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/*
* logger-tail.c - return last lines of a file
*
* Copyright (C) 2003-2021 Sébastien Helleu <flashcode@flashtux.org>
*
* This file is part of WeeChat, the extensible chat client.
*
* WeeChat 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.
*
* WeeChat 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 WeeChat. If not, see <https://www.gnu.org/licenses/>.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include "logger.h"
#include "logger-tail.h"
#define LOGGER_TAIL_BUFSIZE 4096
/*
* Searches for last EOL in a string.
*/
const char *
logger_tail_last_eol (const char *string_start, const char *string_ptr)
{
while (string_ptr >= string_start)
{
if ((string_ptr[0] == '\n') || (string_ptr[0] == '\r'))
return string_ptr;
string_ptr--;
}
/* no end-of-line found in string */
return NULL;
}
/*
* Returns last lines of a file.
*
* Note: result must be freed after use with function logger_tail_free().
*/
struct t_logger_line *
logger_tail_file (const char *filename, int n_lines)
{
int fd;
off_t file_length, file_pos;
size_t to_read;
ssize_t bytes_read;
char buf[LOGGER_TAIL_BUFSIZE + 1];
char *ptr_buf, *pos_eol, *part_of_line, *new_part_of_line;
struct t_logger_line *ptr_line, *new_line;
/* open file */
fd = open (filename, O_RDONLY);
if (fd == -1)
return NULL;
/* seek to the end of file */
file_length = lseek (fd, (off_t)0, SEEK_END);
if (file_length <= 0)
{
close (fd);
return NULL;
}
to_read = file_length;
file_pos = file_length - LOGGER_TAIL_BUFSIZE;
if (file_pos < 0)
file_pos = 0;
else
to_read = LOGGER_TAIL_BUFSIZE;
lseek (fd, file_pos, SEEK_SET);
/* loop until we have "n_lines" lines in list */
part_of_line = NULL;
ptr_line = NULL;
while (n_lines > 0)
{
lseek (fd, file_pos, SEEK_SET);
bytes_read = read (fd, buf, to_read);
if (bytes_read <= 0)
{
if (part_of_line)
free (part_of_line);
logger_tail_free (ptr_line);
close (fd);
return NULL;
}
buf[bytes_read] = '\0';
ptr_buf = buf + bytes_read - 1;
while (ptr_buf && (ptr_buf >= buf))
{
pos_eol = (char *)logger_tail_last_eol (buf, ptr_buf);
if ((pos_eol && (pos_eol[1] || part_of_line)) || (file_pos == 0))
{
/* use data and part_of_line (if existing) to build a new line */
if (!pos_eol)
{
ptr_buf = NULL;
pos_eol = buf;
}
else
{
ptr_buf = pos_eol - 1;
pos_eol[0] = '\0';
pos_eol++;
}
if (part_of_line || pos_eol[0])
{
new_line = malloc (sizeof (*new_line));
if (!new_line)
{
logger_tail_free (ptr_line);
ptr_line = NULL;
break;
}
if (part_of_line)
{
new_line->data = malloc ((strlen (pos_eol) +
strlen (part_of_line) + 1));
if (!new_line->data)
{
free (part_of_line);
free (new_line);
logger_tail_free (ptr_line);
close (fd);
return NULL;
}
strcpy (new_line->data, pos_eol);
strcat (new_line->data, part_of_line);
free (part_of_line);
part_of_line = NULL;
}
else
{
new_line->data = strdup (pos_eol);
}
new_line->next_line = ptr_line;
ptr_line = new_line;
n_lines--;
if (n_lines <= 0)
break;
}
}
else if (!pos_eol)
{
/*
* beginning of read buffer reached without EOL, then we
* add string to part_of_line, we'll use that later
*/
if (part_of_line)
{
new_part_of_line = malloc (strlen (buf) + strlen (part_of_line) + 1);
if (!new_part_of_line)
{
free (part_of_line);
logger_tail_free (ptr_line);
close (fd);
return NULL;
}
strcpy (new_part_of_line, buf);
strcat (new_part_of_line, part_of_line);
free (part_of_line);
part_of_line = new_part_of_line;
}
else
{
part_of_line = malloc (strlen (buf) + 1);
strcpy (part_of_line, buf);
}
ptr_buf = NULL;
}
else
ptr_buf = pos_eol - 1;
}
if (file_pos == 0)
break;
to_read = file_pos;
file_pos -= LOGGER_TAIL_BUFSIZE;
if (file_pos < 0)
file_pos = 0;
else
to_read = LOGGER_TAIL_BUFSIZE;
}
if (part_of_line)
free (part_of_line);
close (fd);
return ptr_line;
}
/*
* Frees structure returned by function "logger_tail_file".
*/
void
logger_tail_free (struct t_logger_line *lines)
{
struct t_logger_line *ptr_line, *next_line;
if (!lines)
return;
ptr_line = lines;
while (ptr_line)
{
next_line = ptr_line->next_line;
if (ptr_line->data)
free (ptr_line->data);
free (ptr_line);
ptr_line = next_line;
}
}
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