Add Iterator.StringReader()

iter_str_reader.go

@@ -0,0 +1,53 @@
+package jsoniter
+
+import "io"
+
+type stringReader struct {
+	eof  bool
+	iter *Iterator
+}
+
+// Read implements io.Reader. There is no provision for resetting the reader
+// after EOF, nor for ensuring that the full JSON string is read to its end.
+func (r *stringReader) Read(p []byte) (n int, err error) {
+	if r.eof {
+		return 0, io.EOF
+	}
+	p = p[:0]
+	iter := r.iter
+	for iter.Error == nil && len(p) < cap(p) {
+		c := iter.readByte()
+		if c == '"' {
+			r.eof = true
+			break
+		}
+		if c == '\\' {
+			// if we don't have room for 2 runes, leave it for the next call
+			if len(p)+8 > cap(p) {
+				iter.unreadByte()
+				break
+			}
+			c = iter.readByte()
+			p = iter.readEscapedChar(c, p)
+		} else {
+			p = append(p, c)
+		}
+	}
+	return len(p), nil
+}
+
+// StringReader provides an io.Reader for the upcoming JSON string value. The
+// consumer absolutely MUST consume the entire string in order to preserve the
+// state of the Iterator. If the next value in the JSON stream is not a string,
+// the returned reader will be nil.
+func (iter *Iterator) StringReader() io.Reader {
+	c := iter.nextToken()
+	if c == '"' {
+		return &stringReader{iter: iter}
+	} else if c == 'n' {
+		iter.skipThreeBytes('u', 'l', 'l')
+		return nil
+	}
+	iter.ReportError("StringReader", `expects " or n, but found `+string([]byte{c}))
+	return nil
+}