Avoid buffering in archive detection if the stream is seekable

extract_test.go

@@ -369,7 +369,7 @@ func TestTarGzMemoryConsumption(t *testing.T) {
  runtime.GC()
  runtime.ReadMemStats(&m)
 
- err = extract.Gz(context.Background(), f, tmpDir.String(), nil)
+ err = extract.Archive(context.Background(), f, tmpDir.String(), nil)
  require.NoError(t, err)
 
  runtime.ReadMemStats(&m2)
@@ -397,7 +397,7 @@ func TestZipMemoryConsumption(t *testing.T) {
  runtime.GC()
  runtime.ReadMemStats(&m)
 
- err = extract.Zip(context.Background(), f, tmpDir.String(), nil)
+ err = extract.Archive(context.Background(), f, tmpDir.String(), nil)
  require.NoError(t, err)
 
  runtime.ReadMemStats(&m2)
@@ -406,9 +406,7 @@ func TestZipMemoryConsumption(t *testing.T) {
  heapUsed = 0
  }
  fmt.Println("Heap memory used during the test:", heapUsed)
- // the .zip file require random access, so the full io.Reader content must be cached, since
- // the test file is 130MB, that's the reason for the high memory consumed.
- require.True(t, heapUsed < 250000000, "heap consumption should be less than 250M but is %d", heapUsed)
+ require.True(t, heapUsed < 5000000, "heap consumption should be less than 5M but is %d", heapUsed)
 }
 
 func download(t require.TestingT, url string, file *paths.Path) error {

extractor.go

@@ -363,7 +363,15 @@ func match(r io.Reader) (io.Reader, types.Type, error) {
  return nil, types.Unknown, err
  }
 
- r = io.MultiReader(bytes.NewBuffer(buffer[:n]), r)
+ if seeker, ok := r.(io.Seeker); ok {
+ // if the stream is seekable, we just rewind it
+ if _, err := seeker.Seek(0, io.SeekStart); err != nil {
+ return nil, types.Unknown, err
+ }
+ } else {
+ // otherwise we create a new reader that will prepend the buffer
+ r = io.MultiReader(bytes.NewBuffer(buffer[:n]), r)
+ }
 
  typ, err := filetype.Match(buffer)