Add top-level GetSpec function to nvcdi API

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-ctk/cdi/generate/generate.go

@@ -187,6 +187,7 @@ func (m command) run(c *cli.Context, cfg *config) error {
 		if err != nil {
 			return fmt.Errorf("failed to convert CDI spec from YAML to JSON: %v", err)
 		}
+		return nil
 	}
 
 	err = writeToOutput(cfg.format, data, outputTo)

pkg/nvcdi/lib.go

@@ -98,7 +98,11 @@ func (l *wrapper) GetSpec() (spec.Interface, error) {
 		return nil, err
 	}
 
-	return spec.New(deviceSpecs, *edits.ContainerEdits)
+	return spec.New(
+		spec.WithDeviceSpecs(deviceSpecs),
+		spec.WithEdits(*edits.ContainerEdits),
+	)
+
 }
 
 // resolveMode resolves the mode for CDI spec generation based on the current system.

pkg/nvcdi/spec/api.go

@@ -16,10 +16,20 @@
 
 package spec
 
-import "github.com/container-orchestrated-devices/container-device-interface/specs-go"
+import (
+	"io"
+
+	"github.com/container-orchestrated-devices/container-device-interface/specs-go"
+)
+
+const (
+	// DetectMinimumVersion is a constant that triggers a spec to detect the minimum required version.
+	DetectMinimumVersion = "DETECT_MINIMUM_VERSION"
+)
 
 // Interface is the interface for the spec API
 type Interface interface {
+	io.WriterTo
 	Save(string) error
 	Raw() *specs.Spec
 }

pkg/nvcdi/spec/builder.go

@@ -0,0 +1,127 @@
+/**
+# Copyright (c) NVIDIA CORPORATION.  All rights reserved.
+#
+# 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 spec
+
+import (
+	"fmt"
+
+	"github.com/container-orchestrated-devices/container-device-interface/pkg/cdi"
+	"github.com/container-orchestrated-devices/container-device-interface/specs-go"
+)
+
+type builder struct {
+	raw         *specs.Spec
+	version     string
+	vendor      string
+	class       string
+	deviceSpecs []specs.Device
+	edits       specs.ContainerEdits
+	format      string
+}
+
+// NewBuilder creates a new spec builder with the supplied options
+func NewBuilder(opts ...Option) *builder {
+	s := &builder{}
+	for _, opt := range opts {
+		opt(s)
+	}
+	if s.version == "" {
+		s.version = DetectMinimumVersion
+	}
+	if s.vendor == "" {
+		s.vendor = "nvidia.com"
+	}
+	if s.class == "" {
+		s.class = "gpu"
+	}
+
+	return s
+}
+
+// Build builds a CDI spec form the spec builder.
+func (o *builder) Build() (*spec, error) {
+	raw := o.raw
+
+	if raw == nil {
+		raw = &specs.Spec{
+			Version:        o.version,
+			Kind:           fmt.Sprintf("%s/%s", o.vendor, o.class),
+			Devices:        o.deviceSpecs,
+			ContainerEdits: o.edits,
+		}
+	}
+
+	if raw.Version == DetectMinimumVersion {
+		minVersion, err := cdi.MinimumRequiredVersion(raw)
+		if err != nil {
+			return nil, fmt.Errorf("failed to get minumum required CDI spec version: %v", err)
+		}
+		raw.Version = minVersion
+	}
+
+	s := spec{
+		Spec:   raw,
+		format: o.format,
+	}
+
+	return &s, nil
+}
+
+// Option defines a function that can be used to configure the spec builder.
+type Option func(*builder)
+
+// WithDeviceSpecs sets the device specs for the spec builder
+func WithDeviceSpecs(deviceSpecs []specs.Device) Option {
+	return func(o *builder) {
+		o.deviceSpecs = deviceSpecs
+	}
+}
+
+// WithEdits sets the container edits for the spec builder
+func WithEdits(edits specs.ContainerEdits) Option {
+	return func(o *builder) {
+		o.edits = edits
+	}
+}
+
+// WithVersion sets the version for the spec builder
+func WithVersion(version string) Option {
+	return func(o *builder) {
+		o.version = version
+	}
+}
+
+// WithVendor sets the vendor for the spec builder
+func WithVendor(vendor string) Option {
+	return func(o *builder) {
+		o.vendor = vendor
+	}
+}
+
+// WithClass sets the class for the spec builder
+func WithClass(class string) Option {
+	return func(o *builder) {
+		o.class = class
+	}
+}
+
+// WithFormat sets the output file format
+func WithFormat(format string) Option {
+	return func(o *builder) {
+		o.format = format
+	}
+}

pkg/nvcdi/spec/spec.go

@@ -17,44 +17,92 @@
 package spec
 
 import (
-	"fmt"
+	"io"
+	"os"
+	"path/filepath"
 
 	"github.com/container-orchestrated-devices/container-device-interface/pkg/cdi"
 	"github.com/container-orchestrated-devices/container-device-interface/specs-go"
 )
 
-type spec specs.Spec
+type spec struct {
+	*specs.Spec
+	format string
+}
 
 var _ Interface = (*spec)(nil)
 
-// New creates a new spec with the specified deivice specs and edits.
+// New creates a new spec with the specified options.
-func New(deviceSpecs []specs.Device, edits specs.ContainerEdits) (Interface, error) {
+func New(opts ...Option) (Interface, error) {
-	s := specs.Spec{
+	return NewBuilder(opts...).Build()
-		// TODO: Should be set through an option
-		Version: "NOT_SET",
-		// TODO: Should be set through an option
-		Kind: "nvidia.com/gpu",
-		// TODO: Should be set through an option
-		Devices: deviceSpecs,
-		// TODO: Should be set through an option
-		ContainerEdits: edits,
-	}
-
-	minVersion, err := cdi.MinimumRequiredVersion(&s)
-	if err != nil {
-		return nil, fmt.Errorf("failed to get minumum required CDI spec version: %v", err)
-	}
-	s.Version = minVersion
-
-	return (*spec)(&s), nil
 }
 
 // Save writes the spec to the specified path and overwrites the file if it exists.
 func (s *spec) Save(path string) error {
-	return cdi.WriteSpec(s, path, true)
+	path = s.normalizePath(path)
+
+	specDir := filepath.Dir(path)
+	registry := cdi.GetRegistry(
+		cdi.WithAutoRefresh(false),
+		cdi.WithSpecDirs(specDir),
+	)
+
+	return registry.SpecDB().WriteSpec(s.Raw(), filepath.Base(path))
+}
+
+// WriteTo writes the spec to the specified writer.
+func (s *spec) WriteTo(w io.Writer) (int64, error) {
+	name, err := cdi.GenerateNameForSpec(s.Raw())
+	if err != nil {
+		return 0, err
+	}
+
+	path := s.normalizePath(name)
+	tmpFile, err := os.CreateTemp("", "*"+filepath.Base(path))
+	if err != nil {
+		return 0, err
+	}
+	defer os.Remove(tmpFile.Name())
+
+	if err := s.Save(tmpFile.Name()); err != nil {
+		return 0, err
+	}
+
+	err = tmpFile.Close()
+	if err != nil {
+		return 0, fmt.Errorf("failed to close temporary file: %w", err)
+	}
+
+	r, err := os.Open(tmpFile.Name())
+	if err != nil {
+		return 0, fmt.Errorf("failed to open temporary file: %w", err)
+	}
+	defer r.Close()
+
+	return io.Copy(w, r)
 }
 
 // Raw returns a pointer to the raw spec.
 func (s *spec) Raw() *specs.Spec {
-	return (*specs.Spec)(s)
+	return s.Spec
+}
+
+// normalizePath ensures that the specified path has a supported extension
+func (s *spec) normalizePath(path string) string {
+	if ext := filepath.Ext(path); ext != ".yaml" && ext != ".json" {
+		path += s.extension()
+	}
+
+	return path
+}
+
+func (s *spec) extension() string {
+	switch s.format {
+	case "json":
+		return ".json"
+	case "yaml", "yml":
+		return ".yaml"
+	}
+
+	return ".yaml"
 }