/* Copyright (C) 1989, 1992, 1993, 1997, 1998, 1999 Aladdin Enterprises.  All rights reserved.

   This file is part of Aladdin Ghostscript.

   Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
   or distributor accepts any responsibility for the consequences of using it,
   or for whether it serves any particular purpose or works at all, unless he
   or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
   License (the "License") for full details.

   Every copy of Aladdin Ghostscript must include a copy of the License,
   normally in a plain ASCII text file named PUBLIC.  The License grants you
   the right to copy, modify and redistribute Aladdin Ghostscript, but only
   under certain conditions described in the License.  Among other things, the
   License requires that the copyright notice and this notice be preserved on
   all copies.
 */

/*$Id: zmath.c $ */
/* Mathematical operators */
#include "math_.h"
#include "ghost.h"
#include "gxfarith.h"
#include "oper.h"
#include "store.h"

/*
 * Many of the procedures in this file are public only so they can be
 * called from the FunctionType 4 interpreter (zfunc4.c).
 */

/*
 * Define the current state of random number generator for operators.  We
 * have to implement this ourselves because the Unix rand doesn't provide
 * anything equivalent to rrand.  Note that the value always lies in the
 * range [0..0x7ffffffe], even if longs are longer than 32 bits.
 *
 * The state must be public so that context switching can save and
 * restore it.  (Even though the Red Book doesn't mention this,
 * we verified with Adobe that this is the case.)
 */
#define zrand_state (i_ctx_p->rand_state)

/* Initialize the random number generator. */
const long rand_state_initial = 1;

/****** NOTE: none of these operators currently ******/
/****** check for floating over- or underflow.	******/

/* <num> sqrt <real> */
int
zsqrt(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    if (num < 0.0)
	return_error(e_rangecheck);
    make_real(op, sqrt(num));
    return 0;
}

/* <num> arccos <real> */
private int
zarccos(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num, result;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    result = acos(num) * radians_to_degrees;
    make_real(op, result);
    return 0;
}

/* <num> arcsin <real> */
private int
zarcsin(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num, result;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    result = asin(num) * radians_to_degrees;
    make_real(op, result);
    return 0;
}

/* <num> <denom> atan <real> */
int
zatan(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double args[2];
    double result;
    int code = num_params(op, 2, args);

    if (code < 0)
	return code;
    if (args[0] == 0) {		/* on X-axis, special case */
	if (args[1] == 0)
	    return_error(e_undefinedresult);
	result = (args[1] < 0 ? 180 : 0);
    } else {
	result = atan2(args[0], args[1]) * radians_to_degrees;
	if (result < 0)
	    result += 360;
    }
    make_real(op - 1, result);
    pop(1);
    return 0;
}

/* <num> cos <real> */
int
zcos(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double angle;
    int code = real_param(op, &angle);

    if (code < 0)
	return code;
    make_real(op, gs_cos_degrees(angle));
    return 0;
}

/* <num> sin <real> */
int
zsin(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double angle;
    int code = real_param(op, &angle);

    if (code < 0)
	return code;
    make_real(op, gs_sin_degrees(angle));
    return 0;
}

/* <base> <exponent> exp <real> */
int
zexp(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double args[2];
    double result;
    double ipart;
    int code = num_params(op, 2, args);

    if (code < 0)
	return code;
    if (args[0] == 0.0 && args[1] == 0.0)
	return_error(e_undefinedresult);
    if (args[0] < 0.0 && modf(args[1], &ipart) != 0.0)
	return_error(e_undefinedresult);
    result = pow(args[0], args[1]);
    make_real(op - 1, result);
    pop(1);
    return 0;
}

/* <posnum> ln <real> */
int
zln(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    if (num <= 0.0)
	return_error(e_rangecheck);
    make_real(op, log(num));
    return 0;
}

/* <posnum> log <real> */
int
zlog(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    double num;
    int code = real_param(op, &num);

    if (code < 0)
	return code;
    if (num <= 0.0)
	return_error(e_rangecheck);
    make_real(op, log10(num));
    return 0;
}

/* - rand <int> */
private int
zrand(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

	/*
	 * We use an algorithm from CACM 31 no. 10, pp. 1192-1201,
	 * October 1988.  According to a posting by Ed Taft on
	 * comp.lang.postscript, Level 2 (Adobe) PostScript interpreters
	 * use this algorithm too:
	 *      x[n+1] = (16807 * x[n]) mod (2^31 - 1)
	 */
#define A 16807
#define M 0x7fffffff
#define Q 127773		/* M / A */
#define R 2836			/* M % A */
    zrand_state = A * (zrand_state % Q) - R * (zrand_state / Q);
    /* Note that zrand_state cannot be 0 here. */
    if (zrand_state <= 0)
	zrand_state += M;
#undef A
#undef M
#undef Q
#undef R
    push(1);
    make_int(op, zrand_state);
    return 0;
}

/* <int> srand - */
private int
zsrand(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    long state;

    check_type(*op, t_integer);
    state = op->value.intval;
#if arch_sizeof_long > 4
    /* Trim the state back to 32 bits. */
    state = (int)state;
#endif
    /*
     * The following somewhat bizarre adjustments are according to
     * public information from Adobe describing their implementation.
     */
    if (state < 1)
	state = -(state % 0x7ffffffe) + 1;
    else if (state > 0x7ffffffe)
	state = 0x7ffffffe;
    zrand_state = state;
    pop(1);
    return 0;
}

/* - rrand <int> */
private int
zrrand(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    push(1);
    make_int(op, zrand_state);
    return 0;
}

/* ------ Initialization procedure ------ */

const op_def zmath_op_defs[] =
{
    {"1arccos", zarccos},	/* extension */
    {"1arcsin", zarcsin},	/* extension */
    {"2atan", zatan},
    {"1cos", zcos},
    {"2exp", zexp},
    {"1ln", zln},
    {"1log", zlog},
    {"0rand", zrand},
    {"0rrand", zrrand},
    {"1sin", zsin},
    {"1sqrt", zsqrt},
    {"1srand", zsrand},
    op_def_end(0)
};
