implement uleb128 parsing

README.rst

@@ -55,6 +55,7 @@ Currently Cockroach exports the following methods:
   - bigint serialization
   - ipv4 parsing
   - null/pkcs7 (un)padding
+  - uleb128
 
 * Bitwise
 

roach/__init__.py

@@ -8,7 +8,7 @@
 from roach.hash.crc import crc32
 from roach.hash.sha import md5, sha1, sha224, sha384, sha256, sha512
 from roach.string.inet import ipv4
-from roach.string.ops import asciiz, hex, unhex
+from roach.string.ops import asciiz, hex, unhex, uleb128
 from roach.structure import Structure
 
 from roach.procmem import (

roach/string/ops.py

@@ -14,6 +14,14 @@ def hex(s):
 def unhex(s):
     return binascii.unhexlify(s)
 
+def uleb128(s):
+    ret = 0
+    for idx in xrange(len(s)):
+        ret += (ord(s[idx]) & 0x7f) << (idx*7)
+        if ord(s[idx]) < 0x80:
+            break
+    return idx+1, ret
+
 class Base64(object):
     def encode(self, s):
         return base64.b64encode(s)

tests/test_string.py

@@ -4,7 +4,7 @@
 
 from roach import (
     int8, uint8, int16, uint16, int32, uint32, int64, uint64, bigint,
-    asciiz, pad, unpad, ipv4, pack, unpack, hex, unhex, base64
+    asciiz, pad, unpad, ipv4, pack, unpack, hex, unhex, base64, uleb128
 )
 
 def test_asciiz():
@@ -14,6 +14,10 @@ def test_hex():
     assert hex("hello") == "68656c6c6f"
     assert unhex("68656c6c6f") == "hello"
 
+def test_uleb128():
+    assert uleb128("\x00") == (1, 0)
+    assert uleb128("\xe5\x8e\x26") == (3, 624485)
+
 def test_pad():
     assert pad("hello!!1", 8) == "hello!!1"
     assert pad("hello", 8) == "hello\x03\x03\x03"