Move client to subpackage

Signed-off-by: Derek McGowan <derek@mcg.dev>

client/signals.go

@@ -0,0 +1,92 @@
+/*
+   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 client
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"syscall"
+
+	"github.com/containerd/containerd/v2/content"
+	"github.com/containerd/containerd/v2/images"
+	"github.com/moby/sys/signal"
+	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// StopSignalLabel is a well-known containerd label for storing the stop
+// signal specified in the OCI image config
+const StopSignalLabel = "io.containerd.image.config.stop-signal"
+
+// GetStopSignal retrieves the container stop signal, specified by the
+// well-known containerd label (StopSignalLabel)
+func GetStopSignal(ctx context.Context, container Container, defaultSignal syscall.Signal) (syscall.Signal, error) {
+	labels, err := container.Labels(ctx)
+	if err != nil {
+		return -1, err
+	}
+
+	if stopSignal, ok := labels[StopSignalLabel]; ok {
+		return signal.ParseSignal(stopSignal)
+	}
+
+	return defaultSignal, nil
+}
+
+// GetOCIStopSignal retrieves the stop signal specified in the OCI image config
+func GetOCIStopSignal(ctx context.Context, image Image, defaultSignal string) (string, error) {
+	_, err := signal.ParseSignal(defaultSignal)
+	if err != nil {
+		return "", err
+	}
+	ic, err := image.Config(ctx)
+	if err != nil {
+		return "", err
+	}
+	if !images.IsConfigType(ic.MediaType) {
+		return "", fmt.Errorf("unknown image config media type %s", ic.MediaType)
+	}
+
+	var (
+		ociimage v1.Image
+		config   v1.ImageConfig
+	)
+	p, err := content.ReadBlob(ctx, image.ContentStore(), ic)
+	if err != nil {
+		return "", err
+	}
+
+	if err = json.Unmarshal(p, &ociimage); err != nil {
+		return "", err
+	}
+	config = ociimage.Config
+
+	if config.StopSignal == "" {
+		return defaultSignal, nil
+	}
+
+	return config.StopSignal, nil
+}
+
+// ParseSignal parses a given string into a syscall.Signal
+// the rawSignal can be a string with "SIG" prefix,
+// or a signal number in string format.
+//
+// Deprecated: Use github.com/moby/sys/signal instead.
+func ParseSignal(rawSignal string) (syscall.Signal, error) {
+	return signal.ParseSignal(rawSignal)
+}