dissect.py

implementations/python/preserves/dissect.py

@@ -0,0 +1,47 @@
+import struct
+from .binary import decode_int, decode_varint
+
+def dissect_items(body, position=0):
+    result = []
+    while body:
+        (count, i) = decode_varint(body)
+        chunk = body[i:i+count]
+        body = body[i+count:]
+        result.append(dissect(chunk, position + i))
+        position = position + i+count
+    return result
+
+def dissect(bs, position=0):
+    tag = bs[0]
+    body = bs[1:]
+    info = None
+    kids = None
+
+    if tag == 0xAA:
+        kids = dissect_items(body, position+1)
+        kids = [kids[i:i+2] for i in range(0, len(kids), 2)]
+    elif tag in [0xA7, 0xA8, 0xA9, 0xBF]:
+        kids = dissect_items(body, position+1)
+    elif tag == 0xAB:
+        kids = [dissect(body, position+1)]
+    elif tag == 0xA2:
+        if len(body) == 4: info = struct.unpack('>f', body)[0]
+        if len(body) == 8: info = struct.unpack('>d', body)[0]
+    elif tag == 0xA3:
+        info = decode_int(body)
+    elif tag == 0xA4:
+        info = body[:-1].decode('utf-8')
+    elif tag == 0xA6:
+        info = body.decode('utf-8')
+
+    if kids is not None:
+        return ((position, len(bs), tag), kids)
+    elif info is not None:
+        return ((position, len(bs), tag), body, info)
+    else:
+        return ((position, len(bs), tag), body)
+
+if __name__ == '__main__':
+    import sys
+    from pprint import pprint
+    pprint(dissect(sys.stdin.buffer.read()))