Add platform match comparer interface

Adds a new platform interface for matching and comparing platforms.
This new interface allows both filtering and ordering of platforms
to support running multiple platform and choosing the best platform.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

client.go

@@ -259,9 +259,10 @@ type RemoteContext struct {
 	// If no resolver is provided, defaults to Docker registry resolver.
 	Resolver remotes.Resolver
 
-	// Platforms defines which platforms to handle when doing the image operation.
+	// PlatformMatcher is used to match the platforms for an image
-	// If this field is empty, content for all platforms will be pulled.
+	// operation and define the preference when a single match is required
-	Platforms []string
+	// from multiple platforms.
+	PlatformMatcher platforms.MatchComparer
 
 	// Unpack is done after an image is pulled to extract into a snapshotter.
 	// If an image is not unpacked on pull, it can be unpacked any time
@@ -283,6 +284,12 @@ type RemoteContext struct {
 	// manifests. If this option is false then any image which resolves
 	// to schema 1 will return an error since schema 1 is not supported.
 	ConvertSchema1 bool
+
+	// Platforms defines which platforms to handle when doing the image operation.
+	// Platforms is ignored when a PlatformMatcher is set, otherwise the
+	// platforms will be used to create a PlatformMatcher with no ordering
+	// preference.
+	Platforms []string
 }
 
 func defaultRemoteContext() *RemoteContext {
@@ -308,6 +315,23 @@ func (c *Client) Fetch(ctx context.Context, ref string, opts ...RemoteOpt) (imag
 		return images.Image{}, errors.New("unpack on fetch not supported, try pull")
 	}
 
+	if fetchCtx.PlatformMatcher == nil {
+		if len(fetchCtx.Platforms) == 0 {
+			fetchCtx.PlatformMatcher = platforms.All
+		} else {
+			var ps []ocispec.Platform
+			for _, s := range fetchCtx.Platforms {
+				p, err := platforms.Parse(s)
+				if err != nil {
+					return images.Image{}, errors.Wrapf(err, "invalid platform %s", s)
+				}
+				ps = append(ps, p)
+			}
+
+			fetchCtx.PlatformMatcher = platforms.Any(ps...)
+		}
+	}
+
 	ctx, done, err := c.WithLease(ctx)
 	if err != nil {
 		return images.Image{}, err
@@ -327,10 +351,19 @@ func (c *Client) Pull(ctx context.Context, ref string, opts ...RemoteOpt) (Image
 		}
 	}
 
-	if len(pullCtx.Platforms) > 1 {
+	if pullCtx.PlatformMatcher == nil {
-		return nil, errors.New("cannot pull multiplatform image locally, try Fetch")
+		if len(pullCtx.Platforms) > 1 {
-	} else if len(pullCtx.Platforms) == 0 {
+			return nil, errors.New("cannot pull multiplatform image locally, try Fetch")
-		pullCtx.Platforms = []string{platforms.Default()}
+		} else if len(pullCtx.Platforms) == 0 {
+			pullCtx.PlatformMatcher = platforms.Default()
+		} else {
+			p, err := platforms.Parse(pullCtx.Platforms[0])
+			if err != nil {
+				return nil, errors.Wrapf(err, "invalid platform %s", pullCtx.Platforms[0])
+			}
+
+			pullCtx.PlatformMatcher = platforms.Only(p)
+		}
 	}
 
 	ctx, done, err := c.WithLease(ctx)
@@ -344,7 +377,7 @@ func (c *Client) Pull(ctx context.Context, ref string, opts ...RemoteOpt) (Image
 		return nil, err
 	}
 
-	i := NewImageWithPlatform(c, img, pullCtx.Platforms[0])
+	i := NewImageWithPlatform(c, img, pullCtx.PlatformMatcher)
 
 	if pullCtx.Unpack {
 		if err := i.Unpack(ctx, pullCtx.Snapshotter); err != nil {
@@ -380,7 +413,7 @@ func (c *Client) fetch(ctx context.Context, rCtx *RemoteContext, ref string) (im
 		// Set any children labels for that content
 		childrenHandler = images.SetChildrenLabels(store, childrenHandler)
 		// Filter children by platforms
-		childrenHandler = images.FilterPlatforms(childrenHandler, rCtx.Platforms...)
+		childrenHandler = images.FilterPlatforms(childrenHandler, rCtx.PlatformMatcher)
 
 		handler = images.Handlers(append(rCtx.BaseHandlers,
 			remotes.FetchHandler(store, fetcher),
@@ -437,13 +470,28 @@ func (c *Client) Push(ctx context.Context, ref string, desc ocispec.Descriptor,
 			return err
 		}
 	}
+	if pushCtx.PlatformMatcher == nil {
+		if len(pushCtx.Platforms) > 0 {
+			var ps []ocispec.Platform
+			for _, platform := range pushCtx.Platforms {
+				p, err := platforms.Parse(platform)
+				if err != nil {
+					return errors.Wrapf(err, "invalid platform %s", platform)
+				}
+				ps = append(ps, p)
+			}
+			pushCtx.PlatformMatcher = platforms.Any(ps...)
+		} else {
+			pushCtx.PlatformMatcher = platforms.All
+		}
+	}
 
 	pusher, err := pushCtx.Resolver.Pusher(ctx, ref)
 	if err != nil {
 		return err
 	}
 
-	return remotes.PushContent(ctx, pusher, desc, c.ContentStore(), pushCtx.Platforms, pushCtx.BaseHandlers...)
+	return remotes.PushContent(ctx, pusher, desc, c.ContentStore(), pushCtx.PlatformMatcher, pushCtx.BaseHandlers...)
 }
 
 // GetImage returns an existing image

client_opts.go

@@ -89,7 +89,7 @@ type RemoteOpt func(*Client, *RemoteContext) error
 // content for
 func WithPlatform(platform string) RemoteOpt {
 	if platform == "" {
-		platform = platforms.Default()
+		platform = platforms.DefaultString()
 	}
 	return func(_ *Client, c *RemoteContext) error {
 		for _, p := range c.Platforms {
@@ -103,6 +103,16 @@ func WithPlatform(platform string) RemoteOpt {
 	}
 }
 
+// WithPlatformMatcher specifies the matcher to use for
+// determining which platforms to pull content for.
+// This value supersedes anything set with `WithPlatform`.
+func WithPlatformMatcher(m platforms.MatchComparer) RemoteOpt {
+	return func(_ *Client, c *RemoteContext) error {
+		c.PlatformMatcher = m
+		return nil
+	}
+}
+
 // WithPullUnpack is used to unpack an image after pull. This
 // uses the snapshotter, content store, and diff service
 // configured for the client.

client_test.go

@@ -185,7 +185,7 @@ func TestImagePull(t *testing.T) {
 
 	ctx, cancel := testContext()
 	defer cancel()
-	_, err = client.Pull(ctx, testImage, WithPlatform(platforms.Default()))
+	_, err = client.Pull(ctx, testImage, WithPlatformMatcher(platforms.Default()))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -304,7 +304,7 @@ func TestImagePullSchema1(t *testing.T) {
 	ctx, cancel := testContext()
 	defer cancel()
 	schema1TestImage := "gcr.io/google_containers/pause:3.0@sha256:0d093c962a6c2dd8bb8727b661e2b5f13e9df884af9945b4cc7088d9350cd3ee"
-	_, err = client.Pull(ctx, schema1TestImage, WithPlatform(platforms.Default()), WithSchema1Conversion)
+	_, err = client.Pull(ctx, schema1TestImage, WithPlatform(platforms.DefaultString()), WithSchema1Conversion)
 	if err != nil {
 		t.Fatal(err)
 	}

cmd/ctr/commands/content/fetch.go

@@ -113,7 +113,7 @@ func NewFetchConfig(ctx context.Context, clicontext *cli.Context) (*FetchConfig,
 	if !clicontext.Bool("all-platforms") {
 		p := clicontext.StringSlice("platform")
 		if len(p) == 0 {
-			p = append(p, platforms.Default())
+			p = append(p, platforms.DefaultString())
 		}
 		config.Platforms = p
 	}

cmd/ctr/commands/images/pull.go

@@ -25,6 +25,7 @@ import (
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/platforms"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/urfave/cli"
 )
@@ -86,26 +87,28 @@ command. As part of this process, we do the following:
 
 		// TODO: Show unpack status
 
-		var p []string
+		var p []ocispec.Platform
 		if context.Bool("all-platforms") {
-			all, err := images.Platforms(ctx, client.ContentStore(), img.Target)
+			p, err = images.Platforms(ctx, client.ContentStore(), img.Target)
 			if err != nil {
 				return errors.Wrap(err, "unable to resolve image platforms")
 			}
-			p = make([]string, len(all))
-			for i := range all {
-				p[i] = platforms.Format(all[i])
-			}
 		} else {
-			p = context.StringSlice("platform")
+			for _, s := range context.StringSlice("platform") {
+				ps, err := platforms.Parse(s)
+				if err != nil {
+					return errors.Wrapf(err, "unable to parse platform %s", s)
+				}
+				p = append(p, ps)
+			}
 		}
 		if len(p) == 0 {
-			p = append(p, platforms.Default())
+			p = append(p, platforms.DefaultSpec())
 		}
 
 		for _, platform := range p {
-			fmt.Printf("unpacking %s %s...\n", platform, img.Target.Digest)
+			fmt.Printf("unpacking %s %s...\n", platforms.Format(platform), img.Target.Digest)
-			i := containerd.NewImageWithPlatform(client, img, platform)
+			i := containerd.NewImageWithPlatform(client, img, platforms.Only(platform))
 			err = i.Unpack(ctx, context.String("snapshotter"))
 			if err != nil {
 				return err

image.go

@@ -63,7 +63,7 @@ func NewImage(client *Client, i images.Image) Image {
 }
 
 // NewImageWithPlatform returns a client image object from the metadata image
-func NewImageWithPlatform(client *Client, i images.Image, platform string) Image {
+func NewImageWithPlatform(client *Client, i images.Image, platform platforms.MatchComparer) Image {
 	return &image{
 		client:   client,
 		i:        i,
@@ -75,7 +75,7 @@ type image struct {
 	client *Client
 
 	i        images.Image
-	platform string
+	platform platforms.MatchComparer
 }
 
 func (i *image) Name() string {
@@ -186,7 +186,7 @@ func (i *image) Unpack(ctx context.Context, snapshotterName string) error {
 	return nil
 }
 
-func (i *image) getLayers(ctx context.Context, platform string) ([]rootfs.Layer, error) {
+func (i *image) getLayers(ctx context.Context, platform platforms.MatchComparer) ([]rootfs.Layer, error) {
 	cs := i.client.ContentStore()
 
 	manifest, err := images.Manifest(ctx, cs, i.i.Target, platform)

images/handlers.go

@@ -182,9 +182,47 @@ func SetChildrenLabels(manager content.Manager, f HandlerFunc) HandlerFunc {
 	}
 }
 
-// FilterPlatforms is a handler wrapper which limits the descriptors returned
+// FilterPlatformList is a handler wrapper which limits the descriptors returned
 // by a handler to the specified platforms.
-func FilterPlatforms(f HandlerFunc, platformList ...string) HandlerFunc {
+func FilterPlatformList(f HandlerFunc, platformList ...string) HandlerFunc {
+	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
+		children, err := f(ctx, desc)
+		if err != nil {
+			return children, err
+		}
+
+		if len(platformList) == 0 {
+			return children, nil
+		}
+
+		var m platforms.Matcher
+
+		if len(platformList) > 0 {
+			ps := make([]ocispec.Platform, len(platformList))
+			for i, platform := range platformList {
+				p, err := platforms.Parse(platform)
+				if err != nil {
+					return nil, err
+				}
+				ps[i] = p
+			}
+			m = platforms.Any(ps...)
+		}
+
+		var descs []ocispec.Descriptor
+		for _, d := range children {
+			if d.Platform == nil || m.Match(*d.Platform) {
+				descs = append(descs, d)
+			}
+		}
+
+		return descs, nil
+	}
+}
+
+// FilterPlatforms is a handler wrapper which limits the descriptors returned
+// based on matching the specified platform matcher.
+func FilterPlatforms(f HandlerFunc, m platforms.Matcher) HandlerFunc {
 	return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		children, err := f(ctx, desc)
 		if err != nil {
@@ -193,20 +231,12 @@ func FilterPlatforms(f HandlerFunc, platformList ...string) HandlerFunc {
 
 		var descs []ocispec.Descriptor
 
-		if len(platformList) == 0 {
+		if m == nil {
 			descs = children
 		} else {
-			for _, platform := range platformList {
+			for _, d := range children {
-				p, err := platforms.Parse(platform)
+				if d.Platform == nil || m.Match(*d.Platform) {
-				if err != nil {
+					descs = append(descs, d)
-					return nil, err
-				}
-				matcher := platforms.NewMatcher(p)
-
-				for _, d := range children {
-					if d.Platform == nil || matcher.Match(*d.Platform) {
-						descs = append(descs, d)
-					}
 				}
 			}
 		}

images/image.go

@@ -19,6 +19,7 @@ package images
 import (
 	"context"
 	"encoding/json"
+	"sort"
 	"strings"
 	"time"
 
@@ -93,7 +94,7 @@ type Store interface {
 //
 // The caller can then use the descriptor to resolve and process the
 // configuration of the image.
-func (image *Image) Config(ctx context.Context, provider content.Provider, platform string) (ocispec.Descriptor, error) {
+func (image *Image) Config(ctx context.Context, provider content.Provider, platform platforms.MatchComparer) (ocispec.Descriptor, error) {
 	return Config(ctx, provider, image.Target, platform)
 }
 
@@ -101,7 +102,7 @@ func (image *Image) Config(ctx context.Context, provider content.Provider, platf
 //
 // These are used to verify that a set of layers unpacked to the expected
 // values.
-func (image *Image) RootFS(ctx context.Context, provider content.Provider, platform string) ([]digest.Digest, error) {
+func (image *Image) RootFS(ctx context.Context, provider content.Provider, platform platforms.MatchComparer) ([]digest.Digest, error) {
 	desc, err := image.Config(ctx, provider, platform)
 	if err != nil {
 		return nil, err
@@ -110,7 +111,7 @@ func (image *Image) RootFS(ctx context.Context, provider content.Provider, platf
 }
 
 // Size returns the total size of an image's packed resources.
-func (image *Image) Size(ctx context.Context, provider content.Provider, platform string) (int64, error) {
+func (image *Image) Size(ctx context.Context, provider content.Provider, platform platforms.MatchComparer) (int64, error) {
 	var size int64
 	return size, Walk(ctx, Handlers(HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		if desc.Size < 0 {
@@ -121,27 +122,22 @@ func (image *Image) Size(ctx context.Context, provider content.Provider, platfor
 	}), FilterPlatforms(ChildrenHandler(provider), platform)), image.Target)
 }
 
+type platformManifest struct {
+	p *ocispec.Platform
+	m *ocispec.Manifest
+}
+
 // Manifest resolves a manifest from the image for the given platform.
 //
 // TODO(stevvooe): This violates the current platform agnostic approach to this
 // package by returning a specific manifest type. We'll need to refactor this
 // to return a manifest descriptor or decide that we want to bring the API in
 // this direction because this abstraction is not needed.`
-func Manifest(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform string) (ocispec.Manifest, error) {
+func Manifest(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform platforms.MatchComparer) (ocispec.Manifest, error) {
 	var (
-		matcher  platforms.Matcher
+		m        []platformManifest
-		m        *ocispec.Manifest
-		p        ocispec.Platform
 		wasIndex bool
 	)
-	if platform != "" {
-		var err error
-		p, err = platforms.Parse(platform)
-		if err != nil {
-			return ocispec.Manifest{}, err
-		}
-		matcher = platforms.NewMatcher(p)
-	}
 
 	if err := Walk(ctx, HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		switch desc.MediaType {
@@ -156,8 +152,8 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 				return nil, err
 			}
 
-			if platform != "" {
+			if platform != nil {
-				if desc.Platform != nil && !matcher.Match(*desc.Platform) {
+				if desc.Platform != nil && !platform.Match(*desc.Platform) {
 					return nil, nil
 				}
 
@@ -172,14 +168,17 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 						return nil, err
 					}
 
-					if !matcher.Match(platforms.Normalize(ocispec.Platform{OS: image.OS, Architecture: image.Architecture})) {
+					if !platform.Match(platforms.Normalize(ocispec.Platform{OS: image.OS, Architecture: image.Architecture})) {
 						return nil, nil
 					}
 
 				}
 			}
 
-			m = &manifest
+			m = append(m, platformManifest{
+				p: desc.Platform,
+				m: &manifest,
+			})
 
 			return nil, nil
 		case MediaTypeDockerSchema2ManifestList, ocispec.MediaTypeImageIndex:
@@ -193,13 +192,13 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 				return nil, err
 			}
 
-			if platform == "" {
+			if platform == nil {
 				return idx.Manifests, nil
 			}
 
 			var descs []ocispec.Descriptor
 			for _, d := range idx.Manifests {
-				if d.Platform == nil || matcher.Match(*d.Platform) {
+				if d.Platform == nil || platform.Match(*d.Platform) {
 					descs = append(descs, d)
 				}
 			}
@@ -214,15 +213,25 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 		return ocispec.Manifest{}, err
 	}
 
-	if m == nil {
+	if len(m) == 0 {
 		err := errors.Wrapf(errdefs.ErrNotFound, "manifest %v", image.Digest)
 		if wasIndex {
-			err = errors.Wrapf(errdefs.ErrNotFound, "no match for current platform %s in manifest %v", platforms.Format(p), image.Digest)
+			err = errors.Wrapf(errdefs.ErrNotFound, "no match for platform in manifest %v", image.Digest)
 		}
 		return ocispec.Manifest{}, err
 	}
 
-	return *m, nil
+	sort.SliceStable(m, func(i, j int) bool {
+		if m[i].p == nil {
+			return false
+		}
+		if m[j].p == nil {
+			return true
+		}
+		return platform.Less(*m[i].p, *m[j].p)
+	})
+
+	return *m[0].m, nil
 }
 
 // Config resolves the image configuration descriptor using a content provided
@@ -230,7 +239,7 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 //
 // The caller can then use the descriptor to resolve and process the
 // configuration of the image.
-func Config(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform string) (ocispec.Descriptor, error) {
+func Config(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform platforms.MatchComparer) (ocispec.Descriptor, error) {
 	manifest, err := Manifest(ctx, provider, image, platform)
 	if err != nil {
 		return ocispec.Descriptor{}, err
@@ -276,7 +285,7 @@ func Platforms(ctx context.Context, provider content.Provider, image ocispec.Des
 // in the provider.
 //
 // If there is a problem resolving content, an error will be returned.
-func Check(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform string) (available bool, required, present, missing []ocispec.Descriptor, err error) {
+func Check(ctx context.Context, provider content.Provider, image ocispec.Descriptor, platform platforms.MatchComparer) (available bool, required, present, missing []ocispec.Descriptor, err error) {
 	mfst, err := Manifest(ctx, provider, image, platform)
 	if err != nil {
 		if errdefs.IsNotFound(err) {

platforms/compare.go

@@ -0,0 +1,192 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package platforms
+
+import specs "github.com/opencontainers/image-spec/specs-go/v1"
+
+// MatchComparer is able to match and compare platforms to
+// filter and sort platforms.
+type MatchComparer interface {
+	Matcher
+
+	Less(specs.Platform, specs.Platform) bool
+}
+
+// Only returns a match comparer for a single platform
+// using default resolution logic for the platform.
+//
+// For ARMv7, will also match ARMv6 and ARMv5
+// For ARMv6, will also match ARMv5
+func Only(platform specs.Platform) MatchComparer {
+	platform = Normalize(platform)
+	if platform.Architecture == "arm" {
+		if platform.Variant == "v7" {
+			return orderedPlatformComparer{
+				matchers: []Matcher{
+					&matcher{
+						Platform: platform,
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v6",
+						},
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v5",
+						},
+					},
+				},
+			}
+		}
+		if platform.Variant == "v6" {
+			return orderedPlatformComparer{
+				matchers: []Matcher{
+					&matcher{
+						Platform: platform,
+					},
+					&matcher{
+						Platform: specs.Platform{
+							Architecture: platform.Architecture,
+							OS:           platform.OS,
+							OSVersion:    platform.OSVersion,
+							OSFeatures:   platform.OSFeatures,
+							Variant:      "v5",
+						},
+					},
+				},
+			}
+		}
+	}
+
+	return singlePlatformComparer{
+		Matcher: &matcher{
+			Platform: platform,
+		},
+	}
+}
+
+// Ordered returns a platform MatchComparer which matches any of the platforms
+// but orders them in order they are provided.
+func Ordered(platforms ...specs.Platform) MatchComparer {
+	matchers := make([]Matcher, len(platforms))
+	for i := range platforms {
+		matchers[i] = NewMatcher(platforms[i])
+	}
+	return orderedPlatformComparer{
+		matchers: matchers,
+	}
+}
+
+// Any returns a platform MatchComparer which matches any of the platforms
+// with no preference for ordering.
+func Any(platforms ...specs.Platform) MatchComparer {
+	matchers := make([]Matcher, len(platforms))
+	for i := range platforms {
+		matchers[i] = NewMatcher(platforms[i])
+	}
+	return anyPlatformComparer{
+		matchers: matchers,
+	}
+}
+
+// All is a platform MatchComparer which matches all platforms
+// with preference for ordering.
+var All MatchComparer = allPlatformComparer{}
+
+type singlePlatformComparer struct {
+	Matcher
+}
+
+func (c singlePlatformComparer) Less(p1, p2 specs.Platform) bool {
+	return c.Match(p1) && !c.Match(p2)
+}
+
+type orderedPlatformComparer struct {
+	matchers []Matcher
+}
+
+func (c orderedPlatformComparer) Match(platform specs.Platform) bool {
+	for _, m := range c.matchers {
+		if m.Match(platform) {
+			return true
+		}
+	}
+	return false
+}
+
+func (c orderedPlatformComparer) Less(p1 specs.Platform, p2 specs.Platform) bool {
+	for _, m := range c.matchers {
+		p1m := m.Match(p1)
+		p2m := m.Match(p2)
+		if p1m && !p2m {
+			return true
+		}
+		if p1m || p2m {
+			return false
+		}
+	}
+	return false
+}
+
+type anyPlatformComparer struct {
+	matchers []Matcher
+}
+
+func (c anyPlatformComparer) Match(platform specs.Platform) bool {
+	for _, m := range c.matchers {
+		if m.Match(platform) {
+			return true
+		}
+	}
+	return false
+}
+
+func (c anyPlatformComparer) Less(p1, p2 specs.Platform) bool {
+	var p1m, p2m bool
+	for _, m := range c.matchers {
+		if !p1m && m.Match(p1) {
+			p1m = true
+		}
+		if !p2m && m.Match(p2) {
+			p2m = true
+		}
+		if p1m && p2m {
+			return false
+		}
+	}
+	// If one matches, and the other does, sort match first
+	return p1m && !p2m
+}
+
+type allPlatformComparer struct{}
+
+func (allPlatformComparer) Match(specs.Platform) bool {
+	return true
+}
+
+func (allPlatformComparer) Less(specs.Platform, specs.Platform) bool {
+	return false
+}

platforms/defaults.go

@@ -22,8 +22,13 @@ import (
 	specs "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-// Default returns the default specifier for the platform.
+// Default returns the default matcher for the platform.
-func Default() string {
+func Default() MatchComparer {
+	return Only(DefaultSpec())
+}
+
+// DefaultString returns the default string specifier for the platform.
+func DefaultString() string {
 	return Format(DefaultSpec())
 }
 

platforms/defaults_test.go

@@ -35,7 +35,7 @@ func TestDefault(t *testing.T) {
 		t.Fatalf("default platform not as expected: %#v != %#v", p, expected)
 	}
 
-	s := Default()
+	s := DefaultString()
 	if s != Format(p) {
 		t.Fatalf("default specifier should match formatted default spec: %v != %v", s, p)
 	}

remotes/handlers.go

@@ -27,6 +27,7 @@ import (
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/log"
+	"github.com/containerd/containerd/platforms"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -155,7 +156,7 @@ func push(ctx context.Context, provider content.Provider, pusher Pusher, desc oc
 //
 // Base handlers can be provided which will be called before any push specific
 // handlers.
-func PushContent(ctx context.Context, pusher Pusher, desc ocispec.Descriptor, provider content.Provider, platforms []string, baseHandlers ...images.Handler) error {
+func PushContent(ctx context.Context, pusher Pusher, desc ocispec.Descriptor, provider content.Provider, platform platforms.MatchComparer, baseHandlers ...images.Handler) error {
 	var m sync.Mutex
 	manifestStack := []ocispec.Descriptor{}
 
@@ -175,7 +176,7 @@ func PushContent(ctx context.Context, pusher Pusher, desc ocispec.Descriptor, pr
 	pushHandler := PushHandler(pusher, provider)
 
 	handlers := append(baseHandlers,
-		images.FilterPlatforms(images.ChildrenHandler(provider), platforms...),
+		images.FilterPlatforms(images.ChildrenHandler(provider), platform),
 		filterHandler,
 		pushHandler,
 	)