormat, level CompressLevel) {
 
 	switch format {
 	case FormatGzip:
+	case FormatLzma:
+		log.Println("Format lzma doesn't support a compression level, using default settings")
+		level = LevelDefault
 	case FormatZstd:
 	default:
 		log.Print("Unknown or no compression format set, using gzip")
@@ -295,6 +300,11 @@ func (archive *Archive) writeCompressed(path string, mode os.FileMode) error {
 		if err != nil {
 			return err
 		}
+	case FormatLzma:
+		compressor, err = xz.NewWriter(fd)
+		if err != nil {
+			return err
+		}
 	case FormatZstd:
 		level := zstd.SpeedDefault
 		switch archive.compress_level {

internal/archive/archive_test.go

@@ -243,6 +243,12 @@ func TestExtractFormatLevel(t *testing.T) {
 			expectedFormat: FormatGzip,
 			expectedLevel:  LevelDefault,
 		},
+		{
+			name:           "lzma, fast",
+			in:             "lzma:fast",
+			expectedFormat: FormatLzma,
+			expectedLevel:  LevelDefault,
+		},
 	}
 
 	for _, test := range tests {