Update leb128

pywasm/leb128.py

@@ -1,16 +1,19 @@
-# https://en.wikipedia.org/wiki/LEB128
-#
-# LEB128 or Little Endian Base 128 is a form of variable-length code
-# compression used to store an arbitrarily large integer in a small number of
-# bytes. LEB128 is used in the DWARF debug file format and the WebAssembly
-# binary encoding for all integer literals.
+"""
+https://en.wikipedia.org/wiki/LEB128
+
+LEB128 or Little Endian Base 128 is a form of variable-length code
+compression used to store an arbitrarily large integer in a small number of
+bytes. LEB128 is used in the DWARF debug file format and the WebAssembly
+binary encoding for all integer literals.
+"""
 
 import typing
 
 
 class _U:
     @staticmethod
     def encode(i: int) -> bytearray:
+        """Encode the int i using unsigned leb128 and return the encoded bytearray."""
         assert i >= 0
         r = []
         while True:
@@ -23,16 +26,24 @@ def encode(i: int) -> bytearray:
 
     @staticmethod
     def decode(b: bytearray) -> int:
+        """Decode the unsigned leb128 encoded bytearray"""
         r = 0
         for i, e in enumerate(b):
             r = r + ((e & 0x7f) << (i * 7))
         return r
 
     @staticmethod
-    def decode_reader(r: typing.BinaryIO) -> (int, int):
+    def decode_reader(r: typing.BinaryIO) -> typing.Tuple[int, int]:
+        """
+        Decode the unsigned leb128 encoded from a reader, it will return two values, the actual number and the number
+        of bytes read.
+        """
         a = bytearray()
         while True:
-            b = ord(r.read(1))
+            b = r.read(1)
+            if len(b) != 1:
+                raise EOFError
+            b = ord(b)
             a.append(b)
             if (b & 0x80) == 0:
                 break
@@ -42,6 +53,7 @@ def decode_reader(r: typing.BinaryIO) -> (int, int):
 class _I:
     @staticmethod
     def encode(i: int) -> bytearray:
+        """Encode the int i using signed leb128 and return the encoded bytearray."""
         r = []
         while True:
             byte = i & 0x7f
@@ -53,6 +65,7 @@ def encode(i: int) -> bytearray:
 
     @staticmethod
     def decode(b: bytearray) -> int:
+        """Decode the signed leb128 encoded bytearray"""
         r = 0
         for i, e in enumerate(b):
             r = r + ((e & 0x7f) << (i * 7))
@@ -61,10 +74,17 @@ def decode(b: bytearray) -> int:
         return r
 
     @staticmethod
-    def decode_reader(r: typing.BinaryIO) -> (int, int):
+    def decode_reader(r: typing.BinaryIO) -> typing.Tuple[int, int]:
+        """
+        Decode the signed leb128 encoded from a reader, it will return two values, the actual number and the number
+        of bytes read.
+        """
         a = bytearray()
         while True:
-            b = ord(r.read(1))
+            b = r.read(1)
+            if len(b) != 1:
+                raise EOFError
+            b = ord(b)
             a.append(b)
             if (b & 0x80) == 0:
                 break