Method bpcRecompressCompressed

copy/compression.go:191–234

bpcRecompressCompressed checks if we should be recompressing a compressed input to another format, and returns a *bpCompressionStepData if so.

(stream *sourceStream, detected bpDetectCompressionStepData)

// bpcRecompressCompressed checks if we should be recompressing a compressed input to another format, and returns a *bpCompressionStepData if so.
func (ic *imageCopier) bpcRecompressCompressed(stream *sourceStream, detected bpDetectCompressionStepData) (*bpCompressionStepData, error) {
	if ic.c.dest.DesiredLayerCompression() == types.Compress && detected.isCompressed &&
		ic.compressionFormat != nil &&
		(ic.compressionFormat.Name() != detected.format.Name() && ic.compressionFormat.Name() != detected.format.BaseVariantName()) {
		// When the blob is compressed, but the desired format is different, it first needs to be decompressed and finally
		// re-compressed using the desired format.
		logrus.Debugf("Blob will be converted")

		decompressed, err := detected.decompressor(stream.reader)
		if err != nil {
			return nil, err
		}
		succeeded := false
		defer func() {
			if !succeeded {
				decompressed.Close()
			}
		}()

		recompressed, annotations := ic.compressedStream(decompressed, *ic.compressionFormat)
		// Note: recompressed must be closed on all return paths.
		stream.reader = recompressed
		stream.info = types.BlobInfo{ // FIXME? Should we preserve more data in src.info? Notably the current approach correctly removes zstd:chunked metadata annotations.
			Digest: "",
			Size:   -1,
		}
		specificVariantName := ic.compressionFormat.Name()
		if specificVariantName == ic.compressionFormat.BaseVariantName() {
			specificVariantName = internalblobinfocache.UnknownCompression
		}
		succeeded = true
		return &bpCompressionStepData{
			operation:                             bpcOpRecompressCompressed,
			uploadedOperation:                     types.PreserveOriginal,
			uploadedAlgorithm:                     ic.compressionFormat,
			uploadedAnnotations:                   annotations,
			srcCompressorBaseVariantName:          detected.srcCompressorBaseVariantName,
			uploadedCompressorBaseVariantName:     ic.compressionFormat.BaseVariantName(),
			uploadedCompressorSpecificVariantName: specificVariantName,
			closers:                               []io.Closer{decompressed, recompressed},
		}, nil
	}
	return nil, nil
}

// bpcDecompressCompressed checks if we should be decompressing a compressed input, and returns a *bpCompressionStepData if so.
func (ic *imageCopier) bpcDecompressCompressed(stream *sourceStream, detected bpDetectCompressionStepData) (*bpCompressionStepData, error) {