/* 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.
*/


/* "Virtual memory" operators */
#include "stat_.h" /* get system header early to avoid name clash on Cygwin */
#include "ghost.h"
#include "gsstruct.h"
#include "oper.h"
#include "estack.h"		/* for checking in restore */
#include "ialloc.h"
#include "idict.h"		/* ditto */
#include "igstate.h"
#include "isave.h"
#include "dstack.h"
#include "stream.h"		/* for files.h */
#include "files.h"		/* for e-stack processing */
#include "store.h"
#include "gsmatrix.h"		/* for gsstate.h */
#include "gsstate.h"

/* Define whether we validate memory before/after save/restore. */
/* Note that we only actually do this if DEBUG is set and -Z? is selected. */
static const bool I_VALIDATE_BEFORE_SAVE = true;
static const bool I_VALIDATE_AFTER_SAVE = true;
static const bool I_VALIDATE_BEFORE_RESTORE = true;
static const bool I_VALIDATE_AFTER_RESTORE = true;

gs_private_st_ptrs1(st_vm_save, vm_save_t, "savetype",
                    vm_save_enum_ptrs, vm_save_reloc_ptrs, gsave);

/* Clean up the stacks and validate storage. */
void
ivalidate_clean_spaces(i_ctx_t *i_ctx_p)
{
    if (gs_debug_c('?')) {
        ref_stack_cleanup(&d_stack);
        ref_stack_cleanup(&e_stack);
        ref_stack_cleanup(&o_stack);
        ivalidate_spaces();
    }
}

/* - save <save> */
int
zsave(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    uint space = icurrent_space;
    vm_save_t *vmsave;
    ulong sid;
    int code;
    gs_gstate *prev;

    if (I_VALIDATE_BEFORE_SAVE)
        ivalidate_clean_spaces(i_ctx_p);
    ialloc_set_space(idmemory, avm_local);
    vmsave = ialloc_struct(vm_save_t, &st_vm_save, "zsave");
    ialloc_set_space(idmemory, space);
    if (vmsave == 0)
        return_error(gs_error_VMerror);
    vmsave->gsave = NULL; /* Ensure constructed enough to destroy safely */
    code = alloc_save_state(idmemory, vmsave, &sid);

    if (code < 0 || sid == 0) {
        ifree_object(vmsave, "zsave");
        if (code < 0)
            return code;
        else
            return_error(gs_error_VMerror);
    }
    if_debug2m('u', imemory, "[u]vmsave "PRI_INTPTR", id = %lu\n",
               (intptr_t) vmsave, (ulong) sid);
    code = gs_gsave_for_save(igs, &prev);
    if (code < 0) {
        alloc_save_t *asave;
        int code2;
        /* dorestore() pops the restore operand off the stack,
           despite dorestore() actually having the save state
           passed to it as a C function parameter. So push a
           sacrificial object.
         */
        push(1);
        make_null(op);
        /* We use dorestore() to discard the save state we
           created above.
         */
        asave = alloc_find_save(idmemory, sid);
        code2 = dorestore(i_ctx_p, asave);
        if (code2 < 0) /* shouldn't happen! */
            return_error(gs_error_Fatal);
        return code;
    }
    vmsave->gsave = prev;
    push(1);
    make_tav(op, t_save, 0, saveid, sid);
    if (I_VALIDATE_AFTER_SAVE)
        ivalidate_clean_spaces(i_ctx_p);
    return 0;
}

/* <save> restore - */
static int restore_check_operand(os_ptr, alloc_save_t **, gs_dual_memory_t *);
static int restore_check_stack(const i_ctx_t *i_ctx_p, const ref_stack_t *, const alloc_save_t *, bool);
static void restore_fix_stack(i_ctx_t *i_ctx_p, ref_stack_t *, const alloc_save_t *, bool);

/* Do as many up front checks of the save object as we reasonably can */
int
restore_check_save(i_ctx_t *i_ctx_p, alloc_save_t **asave)
{
    os_ptr op = osp;
    int code = restore_check_operand(op, asave, idmemory);

    if (code < 0)
        return code;
    if_debug2m('u', imemory, "[u]vmrestore "PRI_INTPTR", id = %lu\n",
               (intptr_t) alloc_save_client_data(*asave),
               (ulong) op->value.saveid);
    if (I_VALIDATE_BEFORE_RESTORE)
        ivalidate_clean_spaces(i_ctx_p);
    /* Check the contents of the stacks. */
    osp--;
    {
        int code;

        if ((code = restore_check_stack(i_ctx_p, &o_stack, *asave, false)) < 0 ||
            (code = restore_check_stack(i_ctx_p, &e_stack, *asave, true)) < 0 ||
            (code = restore_check_stack(i_ctx_p, &d_stack, *asave, false)) < 0
            ) {
            osp++;
            return code;
        }
    }
    osp++;
    return 0;
}

/* the semantics of restore differ slightly between Level 1 and
   Level 2 and later - the latter includes restoring the device
   state (whilst Level 1 didn't have "page devices" as such).
   Hence we have two restore operators - one here (Level 1)
   and one in zdevice2.c (Level 2+). For that reason, the
   operand checking and guts of the restore operation are
   separated so both implementations can use them to best
   effect.
 */
int
dorestore(i_ctx_t *i_ctx_p, alloc_save_t *asave)
{
    bool last;
    vm_save_t *vmsave;
    int code;

    osp--;

    /* Reset l_new in all stack entries if the new save level is zero. */
    /* Also do some special fixing on the e-stack. */
    restore_fix_stack(i_ctx_p, &o_stack, asave, false);
    restore_fix_stack(i_ctx_p, &e_stack, asave, true);
    restore_fix_stack(i_ctx_p, &d_stack, asave, false);
    /* Iteratively restore the state of memory, */
    /* also doing a grestoreall at each step. */
    do {
        vmsave = alloc_save_client_data(alloc_save_current(idmemory));
        /* Restore the graphics state. */
        /* The only time vmsave->gsave should be NULL is if we are
           cleaning up after a VMerror during a save operation.
         */
        if (vmsave->gsave != NULL)
            gs_grestoreall_for_restore(igs, vmsave->gsave);
        /*
         * If alloc_save_space decided to do a second save, the vmsave
         * object was allocated one save level less deep than the
         * current level, so ifree_object won't actually free it;
         * however, it points to a gsave object that definitely
         * *has* been freed.  In order not to trip up the garbage
         * collector, we clear the gsave pointer now.
         */
        vmsave->gsave = 0;
        /* Now it's safe to restore the state of memory. */
        code = alloc_restore_step_in(idmemory, asave);
        if (code < 0)
            return code;
        last = code;
    }
    while (!last);
    {
        uint space = icurrent_space;

        ialloc_set_space(idmemory, avm_local);
        ifree_object(vmsave, "zrestore");
        ialloc_set_space(idmemory, space);
    }
    dict_set_top();		/* reload dict stack cache */
    if (I_VALIDATE_AFTER_RESTORE)
        ivalidate_clean_spaces(i_ctx_p);
    /* If the i_ctx_p LockFilePermissions is true, but the userparams */
    /* we just restored is false, we need to make sure that we do not */
    /* cause an 'invalidaccess' in setuserparams. Temporarily set     */
    /* LockFilePermissions false until the gs_lev2.ps can do a        */
    /* setuserparams from the restored userparam dictionary.          */
    /* NOTE: This is safe to do here, since the restore has           */
    /* successfully completed - this should never come before any     */
    /* operation that can trigger an error                            */
    i_ctx_p->LockFilePermissions = false;
    return 0;
}

int
zrestore(i_ctx_t *i_ctx_p)
{
    alloc_save_t *asave;
    int code = restore_check_save(i_ctx_p, &asave);
    if (code < 0)
        return code;

    return dorestore(i_ctx_p, asave);
}

/* Check the operand of a restore. */
static int
restore_check_operand(os_ptr op, alloc_save_t ** pasave,
                      gs_dual_memory_t *idmem)
{
    vm_save_t *vmsave;
    ulong sid;
    alloc_save_t *asave;

    *pasave = NULL;
    check_type(*op, t_save);
    vmsave = r_ptr(op, vm_save_t);
    if (vmsave == 0)		/* invalidated save */
        return_error(gs_error_invalidrestore);
    sid = op->value.saveid;
    asave = alloc_find_save(idmem, sid);
    if (asave == 0)
        return_error(gs_error_invalidrestore);
    *pasave = asave;
    return 0;
}

/* Check a stack to make sure all its elements are older than a save. */
static int
restore_check_stack(const i_ctx_t *i_ctx_p, const ref_stack_t * pstack,
                    const alloc_save_t * asave, bool is_estack)
{
    ref_stack_enum_t rsenum;

    ref_stack_enum_begin(&rsenum, pstack);
    do {
        const ref *stkp = rsenum.ptr;
        uint size = rsenum.size;

        for (; size; stkp++, size--) {
            const void *ptr;

            switch (r_type(stkp)) {
                case t_array:
                    /*
                     * Zero-length arrays are a special case: see the
                     * t_*array case (label rr:) in igc.c:gc_trace.
                     */
                    if (r_size(stkp) == 0) {
                        /*stkp->value.refs = (void *)0;*/
                        continue;
                    }
                    ptr = stkp->value.refs;
                    break;
                case t_dictionary:
                    ptr = stkp->value.pdict;
                    break;
                case t_file:
                    /* Don't check executable or closed literal */
                    /* files on the e-stack. */
                    {
                        stream *s;

                        if (is_estack &&
                            (r_has_attr(stkp, a_executable) ||
                             file_is_invalid(s, stkp))
                            )
                            continue;
                    }
                    ptr = stkp->value.pfile;
                    break;
                case t_name:
                    /* Names are special because of how they are allocated. */
                    if (alloc_name_is_since_save((const gs_memory_t *)pstack->memory,
                                                 stkp, asave))
                        return_error(gs_error_invalidrestore);
                    continue;
                case t_string:
                    /* Don't check empty executable strings */
                    /* on the e-stack. */
                    if (r_size(stkp) == 0 &&
                        r_has_attr(stkp, a_executable) && is_estack
                        )
                        continue;
                    ptr = stkp->value.bytes;
                    break;
                case t_mixedarray:
                case t_shortarray:
                    /* See the t_array case above. */
                    if (r_size(stkp) == 0) {
                        /*stkp->value.packed = (void *)0;*/
                        continue;
                    }
                    ptr = stkp->value.packed;
                    break;
                case t_device:
                    ptr = stkp->value.pdevice;
                    break;
                case t_fontID:
                case t_struct:
                case t_astruct:
                case t_pdfctx:
                    ptr = stkp->value.pstruct;
                    break;
                case t_save:
                    /* See the comment in isave.h regarding the following. */
                    if (i_ctx_p->language_level <= 2)
                        continue;
                    ptr = alloc_find_save(&gs_imemory, stkp->value.saveid);
                    /*
                     * Invalid save objects aren't supposed to be possible
                     * in LL3, but just in case....
                     */
                    if (ptr == 0)
                        return_error(gs_error_invalidrestore);
                    if (ptr == asave)
                        continue;
                    break;
                default:
                    continue;
            }
            if (alloc_is_since_save(ptr, asave))
                return_error(gs_error_invalidrestore);
        }
    } while (ref_stack_enum_next(&rsenum));
    return 0;		/* OK */
}
/*
 * If the new save level is zero, fix up the contents of a stack
 * by clearing the l_new bit in all the entries (since we can't tolerate
 * values with l_new set if the save level is zero).
 * Also, in any case, fix up the e-stack by replacing empty executable
 * strings and closed executable files that are newer than the save
 * with canonical ones that aren't.
 *
 * Note that this procedure is only called if restore_check_stack succeeded.
 */
static void
restore_fix_stack(i_ctx_t *i_ctx_p, ref_stack_t * pstack,
                  const alloc_save_t * asave, bool is_estack)
{
    ref_stack_enum_t rsenum;

    ref_stack_enum_begin(&rsenum, pstack);
    do {
        ref *stkp = rsenum.ptr;
        uint size = rsenum.size;

        for (; size; stkp++, size--) {
            r_clear_attrs(stkp, l_new);		/* always do it, no harm */
            if (is_estack) {
                ref ofile;

                ref_assign(&ofile, stkp);
                switch (r_type(stkp)) {
                    case t_string:
                        if (r_size(stkp) == 0 &&
                            alloc_is_since_save(stkp->value.bytes,
                                                asave)
                            ) {
                            make_empty_const_string(stkp,
                                                    avm_foreign);
                            break;
                        }
                        continue;
                    case t_file:
                        if (alloc_is_since_save(stkp->value.pfile,
                                                asave)
                            ) {
                            make_invalid_file(i_ctx_p, stkp);
                            break;
                        }
                        continue;
                    default:
                        continue;
                }
                r_copy_attrs(stkp, a_all | a_executable,
                             &ofile);
            }
        }
    } while (ref_stack_enum_next(&rsenum));
}

/* - vmstatus <save_level> <vm_used> <vm_maximum> */
static int
zvmstatus(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    gs_memory_status_t mstat, dstat;

    gs_memory_status(imemory, &mstat);
    if (imemory == imemory_global) {
        gs_memory_status_t sstat;

        gs_memory_status(imemory_system, &sstat);
        mstat.allocated += sstat.allocated;
        mstat.used += sstat.used;
    }
    gs_memory_status(imemory->non_gc_memory, &dstat);
    push(3);
    make_int(op - 2, imemory_save_level(iimemory_local));
    make_int(op - 1, mstat.used);
    make_int(op, mstat.allocated + dstat.allocated - dstat.used);
    return 0;
}

/* ------ Non-standard extensions ------ */

/* <save> .forgetsave - */
static int
zforgetsave(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    alloc_save_t *asave;
    vm_save_t *vmsave;
    int code = restore_check_operand(op, &asave, idmemory);

    if (code < 0)
        return 0;
    vmsave = alloc_save_client_data(asave);
    /* Reset l_new in all stack entries if the new save level is zero. */
    restore_fix_stack(i_ctx_p, &o_stack, asave, false);
    restore_fix_stack(i_ctx_p, &e_stack, asave, false);
    restore_fix_stack(i_ctx_p, &d_stack, asave, false);
    /*
     * Forget the gsaves, by deleting the bottom gstate on
     * the current stack and the top one on the saved stack and then
     * concatenating the stacks together.
     */
    {
        gs_gstate *pgs = igs;
        gs_gstate *last;

        while (gs_gstate_saved(last = gs_gstate_saved(pgs)) != 0)
            pgs = last;
        gs_gstate_swap_saved(last, vmsave->gsave);
        gs_grestore(last);
        gs_grestore(last);
    }
    /* Forget the save in the memory manager. */
    code = alloc_forget_save_in(idmemory, asave);
    if (code < 0)
        return code;
    {
        uint space = icurrent_space;

        ialloc_set_space(idmemory, avm_local);
        /* See above for why we clear the gsave pointer here. */
        vmsave->gsave = 0;
        ifree_object(vmsave, "zrestore");
        ialloc_set_space(idmemory, space);
    }
    pop(1);
    return 0;
}

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

const op_def zvmem_op_defs[] =
{
    {"1.forgetsave", zforgetsave},
    {"1restore", zrestore},
    {"0save", zsave},
    {"0vmstatus", zvmstatus},
    op_def_end(0)
};