+static char *bignum_to_string(const BIGNUM *bn)
+{
+ char *tmp, *ret;
+ size_t len;
+
+ /*
+ * Display large numbers in hex and small numbers in decimal. Converting to
+ * decimal takes quadratic time and is no more useful than hex for large
+ * numbers.
+ */
+ if (BN_num_bits(bn) < 128)
+ return BN_bn2dec(bn);
+
+ tmp = BN_bn2hex(bn);
+ if (tmp == NULL)
+ return NULL;
+
+ len = strlen(tmp) + 3;
+ ret = OPENSSL_malloc(len);
+ if (ret == NULL) {
+ X509V3err(X509V3_F_BIGNUM_TO_STRING, ERR_R_MALLOC_FAILURE);
+ OPENSSL_free(tmp);
+ return NULL;
+ }
+
+ /* Prepend "0x", but place it after the "-" if negative. */
+ if (tmp[0] == '-') {
+ OPENSSL_strlcpy(ret, "-0x", len);
+ OPENSSL_strlcat(ret, tmp + 1, len);
+ } else {
+ OPENSSL_strlcpy(ret, "0x", len);
+ OPENSSL_strlcat(ret, tmp, len);
+ }
+ OPENSSL_free(tmp);
+ return ret;
+}
+