decompressor/tar: add initial implementation based on tgz

This passes the tests, but I am not a go developer and success may not
mean much. See hashicorp#19.

decompress.go

@@ -20,6 +20,7 @@ func init() {
 	Decompressors = map[string]Decompressor{
 		"bz2":     new(Bzip2Decompressor),
 		"gz":      new(GzipDecompressor),
+		"tar":     new(TarDecompressor),
 		"tar.bz2": tbzDecompressor,
 		"tar.gz":  tgzDecompressor,
 		"tbz2":    tbzDecompressor,

decompress_tar.go

@@ -0,0 +1,90 @@
+package getter
+
+import (
+	"archive/tar"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// TarDecompressor is an implementation of Decompressor that unarchives tar files.
+type TarDecompressor struct{}
+
+func (d *TarDecompressor) Decompress(dst, src string, dir bool) error {
+	// If we're going into a directory we should make that first
+	mkdir := dst
+	if !dir {
+		mkdir = filepath.Dir(dst)
+	}
+	if err := os.MkdirAll(mkdir, 0755); err != nil {
+		return err
+	}
+
+	// File first
+	f, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	// nothing to decompress, tar is next
+	tarR := tar.NewReader(f)
+	done := false
+	for {
+		hdr, err := tarR.Next()
+		if err == io.EOF {
+			if !done {
+				// Empty archive
+				return fmt.Errorf("empty archive: %s", src)
+			}
+
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+
+		path := dst
+		if dir {
+			path = filepath.Join(path, hdr.Name)
+		}
+
+		if hdr.FileInfo().IsDir() {
+			if !dir {
+				return fmt.Errorf("expected a single file: %s", src)
+			}
+
+			// A directory, just make the directory and continue unarchiving...
+			if err := os.MkdirAll(path, 0755); err != nil {
+				return err
+			}
+
+			continue
+		}
+
+		// We have a file. If we already decoded, then it is an error
+		if !dir && done {
+			return fmt.Errorf("expected a single file, got multiple: %s", src)
+		}
+
+		// Mark that we're done so future in single file mode errors
+		done = true
+
+		// Open the file for writing
+		dstF, err := os.Create(path)
+		if err != nil {
+			return err
+		}
+		_, err = io.Copy(dstF, tarR)
+		dstF.Close()
+		if err != nil {
+			return err
+		}
+
+		// Chmod the file
+		if err := os.Chmod(path, hdr.FileInfo().Mode()); err != nil {
+			return err
+		}
+	}
+}

decompress_tar_test.go

@@ -0,0 +1,71 @@
+package getter
+
+import (
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+func TestTarDecompressor(t *testing.T) {
+
+	multiplePaths := []string{"dir/", "dir/test2", "test1"}
+	if runtime.GOOS == "windows" {
+		multiplePaths = []string{"dir/", "dir\\test2", "test1"}
+	}
+
+	cases := []TestDecompressCase{
+		{
+			"empty.tar",
+			false,
+			true,
+			nil,
+			"",
+		},
+
+		{
+			"single.tar",
+			false,
+			false,
+			nil,
+			"d3b07384d113edec49eaa6238ad5ff00",
+		},
+
+		{
+			"single.tar",
+			true,
+			false,
+			[]string{"file"},
+			"",
+		},
+
+		{
+			"multiple.tar",
+			true,
+			false,
+			[]string{"file1", "file2"},
+			"",
+		},
+
+		{
+			"multiple.tar",
+			false,
+			true,
+			nil,
+			"",
+		},
+
+		{
+			"multiple_dir.tar",
+			true,
+			false,
+			multiplePaths,
+			"",
+		},
+	}
+
+	for i, tc := range cases {
+		cases[i].Input = filepath.Join("./test-fixtures", "decompress-tar", tc.Input)
+	}
+
+	TestDecompressor(t, new(TarDecompressor), cases)
+}