json: keep track of error offset in SyntaxError

R=rsc
CC=golang-dev
https://golang.org/cl/4430043

diff --git a/src/pkg/json/decode_test.go b/src/pkg/json/decode_test.go
index 49135c4bfe414762c950610c8eea7655f50af0c2..cf8f53bc4a281240dd8eb6c62f25fb2c5ea3c208 100644 (file)
--- a/src/pkg/json/decode_test.go
+++ b/src/pkg/json/decode_test.go
@@ -71,7 +71,7 @@ var unmarshalTests = []unmarshalTest{
        {`{"X":"a", "y":"b", "Z":"c"}`, new(badTag), badTag{"a", "b", "c"}, nil},
 
        // syntax errors
-       {`{"X": "foo", "Y"}`, nil, nil, SyntaxError("invalid character '}' after object key")},
+       {`{"X": "foo", "Y"}`, nil, nil, &SyntaxError{"invalid character '}' after object key", 17}},
 
        // composite tests
        {allValueIndent, new(All), allValue, nil},
@@ -125,12 +125,12 @@ func TestMarshalBadUTF8(t *testing.T) {
 }
 
 func TestUnmarshal(t *testing.T) {
-       var scan scanner
        for i, tt := range unmarshalTests {
+               var scan scanner
                in := []byte(tt.in)
                if err := checkValid(in, &scan); err != nil {
                        if !reflect.DeepEqual(err, tt.err) {
-                               t.Errorf("#%d: checkValid: %v", i, err)
+                               t.Errorf("#%d: checkValid: %#v", i, err)
                                continue
                        }
                }

diff --git a/src/pkg/json/scanner.go b/src/pkg/json/scanner.go
index e98ddef5cc15a4fe9dd2e7b3cb616b4b8d14c8c5..49c2edd545384c7f1eee91ef651dad82a1b365a3 100644 (file)
--- a/src/pkg/json/scanner.go
+++ b/src/pkg/json/scanner.go
@@ -23,6 +23,7 @@ import (
 func checkValid(data []byte, scan *scanner) os.Error {
        scan.reset()
        for _, c := range data {
+               scan.bytes++
                if scan.step(scan, int(c)) == scanError {
                        return scan.err
                }
@@ -56,10 +57,12 @@ func nextValue(data []byte, scan *scanner) (value, rest []byte, err os.Error) {
 }
 
 // A SyntaxError is a description of a JSON syntax error.
-type SyntaxError string
-
-func (e SyntaxError) String() string { return string(e) }
+type SyntaxError struct {
+       msg    string // description of error
+       Offset int64  // error occurred after reading Offset bytes
+}
 
+func (e *SyntaxError) String() string { return e.msg }
 
 // A scanner is a JSON scanning state machine.
 // Callers call scan.reset() and then pass bytes in one at a time
@@ -89,6 +92,9 @@ type scanner struct {
        // 1-byte redo (see undo method)
        redoCode  int
        redoState func(*scanner, int) int
+
+       // total bytes consumed, updated by decoder.Decode
+       bytes int64
 }
 
 // These values are returned by the state transition functions
@@ -148,7 +154,7 @@ func (s *scanner) eof() int {
                return scanEnd
        }
        if s.err == nil {
-               s.err = SyntaxError("unexpected end of JSON input")
+               s.err = &SyntaxError{"unexpected end of JSON input", s.bytes}
        }
        return scanError
 }
@@ -581,7 +587,7 @@ func stateError(s *scanner, c int) int {
 // error records an error and switches to the error state.
 func (s *scanner) error(c int, context string) int {
        s.step = stateError
-       s.err = SyntaxError("invalid character " + quoteChar(c) + " " + context)
+       s.err = &SyntaxError{"invalid character " + quoteChar(c) + " " + context, s.bytes}
        return scanError
 }
 

diff --git a/src/pkg/json/stream.go b/src/pkg/json/stream.go
index cb9b16559ed2bb8d2760cf5250a03829fa291fa5..f143b3f0ade62020b8c0bf0632296b3c85240adc 100644 (file)
--- a/src/pkg/json/stream.go
+++ b/src/pkg/json/stream.go
@@ -23,8 +23,8 @@ 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.
+// 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.
@@ -62,6 +62,7 @@ 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