- {
- int i=0,num;
- char *buf=NULL;
- char *p;
- BIGNUM *t=NULL;
- BN_ULONG *bn_data=NULL,*lp;
-
- i=BN_num_bits(a)*3;
- num=(i/10+i/1000+3)+1;
- bn_data=(BN_ULONG *)OPENSSL_malloc((num/BN_DEC_NUM+1)*sizeof(BN_ULONG));
- buf=(char *)OPENSSL_malloc(num+3);
- if ((buf == NULL) || (bn_data == NULL))
- {
- BNerr(BN_F_BN_BN2DEC,ERR_R_MALLOC_FAILURE);
- goto err;
- }
- if ((t=BN_dup(a)) == NULL) goto err;
-
- p=buf;
- lp=bn_data;
- if (t->neg) *(p++)='-';
- if (t->top == 0)
- {
- *(p++)='0';
- *(p++)='\0';
- }
- else
- {
- i=0;
- while (!BN_is_zero(t))
- {
- *lp=BN_div_word(t,BN_DEC_CONV);
- lp++;
- }
- lp--;
- /* We now have a series of blocks, BN_DEC_NUM chars
- * in length, where the last one needs truncation.
- * The blocks need to be reversed in order. */
- sprintf(p,BN_DEC_FMT1,*lp);
- while (*p) p++;
- while (lp != bn_data)
- {
- lp--;
- sprintf(p,BN_DEC_FMT2,*lp);
- while (*p) p++;
- }
- }
-err:
- if (bn_data != NULL) OPENSSL_free(bn_data);
- if (t != NULL) BN_free(t);
- return(buf);
- }
+{
+ int i = 0, num, ok = 0;
+ char *buf = NULL;
+ char *p;
+ BIGNUM *t = NULL;
+ BN_ULONG *bn_data = NULL, *lp;
+
+ /*-
+ * get an upper bound for the length of the decimal integer
+ * num <= (BN_num_bits(a) + 1) * log(2)
+ * <= 3 * BN_num_bits(a) * 0.1001 + log(2) + 1 (rounding error)
+ * <= BN_num_bits(a)/10 + BN_num_bits/1000 + 1 + 1
+ */
+ i = BN_num_bits(a) * 3;
+ num = (i / 10 + i / 1000 + 1) + 1;
+ bn_data = OPENSSL_malloc((num / BN_DEC_NUM + 1) * sizeof(BN_ULONG));
+ buf = OPENSSL_malloc(num + 3);
+ if ((buf == NULL) || (bn_data == NULL)) {
+ BNerr(BN_F_BN_BN2DEC, ERR_R_MALLOC_FAILURE);
+ goto err;
+ }
+ if ((t = BN_dup(a)) == NULL)
+ goto err;
+
+#define BUF_REMAIN (num+3 - (size_t)(p - buf))
+ p = buf;
+ lp = bn_data;
+ if (BN_is_zero(t)) {
+ *(p++) = '0';
+ *(p++) = '\0';
+ } else {
+ if (BN_is_negative(t))
+ *p++ = '-';
+
+ i = 0;
+ while (!BN_is_zero(t)) {
+ *lp = BN_div_word(t, BN_DEC_CONV);
+ lp++;
+ }
+ lp--;
+ /*
+ * We now have a series of blocks, BN_DEC_NUM chars in length, where
+ * the last one needs truncation. The blocks need to be reversed in
+ * order.
+ */
+ BIO_snprintf(p, BUF_REMAIN, BN_DEC_FMT1, *lp);
+ while (*p)
+ p++;
+ while (lp != bn_data) {
+ lp--;
+ BIO_snprintf(p, BUF_REMAIN, BN_DEC_FMT2, *lp);
+ while (*p)
+ p++;
+ }
+ }
+ ok = 1;
+ err:
+ OPENSSL_free(bn_data);
+ BN_free(t);
+ if (ok)
+ return buf;
+ OPENSSL_free(buf);
+ return NULL;
+}