Support SHA256 as hash function in prefix caching (#15297)

Signed-off-by: Marko Rosenmueller <5467316+dr75@users.noreply.github.com>

vllm/utils.py

@@ -10,6 +10,7 @@ import datetime
 import enum
 import gc
 import getpass
+import hashlib
 import importlib
 import importlib.metadata
 import importlib.util
@@ -17,6 +18,7 @@ import inspect
 import ipaddress
 import multiprocessing
 import os
+import pickle
 import re
 import signal
 import socket
@@ -2442,3 +2444,21 @@ def cprofile(save_file: Optional[str] = None, enabled: bool = True):
         return wrapper
 
     return decorator
+
+
+def sha256(input) -> int:
+    """Hash any picklable Python object using SHA-256.
+
+    The input is serialized using pickle before hashing, which allows
+    arbitrary Python objects to be used. Note that this function does
+    not use a hash seed—if you need one, prepend it explicitly to the input.
+
+    Args:
+        input: Any picklable Python object.
+
+    Returns:
+        An integer representing the SHA-256 hash of the serialized input.
+    """
+    input_bytes = pickle.dumps(input, protocol=pickle.HIGHEST_PROTOCOL)
+    return int.from_bytes(hashlib.sha256(input_bytes).digest(),
+                          byteorder="big")