Added basic support of GZ images

Added ability to build images in the GZ(zlib) format. The compression
level is 5 by default.

Closes (#65)

Signed-off-by: Anton Kremenetsky <anton.kremenetsky@gmail.com>

Author: akremenetsky

genesis_devtools/builder/builder.py

@@ -19,6 +19,7 @@
 import tempfile
 import shutil
 import os
+import gzip
 
 from genesis_devtools.builder import base
 from genesis_devtools.logger import AbstractLogger, DummyLogger
@@ -80,10 +81,23 @@ def _build_image(
         if not os.path.exists(self._images_output_dir):
             os.makedirs(self._images_output_dir)
 
-        shutil.move(
-            os.path.join(output_dir, f"{img.name}.{img.format}"),
-            self._images_output_dir,
-        )
+        # Determine source path to move. If gzip was requested,
+        # compress RAW -> GZ first.
+        if img.format == "gz":
+            self._logger.info(f"Compressing {img.name} to {img.name}.raw.gz")
+            # Source RAW image produced by Packer
+            raw_src = os.path.join(output_dir, f"{img.name}.raw")
+            gz_tgt = os.path.join(
+                self._images_output_dir, f"{img.name}.raw.gz"
+            )
+            # Compress using standard library (gzip uses zlib) with level 5
+            with open(raw_src, "rb") as f_in, gzip.open(
+                gz_tgt, "wb", compresslevel=5
+            ) as f_out:
+                shutil.copyfileobj(f_in, f_out)
+        else:
+            src_path = os.path.join(output_dir, f"{img.name}.{img.format}")
+            shutil.move(src_path, self._images_output_dir)
 
     def fetch_dependency(self, deps_dir: str) -> None:
         """Fetch common dependencies for elements."""

genesis_devtools/builder/packer.py

@@ -216,7 +216,11 @@ def pre_build(
         override = image.override or {}
 
         # Enrich with the image format
-        override["img_format"] = image.format
+        # If compressed gzip is requested, we build a RAW image first
+        # and compress it afterwards in the SimpleBuilder.
+        override["img_format"] = (
+            "raw" if image.format == "gz" else image.format
+        )
 
         # Write the packer variables
         variables = PackerVariable.variable_file_content(override)

genesis_devtools/constants.py

@@ -29,7 +29,7 @@
 
 # Types
 ImageProfileType = tp.Literal["ubuntu_24", "genesis_base"]
-ImageFormatType = tp.Literal["raw", "qcow2"]
+ImageFormatType = tp.Literal["raw", "qcow2", "gz"]
 NetType = tp.Literal["network", "bridge"]
 VersionSuffixType = tp.Literal["latest", "none", "element"]
 DomainState = tp.Literal["all", "inactive", "state-paused"]