.. _sha1messagedigest:



SHA1MessageDigest
=================


Computes SHA-1 digest value of the input message.


Syntax
------


IppStatus ippsSHA1MessageDigest(const Ipp8u \*pMsg, int len, Ipp8u
\*pMD);


Include Files
-------------


``ippcp.h``


Parameters
----------


.. list-table:: 
   :header-rows: 0

   * -     pMsg   
     -  Pointer to the input message.
   * -     len   
     -  Message length in octets.
   * -     pMD   
     -  Pointer to the resultant digest.




Description
-----------


The function uses the selected hash algorithm to compute the digest
value of the entire (non-streaming) input message.


Return Values
-------------


.. list-table:: 
   :header-rows: 0

   * -     ippStsNoErr   
     -  Indicates no error. Any other value indicates an error or warning.
   * -     ippStsNullPtrErr   
     -  Indicates an error condition if any of the specified pointers is NULL.
   * -     ippStsLengthErr   
     -  Indicates an error condition if the input data stream length is less than zero.




Example
-------


The code example below shows SHA1 digest of a message.


.. code-block:: cpp


       //    Compute two SHA1 digests of a message:
       //    1-st will correspond of 1/2 message
       //    2-nd will correspond of whole message
   void SHA1_sample(void){
      // get size of the SHA1 context
      int ctxSize;
      ippsSHA1GetSize(&ctxSize);


      // allocate the SHA1 context
      IppsSHA1State* pCtx = (IppsSHA1State*)( new Ipp8u [ctxSize] );
      // and initialize the context
      ippsSHA1Init(pCtx);
      // define a message
      Ipp8u msg[] = "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq";
      int n;
      // update digest using a piece of message
      for(n=0; n<(sizeof(msg)-1)/2; n++)
         ippsSHA1Update(msg+n, 1, pCtx);
   // clone the SHA1 context
      IppsSHA1State* pCtx2 = (IppsSHA1State*)( new Ipp8u [ctxSize] );
      ippsSHA1Init(pCtx2);
      ippsSHA1Duplicate(pCtx, pCtx2);
    // finalize and extract digest of a half message
      Ipp8u digest[20];
      ippsSHA1Final(digest, pCtx);
      // update digest using the SHA1 clone context
      ippsSHA1Update(msg+n, sizeof(msg)-1-n, pCtx2);


      // finalize and extract digest of a whole message
      Ipp8u digest2[20];
      ippsSHA1Final(digest2, pCtx2);


      delete [] (Ipp8u*)pCtx;
      delete [] (Ipp8u*)pCtx2;
   }