static bool CastToBigNum(mpz_t vo, const struct buffer *buf, bool fRequireMinimal, const size_t nMaxNumSize)
{
if (buf->len > nMaxNumSize)
return false;
const unsigned char *vch = buf->p;
if (fRequireMinimal && buf->len > 0) {
// Check that the number is encoded with the minimum possible
// number of bytes.
//
// If the most-significant-byte - excluding the sign bit - is zero
// then we're not minimal. Note how this test also rejects the
// negative-zero encoding, 0x80.
if ((vch[buf->len - 1] & 0x7f) == 0) {
// One exception: if there's more than one byte and the most
// significant bit of the second-most-significant-byte is set
// it would conflict with the sign bit. An example of this case
// is +-255, which encode to 0xff00 and 0xff80 respectively.
// (big-endian).
if (buf->len <= 1 || (vch[buf->len - 2] & 0x80) == 0) {
return false;
}
}
}
bn_setvch(vo, buf->p, buf->len);
return true;
}
static bool CastToBigNum(BIGNUM *vo, const struct buffer *buf)
{
if (buf->len > nMaxNumSize)
return false;
// Get rid of extra leading zeros:
// buf -> bn -> buf -> bn
BIGNUM bn;
BN_init(&bn);
bn_setvch(&bn, buf->p, buf->len);
GString *bn_s = bn_getvch(&bn);
bn_setvch(vo, bn_s->str, bn_s->len);
g_string_free(bn_s, TRUE);
BN_clear_free(&bn);
return true;
}
cstring *base58_encode(const void *data_, size_t data_len)
{
const unsigned char *data = data_;
BIGNUM bn58, bn0, bn, dv, rem;
BN_CTX *ctx;
ctx = BN_CTX_new();
BN_init(&bn58);
BN_init(&bn0);
BN_init(&bn);
BN_init(&dv);
BN_init(&rem);
BN_set_word(&bn58, 58);
BN_set_word(&bn0, 0);
unsigned char swapbuf[data_len + 1];
bu_reverse_copy(swapbuf, data, data_len);
swapbuf[data_len] = 0;
bn_setvch(&bn, swapbuf, sizeof(swapbuf));
cstring *rs = cstr_new_sz(data_len * 138 / 100 + 1);
while (BN_cmp(&bn, &bn0) > 0) {
if (!BN_div(&dv, &rem, &bn, &bn58, ctx))
goto err_out;
BN_copy(&bn, &dv);
unsigned int c = (int32_t)BN_get_word(&rem);
cstr_append_c(rs, base58_chars[c]);
}
unsigned int i;
for (i = 0; i < data_len; i++) {
if (data[i] == 0)
cstr_append_c(rs, base58_chars[0]);
else
break;
}
cstring *rs_swap = cstr_new_sz(rs->len);
cstr_resize(rs_swap, rs->len);
bu_reverse_copy((unsigned char *) rs_swap->str,
(unsigned char *) rs->str, rs->len);
cstr_free(rs, true);
rs = rs_swap;
out:
BN_clear_free(&bn58);
BN_clear_free(&bn0);
BN_clear_free(&bn);
BN_clear_free(&dv);
BN_clear_free(&rem);
BN_CTX_free(ctx);
return rs;
err_out:
cstr_free(rs, true);
rs = NULL;
goto out;
}
