conky/src/text_object.cc

/*
 *
 * Conky, a system monitor, based on torsmo
 *
 * Any original torsmo code is licensed under the BSD license
 *
 * All code written since the fork of torsmo is licensed under the GPL
 *
 * Please see COPYING for details
 *
 * Copyright (c) 2005-2019 Brenden Matthews, Philip Kovacs, et. al.
 *	(see AUTHORS)
 * All rights reserved.
 *
 * 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 3 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/licenses/>.
 *
 */
#include "text_object.h"
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include "config.h"
#include "conky.h"
#include "logging.h"

void gen_free_opaque(struct text_object *obj) {
  free_and_zero(obj->data.opaque);
}

int gen_false_iftest(struct text_object *) { return 0; }

void gen_print_nothing(struct text_object *, char *, unsigned int) {
  // literally does nothing
}

void gen_print_obj_data_s(struct text_object *obj, char *p,
                          unsigned int p_max_size) {
  if (obj->data.s == nullptr) { return; }
  snprintf(p, p_max_size, "%s", obj->data.s);
}

/* text_object_list
 *
 * this list is special. it looks like this:
 *  nullptr <-- obj1 <--> obj2 <--> ... <--> objN --> NULL
 *            ^-------root_object----------^
 *             directions are reversed here
 *
 * why this is cool:
 * - root_object points both to the start and end of the list
 * - while traversing, the end of the list is always a nullptr pointer
 *   (this works in BOTH directions)
 */

/* append an object or list of objects to the given root object's list */
int append_object(struct text_object *root, struct text_object *obj) {
  struct text_object *end;

  /* hook in start of list to append */
  end = root->prev;
  obj->prev = end;

  /* update pointers of the list to append to */
  if (end != nullptr) {
    if (end->next != nullptr) {
      CRIT_ERR(nullptr, nullptr, "huston, we have a lift-off");
    }
    end->next = obj;
  } else {
    root->next = obj;
  }

  /* find end of appended list to point root->prev there */
  while (obj->next != nullptr) { obj = obj->next; }
  root->prev = obj;

  return 0;
}

/* ifblock handlers for the object list
 *
 * - each if points to it's else or endif
 * - each else points to it's endif
 *
 */

/* possible ifblock types
 * only used internally, so no need to make this public
 */
enum ifblock_type { IFBLOCK_IF = 1, IFBLOCK_ELSE, IFBLOCK_ENDIF };

/* linked list of ifblock objects, building a stack
 * only used internally, so no need to make this public
 */
struct ifblock_stack_obj {
  enum ifblock_type type;
  struct text_object *obj;
  struct ifblock_stack_obj *next;
};

/* push an ifblock object onto the stack
 * in fact, this does a lot more:
 * - IFBLOCK_IF is just pushed onto the stack
 * - IFBLOCK_ELSE updates the "next" pointer of the upmost
 *   object in the stack and is then pushed onto the stack
 * - IFBLOCK_ENDIF updates the "next" pointer of the upmost
 *   object in the stack and then triggers stack popping of
 *   any optional IFBLOCK_ELSE along with it's IFBLOCK_IF
 */
static int push_ifblock(struct ifblock_stack_obj **ifblock_stack_top,
                        struct text_object *obj, enum ifblock_type type) {
  struct ifblock_stack_obj *stackobj;

  switch (type) {
    case IFBLOCK_ENDIF:
      if ((*ifblock_stack_top) == nullptr) {
        CRIT_ERR(nullptr, nullptr, "got an endif without matching if");
      }
      (*ifblock_stack_top)->obj->ifblock_next = obj;
      /* if there's some else in between, remove and free it */
      if ((*ifblock_stack_top)->type == IFBLOCK_ELSE) {
        stackobj = *ifblock_stack_top;
        *ifblock_stack_top = stackobj->next;
        free(stackobj);
      }
      /* finally remove and free the if object */
      stackobj = *ifblock_stack_top;
      *ifblock_stack_top = stackobj->next;
      free(stackobj);
      break;
    case IFBLOCK_ELSE:
      if ((*ifblock_stack_top) == nullptr) {
        CRIT_ERR(nullptr, nullptr, "got an else without matching if");
      }
      (*ifblock_stack_top)->obj->ifblock_next = obj;
      /* falls through */
    case IFBLOCK_IF:
      stackobj = static_cast<ifblock_stack_obj *>(
          malloc(sizeof(struct ifblock_stack_obj)));
      stackobj->type = type;
      stackobj->obj = obj;
      stackobj->next = *ifblock_stack_top;
      *ifblock_stack_top = stackobj;
      break;
    default:
      CRIT_ERR(nullptr, nullptr, "push_ifblock() missuse detected!");
  }
  return 0;
}

/* public functions for client use */

int obj_be_ifblock_if(void **opaque, struct text_object *obj) {
  return push_ifblock(reinterpret_cast<struct ifblock_stack_obj **>(opaque),
                      obj, IFBLOCK_IF);
}
int obj_be_ifblock_else(void **opaque, struct text_object *obj) {
  return push_ifblock(reinterpret_cast<struct ifblock_stack_obj **>(opaque),
                      obj, IFBLOCK_ELSE);
}
int obj_be_ifblock_endif(void **opaque, struct text_object *obj) {
  return push_ifblock(reinterpret_cast<struct ifblock_stack_obj **>(opaque),
                      obj, IFBLOCK_ENDIF);
}

/* check if ifblock stack is empty
 * if so, return true (!= 0)
 */
int ifblock_stack_empty(void **opaque) {
  return static_cast<int>(*opaque == nullptr);
}

void obj_be_plain_text(struct text_object *obj, const char *text) {
  obj->data.s = strdup(text);

  memset(&obj->callbacks, 0, sizeof(obj->callbacks));
  obj->callbacks.print = &gen_print_obj_data_s;
  obj->callbacks.free = &gen_free_opaque;
}