Avoid endless loop when parsing operand in contenstream. Fixes #176

pdf/contentstream/const.go

@@ -0,0 +1,12 @@
+/*
+ * This file is subject to the terms and conditions defined in
+ * file 'LICENSE.md', which is part of this source code package.
+ */
+
+package contentstream
+
+import "errors"
+
+var (
+	ErrInvalidOperand = errors.New("invalid operand")
+)

pdf/contentstream/parser.go

@@ -542,6 +542,7 @@ func (this *ContentStreamParser) parseObject() (PdfObject, error, bool) {
 		} else if bb[0] == '(' {
 			common.Log.Trace("->String!")
 			str, err := this.parseString()
+			common.Log.Trace("(%s)\n", str.String())
 			return &str, err, false
 		} else if bb[0] == '<' && bb[1] != '<' {
 			common.Log.Trace("->Hex String!")
@@ -559,11 +560,12 @@ func (this *ContentStreamParser) parseObject() (PdfObject, error, bool) {
 			dict, err := this.parseDict()
 			return dict, err, false
 		} else {
+			// Otherwise, can be: keyword such as "null", "false", "true" or an operand...
 			common.Log.Trace("->Operand or bool?")
 			// Let's peek farther to find out.
 			bb, _ = this.reader.Peek(5)
 			peekStr := string(bb)
-			common.Log.Trace("Peek str: %s", peekStr)
+			common.Log.Trace("cont Peek str: %s", peekStr)
 
 			if (len(peekStr) > 3) && (peekStr[:4] == "null") {
 				null, err := this.parseNull()
@@ -577,7 +579,13 @@ func (this *ContentStreamParser) parseObject() (PdfObject, error, bool) {
 			}
 
 			operand, err := this.parseOperand()
-			return &operand, err, true
+			if err != nil {
+				return &operand, err, false
+			}
+			if len(operand.String()) < 1 {
+				return &operand, ErrInvalidOperand, false
+			}
+			return &operand, nil, true
 		}
 	}
 }

pdf/core/primitives.go

@@ -209,7 +209,7 @@ func (float *PdfObjectFloat) DefaultWriteString() string {
 }
 
 func (str *PdfObjectString) String() string {
-	return fmt.Sprintf("%s", string(*str))
+	return string(*str)
 }
 
 // DefaultWriteString outputs the object as it is to be written to file.