Merge pull request #22 from tdilo/writer-check-overflow

Check for field overflow when writing attributes

writer.go

@@ -214,6 +214,9 @@ func (w *Writer) WriteAttribute(row int, field int, value interface{}) error {
 	if w.dbf == nil {
 		return errors.New("Initialize DBF by using SetFields first")
 	}
+	if sz := int(w.dbfFields[field].Size); len(buf) > sz {
+		return fmt.Errorf("Unable to write field %v: %q exceeds field length %v", field, buf, sz)
+	}
 
 	seekTo := 1 + int64(w.dbfHeaderLength) + (int64(row) * int64(w.dbfRecordLength))
 	for n := 0; n < field; n++ {

writer_test.go

@@ -129,24 +129,33 @@ func TestWriteAttribute(t *testing.T) {
 		wantData   string
 	}{
 		{"string-0", 0, 0, "test", 1, "test"},
+		{"string-0-overflow-1", 0, 0, "overflo", 0, ""},
+		{"string-0-overflow-n", 0, 0, "overflowing", 0, ""},
 		{"string-3", 3, 0, "things", 301, "things"},
 		{"float-0", 0, 1, 123.44, 7, "123.4400"},
+		{"float-0-overflow-1", 0, 1, 1234.0, 0, ""},
+		{"float-0-overflow-n", 0, 1, 123456789.0, 0, ""},
 		{"int-0", 0, 2, 4242, 15, "4242"},
+		{"int-0-overflow-1", 0, 2, 42424, 0, ""},
+		{"int-0-overflow-n", 0, 2, 42424343, 0, ""},
 	}
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			buf.Reset()
 			s.offset = 0
 
-			w.WriteAttribute(test.row, test.field, test.data)
+			err := w.WriteAttribute(test.row, test.field, test.data)
 
 			if buf.String() != test.wantData {
 				t.Errorf("got data: %v, want: %v", buf.String(), test.wantData)
 			}
 			if s.offset != test.wantOffset {
 				t.Errorf("got seek offset: %v, want: %v", s.offset, test.wantOffset)
 			}
+			if err == nil && test.wantData == "" {
+				t.Error("got no data and no error")
+			}
 		})
 	}
 }