/* 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_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;

            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);
                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)
};