cmd: xxd: add new command

Add xxd command to print file content as hexdump to standard out

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Roger Knecht <rknecht@pm.me>

test/py/tests/test_xxd/conftest.py

@@ -0,0 +1,35 @@
+# SPDX-License-Identifier:      GPL-2.0+
+
+"""Fixture for xxd command test
+"""
+
+import os
+import shutil
+from subprocess import check_call, CalledProcessError
+import pytest
+
+@pytest.fixture(scope='session')
+def xxd_data(u_boot_config):
+    """Set up a file system to be used in xxd tests
+
+    Args:
+        u_boot_config -- U-boot configuration.
+    """
+    mnt_point = u_boot_config.persistent_data_dir + '/test_xxd'
+    image_path = u_boot_config.persistent_data_dir + '/xxd.img'
+
+    try:
+        os.mkdir(mnt_point, mode = 0o755)
+
+        with open(mnt_point + '/hello', 'w', encoding = 'ascii') as file:
+            file.write('hello world\n\x00\x01\x02\x03\x04\x05')
+
+        check_call(f'virt-make-fs --partition=gpt --size=+1M --type=vfat {mnt_point} {image_path}',
+                   shell=True)
+
+        yield image_path
+    except CalledProcessError:
+        pytest.skip('Setup failed')
+    finally:
+        shutil.rmtree(mnt_point)
+        os.remove(image_path)