refactor: add type hints in strings.py and file.py (#1565)

part of #1539

Co-authored-by: Terri Oda <[email protected]>

Author: rhythmrx9

cve_bin_tool/file.py

@@ -11,10 +11,10 @@
 from cve_bin_tool.async_utils import FileIO, run_coroutine
 
 
-async def aio_is_binary(filename):
+async def aio_is_binary(filename: str) -> bool:
     """Read the magic bytes from a file and determine if it is an executable
     binary."""
-    signature = await read_signature(filename)
+    signature: bytes = await read_signature(filename)
     for name, method in inspect.getmembers(
         sys.modules[__name__], predicate=inspect.isfunction
     ):
@@ -24,26 +24,26 @@ async def aio_is_binary(filename):
     return False
 
 
-def is_binary(filename):
+def is_binary(filename: str) -> bool:
     return run_coroutine(aio_is_binary(filename))
 
 
-async def read_signature(filename, length=4):
+async def read_signature(filename: str, length: int = 4) -> bytes:
     """Read the signature, first length bytes, from filename."""
     async with FileIO(filename, "rb") as file_handle:
         return await file_handle.read(length)
 
 
-def check_elf(_filename, signature):
+def check_elf(_filename: str, signature: bytes) -> bool:
     """Check for an ELF signature."""
     return signature == b"\x7f\x45\x4c\x46"
 
 
-def check_pe(_filename, signature):
+def check_pe(_filename: str, signature: bytes) -> bool:
     """Check for windows/dos PE signature, aka 0x5a4d."""
     return signature[:4] == b"\x4d\x5a"
 
 
-def check_fake_test(_filename, signature):
+def check_fake_test(_filename: str, signature: bytes) -> bool:
     """check for fake tests under windows."""
     return signature == b"MZ\x90\x00"

cve_bin_tool/strings.py

@@ -7,22 +7,24 @@
 and MacOS.
 """
 
+from typing import ClassVar, List, Set
+
 from cve_bin_tool.async_utils import FileIO, run_coroutine
 
 
 class Strings:
     # printable characters
-    PRINTABLE = set(range(32, 128))
+    PRINTABLE: ClassVar[Set[int]] = set(range(32, 128))
     # add tab to the printable character
     PRINTABLE.add(9)
 
-    def __init__(self, filename=""):
+    def __init__(self, filename: str = "") -> None:
         self.filename = filename
-        self.output = ""
+        self.output: str = ""
 
-    async def aio_parse(self):
+    async def aio_parse(self) -> str:
         async with FileIO(self.filename, "rb") as f:
-            tmp = []
+            tmp: List[str] = []
             async for line in f:
                 for char in line:
                     # remove all unprintable characters
@@ -33,5 +35,5 @@ async def aio_parse(self):
                         tmp = []
         return self.output
 
-    def parse(self):
+    def parse(self) -> str:
         return run_coroutine(self.aio_parse())