/* Copyright (C) 2001-2006 artofcode LLC.
   All Rights Reserved.
  
  This file is part of GNU ghostscript

  GNU ghostscript is free software; you can redistribute it and/or
  modify it under the terms of the version 2 of the GNU General Public
  License as published by the Free Software Foundation.

  GNU ghostscript is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  ghostscript; see the file COPYING. If not, write to the Free Software Foundation,
  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

*/

/* $Id: zcontrol.c,v 1.7 2007/08/01 14:26:49 jemarch Exp $ */
/* Control operators */
#include "string_.h"
#include "ghost.h"
#include "stream.h"
#include "oper.h"
#include "estack.h"
#include "files.h"
#include "ipacked.h"
#include "iutil.h"
#include "store.h"

/* Forward references */
private int check_for_exec(const_os_ptr);
private int no_cleanup(i_ctx_t *);
private uint count_exec_stack(i_ctx_t *, bool);
private uint count_to_stopped(i_ctx_t *, long);
private int unmatched_exit(os_ptr, op_proc_t);

/* See the comment in opdef.h for an invariant which allows */
/* more efficient implementation of for, loop, and repeat. */

/* <[test0 body0 ...]> .cond - */
private int cond_continue(i_ctx_t *);
private int
zcond(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep = esp;

    /* Push the array on the e-stack and call the continuation. */
    if (!r_is_array(op))
	return_op_typecheck(op);
    check_execute(*op);
    if ((r_size(op) & 1) != 0)
	return_error(e_rangecheck);
    if (r_size(op) == 0)
	return zpop(i_ctx_p);
    check_estack(3);
    esp = ep += 3;
    ref_assign(ep - 2, op);	/* the cond body */
    make_op_estack(ep - 1, cond_continue);
    array_get(imemory, op, 0L, ep);
    esfile_check_cache();
    pop(1);
    return o_push_estack;
}
private int
cond_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep = esp;
    int code;

    /* The top element of the e-stack is the remaining tail of */
    /* the cond body.  The top element of the o-stack should be */
    /* the (boolean) result of the test that is the first element */
    /* of the tail. */
    check_type(*op, t_boolean);
    if (op->value.boolval) {	/* true */
        array_get(imemory, ep, 1L, ep);
	esfile_check_cache();
	code = o_pop_estack;
    } else if (r_size(ep) > 2) {	/* false */
	const ref_packed *elts = ep->value.packed;

	check_estack(2);
	r_dec_size(ep, 2);
	elts = packed_next(elts);
	elts = packed_next(elts);
	ep->value.packed = elts;
	array_get(imemory, ep, 0L, ep + 2);
	make_op_estack(ep + 1, cond_continue);
	esp = ep + 2;
	esfile_check_cache();
	code = o_push_estack;
    } else {			/* fall off end of cond */
	esp = ep - 1;
	code = o_pop_estack;
    }
    pop(1);			/* get rid of the boolean */
    return code;
}

/* <obj> exec - */
int
zexec(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    int code;

    check_op(1);
    code = check_for_exec(op);
    if (code < 0) {
	return code;
    }
    if (!r_has_attr(op, a_executable)) {
	return 0;	/* shortcut, literal object just gets pushed back */
    }
    check_estack(1);
    ++esp;
    ref_assign(esp, op);
    esfile_check_cache();
    pop(1);
    return o_push_estack;
}

/* <obj1> ... <objn> <n> .execn - */
private int
zexecn(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    uint n, i;
    es_ptr esp_orig;

    check_int_leu(*op, max_uint - 1);
    n = (uint) op->value.intval;
    check_op(n + 1);
    check_estack(n);
    esp_orig = esp;
    for (i = 0; i < n; ++i) {
	const ref *rp = ref_stack_index(&o_stack, (long)(i + 1));

	/* Make sure this object is legal to execute. */
	if (ref_type_uses_access(r_type(rp))) {
	    if (!r_has_attr(rp, a_execute) &&
		r_has_attr(rp, a_executable)
		) {
		esp = esp_orig;
		return_error(e_invalidaccess);
	    }
	}
	/* Executable nulls have a special meaning on the e-stack, */
	/* so since they are no-ops, don't push them. */
	if (!r_has_type_attrs(rp, t_null, a_executable)) {
	    ++esp;
	    ref_assign(esp, rp);
	}
    }
    esfile_check_cache();
    pop(n + 1);
    return o_push_estack;
}

/* <obj> superexec - */
private int end_superexec(i_ctx_t *);
private int
zsuperexec(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep;

    check_op(1);
    if (!r_has_attr(op, a_executable))
	return 0;		/* literal object just gets pushed back */
    check_estack(2);
    ep = esp += 3;
    make_mark_estack(ep - 2, es_other, end_superexec); /* error case */
    make_op_estack(ep - 1,  end_superexec); /* normal case */
    ref_assign(ep, op);
    esfile_check_cache();
    pop(1);
    i_ctx_p->in_superexec++;
    return o_push_estack;
}
private int
end_superexec(i_ctx_t *i_ctx_p)
{
    i_ctx_p->in_superexec--;
    return 0;
}

/* <array> <executable> .runandhide <obj>				*/
/* 	before executing  <executable>, <array> is been removed from	*/
/*	the operand stack and placed on the execstack with attributes	*/
/* 	changed to 'noaccess'.						*/
/* 	After execution, the array will be placed on  the top of the	*/
/*	operand stack (on top of any elemetns pushed by <executable>	*/
/*	for both the normal case and for the error case.		*/
private int end_runandhide(i_ctx_t *);
private int err_end_runandhide(i_ctx_t *);
private int
zrunandhide(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep;

    check_op(2);
    if (!r_is_array(op - 1))
	return_op_typecheck(op);
    if (!r_has_attr(op, a_executable))
	return 0;		/* literal object just gets pushed back */
    check_estack(5);
    ep = esp += 5;
    make_mark_estack(ep - 4, es_other, err_end_runandhide); /* error case */
    make_op_estack(ep - 1,  end_runandhide); /* normal case */
    ref_assign(ep, op);
    /* Store the object we are hiding  and it's current tas.type_attrs */
    /* on the exec stack then change to 'noaccess' */
    make_int(ep - 3, (int)op[-1].tas.type_attrs);
    ref_assign(ep - 2, op - 1);
    r_clear_attrs(ep - 2, a_all);
    /* replace the array with a special kind of mark that has a_read access */
    esfile_check_cache();
    pop(2);
    return o_push_estack;
}
private int
runandhide_restore_hidden(i_ctx_t *i_ctx_p, ref *obj, ref *attrs)
{
    os_ptr op = osp;

    push(1);
    /* restore the hidden_object and its type_attrs */
    ref_assign(op, obj);
    r_clear_attrs(op, a_all);
    r_set_attrs(op, attrs->value.intval);
    return 0;
}

/* - %end_runandhide hiddenobject */
private int
end_runandhide(i_ctx_t *i_ctx_p)
{
    int code;

    if ((code = runandhide_restore_hidden(i_ctx_p, esp, esp - 1)) < 0)
        return code;
    esp -= 2;		/* pop the hidden value and its atributes */
    return o_pop_estack;
}

/* restore hidden object for error returns */
private int
err_end_runandhide(i_ctx_t *i_ctx_p)
{
    int code;

    if ((code = runandhide_restore_hidden(i_ctx_p, esp + 3, esp + 2)) < 0)
        return code;
    return 0;
}

/* <bool> <proc> if - */
int
zif(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_proc(*op);
    check_type(op[-1], t_boolean);
    if (op[-1].value.boolval) {
	check_estack(1);
	++esp;
	ref_assign(esp, op);
	esfile_check_cache();
    }
    pop(2);
    return o_push_estack;
}

/* <bool> <proc_true> <proc_false> ifelse - */
int
zifelse(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_proc(*op);
    check_proc(op[-1]);
    check_type(op[-2], t_boolean);
    check_estack(1);
    ++esp;
    if (op[-2].value.boolval) {
	ref_assign(esp, op - 1);
    } else {
	ref_assign(esp, op);
    }
    esfile_check_cache();
    pop(3);
    return o_push_estack;
}

/* <init> <step> <limit> <proc> for - */
private int
    for_pos_int_continue(i_ctx_t *),
    for_neg_int_continue(i_ctx_t *),
    for_real_continue(i_ctx_t *);
int
zfor(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    register es_ptr ep;
    int code;
    float params[3];

 	/* Mostly undocumented, and somewhat bizarre Adobe behavior discovered	*/
	/* with the CET (28-05) and FTS (124-01) is that the proc is not run	*/
	/* if BOTH the initial value and increment are zero.			*/
    if ((code = float_params(op - 1, 3, params)) < 0)
	return code;
    if ( params[0] == 0.0 && params[1] == 0.0 ) {
	pop(4);		/* don't run the proc */
	return 0;
    }
    check_estack(7);
    ep = esp + 6;
    check_proc(*op);
    /* Push a mark, the control variable set to the initial value, */
    /* the increment, the limit, and the procedure, */
    /* and invoke the continuation operator. */
    if (r_has_type(op - 3, t_integer) &&
	r_has_type(op - 2, t_integer)
	) {
	make_int(ep - 4, op[-3].value.intval);
	make_int(ep - 3, op[-2].value.intval);
	switch (r_type(op - 1)) {
	    case t_integer:
		make_int(ep - 2, op[-1].value.intval);
		break;
	    case t_real:
		make_int(ep - 2, (long)op[-1].value.realval);
		break;
	    default:
		return_op_typecheck(op - 1);
	}
	if (ep[-3].value.intval >= 0)
	    make_op_estack(ep, for_pos_int_continue);
	else
	    make_op_estack(ep, for_neg_int_continue);
    } else {
	make_real(ep - 4, params[0]);
	make_real(ep - 3, params[1]);
	make_real(ep - 2, params[2]);
	make_op_estack(ep, for_real_continue);
    }
    make_mark_estack(ep - 5, es_for, no_cleanup);
    ref_assign(ep - 1, op);
    esp = ep;
    pop(4);
    return o_push_estack;
}
/* Continuation operators for for, separate for positive integer, */
/* negative integer, and real. */
/* Execution stack contains mark, control variable, increment, */
/* limit, and procedure (procedure is topmost.) */
/* Continuation operator for positive integers. */
private int
for_pos_int_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    register es_ptr ep = esp;
    long var = ep[-3].value.intval;

    if (var > ep[-1].value.intval) {
	esp -= 5;		/* pop everything */
	return o_pop_estack;
    }
    push(1);
    make_int(op, var);
    ep[-3].value.intval = var + ep[-2].value.intval;
    ref_assign_inline(ep + 2, ep);	/* saved proc */
    esp = ep + 2;
    return o_push_estack;
}
/* Continuation operator for negative integers. */
private int
for_neg_int_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    register es_ptr ep = esp;
    long var = ep[-3].value.intval;

    if (var < ep[-1].value.intval) {
	esp -= 5;		/* pop everything */
	return o_pop_estack;
    }
    push(1);
    make_int(op, var);
    ep[-3].value.intval = var + ep[-2].value.intval;
    ref_assign(ep + 2, ep);	/* saved proc */
    esp = ep + 2;
    return o_push_estack;
}
/* Continuation operator for reals. */
private int
for_real_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep = esp;
    float var = ep[-3].value.realval;
    float incr = ep[-2].value.realval;

    if (incr >= 0 ? (var > ep[-1].value.realval) :
	(var < ep[-1].value.realval)
	) {
	esp -= 5;		/* pop everything */
	return o_pop_estack;
    }
    push(1);
    ref_assign(op, ep - 3);
    ep[-3].value.realval = var + incr;
    esp = ep + 2;
    ref_assign(ep + 2, ep);	/* saved proc */
    return o_push_estack;
}

/*
 * Here we provide an internal variant of 'for' that enumerates the values
 * A, ((N-1)*A+1*B)/N, ((N-2)*A+2*B)/N, ..., B precisely.  The arguments are
 * A (real), N (integer), and B (real).  We need this for loading caches such
 * as the transfer function cache.
 *
 * NOTE: This computation must match the SAMPLE_LOOP_VALUE macro in gscie.h.
 */
private int for_samples_continue(i_ctx_t *);
/* <first> <count> <last> <proc> %for_samples - */
int
zfor_samples(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep;

    check_type(op[-3], t_real);
    check_type(op[-2], t_integer);
    check_type(op[-1], t_real);
    check_proc(*op);
    check_estack(8);
    ep = esp + 7;
    make_mark_estack(ep - 6, es_for, no_cleanup);
    make_int(ep - 5, 0);
    memcpy(ep - 4, op - 3, 3 * sizeof(ref));
    ref_assign(ep - 1, op);
    make_op_estack(ep, for_samples_continue);
    esp = ep;
    pop(4);
    return o_push_estack;
}
/* Continuation procedure */
private int
for_samples_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    es_ptr ep = esp;
    long var = ep[-4].value.intval;
    float a = ep[-3].value.realval;
    long n = ep[-2].value.intval;
    float b = ep[-1].value.realval;

    if (var > n) {
	esp -= 6;		/* pop everything */
	return o_pop_estack;
    }
    push(1);
    make_real(op, ((n - var) * a + var * b) / n);
    ep[-4].value.intval = var + 1;
    ref_assign_inline(ep + 2, ep);	/* saved proc */
    esp = ep + 2;
    return o_push_estack;
}

/* <int> <proc> repeat - */
private int repeat_continue(i_ctx_t *);
int
zrepeat(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    check_proc(*op);
    check_type(op[-1], t_integer);
    if (op[-1].value.intval < 0)
	return_error(e_rangecheck);
    check_estack(5);
    /* Push a mark, the count, and the procedure, and invoke */
    /* the continuation operator. */
    push_mark_estack(es_for, no_cleanup);
    *++esp = op[-1];
    *++esp = *op;
    make_op_estack(esp + 1, repeat_continue);
    pop(2);
    return repeat_continue(i_ctx_p);
}
/* Continuation operator for repeat */
private int
repeat_continue(i_ctx_t *i_ctx_p)
{
    es_ptr ep = esp;		/* saved proc */

    if (--(ep[-1].value.intval) >= 0) {		/* continue */
	esp += 2;
	ref_assign(esp, ep);
	return o_push_estack;
    } else {			/* done */
	esp -= 3;		/* pop mark, count, proc */
	return o_pop_estack;
    }
}

/* <proc> loop */
private int loop_continue(i_ctx_t *);
private int
zloop(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_proc(*op);
    check_estack(4);
    /* Push a mark and the procedure, and invoke */
    /* the continuation operator. */
    push_mark_estack(es_for, no_cleanup);
    *++esp = *op;
    make_op_estack(esp + 1, loop_continue);
    pop(1);
    return loop_continue(i_ctx_p);
}
/* Continuation operator for loop */
private int
loop_continue(i_ctx_t *i_ctx_p)
{
    register es_ptr ep = esp;	/* saved proc */

    ref_assign(ep + 2, ep);
    esp = ep + 2;
    return o_push_estack;
}

/* - exit - */
private int
zexit(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    ref_stack_enum_t rsenum;
    uint scanned = 0;

    ref_stack_enum_begin(&rsenum, &e_stack);
    do {
	uint used = rsenum.size;
	es_ptr ep = rsenum.ptr + used - 1;
	uint count = used;

	for (; count; count--, ep--)
	    if (r_is_estack_mark(ep))
		switch (estack_mark_index(ep)) {
		    case es_for:
			pop_estack(i_ctx_p, scanned + (used - count + 1));
			return o_pop_estack;
		    case es_stopped:
			return_error(e_invalidexit);	/* not a loop */
		}
	scanned += used;
    } while (ref_stack_enum_next(&rsenum));
    /* No mark, quit.  (per Adobe documentation) */
    push(2);
    return unmatched_exit(op, zexit);
}

/*
 * .stopped pushes the following on the e-stack:
 *      - A mark with type = es_stopped and procedure = no_cleanup.
 *      - The result to be pushed on a normal return.
 *      - The signal mask for .stop.
 *      - The procedure %stopped_push, to handle the normal return case.
 */

/* In the normal (no-error) case, pop the mask from the e-stack, */
/* and move the result to the o-stack. */
private int
stopped_push(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    push(1);
    *op = esp[-1];
    esp -= 3;
    return o_pop_estack;
}

/* - stop - */
/* Equivalent to true 1 .stop. */
/* This is implemented in C because if were a pseudo-operator, */
/* the stacks would get restored in case of an error. */
private int
zstop(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    uint count = count_to_stopped(i_ctx_p, 1L);

    if (count) {
	/*
	 * If there are any t_oparrays on the e-stack, they will pop
	 * any new items from the o-stack.  Wait to push the 'true'
	 * until we have run all the unwind procedures.
	 */
	check_ostack(2);
	pop_estack(i_ctx_p, count);
	op = osp;
	push(1);
	make_true(op);
	return o_pop_estack;
    }
    /* No mark, quit.  (per Adobe documentation) */
    push(2);
    return unmatched_exit(op, zstop);
}

/* <result> <mask> .stop - */
private int
zzstop(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    uint count;

    check_type(*op, t_integer);
    count = count_to_stopped(i_ctx_p, op->value.intval);
    if (count) {
	/*
	 * If there are any t_oparrays on the e-stack, they will pop
	 * any new items from the o-stack.  Wait to push the result
	 * until we have run all the unwind procedures.
	 */
	ref save_result;

	check_op(2);
	save_result = op[-1];
	pop(2);
	pop_estack(i_ctx_p, count);
	op = osp;
	push(1);
	*op = save_result;
	return o_pop_estack;
    }
    /* No mark, quit.  (per Adobe documentation) */
    return unmatched_exit(op, zzstop);
}

/* <obj> stopped <stopped> */
/* Equivalent to false 1 .stopped. */
/* This is implemented in C because if were a pseudo-operator, */
/* the stacks would get restored in case of an error. */
private int
zstopped(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_op(1);
    /* Mark the execution stack, and push the default result */
    /* in case control returns normally. */
    check_estack(5);
    push_mark_estack(es_stopped, no_cleanup);
    ++esp;
    make_false(esp);		/* save the result */
    ++esp;
    make_int(esp, 1);		/* save the signal mask */
    push_op_estack(stopped_push);
    push_op_estack(zexec);	/* execute the operand */
    return o_push_estack;
}

/* <obj> <result> <mask> .stopped <result> */
private int
zzstopped(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    check_type(*op, t_integer);
    check_op(3);
    /* Mark the execution stack, and push the default result */
    /* in case control returns normally. */
    check_estack(5);
    push_mark_estack(es_stopped, no_cleanup);
    *++esp = op[-1];		/* save the result */
    *++esp = *op;		/* save the signal mask */
    push_op_estack(stopped_push);
    push_op_estack(zexec);	/* execute the operand */
    pop(2);
    return o_push_estack;
}

/* <mask> .instopped false */
/* <mask> .instopped <result> true */
private int
zinstopped(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    uint count;

    check_type(*op, t_integer);
    count = count_to_stopped(i_ctx_p, op->value.intval);
    if (count) {
	push(1);
	op[-1] = *ref_stack_index(&e_stack, count - 2);		/* default result */
	make_true(op);
    } else
	make_false(op);
    return 0;
}

/* <include_marks> .countexecstack <int> */
/* - countexecstack <int> */
/* countexecstack is an operator solely for the sake of the Genoa tests. */
private int
zcountexecstack(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    push(1);
    make_int(op, count_exec_stack(i_ctx_p, false));
    return 0;
}
private int
zcountexecstack1(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_type(*op, t_boolean);
    make_int(op, count_exec_stack(i_ctx_p, op->value.boolval));
    return 0;
}

/* <array> <include_marks> .execstack <subarray> */
/* <array> execstack <subarray> */
/* execstack is an operator solely for the sake of the Genoa tests. */
private int execstack_continue(i_ctx_t *);
private int execstack2_continue(i_ctx_t *);
private int
push_execstack(i_ctx_t *i_ctx_p, os_ptr op1, bool include_marks,
	       op_proc_t cont)
{
    uint size;
    /*
     * We can't do this directly, because the interpreter
     * might have cached some state.  To force the interpreter
     * to update the stored state, we push a continuation on
     * the exec stack; the continuation is executed immediately,
     * and does the actual transfer.
     */
    uint depth;

    if (!r_is_array(op1))
	return_op_typecheck(op1);
    /* Check the length before the write access per CET 28-03 */
    size = r_size(op1);
    depth = count_exec_stack(i_ctx_p, include_marks);
    if (depth > size)
	return_error(e_rangecheck);
    check_write(*op1);
    {
	int code = ref_stack_store_check(&e_stack, op1, size, 0);

	if (code < 0)
	    return code;
    }
    check_estack(1);
    r_set_size(op1, depth);
    push_op_estack(cont);
    return o_push_estack;
}
private int
zexecstack(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    return push_execstack(i_ctx_p, op, false, execstack_continue);
}
private int
zexecstack2(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_type(*op, t_boolean);
    return push_execstack(i_ctx_p, op - 1, op->value.boolval, execstack2_continue);
}
/* Continuation operator to do the actual transfer. */
/* r_size(op1) was set just above. */
private int
do_execstack(i_ctx_t *i_ctx_p, bool include_marks, os_ptr op1)
{
    os_ptr op = osp;
    ref *arefs = op1->value.refs;
    uint asize = r_size(op1);
    uint i;
    ref *rq;

    /*
     * Copy elements from the stack to the array,
     * optionally skipping executable nulls.
     * Clear the executable bit in any internal operators, and
     * convert t_structs and t_astructs (which can only appear
     * in connection with stack marks, which means that they will
     * probably be freed when unwinding) to something harmless.
     */
    for (i = 0, rq = arefs + asize; rq != arefs; ++i) {
	const ref *rp = ref_stack_index(&e_stack, (long)i);

	if (r_has_type_attrs(rp, t_null, a_executable) && !include_marks)
	    continue;
	--rq;
	ref_assign_old(op1, rq, rp, "execstack");
	switch (r_type(rq)) {
	    case t_operator: {
		uint opidx = op_index(rq);

		if (opidx == 0 || op_def_is_internal(op_index_def(opidx)))
		    r_clear_attrs(rq, a_executable);
		break;
	    }
	    case t_struct:
	    case t_astruct: {
		const char *tname =
		    gs_struct_type_name_string(
				gs_object_type(imemory, rq->value.pstruct));

		make_const_string(rq, a_readonly | avm_foreign,
				  strlen(tname), (const byte *)tname);
		break;
	    }
	    default:
		;
	}
    }
    pop(op - op1);
    return 0;
}
private int
execstack_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    return do_execstack(i_ctx_p, false, op);
}
private int
execstack2_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    return do_execstack(i_ctx_p, op->value.boolval, op - 1);
}

/* - .needinput - */
private int
zneedinput(i_ctx_t *i_ctx_p)
{
    return e_NeedInput;		/* interpreter will exit to caller */
}

/* <obj> <int> .quit - */
private int
zquit(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;

    check_op(2);
    check_type(*op, t_integer);
    return_error(e_Quit);	/* Interpreter will do the exit */
}

/* - currentfile <file> */
private ref *zget_current_file(i_ctx_t *);
private int
zcurrentfile(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    ref *fp;

    push(1);
    /* Check the cache first */
    if (esfile != 0) {
#ifdef DEBUG
	/* Check that esfile is valid. */
	ref *efp = zget_current_file(i_ctx_p);

	if (esfile != efp) {
	    lprintf2("currentfile: esfile=0x%lx, efp=0x%lx\n",
		     (ulong) esfile, (ulong) efp);
	    ref_assign(op, efp);
	} else
#endif
	    ref_assign(op, esfile);
    } else if ((fp = zget_current_file(i_ctx_p)) == 0) {	/* Return an invalid file object. */
	/* This doesn't make a lot of sense to me, */
	/* but it's what the PostScript manual specifies. */
	make_invalid_file(op);
    } else {
	ref_assign(op, fp);
	esfile_set_cache(fp);
    }
    /* Make the returned value literal. */
    r_clear_attrs(op, a_executable);
    return 0;
}
/* Get the current file from which the interpreter is reading. */
private ref *
zget_current_file(i_ctx_t *i_ctx_p)
{
    ref_stack_enum_t rsenum;

    ref_stack_enum_begin(&rsenum, &e_stack);
    do {
	uint count = rsenum.size;
	es_ptr ep = rsenum.ptr + count - 1;

	for (; count; count--, ep--)
	    if (r_has_type_attrs(ep, t_file, a_executable))
		return ep;
    } while (ref_stack_enum_next(&rsenum));
    return 0;
}

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

/* We need to split the table because of the 16-element limit. */
const op_def zcontrol1_op_defs[] = {
    {"1.cond", zcond},
    {"0countexecstack", zcountexecstack},
    {"1.countexecstack", zcountexecstack1},
    {"0currentfile", zcurrentfile},
    {"1exec", zexec},
    {"1.execn", zexecn},
    {"1execstack", zexecstack},
    {"2.execstack", zexecstack2},
    {"0exit", zexit},
    {"2if", zif},
    {"3ifelse", zifelse},
    {"0.instopped", zinstopped},
    {"0.needinput", zneedinput},
    op_def_end(0)
};
const op_def zcontrol2_op_defs[] = {
    {"4for", zfor},
    {"1loop", zloop},
    {"2.quit", zquit},
    {"2repeat", zrepeat},
    {"0stop", zstop},
    {"1.stop", zzstop},
    {"1stopped", zstopped},
    {"2.stopped", zzstopped},
    op_def_end(0)
};
const op_def zcontrol3_op_defs[] = {
		/* Internal operators */
    {"1%cond_continue", cond_continue},
    {"1%execstack_continue", execstack_continue},
    {"2%execstack2_continue", execstack2_continue},
    {"0%for_pos_int_continue", for_pos_int_continue},
    {"0%for_neg_int_continue", for_neg_int_continue},
    {"0%for_real_continue", for_real_continue},
    {"4%for_samples", zfor_samples},
    {"0%for_samples_continue", for_samples_continue},
    {"0%loop_continue", loop_continue},
    {"0%repeat_continue", repeat_continue},
    {"0%stopped_push", stopped_push},
    {"1superexec", zsuperexec},
    {"0%end_superexec", end_superexec},
    {"2.runandhide", zrunandhide},
    {"0%end_runandhide", end_runandhide},
    op_def_end(0)
};

/* ------ Internal routines ------ */

/*
 * Check the operand of exec or stopped.  Return 0 if OK to execute, or a
 * negative error code.  We emulate an apparent bug in Adobe interpreters,
 * which cause an invalidaccess error when 'exec'ing a noaccess literal
 * (other than dictionaries).  We also match the Adobe interpreters in that
 * we catch noaccess executable objects here, rather than waiting for the
 * interpreter to catch them, so that we can signal the error with the
 * object still on the operand stack.
 */
private bool
check_for_exec(const_os_ptr op)
{
    if (!r_has_attr(op, a_execute) && /* only true if noaccess */
	ref_type_uses_access(r_type(op)) &&
	(r_has_attr(op, a_executable) || !r_has_type(op, t_dictionary))
	) {
	return_error(e_invalidaccess);
    }
    return 0;
}

/* Vacuous cleanup routine */
private int
no_cleanup(i_ctx_t *i_ctx_p)
{
    return 0;
}

/*
 * Count the number of elements on the exec stack, with or without
 * the normally invisible elements (*op is a Boolean that indicates this).
 */
private uint
count_exec_stack(i_ctx_t *i_ctx_p, bool include_marks)
{
    uint count = ref_stack_count(&e_stack);

    if (!include_marks) {
	uint i;

	for (i = count; i--;)
	    if (r_has_type_attrs(ref_stack_index(&e_stack, (long)i),
				 t_null, a_executable))
		--count;
    }
    return count;
}

/*
 * Count the number of elements down to and including the first 'stopped'
 * mark on the e-stack with a given mask.  Return 0 if there is no 'stopped'
 * mark.
 */
private uint
count_to_stopped(i_ctx_t *i_ctx_p, long mask)
{
    ref_stack_enum_t rsenum;
    uint scanned = 0;

    ref_stack_enum_begin(&rsenum, &e_stack);
    do {
	uint used = rsenum.size;
	es_ptr ep = rsenum.ptr + used - 1;
	uint count = used;

	for (; count; count--, ep--) {
	    if (r_is_estack_mark(ep)) {
		if (estack_mark_index(ep) == es_stopped &&
		  (ep[2].value.intval & mask) != 0)
		    return scanned + (used - count + 1);
	    }
	}	
	scanned += used;
    } while (ref_stack_enum_next(&rsenum));
    return 0;
}

/*
 * Pop the e-stack, executing cleanup procedures as needed.
 * We could make this more efficient using ref_stack_enum_*,
 * but it isn't used enough to make this worthwhile.
 */
void
pop_estack(i_ctx_t *i_ctx_p, uint count)
{
    uint idx = 0;
    uint popped = 0;

    esfile_clear_cache();
    for (; idx < count; idx++) {
	ref *ep = ref_stack_index(&e_stack, idx - popped);

	if (r_is_estack_mark(ep)) {
	    ref_stack_pop(&e_stack, idx + 1 - popped);
	    popped = idx + 1;
	    (*real_opproc(ep)) (i_ctx_p);
	}
    }
    ref_stack_pop(&e_stack, count - popped);
}

/*
 * Execute a quit in the case of an exit or stop with no appropriate
 * enclosing control scope (loop or stopped).  The caller has already
 * ensured two free slots on the top of the o-stack.
 */
private int
unmatched_exit(os_ptr op, op_proc_t opproc)
{
    make_oper(op - 1, 0, opproc);
    make_int(op, e_invalidexit);
    return_error(e_Quit);
}
