SHA256Fetch.c
Author: cmaier@cmassoc.net

    /*====================================================================*
     *
     *   void SHA256Fetch (struct sha256 * sha256,  uint8_t digest []);
     *
     *   SHA256.h
     *
     *   read the SHA256 digest; this function works like function read()
     *   but the function returns no value and the digest buffer is fixed
     *   length;
     *
     *   to start a digest, use function SHA256Reset(); to write data to
     *   the digest use function SHA256Write();
     *
     *   Read standard FIPS180-2 sec 5.3.2 for an explanation;
     *
     *   Motley Tools by Charles Maier <cmaier@cmassoc.net>;
     *   Copyright (c) 2001-2006 by Charles Maier Associates;
     *   Licensed under the Internet Software Consortium License;
     *
     *--------------------------------------------------------------------*/

    #ifndef SHA256FETCH_SOURCE
    #define SHA256FETCH_SOURCE

    #include "../key/SHA256.h"

    static void encode (uint8_t memory [], uint32_t number)

    {
    	*memory++ = (uint8_t)(number >> 24);
    	*memory++ = (uint8_t)(number >> 16);
    	*memory++ = (uint8_t)(number >> 8);
    	*memory++ = (uint8_t)(number >> 0);
    	return;
    }

    void SHA256Fetch (struct sha256 * sha256, uint8_t digest [])

    {
    	unsigned word;
    	uint8_t bits [8];
    	uint32_t upper = (sha256->count [0] >> 29) | (sha256->count [1] << 3);
    	uint32_t lower = (sha256->count [0] << 3);
    	uint32_t final = (sha256->count [0] & 0x3F);
    	uint32_t extra = (final < 56)? (56 - final): (120 - final);
    	encode (&bits [0], upper);
    	encode (&bits [4], lower);
    	SHA256Write (sha256, sha256->extra, extra);
    	SHA256Write (sha256, bits, sizeof (bits));
    	for (word = 0; word < sizeof (sha256->state) / sizeof (uint32_t); word++)
    	{
    		encode (digest, sha256->state [word]);
    		digest += sizeof (uint32_t);
    	}
    	memset (sha256, 0, sizeof (struct sha256));
    	return;
    }

    #endif

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