.TH LIBJ2_J2I_MUL_J2I 3 LIBJ2
.SH NAME
libj2_j2i_mul_j2i \- Calculate product

.SH SYNOPSIS
.nf
#include <libj2.h>

enum libj2_overflow {
	\fILIBJ2_NO_OVERFLOW\fP = 0,
	\fILIBJ2_POSITIVE_OVERFLOW\fP = 1,
	\fILIBJ2_POSITIVE_OVERFLOW_UNKNOWN\fP = 2,
	\fILIBJ2_NEGATIVE_OVERFLOW\fP = -1,
	\fILIBJ2_NEGATIVE_OVERFLOW_UNKNOWN\fP = -2
};

#define \fILIBJ2_OVERFLOW\fP         LIBJ2_POSITIVE_OVERFLOW
#define \fILIBJ2_OVERFLOW_UNKNOWN\fP LIBJ2_POSITIVE_OVERFLOW_UNKNOWN

void \fBlibj2_j2i_mul_j2i\fP(struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
void \fBlibj2_j2i_mul_j2i_to_j2i\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_j2i_mul_ji\fP(struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
void \fBlibj2_j2i_mul_ji_to_j2i\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_ji_mul_j2i_to_j2i\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
void \fBlibj2_ji_mul_ji_to_j2i\fP(intmax_t \fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);

int \fBlibj2_j2i_mul_j2i_overflow\fP(struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
int \fBlibj2_j2i_mul_j2i_to_j2i_overflow\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);
int \fBlibj2_j2i_mul_ji_overflow\fP(struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
int \fBlibj2_j2i_mul_ji_to_j2i_overflow\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP);
int \fBlibj2_ji_mul_j2i_to_j2i_overflow\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP);

int \fBlibj2_j2i_mul_j2i_overflow_p\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
int \fBlibj2_j2i_mul_ji_overflow_p\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
int \fBlibj2_ji_mul_j2i_overflow_p\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP);

enum libj2_overflow \fBlibj2_j2i_mul_j2i_overflow_p_quick\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP);
enum libj2_overflow \fBlibj2_j2i_mul_ji_overflow_p_quick\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP);
enum libj2_overflow \fBlibj2_ji_mul_j2i_overflow_p_quick\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP);

int \fBlibj2_j2i_mul_j2i_to_j2i_overflow_p\fP(const struct libj2_j2i *\fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP, int *\fIr_set\fP);
int \fBlibj2_j2i_mul_ji_to_j2i_overflow_p\fP(const struct libj2_j2i *\fIa\fP, intmax_t \fIb\fP, struct libj2_j2i *\fIr\fP, int *\fIr_set\fP);
int \fBlibj2_ji_mul_j2i_to_j2i_overflow_p\fP(intmax_t \fIa\fP, const struct libj2_j2i *\fIb\fP, struct libj2_j2i *\fIr\fP, int *\fIr_set\fP);

void \fBlibj2_j2u_mul_j2u\fP(struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP);
void \fBlibj2_j2u_mul_j2u_to_j2u\fP(const struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP, struct libj2_j2u *\fIr\fP);
void \fBlibj2_j2u_mul_ju\fP(struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP);
void \fBlibj2_j2u_mul_ju_to_j2u\fP(const struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP, struct libj2_j2u *\fIr\fP);
void \fBlibj2_ju_mul_j2u_to_j2u\fP(uintmax_t \fIa\fP, const struct libj2_j2u *\fIb\fP, struct libj2_j2u *\fIr\fP);
void \fBlibj2_ju_mul_ju_to_j2u\fP(uintmax_t \fIa\fP, uintmax_t \fIb\fP, struct libj2_j2u *\fIr\fP);
void \fBlibj2_j2u_mul_j2u_destructive\fP(struct libj2_j2u *restrict \fIa\fP, struct libj2_j2u *restrict \fIb\fP);

int \fBlibj2_j2u_mul_j2u_overflow\fP(struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP);
int \fBlibj2_j2u_mul_j2u_to_j2u_overflow\fP(const struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP, struct libj2_j2u *\fIr\fP);
int \fBlibj2_j2u_mul_ju_overflow\fP(struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP);
int \fBlibj2_j2u_mul_ju_to_j2u_overflow\fP(const struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP, struct libj2_j2u *\fIr\fP);
int \fBlibj2_ju_mul_j2u_to_j2u_overflow\fP(uintmax_t \fIa\fP, const struct libj2_j2u *\fIb\fP, struct libj2_j2u *\fIr\fP);
int \fBlibj2_j2u_mul_j2u_overflow_destructive\fP(struct libj2_j2u *restrict \fIa\fP, struct libj2_j2u *restrict \fIb\fP);

int \fBlibj2_j2u_mul_j2u_overflow_p\fP(const struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP);
int \fBlibj2_j2u_mul_ju_overflow_p\fP(const struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP);
int \fBlibj2_ju_mul_j2u_overflow_p\fP(uintmax_t \fIa\fP, const struct libj2_j2u *\fIb\fP);

enum libj2_overflow \fBlibj2_j2u_mul_j2u_overflow_p_quick\fP(const struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP);
enum libj2_overflow \fBlibj2_j2u_mul_ju_overflow_p_quick\fP(const struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP);
enum libj2_overflow \fBlibj2_ju_mul_j2u_overflow_p_quick\fP(uintmax_t \fIa\fP, const struct libj2_j2u *\fIb\fP);

int \fBlibj2_j2u_mul_j2u_to_j2u_overflow_p\fP(const struct libj2_j2u *\fIa\fP, const struct libj2_j2u *\fIb\fP, struct libj2_j2u *\fIr\fP, int *\fIr_set\fP);
int \fBlibj2_j2u_mul_ju_to_j2u_overflow_p\fP(const struct libj2_j2u *\fIa\fP, uintmax_t \fIb\fP, struct libj2_j2u *\fIr\fP, int *\fIr_set\fP);
int \fBlibj2_ju_mul_j2u_to_j2u_overflow_p\fP(uintmax_t \fIa\fP, const struct libj2_j2u *\fIb\fP, struct libj2_j2u *\fIr\fP, int *\fIr_set\fP);
.fi
.PP
Link with
.IR -lj2 .

.SH DESCRIPTION
The above listed functions calculate the
product of the values of
.I a
and
.IR b .
The functions with the parameter
.I r
store the result in
.IR r ,
the other functions store the result in
.IR a ,
except the functions
.BR libj2_j2i_mul_j2i_overflow_p (),
.BR libj2_j2i_mul_ji_overflow_p (),
.BR libj2_ji_mul_j2i_overflow_p (),
.BR libj2_j2u_mul_j2u_overflow_p (),
.BR libj2_j2u_mul_ju_overflow_p (),
.BR libj2_ju_mul_j2u_overflow_p (),
.BR libj2_j2i_mul_j2i_overflow_p_quick (),
.BR libj2_j2i_mul_ji_overflow_p_quick (),
.BR libj2_ji_mul_j2i_overflow_p_quick (),
.BR libj2_j2u_mul_j2u_overflow_p_quick (),
.BR libj2_j2u_mul_ju_overflow_p_quick (),
and
.BR libj2_ju_mul_j2u_overflow_p_quick ()
only predict overflow, and do not calculate
the sum, and therefore does store it anywhere.
.PP
Additionally, in situations where the
.BR libj2_j2i_mul_j2i_overflow_p_quick (),
.BR libj2_j2i_mul_ji_overflow_p_quick (),
.BR libj2_ji_mul_j2i_overflow_p_quick (),
.BR libj2_j2u_mul_j2u_overflow_p_quick (),
.BR libj2_j2u_mul_ju_overflow_p_quick (),
and
.BR libj2_ju_mul_j2u_overflow_p_quick ()
functions return
.I LIBJ2_POSITIVE_OVERFLOW_UNKNOWN
or
.IR LIBJ2_NEGATIVE_OVERFLOW_UNKNOWN ,
the
.BR libj2_j2i_mul_j2i_to_j2i_overflow_p ()
.BR libj2_j2i_mul_ji_to_j2i_overflow_p ()
.BR libj2_ji_mul_j2i_to_j2i_overflow_p ()
.BR libj2_j2u_mul_j2u_to_j2u_overflow_p ()
.BR libj2_j2u_mul_ju_to_j2u_overflow_p (),
and
.BR libj2_ju_mul_j2u_to_j2u_overflow_p ()
functions will calculate the product, store it in
.I r
and set
.I *r_set
to 1; in other situations, those functions will
not modify
.I r
but will set
.I *r_set
to 0.
.PP
The value-returning functions (that is, those
with word
.B overflow
in their name), detect arithmetic overflow.
.PP
The result is truncated to the least significant
bits, as many as can be stored, in case of overflow;
that is, modular arithmetics is used.
.PP
The
.BR libj2_j2u_mul_j2u_destructive ()
and
.BR libj2_j2u_mul_j2u_overflow_destructive ()
functions modifies
.I b
arbitrarily, and do not support
.I a
and
.I b
being the same pointer.
.PP
The arguments are assumed to be
.RI non- NULL .

.SH RETURN VALUE
For functions with a return value, the functions
return +1 if the result is positive but too large
to be represented, -1 if the result is negative
(not only possible with functions where the result is a
.BR "struct libj2_j2i" )
but too large, and 0 otherwise.
For the
.BR libj2_j2i_mul_j2i_overflow_p_quick (),
.BR libj2_j2i_mul_ji_overflow_p_quick (),
.BR libj2_ji_mul_j2i_overflow_p_quick (),
.BR libj2_j2u_mul_j2u_overflow_p_quick (),
.BR libj2_j2u_mul_ju_overflow_p_quick (),
and
.BR libj2_ju_mul_j2u_overflow_p_quick ()
functions, the return value is a
.BR "enum libj2_overflow" ,
which may be unsigned, so to check if the
return value was negative, it is best to
first cast it to an integer, or compare it
directly to the negative constants. Additionally,
these functions will return
.I LIBJ2_POSITIVE_OVERFLOW_UNKNOWN
if the result is positive but if could not
be determined without calculating the
product whether the product is too large to
be represented, and
.I LIBJ2_NEGATIVE_OVERFLOW_UNKNOWN
if the result is negative but if could not
be determined without calculating the
product whether the product is too large to
be represented.
.PP
Since the
.BR libj2_j2u_mul_j2u_overflow_p_quick (),
.BR libj2_j2u_mul_ju_overflow_p_quick (),
and
.BR libj2_ju_mul_j2u_overflow_p_quick ()
functions operate on unsigned integers, they
will never return
.I LIBJ2_NEGATIVE_OVERFLOW
or
.IR LIBJ2_NEGATIVE_OVERFLOW_UNKNOWN .

.SH ERRORS
The above listed functions cannot fail.

.SH HISTORY
The
.BR libj2_j2u_mul_j2u (),
.BR libj2_j2u_mul_j2u_to_j2u (),
.BR libj2_j2u_mul_ju (),
.BR libj2_j2u_mul_ju_to_j2u (),
.BR libj2_ju_mul_j2u_to_j2u (),
.BR libj2_ju_mul_ju_to_j2u (),
.BR libj2_j2u_mul_j2u_destructive (),
.BR libj2_j2u_mul_j2u_overflow (),
.BR libj2_j2u_mul_j2u_to_j2u_overflow (),
.BR libj2_j2u_mul_ju_overflow (),
.BR libj2_j2u_mul_ju_to_j2u_overflow (),
.BR libj2_ju_mul_j2u_to_j2u_overflow (),
.BR libj2_j2u_mul_j2u_overflow_destructive (),
.BR libj2_j2u_mul_j2u_overflow_p (),
.BR libj2_j2u_mul_ju_overflow_p (),
.BR libj2_ju_mul_j2u_overflow_p (),
.BR libj2_j2u_mul_j2u_overflow_p_quick (),
.BR libj2_j2u_mul_ju_overflow_p_quick (),
.BR libj2_ju_mul_j2u_overflow_p_quick (),
.BR libj2_j2u_mul_j2u_to_j2u_overflow_p (),
.BR libj2_j2u_mul_ju_to_j2u_overflow_p (),
and
.BR libj2_ju_mul_j2u_to_j2u_overflow_p ()
functions and the
.IR LIBJ2_NO_OVERFLOW ,
.IR LIBJ2_OVERFLOW ,
and
.IR LIBJ2_OVERFLOW_UNKNOWN
constants were added in version 1.0 of
.BR libj2 .
.PP
The
.BR libj2_j2i_mul_j2i (),
.BR libj2_j2i_mul_j2i_to_j2i (),
.BR libj2_j2i_mul_ji (),
.BR libj2_j2i_mul_ji_to_j2i (),
.BR libj2_ji_mul_j2i_to_j2i (),
.BR libj2_ji_mul_ji_to_j2i (),
.BR libj2_j2i_mul_j2i_overflow (),
.BR libj2_j2i_mul_j2i_to_j2i_overflow (),
.BR libj2_j2i_mul_ji_overflow (),
.BR libj2_j2i_mul_ji_to_j2i_overflow (),
.BR libj2_ji_mul_j2i_to_j2i_overflow (),
.BR libj2_j2i_mul_j2i_overflow_p (),
.BR libj2_j2i_mul_ji_overflow_p (),
.BR libj2_ji_mul_j2i_overflow_p (),
.BR libj2_j2i_mul_j2i_overflow_p_quick (),
.BR libj2_j2i_mul_ji_overflow_p_quick (),
.BR libj2_ji_mul_j2i_overflow_p_quick (),
.BR libj2_j2i_mul_j2i_to_j2i_overflow_p (),
.BR libj2_j2i_mul_ji_to_j2i_overflow_p (),
and
.BR libj2_ji_mul_j2i_to_j2i_overflow_p ()
functions and the
.IR LIBJ2_POSITIVE_OVERFLOW ,
.IR LIBJ2_POSITIVE_OVERFLOW_UNKNOWN ,
.IR LIBJ2_NEGATIVE_OVERFLOW ,
and
.IR LIBJ2_NEGATIVE_OVERFLOW_UNKNOWN
constants were added in version 1.1 of
.BR libj2 .

.SH SEE ALSO
.BR libj2 (7),
.BR libj2_j2i_add_j2i (3),
.BR libj2_j2i_sub_j2i (3),
.BR libj2_j2u_sub_j2u (3),
.BR libj2_j2i_divmod_j2i (3)