/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org */#include "mycrypt.h"#ifdef CTRint ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr){   int x, err;   _ARGCHK(pt != NULL);   _ARGCHK(ct != NULL);   _ARGCHK(ctr != NULL);   if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {       return err;   }      /* is blocklen/padlen valid? */   if (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) ||       ctr->padlen   < 0 || ctr->padlen   > (int)sizeof(ctr->pad)) {      return CRYPT_INVALID_ARG;   }   while (len-- > 0) {      /* is the pad empty? */      if (ctr->padlen == ctr->blocklen) {         /* increment counter */         if (ctr->mode == 0) {            /* little-endian */            for (x = 0; x < ctr->blocklen; x++) {               ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;               if (ctr->ctr[x] != (unsigned char)0) {                  break;               }            }         } else {            /* big-endian */            for (x = ctr->blocklen-1; x >= 0; x--) {               ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;               if (ctr->ctr[x] != (unsigned char)0) {                  break;               }            }         }         /* encrypt it */         cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);         ctr->padlen = 0;      }      *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];   }   return CRYPT_OK;}#endif