conky/src/tailhead.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) 2004, Hannu Saransaari and Lauri Hakkarainen
 * Copyright (c) 2005-2021 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 <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <cctype>
#include <cstring>
#include <memory>
#include "common.h"
#include "config.h"
#include "conky.h"
#include "logging.h"
#include "text_object.h"

#define MAX_HEADTAIL_LINES 30
#define DEFAULT_MAX_HEADTAIL_USES 2

struct headtail {
  int wantedlines{0};
  std::string logfile;
  char *buffer{nullptr};
  int current_use{0};
  int max_uses{0};
  int reported{0};

  headtail() = default;

  ~headtail() { free(buffer); }
};

static void tailstring(char *string, int endofstring, int wantedlines) {
  int i, linescounted = 0;

  string[endofstring] = 0;
  if (endofstring > 0) {
    if (string[endofstring - 1] ==
        '\n') {  // work with or without \n at end of file
      string[endofstring - 1] = 0;
    }
    for (i = endofstring - 1; i >= 0 && linescounted < wantedlines; i--) {
      if (string[i] == '\n') { linescounted++; }
    }
    if (i > 0) { strfold(string, i + 2); }
  }
}

void free_tailhead(struct text_object *obj) {
  auto *ht = static_cast<struct headtail *>(obj->data.opaque);
  obj->data.opaque = nullptr;
  delete ht;
}

void init_tailhead(const char *type, const char *arg, struct text_object *obj,
                   void *free_at_crash) {
  unsigned int args;
  auto *ht = new headtail;

  std::unique_ptr<char[]> tmp(new char[DEFAULT_TEXT_BUFFER_SIZE]);
  memset(tmp.get(), 0, DEFAULT_TEXT_BUFFER_SIZE);

  ht->max_uses = DEFAULT_MAX_HEADTAIL_USES;

  // XXX: Buffer overflow ?
  args = sscanf(arg, "%s %d %d", tmp.get(), &ht->wantedlines, &ht->max_uses);
  if (args < 2 || args > 3) {
    free_tailhead(obj);
    CRIT_ERR(obj, free_at_crash,
             "%s needs a file as 1st and a number of lines as 2nd argument",
             type);
  }
  if (ht->max_uses < 1) {
    free_tailhead(obj);
    CRIT_ERR(obj, free_at_crash,
             "invalid arg for %s, next_check must be larger than 0", type);
  }
  if (ht->wantedlines > 0 && ht->wantedlines <= MAX_HEADTAIL_LINES) {
    ht->logfile = to_real_path(tmp.get());
    ht->buffer = nullptr;
    ht->current_use = 0;
  } else {
    free_tailhead(obj);
    CRIT_ERR(obj, free_at_crash,
             "invalid arg for %s, number of lines must be between 1 and %d",
             type, MAX_HEADTAIL_LINES);
  }
  obj->data.opaque = ht;
}

static void print_tailhead(const char *type, struct text_object *obj, char *p,
                           unsigned int p_max_size) {
  int fd, i, endofstring = 0, linescounted = 0;
  FILE *fp;
  struct stat st {};
  auto *ht = static_cast<struct headtail *>(obj->data.opaque);

  if (ht == nullptr) { return; }

  // empty the buffer and reset the counter if we used it the max number of
  // times
  if ((ht->buffer != nullptr) && ht->current_use >= ht->max_uses - 1) {
    free_and_zero(ht->buffer);
    ht->current_use = 0;
  }
  // use the buffer if possible
  if (ht->buffer != nullptr) {
    strncpy(p, ht->buffer, p_max_size);
    ht->current_use++;
  } else {  // otherwise find the needed data
    if (stat(ht->logfile.c_str(), &st) == 0) {
      if (S_ISFIFO(st.st_mode)) {
        fd = open_fifo(ht->logfile.c_str(), &ht->reported);
        if (fd != -1) {
          if (strcmp(type, "head") == 0) {
            for (i = 0; linescounted < ht->wantedlines; i++) {
              if (read(fd, p + i, 1) <= 0) { break; }
              if (p[i] == '\n') { linescounted++; }
            }
            p[i] = 0;
          } else if (strcmp(type, "tail") == 0) {
            i = read(fd, p, p_max_size - 1);
            tailstring(p, i, ht->wantedlines);
          } else {
            CRIT_ERR(nullptr, nullptr,
                     "If you are seeing this then there is a bug in the code, "
                     "report it !");
          }
        }
        close(fd);
      } else {
        fp = open_file(ht->logfile.c_str(), &ht->reported);
        if (fp != nullptr) {
          if (strcmp(type, "head") == 0) {
            for (i = 0; i < ht->wantedlines; i++) {
              if (fgets(p + endofstring, p_max_size - endofstring, fp) ==
                  nullptr) {
                break;
              }
              endofstring = strlen(p);
            }
          } else if (strcmp(type, "tail") == 0) {
            fseek(fp, -static_cast<long>(p_max_size), SEEK_END);
            i = fread(p, 1, p_max_size - 1, fp);
            tailstring(p, i, ht->wantedlines);
          } else {
            CRIT_ERR(nullptr, nullptr,
                     "If you are seeing this then there is a bug in the code, "
                     "report it !");
          }
          fclose(fp);
        }
      }
      ht->buffer = strdup(p);
    } else {
      CRIT_ERR(nullptr, nullptr, "$%s can't find information about %s", type,
               ht->logfile.c_str());
    }
  }
}

void print_head(struct text_object *obj, char *p, unsigned int p_max_size) {
  print_tailhead("head", obj, p, p_max_size);
}

void print_tail(struct text_object *obj, char *p, unsigned int p_max_size) {
  print_tailhead("tail", obj, p, p_max_size);
}

/* FIXME: use something more general (see also tail.c, head.c */
#define BUFSZ 0x1000

void print_lines(struct text_object *obj, char *p, unsigned int p_max_size) {
  static int rep = 0;
  FILE *fp = open_file(obj->data.s, &rep);
  char buf[BUFSZ];
  int j, lines;

  if (fp == nullptr) {
    snprintf(p, p_max_size, "%s", "File Unreadable");
    return;
  }

  lines = 0;
  while (fgets(buf, BUFSZ, fp) != nullptr) {
    for (j = 0; buf[j] != 0; j++) {
      if (buf[j] == '\n') { lines++; }
    }
  }
  snprintf(p, p_max_size, "%d", lines);
  fclose(fp);
}

void print_words(struct text_object *obj, char *p, unsigned int p_max_size) {
  static int rep = 0;
  FILE *fp = open_file(obj->data.s, &rep);
  char buf[BUFSZ];
  int j, words;
  char inword = 0;

  if (fp == nullptr) {
    snprintf(p, p_max_size, "%s", "File Unreadable");
    return;
  }

  words = 0;
  while (fgets(buf, BUFSZ, fp) != nullptr) {
    for (j = 0; buf[j] != 0; j++) {
      if (isspace(static_cast<unsigned char>(buf[j])) == 0) {
        if (inword == 0) {
          words++;
          inword = 1;
        }
      } else {
        inword = 0;
      }
    }
  }
  snprintf(p, p_max_size, "%d", words);
  fclose(fp);
}