tools: make reader capable of reading big endian encoding

Signed-off-by: Michal Maslanka <michal@redpanda.com>

tools/offline_log_viewer/reader.py

@@ -1,3 +1,4 @@
+from enum import Enum
 import struct
 import collections
 from io import BufferedReader, BytesIO
@@ -9,10 +10,16 @@
                                        ('version', 'compat_version', 'size'))
 
 
+class Endianness(Enum):
+    BIG_ENDIAN = 0
+    LITTLE_ENDIAN = 1
+
+
 class Reader:
-    def __init__(self, stream: BytesIO):
+    def __init__(self, stream, endianness=Endianness.LITTLE_ENDIAN):
         # BytesIO provides .getBuffer(), BufferedReader peek()
         self.stream = BufferedReader(stream)
+        self.endianness = endianness
 
     @staticmethod
     def _decode_zig_zag(v):
@@ -32,29 +39,33 @@ def read_varint(self):
 
         return Reader._decode_zig_zag(result)
 
+    def with_endianness(self, str):
+        ch = '<' if self.endianness == Endianness.LITTLE_ENDIAN else '>'
+        return f"{ch}{str}"
+
     def read_int8(self):
-        return struct.unpack("<b", self.stream.read(1))[0]
+        return struct.unpack(self.with_endianness('b'), self.stream.read(1))[0]
 
     def read_uint8(self):
-        return struct.unpack("<B", self.stream.read(1))[0]
+        return struct.unpack(self.with_endianness('B'), self.stream.read(1))[0]
 
     def read_int16(self):
-        return struct.unpack("<h", self.stream.read(2))[0]
+        return struct.unpack(self.with_endianness('h'), self.stream.read(2))[0]
 
     def read_uint16(self):
-        return struct.unpack("<H", self.stream.read(2))[0]
+        return struct.unpack(self.with_endianness('H'), self.stream.read(2))[0]
 
     def read_int32(self):
-        return struct.unpack("<i", self.stream.read(4))[0]
+        return struct.unpack(self.with_endianness('i'), self.stream.read(4))[0]
 
     def read_uint32(self):
-        return struct.unpack("<I", self.stream.read(4))[0]
+        return struct.unpack(self.with_endianness('I'), self.stream.read(4))[0]
 
     def read_int64(self):
-        return struct.unpack("<q", self.stream.read(8))[0]
+        return struct.unpack(self.with_endianness('q'), self.stream.read(8))[0]
 
     def read_uint64(self):
-        return struct.unpack("<Q", self.stream.read(8))[0]
+        return struct.unpack(self.with_endianness('Q'), self.stream.read(8))[0]
 
     def read_serde_enum(self):
         return self.read_int32()
@@ -70,12 +81,26 @@ def read_string(self):
         len = self.read_int32()
         return self.stream.read(len).decode('utf-8')
 
+    def read_kafka_string(self):
+        len = self.read_int16()
+        return self.stream.read(len).decode('utf-8')
+
+    def read_kafka_bytes(self):
+        len = self.read_int32()
+        return self.stream.read(len)
+
     def read_optional(self, type_read):
         present = self.read_int8()
         if present == 0:
             return None
         return type_read(self)
 
+    def read_kafka_optional_string(self):
+        len = self.read_int16()
+        if len == -1:
+            return None
+        return self.stream.read(len).decode('utf-8')
+
     def read_vector(self, type_read):
         sz = self.read_int32()
         ret = []