Add producer API to write specs

This change adds a SpecProducer that can be used by clients
that are only concerned with outputing specs. A spec producer
is configured on construction to allow for the default output
format, and file permissions to be specified.

Signed-off-by: Evan Lezar <[email protected]>

Author: elezar

api/producer/api.go

@@ -0,0 +1,34 @@
+/*
+   Copyright © 2024 The CDI 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 producer
+
+import cdi "tags.cncf.io/container-device-interface/specs-go"
+
+const (
+	// DefaultSpecFormat defines the default encoding used to write CDI specs.
+	DefaultSpecFormat = SpecFormatYAML
+
+	// SpecFormatJSON defines a CDI spec formatted as JSON.
+	SpecFormatJSON = SpecFormat(".json")
+	// SpecFormatYAML defines a CDI spec formatted as YAML.
+	SpecFormatYAML = SpecFormat(".yaml")
+)
+
+// A SpecValidator is used to validate a CDI spec.
+type SpecValidator interface {
+	Validate(*cdi.Spec) error
+}

api/producer/go.mod

@@ -0,0 +1,20 @@
+module tags.cncf.io/container-device-interface/api/producer
+
+go 1.20
+
+require (
+	github.com/stretchr/testify v1.7.0
+	golang.org/x/sys v0.1.0
+	sigs.k8s.io/yaml v1.3.0
+	tags.cncf.io/container-device-interface/specs-go v0.8.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/mod v0.19.0 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+replace tags.cncf.io/container-device-interface/specs-go => ../../specs-go

api/producer/go.sum

@@ -0,0 +1,21 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/mod v0.19.0 h1:fEdghXQSo20giMthA7cd28ZC+jts4amQ3YMXiP5oMQ8=
+golang.org/x/mod v0.19.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
+golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
+golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+sigs.k8s.io/yaml v1.3.0 h1:a2VclLzOGrwOHDiV8EfBGhvjHvP46CtW5j6POvhYGGo=
+sigs.k8s.io/yaml v1.3.0/go.mod h1:GeOyir5tyXNByN85N/dRIT9es5UQNerPYEKK56eTBm8=

api/producer/options.go

@@ -0,0 +1,61 @@
+/*
+   Copyright © 2024 The CDI 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 producer
+
+import (
+	"fmt"
+	"io/fs"
+)
+
+// An Option defines a functional option for constructing a producer.
+type Option func(*options) error
+
+type options struct {
+	specFormat  SpecFormat
+	overwrite   bool
+	permissions fs.FileMode
+}
+
+// WithSpecFormat sets the output format of a CDI specification.
+func WithSpecFormat(format SpecFormat) Option {
+	return func(o *options) error {
+		switch format {
+		case SpecFormatJSON, SpecFormatYAML:
+			o.specFormat = format
+		default:
+			return fmt.Errorf("invalid CDI spec format %v", format)
+		}
+		return nil
+	}
+}
+
+// WithOverwrite specifies whether a producer should overwrite a CDI spec when
+// saving to file.
+func WithOverwrite(overwrite bool) Option {
+	return func(o *options) error {
+		o.overwrite = overwrite
+		return nil
+	}
+}
+
+// WithPermissions sets the file mode to be used for a saved CDI spec.
+func WithPermissions(permissions fs.FileMode) Option {
+	return func(o *options) error {
+		o.permissions = permissions
+		return nil
+	}
+}

pkg/cdi/spec_linux.go renamed to api/producer/renamein_linux.go

@@ -14,7 +14,7 @@
    limitations under the License.
 */
 
-package cdi
+package producer
 
 import (
 	"fmt"

pkg/cdi/spec_other.go renamed to api/producer/renamein_other.go

@@ -17,7 +17,7 @@
    limitations under the License.
 */
 
-package cdi
+package producer
 
 import (
 	"os"

api/producer/spec-format.go

@@ -0,0 +1,93 @@
+/*
+   Copyright © 2024 The CDI 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 producer
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"path/filepath"
+
+	"sigs.k8s.io/yaml"
+
+	cdi "tags.cncf.io/container-device-interface/specs-go"
+)
+
+// A SpecFormat defines the encoding to use when reading or writing a CDI specification.
+type SpecFormat string
+
+type specFormatter struct {
+	*cdi.Spec
+	options
+}
+
+// WriteTo writes the spec to the specified writer.
+func (p *specFormatter) WriteTo(w io.Writer) (int64, error) {
+	data, err := p.contents()
+	if err != nil {
+		return 0, fmt.Errorf("failed to marshal Spec file: %w", err)
+	}
+
+	n, err := w.Write(data)
+	return int64(n), err
+}
+
+// marshal returns the raw contents of a CDI specification.
+// No validation is performed.
+func (p SpecFormat) marshal(spec *cdi.Spec) ([]byte, error) {
+	switch p {
+	case SpecFormatYAML:
+		data, err := yaml.Marshal(spec)
+		if err != nil {
+			return nil, err
+		}
+		data = append([]byte("---\n"), data...)
+		return data, nil
+	case SpecFormatJSON:
+		return json.Marshal(spec)
+	default:
+		return nil, fmt.Errorf("undefined CDI spec format %v", p)
+	}
+}
+
+// normalizeFilename ensures that the specified filename ends in a supported extension.
+func (p SpecFormat) normalizeFilename(filename string) (string, SpecFormat) {
+	switch filepath.Ext(filename) {
+	case ".json":
+		return filename, SpecFormatJSON
+	case ".yaml":
+		return filename, SpecFormatYAML
+	default:
+		return filename + string(p), p
+	}
+}
+
+// validate performs an explicit validation of the spec.
+// This is currently a placeholder for validation that should be performed when
+// saving a spec.
+func (p *specFormatter) validate() error {
+	return nil
+}
+
+// contents returns the raw contents of a CDI specification.
+// Validation is performed before marshalling the contentent based on the spec format.
+func (p *specFormatter) contents() ([]byte, error) {
+	if err := p.validate(); err != nil {
+		return nil, fmt.Errorf("spec validation failed: %w", err)
+	}
+	return p.specFormat.marshal(p.Spec)
+}

api/producer/writer.go

@@ -0,0 +1,104 @@
+/*
+   Copyright © 2024 The CDI 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 producer
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	cdi "tags.cncf.io/container-device-interface/specs-go"
+)
+
+// A SpecWriter defines a structure for outputting CDI specifications.
+type SpecWriter struct {
+	options
+}
+
+// NewSpecWriter creates a spec writer with the supplied options.
+func NewSpecWriter(opts ...Option) (*SpecWriter, error) {
+	sw := &SpecWriter{
+		options: options{
+			overwrite: true,
+			// TODO: This could be updated to 0644 to be world-readable.
+			permissions: 0600,
+			specFormat:  DefaultSpecFormat,
+		},
+	}
+	for _, opt := range opts {
+		err := opt(&sw.options)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return sw, nil
+}
+
+// Save writes a CDI spec to a file with the specified name.
+// If the filename ends in a supported extension, the format implied by the
+// extension takes precedence over the format with which the SpecWriter was
+// configured.
+func (p *SpecWriter) Save(spec *cdi.Spec, filename string) (string, error) {
+	filename, outputFormat := p.specFormat.normalizeFilename(filename)
+
+	options := p.options
+	options.specFormat = outputFormat
+	specFormatter := specFormatter{
+		Spec:    spec,
+		options: options,
+	}
+
+	dir := filepath.Dir(filename)
+	if dir != "" {
+		if err := os.MkdirAll(dir, 0o755); err != nil {
+			return "", fmt.Errorf("failed to create Spec dir: %w", err)
+		}
+	}
+
+	tmp, err := os.CreateTemp(dir, "spec.*.tmp")
+	if err != nil {
+		return "", fmt.Errorf("failed to create Spec file: %w", err)
+	}
+
+	_, err = specFormatter.WriteTo(tmp)
+	tmp.Close()
+	if err != nil {
+		return "", fmt.Errorf("failed to write Spec file: %w", err)
+	}
+
+	if err := os.Chmod(tmp.Name(), p.permissions); err != nil {
+		return "", fmt.Errorf("failed to set permissions on spec file: %w", err)
+	}
+
+	err = renameIn(dir, filepath.Base(tmp.Name()), filepath.Base(filename), p.overwrite)
+	if err != nil {
+		_ = os.Remove(tmp.Name())
+		return "", fmt.Errorf("failed to write Spec file: %w", err)
+	}
+	return filename, nil
+}
+
+// WriteSpecTo writes the specified spec to the specified writer.
+func (p *SpecWriter) WriteSpecTo(spec *cdi.Spec, w io.Writer) (int64, error) {
+	specFormatter := specFormatter{
+		Spec:    spec,
+		options: p.options,
+	}
+
+	return specFormatter.WriteTo(w)
+}