json: streaming
R=r, cw
CC=golang-dev
https://golang.org/cl/952041
diff --git a/src/pkg/json/stream.go b/src/pkg/json/stream.go
new file mode 100644
index 0000000..d4fb346
--- /dev/null
+++ b/src/pkg/json/stream.go
@@ -0,0 +1,185 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+ "bytes"
+ "io"
+ "os"
+)
+
+// A Decoder reads and decodes JSON objects from an input stream.
+type Decoder struct {
+ r io.Reader
+ buf []byte
+ d decodeState
+ scan scanner
+ err os.Error
+}
+
+// NewDecoder returns a new decoder that reads from r.
+func NewDecoder(r io.Reader) *Decoder {
+ return &Decoder{r: r}
+}
+
+// Decode reads the next JSON-encoded value from the
+// connection and stores it in the value pointed to by v.
+//
+// See the documentation for Unmarshal for details about
+// the conversion of JSON into a Go value.
+func (dec *Decoder) Decode(v interface{}) os.Error {
+ if dec.err != nil {
+ return dec.err
+ }
+
+ n, err := dec.readValue()
+ if err != nil {
+ return err
+ }
+
+ // Don't save err from unmarshal into dec.err:
+ // the connection is still usable since we read a complete JSON
+ // object from it before the error happened.
+ dec.d.init(dec.buf[0:n])
+ err = dec.d.unmarshal(v)
+
+ // Slide rest of data down.
+ rest := copy(dec.buf, dec.buf[n:])
+ dec.buf = dec.buf[0:rest]
+
+ return err
+}
+
+// readValue reads a JSON value into dec.buf.
+// It returns the length of the encoding.
+func (dec *Decoder) readValue() (int, os.Error) {
+ dec.scan.reset()
+
+ scanp := 0
+ var err os.Error
+Input:
+ for {
+ // Look in the buffer for a new value.
+ for i, c := range dec.buf[scanp:] {
+ v := dec.scan.step(&dec.scan, int(c))
+ if v == scanEnd {
+ scanp += i
+ break Input
+ }
+ // scanEnd is delayed one byte.
+ // We might block trying to get that byte from src,
+ // so instead invent a space byte.
+ if v == scanEndObject && dec.scan.step(&dec.scan, ' ') == scanEnd {
+ scanp += i + 1
+ break Input
+ }
+ if v == scanError {
+ dec.err = dec.scan.err
+ return 0, dec.scan.err
+ }
+ }
+ scanp = len(dec.buf)
+
+ // Did the last read have an error?
+ // Delayed until now to allow buffer scan.
+ if err != nil {
+ if err == os.EOF {
+ if dec.scan.step(&dec.scan, ' ') == scanEnd {
+ break Input
+ }
+ if nonSpace(dec.buf) {
+ err = io.ErrUnexpectedEOF
+ }
+ }
+ dec.err = err
+ return 0, err
+ }
+
+ // Make room to read more into the buffer.
+ const minRead = 512
+ if cap(dec.buf)-len(dec.buf) < minRead {
+ newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
+ copy(newBuf, dec.buf)
+ dec.buf = newBuf
+ }
+
+ // Read. Delay error for next iteration (after scan).
+ var n int
+ n, err = dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
+ dec.buf = dec.buf[0 : len(dec.buf)+n]
+ }
+ return scanp, nil
+}
+
+func nonSpace(b []byte) bool {
+ for _, c := range b {
+ if !isSpace(int(c)) {
+ return true
+ }
+ }
+ return false
+}
+
+// An Encoder writes JSON objects to an output stream.
+type Encoder struct {
+ w io.Writer
+ e encodeState
+ err os.Error
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+ return &Encoder{w: w}
+}
+
+// Encode writes the JSON encoding of v to the connection.
+//
+// See the documentation for Marshal for details about the
+// conversion of Go values to JSON.
+func (enc *Encoder) Encode(v interface{}) os.Error {
+ if enc.err != nil {
+ return enc.err
+ }
+ enc.e.Reset()
+ err := enc.e.marshal(v)
+ if err != nil {
+ return err
+ }
+
+ // Terminate each value with a newline.
+ // This makes the output look a little nicer
+ // when debugging, and some kind of space
+ // is required if the encoded value was a number,
+ // so that the reader knows there aren't more
+ // digits coming.
+ enc.e.WriteByte('\n')
+
+ if _, err = enc.w.Write(enc.e.Bytes()); err != nil {
+ enc.err = err
+ }
+ return err
+}
+
+// RawMessage is a raw encoded JSON object.
+// It implements Marshaler and Unmarshaler and can
+// be used to delay JSON decoding or precompute a JSON encoding.
+type RawMessage []byte
+
+// MarshalJSON returns *m as the JSON encoding of m.
+func (m *RawMessage) MarshalJSON() ([]byte, os.Error) {
+ return *m, nil
+}
+
+// UnmarshalJSON sets *m to a copy of data.
+func (m *RawMessage) UnmarshalJSON(data []byte) os.Error {
+ if m == nil {
+ return os.NewError("json.RawMessage: UnmarshalJSON on nil pointer")
+ }
+ *m = bytes.Add((*m)[0:0], data)
+ return nil
+}
+
+var _ Marshaler = (*RawMessage)(nil)
+var _ Unmarshaler = (*RawMessage)(nil)
