libpod: Split out the common code from GetContainerStats

This moves the cgroups code to a new method getPlatformContainerStats.

[NO NEW TESTS NEEDED]

Signed-off-by: Doug Rabson <dfr@rabson.org>

libpod/stats_common.go

@@ -0,0 +1,49 @@
+//go:build linux || freebsd
+// +build linux freebsd
+
+package libpod
+
+import (
+	"fmt"
+
+	"github.com/containers/podman/v4/libpod/define"
+)
+
+// GetContainerStats gets the running stats for a given container.
+// The previousStats is used to correctly calculate cpu percentages. You
+// should pass nil if there is no previous stat for this container.
+func (c *Container) GetContainerStats(previousStats *define.ContainerStats) (*define.ContainerStats, error) {
+	stats := new(define.ContainerStats)
+	stats.ContainerID = c.ID()
+	stats.Name = c.Name()
+
+	if c.config.NoCgroups {
+		return nil, fmt.Errorf("cannot run top on container %s as it did not create a cgroup: %w", c.ID(), define.ErrNoCgroups)
+	}
+
+	if !c.batched {
+		c.lock.Lock()
+		defer c.lock.Unlock()
+		if err := c.syncContainer(); err != nil {
+			return stats, err
+		}
+	}
+
+	// returns stats with the fields' default values respective of their type
+	if c.state.State != define.ContainerStateRunning && c.state.State != define.ContainerStatePaused {
+		return stats, nil
+	}
+
+	if previousStats == nil {
+		previousStats = &define.ContainerStats{
+			// if we have no prev stats use the container start time as prev time
+			// otherwise we cannot correctly calculate the CPU percentage
+			SystemNano: uint64(c.state.StartedTime.UnixNano()),
+		}
+	}
+
+	if err := c.getPlatformContainerStats(stats, previousStats); err != nil {
+		return nil, err
+	}
+	return stats, nil
+}