Added support for reading a string as an io.Reader

iter_str_reader.go

@@ -0,0 +1,45 @@
+package jsoniter
+
+import "io"
+
+// Returns a reader that can be used to read the following string until EOF.
+// Using the reader after EOF is undefined behavior, and so is using the reader
+// when when the current token isn't a string.
+func (iter *Iterator) ReadStringAsReader() (r io.Reader) {
+	c := iter.nextToken()
+	if c == '"' {
+		return iterStrReader{iter}
+	}
+	iter.ReportError("ReadStringAsReader", `expects " or n, but found `+string([]byte{c}))
+	return
+}
+
+var _ io.Reader = iterStrReader{}
+
+type iterStrReader struct {
+	iter *Iterator
+}
+
+func (r iterStrReader) Read(dst []byte) (n int, err error) {
+	for i := r.iter.head; i < r.iter.tail; i++ {
+		// require ascii string and no escape
+		// for: field name, base64, number
+		if r.iter.buf[i] == '"' {
+			n = copy(dst, r.iter.buf[r.iter.head:i])
+			r.iter.head += n + 1
+			err = io.EOF
+			return
+		}
+	}
+
+	n = copy(dst, r.iter.buf[r.iter.head:])
+	r.iter.head += n
+
+	if r.iter.head == r.iter.tail {
+		if !r.iter.loadMore() {
+			err = io.ErrUnexpectedEOF
+		}
+	}
+
+	return
+}

iter_str_reader_test.go

@@ -0,0 +1,35 @@
+package jsoniter
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+)
+
+func ExampleIterator_ReadStringAsReader() {
+	json := bytes.NewBufferString(`{"foo":"abcdefghijklmnopqrstuvwxyz"}`)
+	iter := Parse(ConfigDefault, json, 16)
+
+	_ = iter.ReadObject()
+	r := iter.ReadStringAsReader()
+	buf := make([]byte, 8)
+
+	for {
+		n, err := r.Read(buf)
+		fmt.Println(string(buf[:n]))
+
+		if err != nil {
+			if err != io.EOF {
+				panic(err)
+			}
+			break
+		}
+	}
+
+	// Output:
+	//
+	// abcdefgh
+	// ijklmnop
+	// qrstuvwx
+	// yz
+}