mc/lib/strutil/strescape.c

/*
   Functions for escaping and unescaping strings

   Copyright (C) 2009, 2011
   The Free Software Foundation, Inc.

   Written by:
   Slava Zanko <slavazanko@gmail.com>, 2009;
   Patrick Winnertz <winnie@debian.org>, 2009

   This file is part of the Midnight Commander.

   The Midnight Commander 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.

   The Midnight Commander 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 <config.h>

#include "lib/strescape.h"

/*** global variables ****************************************************************************/

/*** file scope macro definitions ****************************************************************/

/*** file scope type declarations ****************************************************************/

/*** file scope variables ************************************************************************/

static const char ESCAPE_SHELL_CHARS[] = " !#$%()&{}[]`?|<>;*\\\"'";
static const char ESCAPE_REGEX_CHARS[] = "^!#$%()&{}[]`?|<>;*.\\";
static const char ESCAPE_GLOB_CHARS[] = "$*\\?";

/*** file scope functions ************************************************************************/

/*** public functions ****************************************************************************/

char *
strutils_escape (const char *src, gsize src_len, const char *escaped_chars,
                 gboolean escape_non_printable)
{
    GString *ret;
    gsize curr_index;
    /* do NOT break allocation semantics */
    if (src == NULL)
        return NULL;

    if (*src == '\0')
        return strdup ("");

    ret = g_string_new ("");

    if (src_len == (gsize) - 1)
        src_len = strlen (src);

    for (curr_index = 0; curr_index < src_len; curr_index++)
    {
        if (escape_non_printable)
        {
            switch (src[curr_index])
            {
            case '\n':
                g_string_append (ret, "\\n");
                continue;
            case '\t':
                g_string_append (ret, "\\t");
                continue;
            case '\b':
                g_string_append (ret, "\\b");
                continue;
            case '\0':
                g_string_append (ret, "\\0");
                continue;
            }
        }

        if (strchr (escaped_chars, (int) src[curr_index]))
            g_string_append_c (ret, '\\');

        g_string_append_c (ret, src[curr_index]);
    }
    return g_string_free (ret, FALSE);
}

/* --------------------------------------------------------------------------------------------- */
char *
strutils_unescape (const char *src, gsize src_len, const char *unescaped_chars,
                   gboolean unescape_non_printable)
{
    GString *ret;
    gsize curr_index;

    if (src == NULL)
        return NULL;

    if (*src == '\0')
        return strdup ("");

    ret = g_string_sized_new (16);

    if (src_len == (gsize) (-1))
        src_len = strlen (src);
    src_len--;

    for (curr_index = 0; curr_index < src_len; curr_index++)
    {
        if (src[curr_index] != '\\')
        {
            g_string_append_c (ret, src[curr_index]);
            continue;
        }

        curr_index++;

        if (unescaped_chars == ESCAPE_SHELL_CHARS && src[curr_index] == '$')
        {
            /* special case: \$ is used to disallow variable substitution */
            g_string_append_c (ret, '\\');
        }
        else
        {
            if (unescape_non_printable)
            {
                switch (src[curr_index])
                {
                case 'n':
                    g_string_append_c (ret, '\n');
                    continue;
                case 't':
                    g_string_append_c (ret, '\t');
                    continue;
                case 'b':
                    g_string_append_c (ret, '\b');
                    continue;
                case '0':
                    g_string_append_c (ret, '\0');
                    continue;
                }
            }

            if (strchr (unescaped_chars, (int) src[curr_index]) == NULL)
                g_string_append_c (ret, '\\');
        }

        g_string_append_c (ret, src[curr_index]);
    }
    g_string_append_c (ret, src[curr_index]);

    return g_string_free (ret, FALSE);
}

/* --------------------------------------------------------------------------------------------- */

/** To be compatible with the general posix command lines we have to escape
 strings for the command line

 \param src
 string for escaping

 \returns
 return escaped string (which needs to be freed later)
        or NULL when NULL string is passed.
 */
char *
strutils_shell_escape (const char *src)
{
    return strutils_escape (src, -1, ESCAPE_SHELL_CHARS, FALSE);
}

/* --------------------------------------------------------------------------------------------- */

char *
strutils_glob_escape (const char *src)
{
    return strutils_escape (src, -1, ESCAPE_GLOB_CHARS, TRUE);
}

/* --------------------------------------------------------------------------------------------- */

char *
strutils_regex_escape (const char *src)
{
    return strutils_escape (src, -1, ESCAPE_REGEX_CHARS, TRUE);
}

/* --------------------------------------------------------------------------------------------- */

/** Unescape paths or other strings for e.g the internal cd
    shell-unescape within a given buffer (writing to it!)

 \param text
 string for unescaping

 \returns
 return unescaped string (which needs to be freed)
 */
char *
strutils_shell_unescape (const char *text)
{
    return strutils_unescape (text, -1, ESCAPE_SHELL_CHARS, TRUE);
}

/* --------------------------------------------------------------------------------------------- */

char *
strutils_glob_unescape (const char *text)
{
    return strutils_unescape (text, -1, ESCAPE_GLOB_CHARS, TRUE);
}

/* --------------------------------------------------------------------------------------------- */
char *
strutils_regex_unescape (const char *text)
{
    return strutils_unescape (text, -1, ESCAPE_REGEX_CHARS, TRUE);
}

/* --------------------------------------------------------------------------------------------- */

/** Check if char in pointer contain escape'd chars

 \param start
 string for checking

 \param current
 pointer to checked character

 \returns
 return TRUE if string contain escaped chars
 otherwise return FALSE
 */
gboolean
strutils_is_char_escaped (const char *start, const char *current)
{
    int num_esc = 0;

    if (start == NULL || current == NULL || current <= start)
        return FALSE;

    current--;
    while (current >= start && *current == '\\')
    {
        num_esc++;
        current--;
    }
    return (gboolean) num_esc % 2;
}

/* --------------------------------------------------------------------------------------------- */