pkg/cdi: add functions for Spec name generation.

Add convenience functions for generating names for ordinary
and transient Spec files and for removing Spec files created
with WriteSpec().

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

pkg/cdi/cache.go

@@ -17,11 +17,15 @@
 package cdi
 
 import (
+	"io/fs"
+	"os"
 	"path/filepath"
 	"sort"
 	"strings"
 	"sync"
 
+	stderr "errors"
+
 	cdi "github.com/container-orchestrated-devices/container-device-interface/specs-go"
 	"github.com/fsnotify/fsnotify"
 	"github.com/hashicorp/go-multierror"
@@ -255,6 +259,19 @@ func (c *Cache) InjectDevices(ociSpec *oci.Spec, devices ...string) ([]string, e
 	return nil, nil
 }
 
+// highestPrioritySpecDir returns the Spec directory with highest priority
+// and its priority.
+func (c *Cache) highestPrioritySpecDir() (string, int) {
+	if len(c.specDirs) == 0 {
+		return "", -1
+	}
+
+	prio := len(c.specDirs) - 1
+	dir := c.specDirs[prio]
+
+	return dir, prio
+}
+
 // WriteSpec writes a Spec file with the given content into the highest
 // priority Spec directory. If name has a "json" or "yaml" extension it
 // choses the encoding. Otherwise JSON encoding is used with a "json"
@@ -268,12 +285,11 @@ func (c *Cache) WriteSpec(raw *cdi.Spec, name string) error {
 		err     error
 	)
 
-	if len(c.specDirs) == 0 {
+	specDir, prio = c.highestPrioritySpecDir()
+	if specDir == "" {
 		return errors.New("no Spec directories to write to")
 	}
 
-	prio = len(c.specDirs) - 1
-	specDir = c.specDirs[prio]
 	path = filepath.Join(specDir, name)
 	if ext := filepath.Ext(path); ext != ".json" && ext != ".yaml" {
 		path += ".json"
@@ -287,6 +303,35 @@ func (c *Cache) WriteSpec(raw *cdi.Spec, name string) error {
 	return spec.Write(true)
 }
 
+// RemoveSpec removes a Spec with the given name from the highest
+// priority Spec directory. This function can be used to remove a
+// Spec previosuly written by WriteSpec() using the same. If the
+// file exists and its removal fails RemoveSpec returns an error.
+func (c *Cache) RemoveSpec(name string) error {
+	var (
+		specDir string
+		path    string
+		err     error
+	)
+
+	specDir, _ = c.highestPrioritySpecDir()
+	if specDir == "" {
+		return errors.New("no Spec directories to remove from")
+	}
+
+	path = filepath.Join(specDir, name)
+	if ext := filepath.Ext(path); ext != ".json" && ext != ".yaml" {
+		path += ".json"
+	}
+
+	err = os.Remove(path)
+	if err != nil && stderr.Is(err, fs.ErrNotExist) {
+		err = nil
+	}
+
+	return err
+}
+
 // GetDevice returns the cached device for the given qualified name.
 func (c *Cache) GetDevice(device string) *Device {
 	c.Lock()

pkg/cdi/registry.go

@@ -107,6 +107,7 @@ type RegistrySpecDB interface {
 	GetVendorSpecs(vendor string) []*Spec
 	GetSpecErrors(*Spec) []error
 	WriteSpec(raw *cdi.Spec, name string) error
+	RemoveSpec(name string) error
 }
 
 type registry struct {

pkg/cdi/spec.go

@@ -262,3 +262,56 @@ func validateSpec(raw *cdi.Spec) error {
 	}
 	return nil
 }
+
+// GetSpecFileBase returns a Spec file basename.
+func GetSpecFileBase(vendor, class, tag string) string {
+	if tag != "" {
+		return vendor + "-" + class + "-" + tag
+	}
+	return vendor + "-" + class
+
+}
+
+// GenerateSpecName generates a vendor+class scoped Spec file name. The
+// name can be passed to WriteSpec() to write a Spec file to the file
+// system.
+//
+// vendor and class should match the vendor and class of the CDI Spec.
+// The file name is generated without a ".json" or ".yaml" extension.
+// The caller can append the desired extension to choose a particular
+// encoding. Otherwise WriteSpec() will use its default encoding.
+//
+// This function always returns the same name for the same vendor/class
+// combination. Therefore it cannot be used as such to generate multiple
+// Spec file names for a single vendor and class.
+func GenerateSpecName(vendor, class string) string {
+	return vendor + "-" + class
+}
+
+// GenerateTransientSpecName generates a vendor+class scoped transient
+// Spec file name. The name can be passed to WriteSpec() to write a Spec
+// file to the file system.
+
+// Transient Specs are those whose lifecycle is tied to that of some
+// external entity, for instance a container. vendor and class should
+// match the vendor and class of the CDI Spec. driver can be left empty
+// if only a single CDI user is generating transient Spec files for the
+// given vendor/class combination on the host. Otherwise driver should
+// uniquely identify the caller among those that use the same vendor
+// and class. transientID should uniquely identify the external entity
+// within the scope of the caller/driver.
+//
+// The file name is generated without a ".json" or ".yaml" extension.
+// The caller can append the desired extension to choose a particular
+// encoding. Otherwise WriteSpec() will use its default encoding.
+func GenerateTransientSpecName(vendor, class, driver, transientID string) string {
+	name := vendor + "-" + class
+
+	if driver != "" {
+		name += "+" + driver
+	}
+
+	name = "transient." + name + "_" + transientID
+
+	return name
+}