/
base.go
121 lines (108 loc) · 3.24 KB
/
base.go
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/* ****************************************************************************
* Copyright 2020 51 Degrees Mobile Experts Limited (51degrees.com)
*
* 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 swan
import (
"bytes"
"encoding"
"encoding/base64"
"github.com/SWAN-community/common-go"
"github.com/SWAN-community/owid-go"
)
// Base used with any SWAN field.
type Base struct {
Version byte `json:"version"` // Used to indicate the version encoding of the type.
OWID *owid.OWID `json:"source"` // OWID related to the structure
}
// writeData writes the version before calling the function.
func (b *Base) writeData(u *bytes.Buffer, f func(*bytes.Buffer) error) error {
err := common.WriteByte(u, b.Version)
if err != nil {
return err
}
err = f(u)
if err != nil {
return err
}
return nil
}
// marshalOwid returns a byte array of all the data needed by an OWID.
func (b *Base) marshalOwid(f func(*bytes.Buffer) error) ([]byte, error) {
var u bytes.Buffer
err := b.writeData(&u, f)
if err != nil {
return nil, err
}
return u.Bytes(), nil
}
// marshalBinary marshals the version, calls the function to add more data, and
// finishes by adding the OWID before returning the byte array.
func (b *Base) marshalBinary(f func(*bytes.Buffer) error) ([]byte, error) {
var u bytes.Buffer
err := b.writeData(&u, f)
if err != nil {
return nil, err
}
err = b.OWID.ToBuffer(&u)
if err != nil {
return nil, err
}
return u.Bytes(), nil
}
// toBase64 encodes the marshalBinary result as a base64 string.
func (b *Base) toBase64(f func(*bytes.Buffer) error) (string, error) {
d, err := b.marshalBinary(f)
if err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(d), nil
}
// unmarshalBinary handles converting a byte array into all the fields of a
// structure that inherits from Base.
// m the marshaler for the OWID
// d the byte array with the data
// f function to add the content from the caller
func (b *Base) unmarshalBinary(
m owid.Marshaler,
d []byte,
f func(*bytes.Buffer) error) error {
var err error
u := bytes.NewBuffer(d)
// Read the version first.
b.Version, err = common.ReadByte(u)
if err != nil {
return err
}
// Call the provided function to read the fields for the calling type.
err = f(u)
if err != nil {
return err
}
// Finally read the OWID data passing
b.OWID, err = owid.FromBuffer(u, m)
if err != nil {
return err
}
return nil
}
// unmarshalString uses the unmarshaler to read the byte array contained in the
// base64 encoded string.
func unmarshalString(b encoding.BinaryUnmarshaler, s string) error {
d, err := base64.StdEncoding.DecodeString(s)
if err != nil {
return err
}
return b.UnmarshalBinary(d)
}