Initial commit

app/hasher.py

@@ -0,0 +1,30 @@
+"""Streaming file hashing (stdlib only)."""
+import hashlib
+import zlib
+
+CHUNK = 1 << 23  # 8 MiB read chunks
+
+
+class HashCancelled(Exception):
+    """Raised when hashing is cancelled mid-read."""
+
+
+def hash_file(path, cancel=None):
+    crc = 0
+    md5 = hashlib.md5()
+    sha1 = hashlib.sha1()
+    with open(path, "rb") as f:
+        while True:
+            if cancel is not None and cancel.is_set():
+                raise HashCancelled()
+            block = f.read(CHUNK)
+            if not block:
+                break
+            crc = zlib.crc32(block, crc)
+            md5.update(block)
+            sha1.update(block)
+    return {
+        "crc32": f"{crc & 0xFFFFFFFF:08X}",
+        "md5": md5.hexdigest().upper(),
+        "sha1": sha1.hexdigest().upper(),
+    }