1 files changed, 243 insertions, 0 deletions
diff --git a/src/mongo/gotools/common/json/stream.go b/src/mongo/gotools/common/json/stream.go
new file mode 100644
index 00000000000..58443f211ec
--- /dev/null
+++ b/src/mongo/gotools/common/json/stream.go
@@ -0,0 +1,243 @@
+// 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"
+	"errors"
+	"io"
+)
+
+// A Decoder reads and decodes JSON objects from an input stream.
+type Decoder struct {
+	R    io.Reader
+	Buf  []byte
+	d    decodeState
+	scan scanner
+	err  error
+}
+
+// NewDecoder returns a new decoder that reads from r.
+//
+// The decoder introduces its own buffering and may
+// read data from r beyond the JSON values requested.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{R: r}
+}
+
+// UseNumber causes the Decoder to unmarshal a number into an interface{} as a
+// Number instead of as a float64.
+func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
+
+// Decode reads the next JSON-encoded value from its
+// input 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) DecodeMap() (map[string]interface{}, error) {
+	if dec.err != nil {
+		return nil, dec.err
+	}
+
+	n, err := dec.readValue()
+	if err != nil {
+		return nil, 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])
+	out, err := dec.d.unmarshalMap()
+
+	// Slide rest of data down.
+	rest := copy(dec.Buf, dec.Buf[n:])
+	dec.Buf = dec.Buf[0:rest]
+
+	return out, err
+}
+
+func (dec *Decoder) ScanObject() ([]byte, error) {
+	if dec.err != nil {
+		return nil, dec.err
+	}
+
+	n, err := dec.readValue()
+	if err != nil {
+		return nil, err
+	}
+
+	outbuf := make([]byte, n)
+	copy(outbuf, dec.Buf[0:n])
+	// Slide rest of data down.
+	rest := copy(dec.Buf, dec.Buf[n:])
+	dec.Buf = dec.Buf[0:rest]
+	return outbuf, nil
+
+}
+
+func (dec *Decoder) Decode(v interface{}) 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
+}
+
+// Buffered returns a reader of the data remaining in the Decoder's
+// buffer. The reader is valid until the next call to Decode.
+func (dec *Decoder) Buffered() io.Reader {
+	return bytes.NewReader(dec.Buf)
+}
+
+// readValue reads a JSON value into dec.Buf.
+// It returns the length of the encoding.
+func (dec *Decoder) readValue() (int, error) {
+	dec.scan.reset()
+
+	scanp := 0
+	var err error
+Input:
+	for {
+		// Look in the buffer for a new value.
+		for i, c := range dec.Buf[scanp:] {
+			dec.scan.bytes++
+			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 || v == scanEndArray) && 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 == io.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(rune(c)) {
+			return true
+		}
+	}
+	return false
+}
+
+// An Encoder writes JSON objects to an output stream.
+type Encoder struct {
+	w   io.Writer
+	e   encodeState
+	err 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 stream,
+// followed by a newline character.
+//
+// See the documentation for Marshal for details about the
+// conversion of Go values to JSON.
+func (enc *Encoder) Encode(v interface{}) error {
+	if enc.err != nil {
+		return enc.err
+	}
+	e := newEncodeState()
+	err := 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.
+	e.WriteByte('\n')
+
+	if _, err = enc.w.Write(e.Bytes()); err != nil {
+		enc.err = err
+	}
+	encodeStatePool.Put(e)
+	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, error) {
+	return *m, nil
+}
+
+// UnmarshalJSON sets *m to a copy of data.
+func (m *RawMessage) UnmarshalJSON(data []byte) error {
+	if m == nil {
+		return errors.New("json.RawMessage: UnmarshalJSON on nil pointer")
+	}
+	*m = append((*m)[0:0], data...)
+	return nil
+}
+
+var _ Marshaler = (*RawMessage)(nil)
+var _ Unmarshaler = (*RawMessage)(nil)