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common.go
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common.go
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package manifest
import (
"fmt"
compressiontypes "github.com/containers/image/v5/pkg/compression/types"
"github.com/containers/image/v5/types"
"github.com/sirupsen/logrus"
)
// layerInfosToStrings converts a list of layer infos, presumably obtained from a Manifest.LayerInfos()
// method call, into a format suitable for inclusion in a types.ImageInspectInfo structure.
func layerInfosToStrings(infos []LayerInfo) []string {
layers := make([]string, len(infos))
for i, info := range infos {
layers[i] = info.Digest.String()
}
return layers
}
// compressionMIMETypeSet describes a set of MIME type “variants” that represent differently-compressed
// versions of “the same kind of content”.
// The map key is the return value of compressiontypes.Algorithm.Name(), or mtsUncompressed;
// the map value is a MIME type, or mtsUnsupportedMIMEType to mean "recognized but unsupported".
type compressionMIMETypeSet map[string]string
const mtsUncompressed = "" // A key in compressionMIMETypeSet for the uncompressed variant
const mtsUnsupportedMIMEType = "" // A value in compressionMIMETypeSet that means “recognized but unsupported”
// findCompressionMIMETypeSet returns a pointer to a compressionMIMETypeSet in variantTable that contains a value of mimeType, or nil if not found
func findCompressionMIMETypeSet(variantTable []compressionMIMETypeSet, mimeType string) compressionMIMETypeSet {
for _, variants := range variantTable {
for _, mt := range variants {
if mt == mimeType {
return variants
}
}
}
return nil
}
// compressionVariantMIMEType returns a variant of mimeType for the specified algorithm (which may be nil
// to mean "no compression"), based on variantTable.
// The returned error will be a ManifestLayerCompressionIncompatibilityError if mimeType has variants
// that differ only in what type of compression is applied, but it can't be combined with this
// algorithm to produce an updated MIME type that complies with the standard that defines mimeType.
// If the compression algorithm is unrecognized, or mimeType is not known to have variants that
// differ from it only in what type of compression has been applied, the returned error will not be
// a ManifestLayerCompressionIncompatibilityError.
func compressionVariantMIMEType(variantTable []compressionMIMETypeSet, mimeType string, algorithm *compressiontypes.Algorithm) (string, error) {
if mimeType == mtsUnsupportedMIMEType { // Prevent matching against the {algo:mtsUnsupportedMIMEType} entries
return "", fmt.Errorf("cannot update unknown MIME type")
}
variants := findCompressionMIMETypeSet(variantTable, mimeType)
if variants != nil {
name := mtsUncompressed
if algorithm != nil {
name = algorithm.BaseVariantName()
}
if res, ok := variants[name]; ok {
if res != mtsUnsupportedMIMEType {
return res, nil
}
if name != mtsUncompressed {
return "", ManifestLayerCompressionIncompatibilityError{fmt.Sprintf("%s compression is not supported for type %q", name, mimeType)}
}
return "", ManifestLayerCompressionIncompatibilityError{fmt.Sprintf("uncompressed variant is not supported for type %q", mimeType)}
}
if name != mtsUncompressed {
return "", ManifestLayerCompressionIncompatibilityError{fmt.Sprintf("unknown compressed with algorithm %s variant for type %s", name, mimeType)}
}
// We can't very well say “the idea of no compression is unknown”
return "", ManifestLayerCompressionIncompatibilityError{fmt.Sprintf("uncompressed variant is not supported for type %q", mimeType)}
}
if algorithm != nil {
return "", fmt.Errorf("unsupported MIME type for compression: %s", mimeType)
}
return "", fmt.Errorf("unsupported MIME type for decompression: %s", mimeType)
}
// updatedMIMEType returns the result of applying edits in updated (MediaType, CompressionOperation) to
// mimeType, based on variantTable. It may use updated.Digest for error messages.
// The returned error will be a ManifestLayerCompressionIncompatibilityError if mimeType has variants
// that differ only in what type of compression is applied, but applying updated.CompressionOperation
// and updated.CompressionAlgorithm to it won't produce an updated MIME type that complies with the
// standard that defines mimeType.
func updatedMIMEType(variantTable []compressionMIMETypeSet, mimeType string, updated types.BlobInfo) (string, error) {
// Note that manifests in containers-storage might be reporting the
// wrong media type since the original manifests are stored while layers
// are decompressed in storage. Hence, we need to consider the case
// that an already {de}compressed layer should be {de}compressed;
// compressionVariantMIMEType does that by not caring whether the original is
// {de}compressed.
switch updated.CompressionOperation {
case types.PreserveOriginal:
// Force a change to the media type if we're being told to use a particular compressor,
// since it might be different from the one associated with the media type. Otherwise,
// try to keep the original media type.
if updated.CompressionAlgorithm != nil {
return compressionVariantMIMEType(variantTable, mimeType, updated.CompressionAlgorithm)
}
// Keep the original media type.
return mimeType, nil
case types.Decompress:
return compressionVariantMIMEType(variantTable, mimeType, nil)
case types.Compress:
if updated.CompressionAlgorithm == nil {
logrus.Debugf("Error preparing updated manifest: blob %q was compressed but does not specify by which algorithm: falling back to use the original blob", updated.Digest)
return mimeType, nil
}
return compressionVariantMIMEType(variantTable, mimeType, updated.CompressionAlgorithm)
default:
return "", fmt.Errorf("unknown compression operation (%d)", updated.CompressionOperation)
}
}
// ManifestLayerCompressionIncompatibilityError indicates that a specified compression algorithm
// could not be applied to a layer MIME type. A caller that receives this should either retry
// the call with a different compression algorithm, or attempt to use a different manifest type.
type ManifestLayerCompressionIncompatibilityError struct {
text string
}
func (m ManifestLayerCompressionIncompatibilityError) Error() string {
return m.text
}
// compressionVariantsRecognizeMIMEType returns true if variantTable contains data about compressing/decompressing layers with mimeType
// Note that the caller still needs to worry about a specific algorithm not being supported.
func compressionVariantsRecognizeMIMEType(variantTable []compressionMIMETypeSet, mimeType string) bool {
if mimeType == mtsUnsupportedMIMEType { // Prevent matching against the {algo:mtsUnsupportedMIMEType} entries
return false
}
variants := findCompressionMIMETypeSet(variantTable, mimeType)
return variants != nil // Alternatively, this could be len(variants) > 1, but really the caller should ask about a specific algorithm.
}
// imgInspectLayersFromLayerInfos converts a list of layer infos, presumably obtained from a Manifest.LayerInfos()
// method call, into a format suitable for inclusion in a types.ImageInspectInfo structure.
func imgInspectLayersFromLayerInfos(infos []LayerInfo) []types.ImageInspectLayer {
layers := make([]types.ImageInspectLayer, len(infos))
for i, info := range infos {
layers[i].MIMEType = info.MediaType
layers[i].Digest = info.Digest
layers[i].Size = info.Size
layers[i].Annotations = info.Annotations
}
return layers
}