/
json.go
171 lines (152 loc) · 3.42 KB
/
json.go
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// Package json provides an encoder/decoder for JSON quad formats
package json
import (
"encoding/json"
"errors"
"fmt"
"io"
"github.com/cayleygraph/quad"
)
func init() {
quad.RegisterFormat(quad.Format{
Name: "json",
Ext: []string{".json"},
Mime: []string{"application/json"},
Writer: func(w io.Writer) quad.WriteCloser { return NewWriter(w) },
Reader: func(r io.Reader) quad.ReadCloser { return NewReader(r) },
MarshalValue: func(v quad.Value) ([]byte, error) {
return json.Marshal(quad.ToString(v))
},
UnmarshalValue: func(b []byte) (quad.Value, error) {
var s *string
if err := json.Unmarshal(b, &s); err != nil {
return nil, err
} else if s == nil {
return nil, nil
}
return quad.StringToValue(*s), nil
},
})
quad.RegisterFormat(quad.Format{
Name: "json-stream",
Mime: []string{"application/x-json-stream"},
Writer: func(w io.Writer) quad.WriteCloser { return NewStreamWriter(w) },
Reader: func(r io.Reader) quad.ReadCloser { return NewStreamReader(r) },
})
}
func NewReader(r io.Reader) *Reader {
var quads []quad.Quad
err := json.NewDecoder(r).Decode(&quads)
return &Reader{ // TODO(dennwc): stream-friendly reader
quads: quads,
err: err,
}
}
type Reader struct {
quads []quad.Quad
n int
err error
}
func (r *Reader) ReadQuad() (quad.Quad, error) {
if r.err != nil {
return quad.Quad{}, r.err
}
if r.n >= len(r.quads) {
return quad.Quad{}, io.EOF
}
q := r.quads[r.n]
r.n++
if !q.IsValid() {
return quad.Quad{}, fmt.Errorf("invalid quad at index %d. %s", r.n-1, q)
}
return q, nil
}
func (r *Reader) Close() error { return nil }
func NewStreamReader(r io.Reader) *StreamReader {
return &StreamReader{dec: json.NewDecoder(r)}
}
type StreamReader struct {
dec *json.Decoder
err error
}
func (r *StreamReader) ReadQuad() (quad.Quad, error) {
if r.err != nil {
return quad.Quad{}, r.err
}
var q quad.Quad
r.err = r.dec.Decode(&q)
return q, r.err
}
func (r *StreamReader) Close() error { return nil }
func NewWriter(w io.Writer) *Writer {
return &Writer{w: w}
}
type Writer struct {
w io.Writer
written bool
closed bool
}
func (w *Writer) WriteQuad(q quad.Quad) error {
if w.closed {
return errors.New("closed")
} else if !q.IsValid() {
return quad.ErrInvalid
}
if !w.written {
if _, err := w.w.Write([]byte("[\n\t")); err != nil {
return err
}
w.written = true
} else {
if _, err := w.w.Write([]byte(",\n\t")); err != nil {
return err
}
}
data, err := json.Marshal(q)
if err != nil {
return err
}
_, err = w.w.Write(data)
return err
}
func (w *Writer) WriteQuads(buf []quad.Quad) (int, error) {
for i, q := range buf {
if err := w.WriteQuad(q); err != nil {
return i, err
}
}
return len(buf), nil
}
func (w *Writer) Close() error {
if w.closed {
return nil
}
w.closed = true
if !w.written {
_, err := w.w.Write([]byte("null\n"))
return err
}
_, err := w.w.Write([]byte("\n]\n"))
return err
}
func NewStreamWriter(w io.Writer) *StreamWriter {
return &StreamWriter{enc: json.NewEncoder(w)}
}
type StreamWriter struct {
enc *json.Encoder
}
func (w *StreamWriter) WriteQuad(q quad.Quad) error {
if !q.IsValid() {
return quad.ErrInvalid
}
return w.enc.Encode(q)
}
func (w *StreamWriter) WriteQuads(buf []quad.Quad) (int, error) {
for i, q := range buf {
if err := w.WriteQuad(q); err != nil {
return i, err
}
}
return len(buf), nil
}
func (w *StreamWriter) Close() error { return nil }