fixes #144, using bytes.Buffer for more efficient string building

pdf/core/parser.go

@@ -152,21 +152,21 @@ func (parser *PdfParser) readComment() (string, error) {
 
 // Read a single line of text from current position.
 func (parser *PdfParser) readTextLine() (string, error) {
-	lineStr := ""
+	var r bytes.Buffer
 	for {
 		bb, err := parser.reader.Peek(1)
 		if err != nil {
 			common.Log.Debug("Error %s", err.Error())
-			return lineStr, err
+			return r.String(), err
 		}
 		if (bb[0] != '\r') && (bb[0] != '\n') {
 			b, _ := parser.reader.ReadByte()
-			lineStr += string(b)
+			r.WriteByte(b)
 		} else {
 			break
 		}
 	}
-	return lineStr, nil
+	return r.String(), nil
 }
 
 // Parse a name starting with '/'.

pdf/core/parser_test.go

@@ -102,6 +102,21 @@ func TestStringParsing(t *testing.T) {
 	}
 }
 
+func TestReadTextLine(t *testing.T) {
+	// reading text ling + rewinding should be idempotent, that is:
+	// if we rewind back len(str) bytes after reading string str we should arrive at beginning of str
+	rawText := "abc\xb0cde"
+	parser := PdfParser{}
+	parser.rs, parser.reader, parser.fileSize = makeReaderForText(rawText)
+	s, err := parser.readTextLine()
+	if err != nil && err != io.EOF {
+		t.Errorf("Unable to parse string, error: %s", err)
+	}
+	if parser.GetFileOffset() != int64(len(s)) {
+		t.Errorf("File offset after reading string of length %d is %d", len(s), parser.GetFileOffset())
+	}
+}
+
 func TestBinStringParsing(t *testing.T) {
 	// From an example O entry in Encrypt dictionary.
 	rawText1 := "(\xE6\x00\xEC\xC2\x02\x88\xAD\x8B\\r\x64\xA9" +