Add a Layout.read_bytes() method that reads a layout from a byte array in Python or Ruby.

This is much more convenient and a bit more efficient than writing the bytes
to a temporary file and reading that back in. It's useful when we have received
a layout over the network or embedded in some file.

This makes a copy of the bytes but there doesn't seem to be any way to avoid that
currently.

src/db/db/gsiDeclDbReader.cc

@@ -433,6 +433,15 @@ namespace gsi
     return reader.read (*layout, options);
   }
 
+  static db::LayerMap
+  load_bytes_with_options (db::Layout *layout, const std::vector<char> &bytes, const db::LoadLayoutOptions &options)
+  {
+    tl::InputMemoryStream byte_stream (bytes.data(), bytes.size());
+    tl::InputStream stream (byte_stream);
+    db::Reader reader (stream);
+    return reader.read (*layout, options);
+  }
+
   //  extend the layout class by two reader methods
   static
   gsi::ClassExt<db::Layout> layout_reader_decl (
@@ -454,6 +463,16 @@ namespace gsi
       "@return A layer map that contains the mapping used by the reader including the layers that have been created."
       "\n"
       "This method has been added in version 0.18."
+    ) +
+    gsi::method_ext ("read_bytes", &load_bytes_with_options, gsi::arg ("bytes"), gsi::arg ("options"),
+      "@brief Load the layout from the given bytes array with options\n"
+      "The format of the file is determined automatically and automatic unzipping is provided. "
+      "In this version, some reader options can be specified. "
+      "@param bytes The data to load.\n"
+      "@param options The options object specifying further options for the reader.\n"
+      "@return A layer map that contains the mapping used by the reader including the layers that have been created."
+      "\n"
+      "This method has been added in version 0.29."
     ),
     ""
   );

testdata/python/dbLayoutTest.py

@@ -1200,6 +1200,27 @@ class DBLayoutTest(unittest.TestCase):
     self.assertEqual(str(t), "r180 0,0")
     
 
+  def test_read_bytes(self):
+
+    testtmp = os.getenv("TESTTMP_WITH_NAME", os.getenv("TESTTMP", "."))
+
+    file_gds = os.path.join(testtmp, "bytes.gds")
+
+    ly = pya.Layout()
+    top = ly.create_cell("TOP")
+    l1 = ly.layer(1, 0)
+    shape = top.shapes(l1).insert(pya.Box(0, 10, 20, 30))
+    ly.write(file_gds)
+
+    with open(file_gds, "rb") as f:
+      byte_buffer = f.read()
+
+    ly2 = pya.Layout()
+    ly2.read_bytes(byte_buffer, pya.LoadLayoutOptions())
+    l2 = ly2.layer(1, 0)
+    self.assertEqual(ly2.top_cell().bbox().to_s(), "(0,10;20,30)")
+
+
 # run unit tests
 if __name__ == '__main__':
   suite = unittest.TestLoader().loadTestsFromTestCase(DBLayoutTest)