A little SHA in the C

gistfile1.c

char *sha256_hexdigest(const void *buf_to_hash, size_t buf_len, char *hexdigest)
{
  uint8_t binary_hash[SHA256_DIGEST_LENGTH];
  uint8_t *digest;
  SHA256_CTX context;
  int i;

  SHA256_Init(&context);
  SHA256_Update(&context, buf_to_hash, buf_len);
  SHA256_Final(binary_hash, &context);

  for (digest = hexdigest, i = 0; i < SHA256_DIGEST_LENGTH; i++)
  {
    digest += sprintf(digest, "%02x", binary_hash[i]);
  }

  return hexdigest;
}