Merge pull request #55 from equinor/too-large-padbytes

Avoid crash on too large padbyte values

lib/src/io.cpp

@@ -279,8 +279,15 @@ record& stream::at( int i, record& rec ) noexcept (false) {
 
     this->fs.seekg( tell );
 
-    const auto chop = []( std::vector< char >& vec, int bytes ) {
-        vec.erase( vec.end() - bytes, vec.end() );
+    const auto chop = [](std::vector< char >& vec, int bytes) {
+        const int size = vec.size();
+        const int new_size = (std::max)(0, size - bytes);
+
+        if (size - bytes < 0) {
+            // TODO: user-warning
+            // const auto msg = "at::chop() would remove more bytes than read";
+        }
+        vec.resize(new_size);
     };
 
     while (true) {

python/tests/test_core.py

@@ -278,3 +278,13 @@ def test_load_pre_vrl_garbage():
 def test_load_file_with_broken_utf8():
     with dlisio.load('data/broken-degree-symbol.dlis') as f:
         pass
+
+def test_padbytes_as_large_as_record():
+    # 180-byte long explicit record with padding, and padbytes are set to 180
+    # (leaving the resulting len(data) == 0)
+    f = dlisio.open('data/padbytes-large-as-record.dlis')
+    f.reindex([0], [180])
+
+    rec = f.extract([0])[0]
+    assert rec.explicit
+    assert len(memoryview(rec)) == 0