Implements the IsNonCompressedTarball directly in go instead of relying on file

Author: mdzhigarov

fileutil/fakes/fake_compressor.go

@@ -26,6 +26,9 @@ type FakeCompressor struct {
 
 	CleanUpTarballPath string
 	CleanUpErr         error
+
+	IsNonCompressedResult bool
+	IsNonCompressedErr    error
 }
 
 func NewFakeCompressor() *FakeCompressor {
@@ -66,7 +69,7 @@ func (fc *FakeCompressor) DecompressFileToDir(tarballPath string, dir string, op
 }
 
 func (fc *FakeCompressor) IsNonCompressedTarball(path string) (bool, error) {
-	return false, nil
+	return fc.IsNonCompressedResult, fc.IsNonCompressedErr
 }
 
 func (fc *FakeCompressor) CleanUp(tarballPath string) error {

fileutil/tarball_compressor.go

@@ -1,14 +1,24 @@
 package fileutil
 
 import (
+	"bytes"
 	"fmt"
+	"os"
 	"runtime"
-	"strings"
 
 	bosherr "github.com/cloudfoundry/bosh-utils/errors"
 	boshsys "github.com/cloudfoundry/bosh-utils/system"
 )
 
+var (
+	gzipMagic   = []byte{0x1f, 0x8b}
+	bzip2Magic  = []byte{0x42, 0x5a, 0x68} // "BZh"
+	xzMagic     = []byte{0xfd, 0x37, 0x7a, 0x58, 0x5a, 0x00}
+	zstdMagic   = []byte{0x28, 0xb5, 0x2f, 0xfd}
+	ustarMagic  = []byte("ustar")
+	ustarOffset = 257 // Offset of the TAR magic string in the file
+)
+
 type tarballCompressor struct {
 	cmdRunner boshsys.CmdRunner
 	fs        boshsys.FileSystem
@@ -82,13 +92,35 @@ func (c tarballCompressor) DecompressFileToDir(tarballPath string, dir string, o
 }
 
 func (c tarballCompressor) IsNonCompressedTarball(path string) (bool, error) {
-	stdout, _, exitStatus, err := c.cmdRunner.RunCommand("file", path)
-	if err != nil || exitStatus != 0 {
-		return false, err
+	f, err := c.fs.OpenFile(path, os.O_RDONLY, 0644)
+	if err != nil {
+		return false, fmt.Errorf("could not open file: %w", err)
+	}
+	defer f.Close()
+
+	// Read the first 512 bytes to check both compression headers and the TAR header.
+	// Ignore the error from reading a partial buffer, which is fine for short files.
+	buffer := make([]byte, 512)
+	_, _ = f.Read(buffer)
+
+	// 1. Check for compression first.
+	if bytes.HasPrefix(buffer, gzipMagic) ||
+		bytes.HasPrefix(buffer, bzip2Magic) ||
+		bytes.HasPrefix(buffer, xzMagic) ||
+		bytes.HasPrefix(buffer, zstdMagic) {
+		return false, nil
+	}
+
+	// 2. If NOT compressed, check for the TAR magic string at its specific offset.
+	// Ensure the buffer is long enough to contain the TAR header magic string.
+	if len(buffer) > ustarOffset+len(ustarMagic) {
+		magicBytes := buffer[ustarOffset : ustarOffset+len(ustarMagic)]
+		if bytes.Equal(magicBytes, ustarMagic) {
+			return true, nil
+		}
 	}
 
-	fileOutputStr := strings.TrimSpace(stdout)
-	return strings.Contains(fileOutputStr, "POSIX tar archive"), nil
+	return false, nil
 }
 
 func (c tarballCompressor) CleanUp(tarballPath string) error {

fileutil/tarball_compressor_test.go

@@ -274,119 +274,84 @@ var _ = Describe("tarballCompressor", func() {
 	})
 
 	Describe("IsNonCompressedTarball", func() {
-		It("returns true for non-compressed tarball files", func() {
-			cmdRunner := fakesys.NewFakeCmdRunner()
-			compressor := NewTarballCompressor(cmdRunner, fs)
-
-			// Mock the file command output for a non-compressed tarball
-			cmdRunner.AddCmdResult("file /test/file.tar", fakesys.FakeCmdResult{
-				Stdout:     "/test/file.tar: POSIX tar archive\n",
-				Stderr:     "",
-				ExitStatus: 0,
-			})
+		It("returns true for non-compressed tarball created with NoCompression=true", func() {
+			tgzName, err := compressor.CompressFilesInDir(testAssetsFixtureDir, CompressorOptions{NoCompression: true})
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tgzName)
 
-			result, err := compressor.IsNonCompressedTarball("/test/file.tar")
+			result, err := compressor.IsNonCompressedTarball(tgzName)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(result).To(BeTrue())
-
-			Expect(1).To(Equal(len(cmdRunner.RunCommands)))
-			Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"file", "/test/file.tar"}))
 		})
 
-		It("returns false for compressed tarball files", func() {
-			cmdRunner := fakesys.NewFakeCmdRunner()
-			compressor := NewTarballCompressor(cmdRunner, fs)
-
-			// Mock the file command output for a compressed tarball
-			cmdRunner.AddCmdResult("file /test/file.tgz", fakesys.FakeCmdResult{
-				Stdout:     "/test/file.tgz: gzip compressed data, from Unix, original size modulo 2^32 1024\n",
-				Stderr:     "",
-				ExitStatus: 0,
-			})
+		It("returns false for compressed tarball created with NoCompression=false", func() {
+			tgzName, err := compressor.CompressFilesInDir(testAssetsFixtureDir, CompressorOptions{NoCompression: false})
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tgzName)
 
-			result, err := compressor.IsNonCompressedTarball("/test/file.tgz")
+			result, err := compressor.IsNonCompressedTarball(tgzName)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(result).To(BeFalse())
-
-			Expect(1).To(Equal(len(cmdRunner.RunCommands)))
-			Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"file", "/test/file.tgz"}))
 		})
 
-		It("returns false for non-tarball files", func() {
-			cmdRunner := fakesys.NewFakeCmdRunner()
-			compressor := NewTarballCompressor(cmdRunner, fs)
-
-			// Mock the file command output for a regular text file
-			cmdRunner.AddCmdResult("file /test/file.txt", fakesys.FakeCmdResult{
-				Stdout:     "/test/file.txt: ASCII text\n",
-				Stderr:     "",
-				ExitStatus: 0,
-			})
+		It("returns false for compressed tarball created with default options", func() {
+			tgzName, err := compressor.CompressFilesInDir(testAssetsFixtureDir, CompressorOptions{})
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tgzName)
 
-			result, err := compressor.IsNonCompressedTarball("/test/file.txt")
+			result, err := compressor.IsNonCompressedTarball(tgzName)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(result).To(BeFalse())
+		})
 
-			Expect(1).To(Equal(len(cmdRunner.RunCommands)))
-			Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"file", "/test/file.txt"}))
+		It("returns error for non-existent file", func() {
+			result, err := compressor.IsNonCompressedTarball("/nonexistent/file.tar")
+			Expect(err).To(HaveOccurred())
+			Expect(result).To(BeFalse())
 		})
 
-		It("returns error when file command fails", func() {
-			cmdRunner := fakesys.NewFakeCmdRunner()
-			compressor := NewTarballCompressor(cmdRunner, fs)
+		It("returns error for non-tarball file", func() {
+			tempFile, err := fs.TempFile("test-non-tarball")
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tempFile.Name())
 
-			// Mock the file command to return an error
-			cmdRunner.AddCmdResult("file /test/nonexistent.tar", fakesys.FakeCmdResult{
-				Stdout:     "",
-				Stderr:     "file: cannot open `/test/nonexistent.tar' (No such file or directory)\n",
-				ExitStatus: 1,
-			})
+			err = fs.WriteFileString(tempFile.Name(), "This is not a tar file")
+			Expect(err).ToNot(HaveOccurred())
 
-			result, _ := compressor.IsNonCompressedTarball("/test/nonexistent.tar")
+			result, err := compressor.IsNonCompressedTarball(tempFile.Name())
+			Expect(err).ToNot(HaveOccurred())
 			Expect(result).To(BeFalse())
-
-			Expect(1).To(Equal(len(cmdRunner.RunCommands)))
-			Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"file", "/test/nonexistent.tar"}))
 		})
 
-		It("returns error when file command execution fails", func() {
-			cmdRunner := fakesys.NewFakeCmdRunner()
-			compressor := NewTarballCompressor(cmdRunner, fs)
-
-			// Mock the file command to return an execution error
-			cmdRunner.AddCmdResult("file /test/file.tar", fakesys.FakeCmdResult{
-				Stdout:     "",
-				Stderr:     "",
-				ExitStatus: 0,
-				Error:      errors.New("command execution failed"),
-			})
+		It("returns error for empty file", func() {
+			tempFile, err := fs.TempFile("test-empty-file")
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tempFile.Name())
+			tempFile.Close()
 
-			result, err := compressor.IsNonCompressedTarball("/test/file.tar")
-			Expect(err).To(HaveOccurred())
-			Expect(err.Error()).To(ContainSubstring("command execution failed"))
+			result, err := compressor.IsNonCompressedTarball(tempFile.Name())
+			Expect(err).ToNot(HaveOccurred())
 			Expect(result).To(BeFalse())
-
-			Expect(1).To(Equal(len(cmdRunner.RunCommands)))
-			Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"file", "/test/file.tar"}))
 		})
 
-		It("handles file command output with extra whitespace", func() {
-			cmdRunner := fakesys.NewFakeCmdRunner()
-			compressor := NewTarballCompressor(cmdRunner, fs)
+		It("correctly identifies tarballs created with CompressSpecificFilesInDir", func() {
+			files := []string{"app.stdout.log", "app.stderr.log"}
 
-			// Mock the file command output with extra whitespace
-			cmdRunner.AddCmdResult("file /test/file.tar", fakesys.FakeCmdResult{
-				Stdout:     "  /test/file.tar: POSIX tar archive  \n",
-				Stderr:     "",
-				ExitStatus: 0,
-			})
+			tgzName, err := compressor.CompressSpecificFilesInDir(testAssetsFixtureDir, files, CompressorOptions{NoCompression: true})
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tgzName)
 
-			result, err := compressor.IsNonCompressedTarball("/test/file.tar")
+			result, err := compressor.IsNonCompressedTarball(tgzName)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(result).To(BeTrue())
 
-			Expect(1).To(Equal(len(cmdRunner.RunCommands)))
-			Expect(cmdRunner.RunCommands[0]).To(Equal([]string{"file", "/test/file.tar"}))
+			tgzName2, err := compressor.CompressSpecificFilesInDir(testAssetsFixtureDir, files, CompressorOptions{NoCompression: false})
+			Expect(err).ToNot(HaveOccurred())
+			defer os.Remove(tgzName2)
+
+			result2, err := compressor.IsNonCompressedTarball(tgzName2)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(result2).To(BeFalse())
 		})
 	})