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Go: use multiple return values 

The compiler has made it more obvious where we eat error messages.
This commit is contained in:
Přemysl Eric Janouch 2018-10-04 13:07:47 +02:00
parent 50578fe99f
commit 9ac8360979
Signed by: p
GPG Key ID: A0420B94F92B9493
1 changed files with 77 additions and 75 deletions
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152
pdf/pdf.go
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@ -68,7 +68,7 @@ const (
type Object struct {
Kind ObjectKind
// End (error message), Comment/Keyword/Name/String
// Comment/Keyword/Name/String
String string
// Bool, Numeric
Number float64
@ -92,11 +92,7 @@ func (o *Object) IsUint() bool {
}
// A slew of constructors that will hopefully get all inlined.
// TODO(p): We should probably ditch NewError for multiple return values.
// It could be a private function that returns New(End) and error.
func NewEOF() Object { return Object{Kind: End} }
func NewError(e string) Object { return Object{Kind: End, String: e} }
func NewComment(c string) Object { return Object{Kind: Comment, String: c} }
func NewKeyword(k string) Object { return Object{Kind: Keyword, String: k} }
func New(kind ObjectKind) Object { return Object{Kind: kind} }
@ -133,6 +129,8 @@ func NewReference(n, generation uint) Object {
return Object{Kind: Reference, N: n, Generation: generation}
}
func newError(msg string) (Object, error) { return New(End), errors.New(msg) }
// -----------------------------------------------------------------------------
const (
@ -205,13 +203,13 @@ func (lex *Lexer) unescape(ch byte) byte {
return ch
}
func (lex *Lexer) string() Object {
func (lex *Lexer) string() (Object, error) {
var value []byte
parens := 1
for {
ch, ok := lex.read()
if !ok {
return NewError("unexpected end of string")
return newError("unexpected end of string")
}
if lex.eatNewline(ch) {
ch = '\n'
@ -223,7 +221,7 @@ func (lex *Lexer) string() Object {
}
} else if ch == '\\' {
if ch, ok = lex.read(); !ok {
return NewError("unexpected end of string")
return newError("unexpected end of string")
} else if lex.eatNewline(ch) {
continue
} else {
@ -232,19 +230,19 @@ func (lex *Lexer) string() Object {
}
value = append(value, ch)
}
return NewString(string(value))
return NewString(string(value)), nil
}
func (lex *Lexer) stringHex() Object {
func (lex *Lexer) stringHex() (Object, error) {
var value, buf []byte
for {
ch, ok := lex.read()
if !ok {
return NewError("unexpected end of hex string")
return newError("unexpected end of hex string")
} else if ch == '>' {
break
} else if strings.IndexByte(hexAlphabet, ch) < 0 {
return NewError("invalid hex string")
return newError("invalid hex string")
} else if buf = append(buf, ch); len(buf) == 2 {
u, _ := strconv.ParseUint(string(buf), 16, 8)
value = append(value, byte(u))
@ -255,10 +253,10 @@ func (lex *Lexer) stringHex() Object {
u, _ := strconv.ParseUint(string(buf)+"0", 16, 8)
value = append(value, byte(u))
}
return NewString(string(value))
return NewString(string(value)), nil
}
func (lex *Lexer) name() Object {
func (lex *Lexer) name() (Object, error) {
var value []byte
for {
ch, ok := lex.peek()
@ -277,7 +275,7 @@ func (lex *Lexer) name() Object {
lex.read()
}
if len(hexa) != 2 {
return NewError("invalid name hexa escape")
return newError("invalid name hexa escape")
}
u, _ := strconv.ParseUint(string(value), 16, 8)
ch = byte(u)
@ -285,12 +283,12 @@ func (lex *Lexer) name() Object {
value = append(value, ch)
}
if len(value) == 0 {
return NewError("unexpected end of name")
return newError("unexpected end of name")
}
return NewName(string(value))
return NewName(string(value)), nil
}
func (lex *Lexer) comment() Object {
func (lex *Lexer) comment() (Object, error) {
var value []byte
for {
ch, ok := lex.peek()
@ -300,11 +298,11 @@ func (lex *Lexer) comment() Object {
value = append(value, ch)
lex.read()
}
return NewComment(string(value))
return NewComment(string(value)), nil
}
// XXX: Maybe invalid numbers should rather be interpreted as keywords.
func (lex *Lexer) number() Object {
func (lex *Lexer) number() (Object, error) {
var value []byte
ch, ok := lex.peek()
if ch == '-' {
@ -327,16 +325,16 @@ func (lex *Lexer) number() Object {
lex.read()
}
if !digits {
return NewError("invalid number")
return newError("invalid number")
}
f, _ := strconv.ParseFloat(string(value), 64)
return NewNumeric(f)
return NewNumeric(f), nil
}
func (lex *Lexer) Next() Object {
func (lex *Lexer) Next() (Object, error) {
ch, ok := lex.peek()
if !ok {
return NewEOF()
return New(End), nil
}
if strings.IndexByte("-0123456789.", ch) >= 0 {
return lex.number()
@ -355,13 +353,13 @@ func (lex *Lexer) Next() Object {
switch v := string(value); v {
case "":
case "null":
return New(Nil)
return New(Nil), nil
case "true":
return NewBool(true)
return NewBool(true), nil
case "false":
return NewBool(false)
return NewBool(false), nil
default:
return NewKeyword(v)
return NewKeyword(v), nil
}
switch ch, _ := lex.read(); ch {
@ -372,29 +370,29 @@ func (lex *Lexer) Next() Object {
case '(':
return lex.string()
case '[':
return New(BArray)
return New(BArray), nil
case ']':
return New(EArray)
return New(EArray), nil
case '<':
if ch, _ := lex.peek(); ch == '<' {
lex.read()
return New(BDict)
return New(BDict), nil
}
return lex.stringHex()
case '>':
if ch, _ := lex.peek(); ch == '>' {
lex.read()
return New(EDict)
return New(EDict), nil
}
return NewError("unexpected '>'")
return newError("unexpected '>'")
default:
if lex.eatNewline(ch) {
return New(NL)
return New(NL), nil
}
if strings.IndexByte(whitespace, ch) >= 0 {
return lex.Next()
}
return NewError("unexpected input")
return newError("unexpected input")
}
}
@ -501,10 +499,10 @@ type Updater struct {
Trailer map[string]Object
}
func (u *Updater) parseIndirect(lex *Lexer, stack *[]Object) Object {
func (u *Updater) parseIndirect(lex *Lexer, stack *[]Object) (Object, error) {
lenStack := len(*stack)
if lenStack < 2 {
return NewError("missing object ID pair")
return newError("missing object ID pair")
}
n := (*stack)[lenStack-2]
@ -512,14 +510,14 @@ func (u *Updater) parseIndirect(lex *Lexer, stack *[]Object) Object {
*stack = (*stack)[:lenStack-2]
if !g.IsUint() || !n.IsUint() {
return NewError("invalid object ID pair")
return newError("invalid object ID pair")
}
var inner []Object
for {
object := u.parse(lex, &inner)
object, _ := u.parse(lex, &inner)
if object.Kind == End {
return NewError("object doesn't end")
return newError("object doesn't end")
}
if object.Kind == Keyword && object.String == "endobj" {
break
@ -527,15 +525,15 @@ func (u *Updater) parseIndirect(lex *Lexer, stack *[]Object) Object {
inner = append(inner, object)
}
if len(inner) != 1 {
return NewError("indirect objects must contain exactly one object")
return newError("indirect objects must contain exactly one object")
}
return NewIndirect(inner[0], uint(n.Number), uint(g.Number))
return NewIndirect(inner[0], uint(n.Number), uint(g.Number)), nil
}
func (u *Updater) parseR(stack *[]Object) Object {
func (u *Updater) parseR(stack *[]Object) (Object, error) {
lenStack := len(*stack)
if lenStack < 2 {
return NewError("missing reference ID pair")
return newError("missing reference ID pair")
}
n := (*stack)[lenStack-2]
@ -543,14 +541,16 @@ func (u *Updater) parseR(stack *[]Object) Object {
*stack = (*stack)[:lenStack-2]
if !g.IsUint() || !n.IsUint() {
return NewError("invalid reference ID pair")
return newError("invalid reference ID pair")
}
return NewReference(uint(n.Number), uint(g.Number))
return NewReference(uint(n.Number), uint(g.Number)), nil
}
/// parse reads an object at the lexer's position. Not a strict parser.
func (u *Updater) parse(lex *Lexer, stack *[]Object) Object {
switch token := lex.Next(); token.Kind {
// parse reads an object at the lexer's position. Not a strict parser.
//
// TODO(p): We should fix all uses of this not to eat the error.
func (u *Updater) parse(lex *Lexer, stack *[]Object) (Object, error) {
switch token, err := lex.Next(); token.Kind {
case NL, Comment:
// These are not important to parsing,
// not even for this procedure's needs.
@ -558,22 +558,22 @@ func (u *Updater) parse(lex *Lexer, stack *[]Object) Object {
case BArray:
var array []Object
for {
object := u.parse(lex, &array)
object, _ := u.parse(lex, &array)
if object.Kind == End {
return NewError("array doesn't end")
return newError("array doesn't end")
}
if object.Kind == EArray {
break
}
array = append(array, object)
}
return NewArray(array)
return NewArray(array), nil
case BDict:
var array []Object
for {
object := u.parse(lex, &array)
object, _ := u.parse(lex, &array)
if object.Kind == End {
return NewError("dictionary doesn't end")
return newError("dictionary doesn't end")
}
if object.Kind == EDict {
break
@ -581,16 +581,16 @@ func (u *Updater) parse(lex *Lexer, stack *[]Object) Object {
array = append(array, object)
}
if len(array)%2 != 0 {
return NewError("unbalanced dictionary")
return newError("unbalanced dictionary")
}
dict := make(map[string]Object)
for i := 0; i < len(array); i += 2 {
if array[i].Kind != Name {
return NewError("invalid dictionary key type")
return newError("invalid dictionary key type")
}
dict[array[i].String] = array[i+1]
}
return NewDict(dict)
return NewDict(dict), nil
case Keyword:
// Appears in the document body, typically needs
// to access the cross-reference table.
@ -600,7 +600,7 @@ func (u *Updater) parse(lex *Lexer, stack *[]Object) Object {
// streams can use the Object.String member.
switch token.String {
case "stream":
return NewError("streams are not supported yet")
return newError("streams are not supported yet")
case "obj":
return u.parseIndirect(lex, stack)
case "R":
@ -608,18 +608,18 @@ func (u *Updater) parse(lex *Lexer, stack *[]Object) Object {
}
fallthrough
default:
return token
return token, err
}
}
func (u *Updater) loadXref(lex *Lexer, loadedEntries map[uint]struct{}) error {
var throwawayStack []Object
if keyword := u.parse(lex,
if keyword, _ := u.parse(lex,
&throwawayStack); keyword.Kind != Keyword || keyword.String != "xref" {
return errors.New("invalid xref table")
}
for {
object := u.parse(lex, &throwawayStack)
object, _ := u.parse(lex, &throwawayStack)
if object.Kind == End {
return errors.New("unexpected EOF while looking for the trailer")
}
@ -627,16 +627,16 @@ func (u *Updater) loadXref(lex *Lexer, loadedEntries map[uint]struct{}) error {
break
}
second := u.parse(lex, &throwawayStack)
second, _ := u.parse(lex, &throwawayStack)
if !object.IsUint() || !second.IsUint() {
return errors.New("invalid xref section header")
}
start, count := uint(object.Number), uint(second.Number)
for i := uint(0); i < count; i++ {
off := u.parse(lex, &throwawayStack)
gen := u.parse(lex, &throwawayStack)
key := u.parse(lex, &throwawayStack)
off, _ := u.parse(lex, &throwawayStack)
gen, _ := u.parse(lex, &throwawayStack)
key, _ := u.parse(lex, &throwawayStack)
if !off.IsInteger() || off.Number < 0 ||
off.Number > float64(len(u.Document)) ||
!gen.IsInteger() || gen.Number < 0 || gen.Number > 65535 ||
@ -710,7 +710,7 @@ func (u *Updater) Initialize() error {
return err
}
trailer := u.parse(&lex, &throwawayStack)
trailer, _ := u.parse(&lex, &throwawayStack)
if trailer.Kind != Dict {
return errors.New("invalid trailer dictionary")
}
@ -742,30 +742,32 @@ func (u *Updater) Initialize() error {
// Get retrieves an object by its number and generation--may return
// Nil or End with an error.
func (u *Updater) Get(n, generation uint) Object {
//
// TODO(p): We should fix all uses of this not to eat the error.
func (u *Updater) Get(n, generation uint) (Object, error) {
if n >= u.xrefSize {
return New(Nil)
return New(Nil), nil
}
ref := u.xref[n]
if !ref.nonfree || ref.generation != generation ||
ref.offset >= int64(len(u.Document)) {
return New(Nil)
return New(Nil), nil
}
lex := Lexer{u.Document[ref.offset:]}
var stack []Object
for {
object := u.parse(&lex, &stack)
object, err := u.parse(&lex, &stack)
if object.Kind == End {
return object
return object, err
}
if object.Kind != Indirect {
stack = append(stack, object)
} else if object.N != n || object.Generation != generation {
return NewError("object mismatch")
return newError("object mismatch")
} else {
return object.Array[0]
return object.Array[0], nil
}
}
}
@ -883,7 +885,7 @@ func NewDate(ts time.Time) Object {
// GetFirstPage retrieves the first page of the document or a Nil object.
func GetFirstPage(pdf *Updater, nodeN, nodeGeneration uint) Object {
obj := pdf.Get(nodeN, nodeGeneration)
obj, _ := pdf.Get(nodeN, nodeGeneration)
if obj.Kind != Dict {
return New(Nil)
}
@ -1104,7 +1106,7 @@ func Sign(document []byte, key crypto.PrivateKey, certs []*x509.Certificate) (
if !ok || rootRef.Kind != Reference {
return nil, errors.New("trailer does not contain a reference to Root")
}
root := pdf.Get(rootRef.N, rootRef.Generation)
root, _ := pdf.Get(rootRef.N, rootRef.Generation)
if root.Kind != Dict {
return nil, errors.New("invalid Root dictionary reference")
}