[PATCH v7 9/9] qcow2_format.py: support dumping metadata in JSON format

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

Implementation of dumping QCOW2 image metadata.
The sample output:
{
    "Header_extensions": [
        {
            "name": "Feature table",
            "magic": 1745090647,
            "length": 192,
            "data_str": "<binary>"
        },
        {
            "name": "Bitmaps",
            "magic": 595929205,
            "length": 24,
            "data": {
                "nb_bitmaps": 2,
                "reserved32": 0,
                "bitmap_directory_size": 64,
                "bitmap_directory_offset": 1048576,
                "entries": [
                    {
                        "name": "bitmap-1",
                        "bitmap_table_offset": 589824,
                        "bitmap_table_size": 1,
                        "flags": [
                            "auto"
                        ],
                        "type": 1,
                        "granularity_bits": 16,
                        "name_size": 8,
                        "extra_data_size": 0,
                        "bitmap_table": {
                            "table_entries": [
                                {
                                    "type": "serialized",
                                    "offset": 655360
                                },
                                ...

Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 tests/qemu-iotests/qcow2_format.py | 60 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/tests/qemu-iotests/qcow2_format.py b/tests/qemu-iotests/qcow2_format.py
index bdd5f68..35daec9 100644
--- a/tests/qemu-iotests/qcow2_format.py
+++ b/tests/qemu-iotests/qcow2_format.py
@@ -18,6 +18,15 @@
 
 import struct
 import string
+import json
+
+
+class ComplexEncoder(json.JSONEncoder):
+    def default(self, obj):
+        if hasattr(obj, 'get_fields_dict'):
+            return obj.get_fields_dict()
+        else:
+            return json.JSONEncoder.default(self, obj)
 
 
 class Qcow2Field:
@@ -95,6 +104,11 @@ class Qcow2Struct(metaclass=Qcow2StructMeta):
         self.fields_dict = self.__dict__.copy()
 
     def dump(self, dump_json=None):
+        if dump_json:
+            print(json.dumps(self.get_fields_dict(), indent=4,
+                             cls=ComplexEncoder))
+            return
+
         for f in self.fields:
             value = self.__dict__[f[2]]
             if isinstance(f[1], str):
@@ -150,6 +164,9 @@ class Qcow2BitmapExt(Qcow2Struct):
         for bm in self.bitmaps:
             bm.dump_bitmap_dir_entry(dump_json)
 
+    def get_fields_dict(self):
+        return self.fields_dict
+
 
 BME_FLAG_IN_USE = 1 << 0
 BME_FLAG_AUTO = 1 << 1
@@ -202,6 +219,12 @@ class Qcow2BitmapDirEntry(Qcow2Struct):
         super().dump()
         self.bitmap_table.print_bitmap_table(self.cluster_size)
 
+    def get_fields_dict(self):
+        bmp_name = dict(name=self.name)
+        bme_dict = {**bmp_name, **self.fields_dict}
+        bme_dict['flags'] = self.bitmap_flags
+        return bme_dict
+
 
 class Qcow2BitmapTableEntry:
 
@@ -217,6 +240,9 @@ class Qcow2BitmapTableEntry:
         else:
             self.type = 'all-zeroes'
 
+    def get_fields_dict(self):
+        return dict(type=self.type, offset=self.offset)
+
 
 class Qcow2BitmapTable:
 
@@ -232,6 +258,18 @@ class Qcow2BitmapTable:
             print(f'{i:<14} {entry.type:<15} {entry.offset:<24} {cluster_size}')
         print("")
 
+    def get_fields_dict(self):
+        return dict(table_entries=self.entries)
+
+
+class Qcow2HeaderExtensionsDoc:
+
+    def __init__(self, extensions):
+        self.extensions = extensions
+
+    def get_fields_dict(self):
+        return dict(Header_extensions=self.extensions)
+
 
 QCOW2_EXT_MAGIC_BITMAPS = 0x23852875
 
@@ -247,6 +285,9 @@ class QcowHeaderExtension(Qcow2Struct):
             0x44415441: 'Data file'
         }
 
+        def get_fields_dict(self):
+            return self.mapping.get(self.value, "<unknown>")
+
     fields = (
         ('u32', Magic, 'magic'),
         ('u32', '{}', 'length')
@@ -307,6 +348,16 @@ class QcowHeaderExtension(Qcow2Struct):
         else:
             self.obj.dump(dump_json)
 
+    def get_fields_dict(self):
+        ext_name = dict(name=self.Magic(self.magic))
+        he_dict = {**ext_name, **self.fields_dict}
+        if self.obj is not None:
+            he_dict.update(data=self.obj)
+        else:
+            he_dict.update(data_str=self.data_str)
+
+        return he_dict
+
     @classmethod
     def create(cls, magic, data):
         return QcowHeaderExtension(magic, len(data), data)
@@ -409,7 +460,16 @@ class QcowHeader(Qcow2Struct):
         fd.write(buf)
 
     def dump_extensions(self, dump_json=None):
+        if dump_json:
+            ext_doc = Qcow2HeaderExtensionsDoc(self.extensions)
+            print(json.dumps(ext_doc.get_fields_dict(), indent=4,
+                             cls=ComplexEncoder))
+            return
+
         for ex in self.extensions:
             print('Header extension:')
             ex.dump(dump_json)
             print()
+
+    def get_fields_dict(self):
+        return self.fields_dict
-- 
1.8.3.1