X-Git-Url: http://wagner.pp.ru/gitweb/?a=blobdiff_plain;f=ctypescrypto%2Fdigest.py;h=0098ab4109a36c15b3dd144624a62a18b5530317;hb=297667fab5c13886d82b037e74c84459f52e829c;hp=df4e58071a13c98e96b05e56710e86141407bd5b;hpb=eeb4a6511bf02295c802a6b55bfad226b01fa126;p=oss%2Fctypescrypto.git

diff --git a/ctypescrypto/digest.py b/ctypescrypto/digest.py
index df4e580..0098ab4 100644
--- a/ctypescrypto/digest.py
+++ b/ctypescrypto/digest.py
@@ -81,15 +81,23 @@ class Digest:
 	def __del__(self):
 		self._clean_ctx()
 
-	def update(self, data):
+	def update(self, data, length=None):
 		"""
-			Hashes given byte string as data
+			Hashes given byte string 
+
+			@param data - string to hash
+			@param length - if not specifed, entire string is hashed,
+					otherwise only first length bytes
 		"""
 		if self.digest_finalized:
 			raise DigestError, "No updates allowed"
 		if type(data) != type(""):
 			raise TypeError, "A string is expected"
-		result = libcrypto.EVP_DigestUpdate(self.ctx, c_char_p(data), len(data))
+		if length is None:
+			length=len(data)
+		elif length> len(data):
+			raise ValueError("Specified length is greater than length of data")
+		result = libcrypto.EVP_DigestUpdate(self.ctx, c_char_p(data), length)
 		if result != 1:
 			raise DigestError, "Unable to update digest"