/*
 * 'OpenSSL for Ruby' project
 * Copyright (C) 2001-2002  Technorama team <oss-ruby@technorama.net>
 * All rights reserved.
 */
/*
 * This program is licensed under the same licence as Ruby.
 * (See the file 'COPYING'.)
 */
/* modified by Michal Rokos <m.rokos@sh.cvut.cz> */
#include "ossl.h"

#define NewBN(klass) \
  TypedData_Wrap_Struct((klass), &ossl_bn_type, 0)
#define SetBN(obj, bn) do { \
  if (!(bn)) { \
    ossl_raise(rb_eRuntimeError, "BN wasn't initialized!"); \
  } \
  RTYPEDDATA_DATA(obj) = (bn); \
} while (0)

#define GetBN(obj, bn) do { \
  TypedData_Get_Struct((obj), BIGNUM, &ossl_bn_type, (bn)); \
  if (!(bn)) { \
    ossl_raise(rb_eRuntimeError, "BN wasn't initialized!"); \
  } \
} while (0)

static void
ossl_bn_free(void *ptr)
{
    BN_clear_free(ptr);
}

static const rb_data_type_t ossl_bn_type = {
    "OpenSSL/BN",
    {
	0, ossl_bn_free,
    },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED | RUBY_TYPED_FROZEN_SHAREABLE,
};

/*
 * Classes
 */
VALUE cBN;

/* Document-class: OpenSSL::BNError
 *
 * Generic Error for all of OpenSSL::BN (big num)
 */
static VALUE eBNError;

/*
 * Public
 */
VALUE
ossl_bn_new(const BIGNUM *bn)
{
    BIGNUM *newbn;
    VALUE obj;

    obj = NewBN(cBN);
    newbn = bn ? BN_dup(bn) : BN_new();
    if (!newbn) {
	ossl_raise(eBNError, NULL);
    }
    SetBN(obj, newbn);

    return obj;
}

static BIGNUM *
integer_to_bnptr(VALUE obj, BIGNUM *orig)
{
    BIGNUM *bn;

    if (FIXNUM_P(obj)) {
	long i;
	unsigned char bin[sizeof(long)];
	long n = FIX2LONG(obj);
	unsigned long un = labs(n);

	for (i = sizeof(long) - 1; 0 <= i; i--) {
	    bin[i] = un & 0xff;
	    un >>= 8;
	}

	bn = BN_bin2bn(bin, sizeof(bin), orig);
	if (!bn)
	    ossl_raise(eBNError, "BN_bin2bn");
	if (n < 0)
	    BN_set_negative(bn, 1);
    }
    else { /* assuming Bignum */
	size_t len = rb_absint_size(obj, NULL);
	unsigned char *bin;
	VALUE buf;
	int sign;

	if (INT_MAX < len) {
	    rb_raise(eBNError, "bignum too long");
	}
	bin = (unsigned char*)ALLOCV_N(unsigned char, buf, len);
	sign = rb_integer_pack(obj, bin, len, 1, 0, INTEGER_PACK_BIG_ENDIAN);

	bn = BN_bin2bn(bin, (int)len, orig);
	ALLOCV_END(buf);
	if (!bn)
	    ossl_raise(eBNError, "BN_bin2bn");
	if (sign < 0)
	    BN_set_negative(bn, 1);
    }

    return bn;
}

static VALUE
try_convert_to_bn(VALUE obj)
{
    BIGNUM *bn;
    VALUE newobj = Qnil;

    if (rb_obj_is_kind_of(obj, cBN))
	return obj;
    if (RB_INTEGER_TYPE_P(obj)) {
	newobj = NewBN(cBN); /* Handle potential mem leaks */
	bn = integer_to_bnptr(obj, NULL);
	SetBN(newobj, bn);
    }

    return newobj;
}

BIGNUM *
ossl_bn_value_ptr(volatile VALUE *ptr)
{
    VALUE tmp;
    BIGNUM *bn;

    tmp = try_convert_to_bn(*ptr);
    if (NIL_P(tmp))
	ossl_raise(rb_eTypeError, "Cannot convert into OpenSSL::BN");
    GetBN(tmp, bn);
    *ptr = tmp;

    return bn;
}

/*
 * Private
 */

#ifdef HAVE_RB_EXT_RACTOR_SAFE
static void
ossl_bn_ctx_free(void *ptr)
{
    BN_CTX *ctx = (BN_CTX *)ptr;
    BN_CTX_free(ctx);
}

static struct rb_ractor_local_storage_type ossl_bn_ctx_key_type = {
    NULL, // mark
    ossl_bn_ctx_free,
};

static rb_ractor_local_key_t ossl_bn_ctx_key;

BN_CTX *
ossl_bn_ctx_get(void)
{
    // stored in ractor local storage

    BN_CTX *ctx = rb_ractor_local_storage_ptr(ossl_bn_ctx_key);
    if (!ctx) {
        if (!(ctx = BN_CTX_new())) {
            ossl_raise(rb_eRuntimeError, "Cannot init BN_CTX");
        }
        rb_ractor_local_storage_ptr_set(ossl_bn_ctx_key, ctx);
    }
    return ctx;
}
#else
// for ruby 2.x
static BN_CTX *gv_ossl_bn_ctx;

BN_CTX *
ossl_bn_ctx_get(void)
{
    if (gv_ossl_bn_ctx == NULL) {
        if (!(gv_ossl_bn_ctx = BN_CTX_new())) {
            ossl_raise(rb_eRuntimeError, "Cannot init BN_CTX");
        }
    }
    return gv_ossl_bn_ctx;
}

void
ossl_bn_ctx_free(void)
{
    BN_CTX_free(gv_ossl_bn_ctx);
    gv_ossl_bn_ctx = NULL;
}
#endif

static VALUE
ossl_bn_alloc(VALUE klass)
{
    BIGNUM *bn;
    VALUE obj = NewBN(klass);

    if (!(bn = BN_new())) {
	ossl_raise(eBNError, NULL);
    }
    SetBN(obj, bn);

    return obj;
}

/*
 * call-seq:
 *    OpenSSL::BN.new(bn) -> aBN
 *    OpenSSL::BN.new(integer) -> aBN
 *    OpenSSL::BN.new(string, base = 10) -> aBN
 *
 * Construct a new \OpenSSL BIGNUM object.
 *
 * If +bn+ is an Integer or OpenSSL::BN, a new instance of OpenSSL::BN
 * representing the same value is returned. See also Integer#to_bn for the
 * short-hand.
 *
 * If a String is given, the content will be parsed according to +base+.
 *
 * +string+::
 *   The string to be parsed.
 * +base+::
 *   The format. Must be one of the following:
 *   - +0+  - MPI format. See the man page BN_mpi2bn(3) for details.
 *   - +2+  - Variable-length and big-endian binary encoding of a positive
 *     number.
 *   - +10+ - Decimal number representation, with a leading '-' for a negative
 *     number.
 *   - +16+ - Hexadecimal number representation, with a leading '-' for a
 *     negative number.
 */
static VALUE
ossl_bn_initialize(int argc, VALUE *argv, VALUE self)
{
    BIGNUM *bn;
    VALUE str, bs;
    int base = 10;
    char *ptr;

    if (rb_scan_args(argc, argv, "11", &str, &bs) == 2) {
	base = NUM2INT(bs);
    }

    if (NIL_P(str)) {
        ossl_raise(rb_eArgError, "invalid argument");
    }

    rb_check_frozen(self);
    if (RB_INTEGER_TYPE_P(str)) {
	GetBN(self, bn);
	integer_to_bnptr(str, bn);

	return self;
    }

    if (RTEST(rb_obj_is_kind_of(str, cBN))) {
	BIGNUM *other;

	GetBN(self, bn);
	GetBN(str, other); /* Safe - we checked kind_of? above */
	if (!BN_copy(bn, other)) {
	    ossl_raise(eBNError, NULL);
	}
	return self;
    }

    GetBN(self, bn);
    switch (base) {
    case 0:
        ptr = StringValuePtr(str);
        if (!BN_mpi2bn((unsigned char *)ptr, RSTRING_LENINT(str), bn)) {
	    ossl_raise(eBNError, NULL);
	}
	break;
    case 2:
        ptr = StringValuePtr(str);
        if (!BN_bin2bn((unsigned char *)ptr, RSTRING_LENINT(str), bn)) {
	    ossl_raise(eBNError, NULL);
	}
	break;
    case 10:
	if (!BN_dec2bn(&bn, StringValueCStr(str))) {
	    ossl_raise(eBNError, NULL);
	}
	break;
    case 16:
	if (!BN_hex2bn(&bn, StringValueCStr(str))) {
	    ossl_raise(eBNError, NULL);
	}
	break;
    default:
	ossl_raise(rb_eArgError, "invalid radix %d", base);
    }
    return self;
}

/*
 * call-seq:
 *    bn.to_s(base = 10) -> string
 *
 * Returns the string representation of the bignum.
 *
 * BN.new can parse the encoded string to convert back into an OpenSSL::BN.
 *
 * +base+::
 *   The format. Must be one of the following:
 *   - +0+  - MPI format. See the man page BN_bn2mpi(3) for details.
 *   - +2+  - Variable-length and big-endian binary encoding. The sign of
 *     the bignum is ignored.
 *   - +10+ - Decimal number representation, with a leading '-' for a negative
 *     bignum.
 *   - +16+ - Hexadecimal number representation, with a leading '-' for a
 *     negative bignum.
 */
static VALUE
ossl_bn_to_s(int argc, VALUE *argv, VALUE self)
{
    BIGNUM *bn;
    VALUE str, bs;
    int base = 10, len;
    char *buf;

    if (rb_scan_args(argc, argv, "01", &bs) == 1) {
	base = NUM2INT(bs);
    }
    GetBN(self, bn);
    switch (base) {
    case 0:
	len = BN_bn2mpi(bn, NULL);
        str = rb_str_new(0, len);
	if (BN_bn2mpi(bn, (unsigned char *)RSTRING_PTR(str)) != len)
	    ossl_raise(eBNError, NULL);
	break;
    case 2:
	len = BN_num_bytes(bn);
        str = rb_str_new(0, len);
	if (BN_bn2bin(bn, (unsigned char *)RSTRING_PTR(str)) != len)
	    ossl_raise(eBNError, NULL);
	break;
    case 10:
	if (!(buf = BN_bn2dec(bn))) ossl_raise(eBNError, NULL);
	str = ossl_buf2str(buf, rb_long2int(strlen(buf)));
	break;
    case 16:
	if (!(buf = BN_bn2hex(bn))) ossl_raise(eBNError, NULL);
	str = ossl_buf2str(buf, rb_long2int(strlen(buf)));
	break;
    default:
	ossl_raise(rb_eArgError, "invalid radix %d", base);
    }

    return str;
}

/*
 * call-seq:
 *    bn.to_i => integer
 */
static VALUE
ossl_bn_to_i(VALUE self)
{
    BIGNUM *bn;
    char *txt;
    VALUE num;

    GetBN(self, bn);

    if (!(txt = BN_bn2hex(bn))) {
	ossl_raise(eBNError, NULL);
    }
    num = rb_cstr_to_inum(txt, 16, Qtrue);
    OPENSSL_free(txt);

    return num;
}

static VALUE
ossl_bn_to_bn(VALUE self)
{
    return self;
}

static VALUE
ossl_bn_coerce(VALUE self, VALUE other)
{
    switch(TYPE(other)) {
    case T_STRING:
	self = ossl_bn_to_s(0, NULL, self);
	break;
    case T_FIXNUM:
    case T_BIGNUM:
	self = ossl_bn_to_i(self);
	break;
    default:
	if (!RTEST(rb_obj_is_kind_of(other, cBN))) {
	    ossl_raise(rb_eTypeError, "Don't know how to coerce");
	}
    }
    return rb_assoc_new(other, self);
}

#define BIGNUM_BOOL1(func)				\
    static VALUE					\
    ossl_bn_##func(VALUE self)				\
    {							\
	BIGNUM *bn;					\
	GetBN(self, bn);				\
	if (BN_##func(bn)) {				\
	    return Qtrue;				\
	}						\
	return Qfalse;					\
    }

/*
 * Document-method: OpenSSL::BN#zero?
 * call-seq:
 *   bn.zero? => true | false
 */
BIGNUM_BOOL1(is_zero)

/*
 * Document-method: OpenSSL::BN#one?
 * call-seq:
 *   bn.one? => true | false
 */
BIGNUM_BOOL1(is_one)

/*
 * Document-method: OpenSSL::BN#odd?
 * call-seq:
 *   bn.odd? => true | false
 */
BIGNUM_BOOL1(is_odd)

/*
 * call-seq:
 *   bn.negative? => true | false
 */
static VALUE
ossl_bn_is_negative(VALUE self)
{
    BIGNUM *bn;

    GetBN(self, bn);
    if (BN_is_zero(bn))
	return Qfalse;
    return BN_is_negative(bn) ? Qtrue : Qfalse;
}

#define BIGNUM_1c(func)					\
    static VALUE					\
    ossl_bn_##func(VALUE self)				\
    {							\
	BIGNUM *bn, *result;				\
	VALUE obj;					\
	GetBN(self, bn);				\
	obj = NewBN(rb_obj_class(self));		\
	if (!(result = BN_new())) {			\
	    ossl_raise(eBNError, NULL);			\
	}						\
	if (BN_##func(result, bn, ossl_bn_ctx) <= 0) {	\
	    BN_free(result);				\
	    ossl_raise(eBNError, NULL);			\
	}						\
	SetBN(obj, result);				\
	return obj;					\
    }

/*
 * Document-method: OpenSSL::BN#sqr
 * call-seq:
 *   bn.sqr => aBN
 */
BIGNUM_1c(sqr)

#define BIGNUM_2(func)					\
    static VALUE					\
    ossl_bn_##func(VALUE self, VALUE other)		\
    {							\
	BIGNUM *bn1, *bn2 = GetBNPtr(other), *result;	\
	VALUE obj;					\
	GetBN(self, bn1);				\
	obj = NewBN(rb_obj_class(self));		\
	if (!(result = BN_new())) {			\
	    ossl_raise(eBNError, NULL);			\
	}						\
	if (BN_##func(result, bn1, bn2) <= 0) {		\
	    BN_free(result);				\
	    ossl_raise(eBNError, NULL);			\
	}						\
	SetBN(obj, result);				\
	return obj;					\
    }

/*
 * Document-method: OpenSSL::BN#+
 * call-seq:
 *   bn + bn2 => aBN
 */
BIGNUM_2(add)

/*
 * Document-method: OpenSSL::BN#-
 * call-seq:
 *   bn - bn2 => aBN
 */
BIGNUM_2(sub)

#define BIGNUM_2c(func)						\
    static VALUE						\
    ossl_bn_##func(VALUE self, VALUE other)			\
    {								\
	BIGNUM *bn1, *bn2 = GetBNPtr(other), *result;		\
	VALUE obj;						\
	GetBN(self, bn1);					\
	obj = NewBN(rb_obj_class(self));			\
	if (!(result = BN_new())) {				\
	    ossl_raise(eBNError, NULL);				\
	}							\
	if (BN_##func(result, bn1, bn2, ossl_bn_ctx) <= 0) {	\
	    BN_free(result);					\
	    ossl_raise(eBNError, NULL);				\
	}							\
	SetBN(obj, result);					\
	return obj;						\
    }

/*
 * Document-method: OpenSSL::BN#*
 * call-seq:
 *   bn * bn2 => aBN
 */
BIGNUM_2c(mul)

/*
 * Document-method: OpenSSL::BN#%
 * call-seq:
 *   bn % bn2 => aBN
 */
BIGNUM_2c(mod)

/*
 * Document-method: OpenSSL::BN#**
 * call-seq:
 *   bn ** bn2 => aBN
 */
BIGNUM_2c(exp)

/*
 * Document-method: OpenSSL::BN#gcd
 * call-seq:
 *   bn.gcd(bn2) => aBN
 */
BIGNUM_2c(gcd)

/*
 * Document-method: OpenSSL::BN#mod_sqr
 * call-seq:
 *   bn.mod_sqr(bn2) => aBN
 */
BIGNUM_2c(mod_sqr)

#define BIGNUM_2cr(func)					\
    static VALUE						\
    ossl_bn_##func(VALUE self, VALUE other)			\
    {								\
	BIGNUM *bn1, *bn2 = GetBNPtr(other), *result;		\
	VALUE obj;						\
	GetBN(self, bn1);					\
	obj = NewBN(rb_obj_class(self));			\
	if (!(result = BN_##func(NULL, bn1, bn2, ossl_bn_ctx)))	\
	    ossl_raise(eBNError, NULL);				\
	SetBN(obj, result);					\
	return obj;						\
    }

/*
 * Document-method: OpenSSL::BN#mod_sqrt
 * call-seq:
 *   bn.mod_sqrt(bn2) => aBN
 */
BIGNUM_2cr(mod_sqrt)

/*
 * Document-method: OpenSSL::BN#mod_inverse
 * call-seq:
 *    bn.mod_inverse(bn2) => aBN
 */
BIGNUM_2cr(mod_inverse)

/*
 * call-seq:
 *    bn1 / bn2 => [result, remainder]
 *
 * Division of OpenSSL::BN instances
 */
static VALUE
ossl_bn_div(VALUE self, VALUE other)
{
    BIGNUM *bn1, *bn2 = GetBNPtr(other), *r1, *r2;
    VALUE klass, obj1, obj2;

    GetBN(self, bn1);

    klass = rb_obj_class(self);
    obj1 = NewBN(klass);
    obj2 = NewBN(klass);
    if (!(r1 = BN_new())) {
	ossl_raise(eBNError, NULL);
    }
    if (!(r2 = BN_new())) {
	BN_free(r1);
	ossl_raise(eBNError, NULL);
    }
    if (!BN_div(r1, r2, bn1, bn2, ossl_bn_ctx)) {
	BN_free(r1);
	BN_free(r2);
	ossl_raise(eBNError, NULL);
    }
    SetBN(obj1, r1);
    SetBN(obj2, r2);

    return rb_ary_new3(2, obj1, obj2);
}

#define BIGNUM_3c(func)						\
    static VALUE						\
    ossl_bn_##func(VALUE self, VALUE other1, VALUE other2)	\
    {								\
	BIGNUM *bn1, *bn2 = GetBNPtr(other1);			\
	BIGNUM *bn3 = GetBNPtr(other2), *result;		\
	VALUE obj;						\
	GetBN(self, bn1);					\
	obj = NewBN(rb_obj_class(self));			\
	if (!(result = BN_new())) {				\
	    ossl_raise(eBNError, NULL);				\
	}							\
	if (BN_##func(result, bn1, bn2, bn3, ossl_bn_ctx) <= 0) { \
	    BN_free(result);					\
	    ossl_raise(eBNError, NULL);				\
	}							\
	SetBN(obj, result);					\
	return obj;						\
    }

/*
 * Document-method: OpenSSL::BN#mod_add
 * call-seq:
 *   bn.mod_add(bn1, bn2) -> aBN
 */
BIGNUM_3c(mod_add)

/*
 * Document-method: OpenSSL::BN#mod_sub
 * call-seq:
 *   bn.mod_sub(bn1, bn2) -> aBN
 */
BIGNUM_3c(mod_sub)

/*
 * Document-method: OpenSSL::BN#mod_mul
 * call-seq:
 *   bn.mod_mul(bn1, bn2) -> aBN
 */
BIGNUM_3c(mod_mul)

/*
 * Document-method: OpenSSL::BN#mod_exp
 * call-seq:
 *   bn.mod_exp(bn1, bn2) -> aBN
 */
BIGNUM_3c(mod_exp)

#define BIGNUM_BIT(func)				\
    static VALUE					\
    ossl_bn_##func(VALUE self, VALUE bit)		\
    {							\
	BIGNUM *bn;					\
	rb_check_frozen(self);				\
	GetBN(self, bn);				\
	if (BN_##func(bn, NUM2INT(bit)) <= 0) {		\
	    ossl_raise(eBNError, NULL);			\
	}						\
	return self;					\
    }

/*
 * Document-method: OpenSSL::BN#set_bit!
 * call-seq:
 *   bn.set_bit!(bit) -> self
 */
BIGNUM_BIT(set_bit)

/*
 * Document-method: OpenSSL::BN#clear_bit!
 * call-seq:
 *   bn.clear_bit!(bit) -> self
 */
BIGNUM_BIT(clear_bit)

/*
 * Document-method: OpenSSL::BN#mask_bit!
 * call-seq:
 *   bn.mask_bit!(bit) -> self
 */
BIGNUM_BIT(mask_bits)

/*
 * call-seq:
 *   bn.bit_set?(bit) => true | false
 *
 * Tests bit _bit_ in _bn_ and returns +true+ if set, +false+ if not set.
 */
static VALUE
ossl_bn_is_bit_set(VALUE self, VALUE bit)
{
    int b;
    BIGNUM *bn;

    b = NUM2INT(bit);
    GetBN(self, bn);
    if (BN_is_bit_set(bn, b)) {
	return Qtrue;
    }
    return Qfalse;
}

#define BIGNUM_SHIFT(func)				\
    static VALUE					\
    ossl_bn_##func(VALUE self, VALUE bits)		\
    {							\
	BIGNUM *bn, *result;				\
	int b;						\
	VALUE obj;					\
	b = NUM2INT(bits);				\
	GetBN(self, bn);				\
	obj = NewBN(rb_obj_class(self));		\
	if (!(result = BN_new())) {			\
		ossl_raise(eBNError, NULL);		\
	}						\
	if (BN_##func(result, bn, b) <= 0) {		\
		BN_free(result);			\
		ossl_raise(eBNError, NULL);		\
	}						\
	SetBN(obj, result);				\
	return obj;					\
    }

/*
 * Document-method: OpenSSL::BN#<<
 * call-seq:
 *   bn << bits -> aBN
 */
BIGNUM_SHIFT(lshift)

/*
 * Document-method: OpenSSL::BN#>>
 * call-seq:
 *   bn >> bits -> aBN
 */
BIGNUM_SHIFT(rshift)

#define BIGNUM_SELF_SHIFT(func)				\
    static VALUE					\
    ossl_bn_self_##func(VALUE self, VALUE bits)		\
    {							\
	BIGNUM *bn;					\
	int b;						\
	rb_check_frozen(self);				\
	b = NUM2INT(bits);				\
	GetBN(self, bn);				\
	if (BN_##func(bn, bn, b) <= 0)			\
		ossl_raise(eBNError, NULL);		\
	return self;					\
    }

/*
 * Document-method: OpenSSL::BN#lshift!
 * call-seq:
 *   bn.lshift!(bits) -> self
 */
BIGNUM_SELF_SHIFT(lshift)

/*
 * Document-method: OpenSSL::BN#rshift!
 * call-seq:
 *   bn.rshift!(bits) -> self
 */
BIGNUM_SELF_SHIFT(rshift)

/*
 * call-seq:
 *    BN.rand(bits [, fill [, odd]]) -> aBN
 *
 * Generates a cryptographically strong pseudo-random number of +bits+.
 *
 * See also the man page BN_rand(3).
 */
static VALUE
ossl_bn_s_rand(int argc, VALUE *argv, VALUE klass)
{
    BIGNUM *result;
    int bottom = 0, top = 0, b;
    VALUE bits, fill, odd, obj;

    switch (rb_scan_args(argc, argv, "12", &bits, &fill, &odd)) {
      case 3:
        bottom = (odd == Qtrue) ? 1 : 0;
        /* FALLTHROUGH */
      case 2:
        top = NUM2INT(fill);
    }
    b = NUM2INT(bits);
    obj = NewBN(klass);
    if (!(result = BN_new())) {
        ossl_raise(eBNError, "BN_new");
    }
    if (BN_rand(result, b, top, bottom) <= 0) {
        BN_free(result);
        ossl_raise(eBNError, "BN_rand");
    }
    SetBN(obj, result);
    return obj;
}

/*
 * call-seq:
 *    BN.rand_range(range) -> aBN
 *
 * Generates a cryptographically strong pseudo-random number in the range
 * 0...+range+.
 *
 * See also the man page BN_rand_range(3).
 */
static VALUE
ossl_bn_s_rand_range(VALUE klass, VALUE range)
{
    BIGNUM *bn = GetBNPtr(range), *result;
    VALUE obj = NewBN(klass);
    if (!(result = BN_new()))
        ossl_raise(eBNError, "BN_new");
    if (BN_rand_range(result, bn) <= 0) {
        BN_free(result);
        ossl_raise(eBNError, "BN_rand_range");
    }
    SetBN(obj, result);
    return obj;
}

/*
 * call-seq:
 *    BN.generate_prime(bits, [, safe [, add [, rem]]]) => bn
 *
 * Generates a random prime number of bit length _bits_. If _safe_ is set to
 * +true+, generates a safe prime. If _add_ is specified, generates a prime that
 * fulfills condition <tt>p % add = rem</tt>.
 *
 * === Parameters
 * * _bits_ - integer
 * * _safe_ - boolean
 * * _add_ - BN
 * * _rem_ - BN
 */
static VALUE
ossl_bn_s_generate_prime(int argc, VALUE *argv, VALUE klass)
{
    BIGNUM *add = NULL, *rem = NULL, *result;
    int safe = 1, num;
    VALUE vnum, vsafe, vadd, vrem, obj;

    rb_scan_args(argc, argv, "13", &vnum, &vsafe, &vadd, &vrem);

    num = NUM2INT(vnum);

    if (vsafe == Qfalse) {
	safe = 0;
    }
    if (!NIL_P(vadd)) {
	add = GetBNPtr(vadd);
	rem = NIL_P(vrem) ? NULL : GetBNPtr(vrem);
    }
    obj = NewBN(klass);
    if (!(result = BN_new())) {
	ossl_raise(eBNError, NULL);
    }
    if (!BN_generate_prime_ex(result, num, safe, add, rem, NULL)) {
	BN_free(result);
	ossl_raise(eBNError, NULL);
    }
    SetBN(obj, result);

    return obj;
}

#define BIGNUM_NUM(func)			\
    static VALUE 				\
    ossl_bn_##func(VALUE self)			\
    {						\
	BIGNUM *bn;				\
	GetBN(self, bn);			\
	return INT2NUM(BN_##func(bn));		\
    }

/*
 * Document-method: OpenSSL::BN#num_bytes
 * call-seq:
 *   bn.num_bytes => integer
 */
BIGNUM_NUM(num_bytes)

/*
 * Document-method: OpenSSL::BN#num_bits
 * call-seq:
 *   bn.num_bits => integer
 */
BIGNUM_NUM(num_bits)

static VALUE
ossl_bn_copy(VALUE self, VALUE other)
{
    BIGNUM *bn1, *bn2;

    rb_check_frozen(self);

    if (self == other) return self;

    GetBN(self, bn1);
    bn2 = GetBNPtr(other);

    if (!BN_copy(bn1, bn2)) {
	ossl_raise(eBNError, NULL);
    }
    return self;
}

/*
 * call-seq:
 *   +bn -> aBN
 */
static VALUE
ossl_bn_uplus(VALUE self)
{
    VALUE obj;
    BIGNUM *bn1, *bn2;

    GetBN(self, bn1);
    obj = NewBN(cBN);
    bn2 = BN_dup(bn1);
    if (!bn2)
	ossl_raise(eBNError, "BN_dup");
    SetBN(obj, bn2);

    return obj;
}

/*
 * call-seq:
 *   -bn -> aBN
 */
static VALUE
ossl_bn_uminus(VALUE self)
{
    VALUE obj;
    BIGNUM *bn1, *bn2;

    GetBN(self, bn1);
    obj = NewBN(cBN);
    bn2 = BN_dup(bn1);
    if (!bn2)
	ossl_raise(eBNError, "BN_dup");
    SetBN(obj, bn2);
    BN_set_negative(bn2, !BN_is_negative(bn2));

    return obj;
}

/*
 * call-seq:
 *   bn.abs -> aBN
 */
static VALUE
ossl_bn_abs(VALUE self)
{
    BIGNUM *bn1;

    GetBN(self, bn1);
    if (BN_is_negative(bn1)) {
        return ossl_bn_uminus(self);
    }
    else {
        return ossl_bn_uplus(self);
    }
}

#define BIGNUM_CMP(func)				\
    static VALUE					\
    ossl_bn_##func(VALUE self, VALUE other)		\
    {							\
	BIGNUM *bn1, *bn2 = GetBNPtr(other);		\
	GetBN(self, bn1);				\
	return INT2NUM(BN_##func(bn1, bn2));		\
    }

/*
 * Document-method: OpenSSL::BN#cmp
 * call-seq:
 *   bn.cmp(bn2) => integer
 */
/*
 * Document-method: OpenSSL::BN#<=>
 * call-seq:
 *   bn <=> bn2 => integer
 */
BIGNUM_CMP(cmp)

/*
 * Document-method: OpenSSL::BN#ucmp
 * call-seq:
 *   bn.ucmp(bn2) => integer
 */
BIGNUM_CMP(ucmp)

/*
 *  call-seq:
 *     bn == obj => true or false
 *
 *  Returns +true+ only if _obj_ has the same value as _bn_. Contrast this
 *  with OpenSSL::BN#eql?, which requires obj to be OpenSSL::BN.
 */
static VALUE
ossl_bn_eq(VALUE self, VALUE other)
{
    BIGNUM *bn1, *bn2;

    GetBN(self, bn1);
    other = try_convert_to_bn(other);
    if (NIL_P(other))
	return Qfalse;
    GetBN(other, bn2);

    if (!BN_cmp(bn1, bn2)) {
	return Qtrue;
    }
    return Qfalse;
}

/*
 *  call-seq:
 *     bn.eql?(obj) => true or false
 *
 *  Returns <code>true</code> only if <i>obj</i> is a
 *  <code>OpenSSL::BN</code> with the same value as <i>bn</i>. Contrast this
 *  with OpenSSL::BN#==, which performs type conversions.
 */
static VALUE
ossl_bn_eql(VALUE self, VALUE other)
{
    BIGNUM *bn1, *bn2;

    if (!rb_obj_is_kind_of(other, cBN))
	return Qfalse;
    GetBN(self, bn1);
    GetBN(other, bn2);

    return BN_cmp(bn1, bn2) ? Qfalse : Qtrue;
}

/*
 *  call-seq:
 *     bn.hash => Integer
 *
 *  Returns a hash code for this object.
 *
 *  See also Object#hash.
 */
static VALUE
ossl_bn_hash(VALUE self)
{
    BIGNUM *bn;
    VALUE tmp, hash;
    unsigned char *buf;
    int len;

    GetBN(self, bn);
    len = BN_num_bytes(bn);
    buf = ALLOCV(tmp, len);
    if (BN_bn2bin(bn, buf) != len) {
	ALLOCV_END(tmp);
	ossl_raise(eBNError, "BN_bn2bin");
    }

    hash = ST2FIX(rb_memhash(buf, len));
    ALLOCV_END(tmp);

    return hash;
}

/*
 * call-seq:
 *    bn.prime? => true | false
 *    bn.prime?(checks) => true | false
 *
 * Performs a Miller-Rabin probabilistic primality test for +bn+.
 *
 * <b>+checks+ parameter is deprecated in version 3.0.</b> It has no effect.
 */
static VALUE
ossl_bn_is_prime(int argc, VALUE *argv, VALUE self)
{
    BIGNUM *bn;
    int ret;

    rb_check_arity(argc, 0, 1);
    GetBN(self, bn);

#ifdef HAVE_BN_CHECK_PRIME
    ret = BN_check_prime(bn, ossl_bn_ctx, NULL);
    if (ret < 0)
        ossl_raise(eBNError, "BN_check_prime");
#else
    ret = BN_is_prime_fasttest_ex(bn, BN_prime_checks, ossl_bn_ctx, 1, NULL);
    if (ret < 0)
        ossl_raise(eBNError, "BN_is_prime_fasttest_ex");
#endif
    return ret ? Qtrue : Qfalse;
}

/*
 * call-seq:
 *    bn.prime_fasttest? => true | false
 *    bn.prime_fasttest?(checks) => true | false
 *    bn.prime_fasttest?(checks, trial_div) => true | false
 *
 * Performs a Miller-Rabin probabilistic primality test for +bn+.
 *
 * <b>Deprecated in version 3.0.</b> Use #prime? instead.
 *
 * +checks+ and +trial_div+ parameters no longer have any effect.
 */
static VALUE
ossl_bn_is_prime_fasttest(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 0, 2);
    return ossl_bn_is_prime(0, argv, self);
}

/*
 * call-seq:
 *    bn.get_flags(flags) => flags
 *
 * Returns the flags on the BN object.
 * The argument is used as a bit mask.
 *
 * === Parameters
 * * _flags_ - integer
 */
static VALUE
ossl_bn_get_flags(VALUE self, VALUE arg)
{
    BIGNUM *bn;
    GetBN(self, bn);

    return INT2NUM(BN_get_flags(bn, NUM2INT(arg)));
}

/*
 * call-seq:
 *    bn.set_flags(flags) => nil
 *
 * Enables the flags on the BN object.
 * Currently, the flags argument can contain zero of OpenSSL::BN::CONSTTIME.
 */
static VALUE
ossl_bn_set_flags(VALUE self, VALUE arg)
{
    BIGNUM *bn;
    GetBN(self, bn);

    rb_check_frozen(self);
    BN_set_flags(bn, NUM2INT(arg));
    return Qnil;
}

/*
 * INIT
 * (NOTE: ordering of methods is the same as in 'man bn')
 */
void
Init_ossl_bn(void)
{
#if 0
    mOSSL = rb_define_module("OpenSSL");
    eOSSLError = rb_define_class_under(mOSSL, "OpenSSLError", rb_eStandardError);
#endif

#ifdef HAVE_RB_EXT_RACTOR_SAFE
    ossl_bn_ctx_key = rb_ractor_local_storage_ptr_newkey(&ossl_bn_ctx_key_type);
#else
    ossl_bn_ctx_get();
#endif

    eBNError = rb_define_class_under(mOSSL, "BNError", eOSSLError);

    cBN = rb_define_class_under(mOSSL, "BN", rb_cObject);

    rb_define_alloc_func(cBN, ossl_bn_alloc);
    rb_define_method(cBN, "initialize", ossl_bn_initialize, -1);

    rb_define_method(cBN, "initialize_copy", ossl_bn_copy, 1);
    rb_define_method(cBN, "copy", ossl_bn_copy, 1);

    /* swap (=coerce?) */

    rb_define_method(cBN, "num_bytes", ossl_bn_num_bytes, 0);
    rb_define_method(cBN, "num_bits", ossl_bn_num_bits, 0);
    /* num_bits_word */

    rb_define_method(cBN, "+@", ossl_bn_uplus, 0);
    rb_define_method(cBN, "-@", ossl_bn_uminus, 0);
    rb_define_method(cBN, "abs", ossl_bn_abs, 0);

    rb_define_method(cBN, "+", ossl_bn_add, 1);
    rb_define_method(cBN, "-", ossl_bn_sub, 1);
    rb_define_method(cBN, "*", ossl_bn_mul, 1);
    rb_define_method(cBN, "sqr", ossl_bn_sqr, 0);
    rb_define_method(cBN, "/", ossl_bn_div, 1);
    rb_define_method(cBN, "%", ossl_bn_mod, 1);
    /* nnmod */

    rb_define_method(cBN, "mod_add", ossl_bn_mod_add, 2);
    rb_define_method(cBN, "mod_sub", ossl_bn_mod_sub, 2);
    rb_define_method(cBN, "mod_mul", ossl_bn_mod_mul, 2);
    rb_define_method(cBN, "mod_sqr", ossl_bn_mod_sqr, 1);
    rb_define_method(cBN, "mod_sqrt", ossl_bn_mod_sqrt, 1);
    rb_define_method(cBN, "**", ossl_bn_exp, 1);
    rb_define_method(cBN, "mod_exp", ossl_bn_mod_exp, 2);
    rb_define_method(cBN, "gcd", ossl_bn_gcd, 1);

    /* add_word
     * sub_word
     * mul_word
     * div_word
     * mod_word */

    rb_define_method(cBN, "cmp", ossl_bn_cmp, 1);
    rb_define_alias(cBN, "<=>", "cmp");
    rb_define_method(cBN, "ucmp", ossl_bn_ucmp, 1);
    rb_define_method(cBN, "eql?", ossl_bn_eql, 1);
    rb_define_method(cBN, "hash", ossl_bn_hash, 0);
    rb_define_method(cBN, "==", ossl_bn_eq, 1);
    rb_define_alias(cBN, "===", "==");
    rb_define_method(cBN, "zero?", ossl_bn_is_zero, 0);
    rb_define_method(cBN, "one?", ossl_bn_is_one, 0);
    /* is_word */
    rb_define_method(cBN, "odd?", ossl_bn_is_odd, 0);
    rb_define_method(cBN, "negative?", ossl_bn_is_negative, 0);

    /* zero
     * one
     * value_one - DON'T IMPL.
     * set_word
     * get_word */

    rb_define_singleton_method(cBN, "rand", ossl_bn_s_rand, -1);
    rb_define_singleton_method(cBN, "rand_range", ossl_bn_s_rand_range, 1);
    rb_define_alias(rb_singleton_class(cBN), "pseudo_rand", "rand");
    rb_define_alias(rb_singleton_class(cBN), "pseudo_rand_range", "rand_range");

    rb_define_singleton_method(cBN, "generate_prime", ossl_bn_s_generate_prime, -1);
    rb_define_method(cBN, "prime?", ossl_bn_is_prime, -1);
    rb_define_method(cBN, "prime_fasttest?", ossl_bn_is_prime_fasttest, -1);

    rb_define_method(cBN, "set_bit!", ossl_bn_set_bit, 1);
    rb_define_method(cBN, "clear_bit!", ossl_bn_clear_bit, 1);
    rb_define_method(cBN, "bit_set?", ossl_bn_is_bit_set, 1);
    rb_define_method(cBN, "mask_bits!", ossl_bn_mask_bits, 1);
    rb_define_method(cBN, "<<", ossl_bn_lshift, 1);
    rb_define_method(cBN, ">>", ossl_bn_rshift, 1);
    rb_define_method(cBN, "lshift!", ossl_bn_self_lshift, 1);
    rb_define_method(cBN, "rshift!", ossl_bn_self_rshift, 1);
    /* lshift1 - DON'T IMPL. */
    /* rshift1 - DON'T IMPL. */

    rb_define_method(cBN, "get_flags", ossl_bn_get_flags, 1);
    rb_define_method(cBN, "set_flags", ossl_bn_set_flags, 1);

#ifdef BN_FLG_CONSTTIME
    rb_define_const(cBN, "CONSTTIME", INT2NUM(BN_FLG_CONSTTIME));
#endif
    /* BN_FLG_MALLOCED and BN_FLG_STATIC_DATA seems for C programming.
     * Allowing them leads to memory leak.
     * So, for now, they are not exported
#ifdef BN_FLG_MALLOCED
    rb_define_const(cBN, "MALLOCED", INT2NUM(BN_FLG_MALLOCED));
#endif
#ifdef BN_FLG_STATIC_DATA
    rb_define_const(cBN, "STATIC_DATA", INT2NUM(BN_FLG_STATIC_DATA));
#endif
    */

    /*
     * bn2bin
     * bin2bn
     * bn2hex
     * bn2dec
     * hex2bn
     * dec2bn - all these are implemented in ossl_bn_initialize, and ossl_bn_to_s
     * print - NOT IMPL.
     * print_fp - NOT IMPL.
     * bn2mpi
     * mpi2bn
     */
    rb_define_method(cBN, "to_s", ossl_bn_to_s, -1);
    rb_define_method(cBN, "to_i", ossl_bn_to_i, 0);
    rb_define_alias(cBN, "to_int", "to_i");
    rb_define_method(cBN, "to_bn", ossl_bn_to_bn, 0);
    rb_define_method(cBN, "coerce", ossl_bn_coerce, 1);

    /*
     * TODO:
     * But how to: from_bin, from_mpi? PACK?
     * to_bin
     * to_mpi
     */

    rb_define_method(cBN, "mod_inverse", ossl_bn_mod_inverse, 1);

    /* RECiProcal
     * MONTgomery */
}
