Merge branch 'lukeshu/fuzz-err'

1 files changed, 22 insertions, 6 deletions

diff --git a/decode_scan.go b/decode_scan.go
index 63694c4..7ef3e71 100644
--- a/decode_scan.go
+++ b/decode_scan.go
@@ -6,6 +6,7 @@ package lowmemjson
 
 import (
 	"io"
+	"unicode/utf8"
 
 	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
@@ -22,10 +23,11 @@ type runeTypeScanner struct {
 	rTypeOK bool
 	repeat  bool
 
-	rRune rune
-	rSize int
-	rType jsonparse.RuneType
-	rErr  error
+	rRune   rune
+	rSize   int
+	rIsRune bool
+	rType   jsonparse.RuneType
+	rErr    error
 }
 
 // The returned error is a *ReadError, a *SyntaxError, or nil.
@@ -55,7 +57,18 @@ func (sc *runeTypeScanner) ReadRuneType() (rune, int, jsonparse.RuneType, error)
 		sc.offset += int64(sc.rSize)
 		switch err {
 		case nil:
-			sc.rType, err = sc.parser.HandleRune(sc.rRune)
+			sc.rIsRune = true
+			if sc.rRune == utf8.RuneError && sc.rSize == 1 {
+				if bs, ok := sc.inner.(io.ByteScanner); ok {
+					_ = bs.UnreadByte() // UnreadRune doesn't back up the ReadByte-pos
+					b, _ := bs.ReadByte()
+					_ = bs.UnreadByte()
+					_, _, _ = sc.inner.ReadRune()
+					sc.rRune = rune(b)
+					sc.rIsRune = false
+				}
+			}
+			sc.rType, err = sc.parser.HandleRune(sc.rRune, sc.rIsRune)
 			if err != nil {
 				sc.rErr = &DecodeSyntaxError{
 					Offset: sc.offset - int64(sc.rSize),
@@ -92,6 +105,9 @@ func (sc *runeTypeScanner) ReadRuneType() (rune, int, jsonparse.RuneType, error)
 		}
 	}
 	sc.repeat = false
+	if sc.rSize > 0 && !sc.rIsRune {
+		return utf8.RuneError, sc.rSize, sc.rType, sc.rErr
+	}
 	return sc.rRune, sc.rSize, sc.rType, sc.rErr
 }
 
@@ -124,7 +140,7 @@ func (sc *runeTypeScanner) PopReadBarrier() {
 	case sc.repeat:
 		// re-figure the rType and rErr
 		var err error
-		sc.rType, err = sc.parser.HandleRune(sc.rRune)
+		sc.rType, err = sc.parser.HandleRune(sc.rRune, sc.rIsRune)
 		if err != nil {
 			sc.rErr = &DecodeSyntaxError{
 				Offset: sc.offset - int64(sc.rSize),