Update documentation

1 files changed, 10 insertions, 0 deletions

diff --git a/asn.h b/asn.h
index fc61b785..658fe2b5 100644
--- a/asn.h
+++ b/asn.h
@@ -197,12 +197,22 @@ CRYPTOPP_DLL size_t CRYPTOPP_API BERDecodeDate(BufferedTransformation &bt, SecBy
 /// \param strLen the length of the string

 /// \param unusedBits the number of unused bits

 /// \returns the number of octets used for the encoding

+/// \details The caller is responsible for shifting octets if unusedBits is

+///  not 0. For example, to DER encode a web server X.509 key usage, the 101b

+///  bit mask is often used (digitalSignature and keyEncipherment). In this

+///  case <tt>str</tt> is one octet with a value=0xa0 and unusedBits=5. The

+///  value 0xa0 is <tt>101b << 5</tt>.

 CRYPTOPP_DLL size_t CRYPTOPP_API DEREncodeBitString(BufferedTransformation &bt, const byte *str, size_t strLen, unsigned int unusedBits=0);

 

 /// \brief DER decode bit string

 /// \param bt BufferedTransformation object for reading

 /// \param str the decoded string

 /// \param unusedBits the number of unused bits

+/// \details The caller is responsible for shifting octets if unusedBits is

+///  not 0. For example, to DER encode a web server X.509 key usage, the 101b

+///  bit mask is often used (digitalSignature and keyEncipherment). In this

+///  case <tt>str</tt> is one octet with a value=0xa0 and unusedBits=5. The

+///  value 0xa0 is <tt>101b << 5</tt>.

 CRYPTOPP_DLL size_t CRYPTOPP_API BERDecodeBitString(BufferedTransformation &bt, SecByteBlock &str, unsigned int &unusedBits);

 

 /// \brief BER decode and DER re-encode