/* Copyright (C) 2001-2023 Artifex Software, Inc.

   All Rights Reserved.

   This software is provided AS-IS with no warranty, either express or

   implied.

   This software is distributed under license and may not be copied,

   modified or distributed except as expressly authorized under the terms

   of the license contained in the file LICENSE in this distribution.

   Refer to licensing information at http://www.artifex.com or contact

   Artifex Software, Inc.,  39 Mesa Street, Suite 108A, San Francisco,

   CA 94129, USA, for further information.

*/

/* Operand stack operators */

#include "memory_.h"

#include "ghost.h"

#include "ialloc.h"

#include "istack.h"

#include "oper.h"

#include "store.h"

/* <obj> pop - */

int

zpop(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    check_op(1);

    pop(1);

    return 0;

}

/* <obj1> <obj2> exch <obj2> <obj1> */

int

zexch(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    ref next;

    check_op(2);

    ref_assign_inline(&next, op - 1);

    ref_assign_inline(op - 1, op);

    ref_assign_inline(op, &next);

    return 0;

}

/* <obj> dup <obj> <obj> */

int

zdup(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    check_op(1);

    push(1);

    ref_assign_inline(op, op - 1);

    return 0;

}

/* <obj_n> ... <obj_0> <n> index <obj_n> ... <obj_0> <obj_n> */

int

zindex(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    register os_ptr opn;

    check_op(1);

    check_type(*op, t_integer);

    if ((ulong)op->value.intval >= (ulong)(op - osbot)) {

        /* Might be in an older stack block. */

        ref *elt;

        if (op->value.intval < 0)

            return_error(gs_error_rangecheck);

        elt = ref_stack_index(&o_stack, op->value.intval + 1);

        if (elt == 0)

            return_error(gs_error_stackunderflow);

        ref_assign(op, elt);

        return 0;

    }

    opn = op + ~(int)op->value.intval;

    ref_assign_inline(op, opn);

    return 0;

}

/* <obj_n> ... <obj_0> <n> .argindex <obj_n> ... <obj_0> <obj_n> */

static int

zargindex(i_ctx_t *i_ctx_p)

{

    int code = zindex(i_ctx_p);

    /*

     * Pseudo-operators should use .argindex rather than index to access

     * their arguments on the stack, so that if there aren't enough, the

     * result will be a stackunderflow rather than a rangecheck.  (This is,

     * in fact, the only reason this operator exists.)

     */

    if (code == gs_error_rangecheck && osp->value.intval >= 0)

        code = gs_note_error(gs_error_stackunderflow);

    return code;

}

/* <obj_n-1> ... <obj_0> <n> <i> roll */

/*      <obj_(i-1)_mod_ n> ... <obj_0> <obj_n-1> ... <obj_i_mod_n> */

int

zroll(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    os_ptr op1 = op - 1;

    int count, mod;

    register os_ptr from, to;

    register int n;

    check_type(*op1, t_integer);

    check_type(*op, t_integer);

    if ((uint) op1->value.intval > (uint)(op1 - osbot)) {

        /*

         * The data might span multiple stack blocks.

         * There are efficient ways to handle this situation,

         * but they're more complicated than seems worth implementing;

         * for now, do something very simple and inefficient.

         */

        int left, i;

        if (op1->value.intval < 0)

            return_error(gs_error_rangecheck);

        if (op1->value.intval + 2 > (int)ref_stack_count(&o_stack))

            return_error(gs_error_stackunderflow);

        count = op1->value.intval;

        if (count <= 1) {

            pop(2);

            return 0;

        }

        mod = op->value.intval;

        if (mod >= count)

            mod %= count;

        else if (mod < 0) {

            mod %= count;

            if (mod < 0)

                mod += count; /* can't assume % means mod! */

        }

        /* Use the chain rotation algorithm mentioned below. */

        for (i = 0, left = count; left; i++) {

            ref *elt = ref_stack_index(&o_stack, i + 2);

            ref save;

            int j, k;

            ref *next;

            if (elt == NULL)

                return_error(gs_error_stackunderflow);

            save = *elt;

            for (j = i, left--;; j = k, elt = next, left--) {

                k = (j + mod) % count;

                if (k == i)

                    break;

                next = ref_stack_index(&o_stack, k + 2);

                if (next == NULL)

                    return_error(gs_error_stackunderflow);

                ref_assign(elt, next);

            }

            *elt = save;

        }

        pop(2);

        return 0;

    }

    count = op1->value.intval;

    if (count <= 1) {

        pop(2);

        return 0;

    }

    mod = op->value.intval;

    /*

     * The elegant approach, requiring no extra space, would be to

     * rotate the elements in chains separated by mod elements.

     * Instead, we simply check to make sure there is enough space

     * above op to do the roll in two block moves.

     * Unfortunately, we can't count on memcpy doing the right thing

     * in *either* direction.

     */

    switch (mod) {

        case 1:   /* common special case */

            pop(2);

            op -= 2;

            {

                ref top;

                ref_assign_inline(&top, op);

                for (from = op, n = count; --n; from--)

                    ref_assign_inline(from, from - 1);

                ref_assign_inline(from, &top);

            }

            return 0;

        case -1:    /* common special case */

            pop(2);

            op -= 2;

            {

                ref bot;

                to = op - count + 1;

                ref_assign_inline(&bot, to);

                for (n = count; --n; to++)

                    ref_assign(to, to + 1);

                ref_assign_inline(to, &bot);

            }

            return 0;

    }

    if (mod < 0) {

        mod += count;

        if (mod < 0) {

            mod %= count;

            if (mod < 0)

                mod += count; /* can't assume % means mod! */

        }

    } else if (mod >= count)

        mod %= count;

    if (mod <= count >> 1) {

        /* Move everything up, then top elements down. */

        if (mod >= ostop - op) {

            o_stack.requested = mod;

            return_error(gs_error_stackoverflow);

        }

        pop(2);

        op -= 2;

        for (to = op + mod, from = op, n = count; n--; to--, from--)

            ref_assign(to, from);

        memcpy((char *)(from + 1), (char *)(op + 1), mod * sizeof(ref));

    } else {

        /* Move bottom elements up, then everything down. */

        mod = count - mod;

        if (mod >= ostop - op) {

            o_stack.requested = mod;

            return_error(gs_error_stackoverflow);

        }

        pop(2);

        op -= 2;

        to = op - count + 1;

        memcpy((char *)(op + 1), (char *)to, mod * sizeof(ref));

        for (from = to + mod, n = count; n--; to++, from++)

            ref_assign(to, from);

    }

    return 0;

}

/* |- ... clear |- */

/* The function name is changed, because the IRIS library has */

/* a function called zclear. */

static int

zclear_stack(i_ctx_t *i_ctx_p)

{

    ref_stack_clear(&o_stack);

    return 0;

}

/* |- <obj_n-1> ... <obj_0> count <obj_n-1> ... <obj_0> <n> */

static int

zcount(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    push(1);

    make_int(op, ref_stack_count(&o_stack) - 1);

    return 0;

}

/* - mark <mark> */

static int

zmark(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    push(1);

    make_mark(op);

    return 0;

}

/* <mark> ... cleartomark */

int

zcleartomark(i_ctx_t *i_ctx_p)

{

    uint count = ref_stack_counttomark(&o_stack);

    if (count == 0)

        return_error(gs_error_unmatchedmark);

    ref_stack_pop(&o_stack, count);

    return 0;

}

/* <mark> <obj_n-1> ... <obj_0> counttomark */

/*      <mark> <obj_n-1> ... <obj_0> <n> */

static int

zcounttomark(i_ctx_t *i_ctx_p)

{

    os_ptr op = osp;

    uint count = ref_stack_counttomark(&o_stack);

    if (count == 0)

        return_error(gs_error_unmatchedmark);

    push(1);

    make_int(op, count - 1);

    return 0;

}

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

const op_def zstack_op_defs[] =

{

    {"2.argindex", zargindex},

    {"0clear", zclear_stack},

    {"0cleartomark", zcleartomark},

    {"0count", zcount},

    {"0counttomark", zcounttomark},

    {"1dup", zdup},

    {"2exch", zexch},

    {"2index", zindex},

    {"0mark", zmark},

    {"1pop", zpop},

    {"2roll", zroll},

    op_def_end(0)

};