/*
 * Copyright (C) 2015 Oracle.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, see http://www.gnu.org/copyleft/gpl.txt
 */

#include "smatch.h"
#include "smatch_slist.h"
#include "smatch_extra.h"

static bool is_non_null_array(struct expression *expr)
{
        struct symbol *type;
        struct symbol *sym;
        struct symbol *tmp;
        int i;

        type = get_type(expr);
        if (!type || type->type != SYM_ARRAY)
                return 0;
        if (expr->type == EXPR_SYMBOL)
                return 1;
        if (implied_not_equal(expr, 0))
                return 1;

        /* verify that it's not the first member of the struct */
        if (expr->type != EXPR_DEREF || !expr->member)
                return 0;
        sym = expr_to_sym(expr);
        if (!sym)
                return 0;
        type = get_real_base_type(sym);
        if (!type || type->type != SYM_PTR)
                return 0;
        type = get_real_base_type(type);
        if (type->type != SYM_STRUCT)
                return 0;

        i = 0;
        FOR_EACH_PTR(type->symbol_list, tmp) {
                i++;
                if (!tmp->ident)
                        continue;
                if (strcmp(expr->member->name, tmp->ident->name) == 0) {
                        if (i == 1)
                                return 0;
                        return 1;
                }
        } END_FOR_EACH_PTR(tmp);

        return 0;
}

static bool matches_anonymous_union(struct symbol *sym, const char *member_name)
{
        struct symbol *type, *tmp;

        if (sym->ident)
                return false;
        type = get_real_base_type(sym);
        if (!type || type->type != SYM_UNION)
                return false;

        FOR_EACH_PTR(type->symbol_list, tmp) {
                if (tmp->ident &&
                    strcmp(member_name, tmp->ident->name) == 0) {
                        return true;
                }
        } END_FOR_EACH_PTR(tmp);

        return false;
}

int get_member_offset(struct symbol *type, const char *member_name)
{
        struct symbol *tmp;
        int offset;
        int bits;

        if (!type || type->type != SYM_STRUCT)
                return -1;

        bits = 0;
        offset = 0;
        FOR_EACH_PTR(type->symbol_list, tmp) {
                if (bits_to_bytes(bits + type_bits(tmp)) > tmp->ctype.alignment) {
                        offset += bits_to_bytes(bits);
                        bits = 0;
                }
                offset = ALIGN(offset, tmp->ctype.alignment);
                if (tmp->ident &&
                    strcmp(member_name, tmp->ident->name) == 0) {
                        return offset;
                }
                if (matches_anonymous_union(tmp, member_name))
                        return offset;
                if (!(type_bits(tmp) % 8) && type_bits(tmp) / 8 == type_bytes(tmp))
                        offset += type_bytes(tmp);
                else
                        bits += type_bits(tmp);
        } END_FOR_EACH_PTR(tmp);
        return -1;
}

int get_member_offset_from_deref(struct expression *expr)
{
        struct symbol *type;
        struct ident *member;
        int offset;

        /*
         * FIXME: This doesn't handle foo.u.bar correctly.
         *
         */

        if (expr->type != EXPR_DEREF)  /* hopefully, this doesn't happen */
                return -1;

        if (expr->member_offset >= 0)
                return expr->member_offset;

        member = expr->member;
        if (!member)
                return -1;

        type = get_type(expr->deref);
        if (type_is_ptr(type))
                type = get_real_base_type(type);
        if (!type || type->type != SYM_STRUCT)
                return -1;

        offset = get_member_offset(type, member->name);
        if (offset >= 0)
                expr->member_offset = offset;
        return offset;
}

static void add_offset_to_pointer(struct range_list **rl, int offset)
{
        sval_t min, max, remove, sval;
        struct range_list *orig = *rl;

        /*
         * Ha ha.  Treating zero as a special case means I'm correct at least a
         * tiny fraction of the time.  Which is better than nothing.
         *
         */
        if (offset == 0)
                return;

        if (is_unknown_ptr(orig))
                return;

        /*
         * This function doesn't necessarily work how you might expect...
         *
         * Say you have s64min-(-1),1-s64max and you add 8 then I guess what
         * we want to say is maybe something like 9-s64max.  This shows that the
         * min it could be is 9 which is potentially useful information.  But
         * if we start with (-12),5000000-57777777 and we add 8 then we'd want
         * the result to be (-4),5000008-57777777 but (-4),5000000-57777777 is
         * also probably acceptable.  If you start with s64min-s64max then the
         * result should be 8-s64max.
         *
         */

        /* We do the math on void pointer type, because this isn't "&v + 16" it
         * is &v->sixteenth_byte.
         */
        orig = cast_rl(&ptr_ctype, orig);
        min = sval_type_min(&ptr_ctype);
        min.value = offset;
        max = sval_type_max(&ptr_ctype);

        if (!orig || is_whole_rl(orig)) {
                *rl = alloc_rl(min, max);
                return;
        }

        /* no wrap around */
        max.uvalue = rl_max(orig).uvalue;
        if (max.uvalue > sval_type_max(&ptr_ctype).uvalue - offset) {
                remove = sval_type_max(&ptr_ctype);
                remove.uvalue -= offset;
                orig = remove_range(orig, remove, max);
        }

        sval.type = &int_ctype;
        sval.value = offset;

        *rl = rl_binop(orig, '+', alloc_rl(sval, sval));
}

static struct range_list *where_allocated_rl(struct symbol *sym)
{
        if (!sym)
                return NULL;

        /* This should just be the mtag if it's not on the stack */
        return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
}

static bool handle_fn_address(struct expression *expr, struct range_list **rl)
{
        struct symbol *type;

        if (expr->type == EXPR_PREOP && expr->op == '&')
                expr = strip_expr(expr->unop);

        if (expr->type != EXPR_SYMBOL)
                return false;

        type = get_type(expr);
        if (!type || type->type != SYM_FN)
                return false;

        *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
        return true;
}

int get_address_rl(struct expression *expr, struct range_list **rl)
{
        struct expression *unop;

        /*
         * Ugh...  This function is bad.  It doesn't work where it's supposed to
         * and it does more than it really should.  It shouldn't handle string
         * literals I think...
         *
         * There are several complications.  For arrays and functions the "&foo"
         * "foo" are equivalent.  But the problem is that we're also passing in
         * foo->array[] and foo->fn.
         *
         * Then, when we have foo->bar.baz.one.two; that needs to be handled
         * correctly but right now, it is not.
         *
         */

        expr = strip_expr(expr);
        if (!expr)
                return 0;

        /*
         * For functions &fn and fn are equivalent.  I don't know if this is
         * really the right place to handle it, but let's just get it out of the
         * way for now.
         *
         */
        if (handle_fn_address(expr, rl))
                return 1;

        /*
         * For arrays, &foo->array and foo->array are equivalent.
         *
         */
        if (expr->type == EXPR_PREOP && expr->op == '&') {
                expr = strip_expr(expr->unop);
        } else {
                struct symbol *type;

                type = get_type(expr);
                if (!type || type->type != SYM_ARRAY)
                        return 0;
        }

        if (expr->type == EXPR_SYMBOL) {
                *rl = where_allocated_rl(expr->symbol);
                return 1;
        }

        if (is_array(expr)) {
                struct expression *array;
                struct expression *offset_expr;
                struct range_list *array_rl, *offset_rl, *bytes_rl, *res;
                struct symbol *type;
                sval_t bytes;

                array = get_array_base(expr);
                offset_expr = get_array_offset(expr);

                type = get_type(array);
                type = get_real_base_type(type);
                bytes.type = ssize_t_ctype;
                bytes.uvalue = type_bytes(type);
                bytes_rl = alloc_rl(bytes, bytes);

                get_absolute_rl(array, &array_rl);
                get_absolute_rl(offset_expr, &offset_rl);

                if (type_bytes(type)) {
                        res = rl_binop(offset_rl, '*', bytes_rl);
                        res = rl_binop(res, '+', array_rl);
                        *rl = res;
                        return true;
                }

                if (implied_not_equal(array, 0) ||
                    implied_not_equal(offset_expr, 0)) {
                        *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
                        return 1;
                }

                return 0;
        }

        if (expr->type == EXPR_DEREF && expr->member) {
                struct range_list *unop_rl;
                int offset;

                offset = get_member_offset_from_deref(expr);
                unop = strip_expr(expr->unop);
                if (unop->type == EXPR_PREOP && unop->op == '*')
                        unop = strip_expr(unop->unop);

                if (offset >= 0 &&
                    get_implied_rl(unop, &unop_rl) &&
                    !is_whole_rl(unop_rl)) {
                        *rl = unop_rl;
                        add_offset_to_pointer(rl, offset);
                        return 1;
                }

                if (implied_not_equal(unop, 0) || offset > 0) {
                        *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
                        return 1;
                }

                return 0;
        }

        if (is_non_null_array(expr)) {
                *rl = alloc_rl(array_min_sval, array_max_sval);
                return 1;
        }

        return 0;
}