unicorn/glib_compat/gpattern.c

/* GLIB - Library of useful routines for C programming
 * Copyright (C) 1995-1997, 1999  Peter Mattis, Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 */

#include <string.h>

#include "gpattern.h"

#include "gmacros.h"
#include "gmessages.h"
#include "gmem.h"

/**
 * SECTION:patterns
 * @title: Glob-style pattern matching
 * @short_description: matches strings against patterns containing '*'
 *                     (wildcard) and '?' (joker)
 *
 * The g_pattern_match* functions match a string
 * against a pattern containing '*' and '?' wildcards with similar
 * semantics as the standard glob() function: '*' matches an arbitrary,
 * possibly empty, string, '?' matches an arbitrary character.
 *
 * Note that in contrast to glob(), the '/' character can be matched by
 * the wildcards, there are no '[...]' character ranges and '*' and '?'
 * can not be escaped to include them literally in a pattern.
 *
 * When multiple strings must be matched against the same pattern, it
 * is better to compile the pattern to a #GPatternSpec using
 * g_pattern_spec_new() and use g_pattern_match_string() instead of
 * g_pattern_match_simple(). This avoids the overhead of repeated
 * pattern compilation.
 **/

/**
 * GPatternSpec:
 *
 * A GPatternSpec struct is the 'compiled' form of a pattern. This
 * structure is opaque and its fields cannot be accessed directly.
 */

/* keep enum and structure of gpattern.c and patterntest.c in sync */
typedef enum
{
    G_MATCH_ALL,       /* "*A?A*" */
    G_MATCH_ALL_TAIL,  /* "*A?AA" */
    G_MATCH_HEAD,      /* "AAAA*" */
    G_MATCH_TAIL,      /* "*AAAA" */
    G_MATCH_EXACT,     /* "AAAAA" */
    G_MATCH_LAST
} GMatchType;

struct _GPatternSpec
{
    GMatchType match_type;
    guint      pattern_length;
    guint      min_length;
    guint      max_length;
    gchar     *pattern;
};


/* --- functions --- */
static inline gboolean g_pattern_ph_match (const gchar *match_pattern,
        const gchar *match_string,
        gboolean    *wildcard_reached_p)
{
    const gchar *pattern, *string;
    gchar ch;

    pattern = match_pattern;
    string = match_string;

    ch = *pattern;
    pattern++;
    while (ch)
    {
        switch (ch)
        {
            case '?':
                if (!*string)
                    return FALSE;
                string = string + 1;
                break;

            case '*':
                *wildcard_reached_p = TRUE;
                do
                {
                    ch = *pattern;
                    pattern++;
                    if (ch == '?')
                    {
                        if (!*string)
                            return FALSE;
                        string = string + 1;
                    }
                }
                while (ch == '*' || ch == '?');
                if (!ch)
                    return TRUE;
                do
                {
                    gboolean next_wildcard_reached = FALSE;
                    while (ch != *string)
                    {
                        if (!*string)
                            return FALSE;
                        string = string + 1;
                    }
                    string++;
                    if (g_pattern_ph_match (pattern, string, &next_wildcard_reached))
                        return TRUE;
                    if (next_wildcard_reached)
                        /* the forthcoming pattern substring up to the next wildcard has
                         * been matched, but a mismatch occurred for the rest of the
                         * pattern, following the next wildcard.
                         * there's no need to advance the current match position any
                         * further if the rest pattern will not match.
                         */
                        return FALSE;
                }
                while (*string);
                break;

            default:
                if (ch == *string)
                    string++;
                else
                    return FALSE;
                break;
        }

        ch = *pattern;
        pattern++;
    }

    return *string == 0;
}

static gchar *string_reverse(const gchar *string, gint string_length)
{
    gchar *new_string;
    gint i, j;
    if (string == NULL || string_length <= 0) {
        return NULL;
    }

    new_string = g_new(gchar, string_length + 1);
    if (new_string) {
        for (i = 0; i < string_length; i++) {
            j = string_length - i - 1;
            new_string[j] = string[i];
        }
        new_string[string_length] = 0;
    }

    return new_string;
}

/**
 * g_pattern_match:
 * @pspec: a #GPatternSpec
 * @string_length: the length of @string (in bytes, i.e. strlen(),
 *     not g_utf8_strlen())
 * @string: the UTF-8 encoded string to match
 * @string_reversed: (nullable): the reverse of @string or %NULL
 *
 * Matches a string against a compiled pattern. Passing the correct
 * length of the string given is mandatory. The reversed string can be
 * omitted by passing %NULL, this is more efficient if the reversed
 * version of the string to be matched is not at hand, as
 * g_pattern_match() will only construct it if the compiled pattern
 * requires reverse matches.
 *
 * Note that, if the user code will (possibly) match a string against a
 * multitude of patterns containing wildcards, chances are high that
 * some patterns will require a reversed string. In this case, it's
 * more efficient to provide the reversed string to avoid multiple
 * constructions thereof in the various calls to g_pattern_match().
 *
 * Note also that the reverse of a UTF-8 encoded string can in general
 * not be obtained by g_strreverse(). This works only if the string
 * does not contain any multibyte characters. GLib offers the
 * g_utf8_strreverse() function to reverse UTF-8 encoded strings.
 *
 * Returns: %TRUE if @string matches @pspec
 **/
gboolean g_pattern_match (GPatternSpec *pspec,
        guint         string_length,
        const gchar  *string,
        const gchar  *string_reversed)
{
    g_return_val_if_fail (pspec != NULL, FALSE);
    g_return_val_if_fail (string != NULL, FALSE);

    if (string_length < pspec->min_length ||
            string_length > pspec->max_length)
        return FALSE;

    switch (pspec->match_type)
    {
        gboolean dummy;
        case G_MATCH_ALL:
        return g_pattern_ph_match (pspec->pattern, string, &dummy);
        case G_MATCH_ALL_TAIL:
        if (string_reversed)
            return g_pattern_ph_match (pspec->pattern, string_reversed, &dummy);
        else
        {
            gboolean result;
            gchar *tmp;
            tmp = string_reverse (string, string_length);
            result = g_pattern_ph_match (pspec->pattern, tmp, &dummy);
            g_free (tmp);
            return result;
        }
        case G_MATCH_HEAD:
        if (pspec->pattern_length == string_length)
            return strcmp (pspec->pattern, string) == 0;
        else if (pspec->pattern_length)
            return strncmp (pspec->pattern, string, pspec->pattern_length) == 0;
        else
            return TRUE;
        case G_MATCH_TAIL:
        if (pspec->pattern_length)
            return strcmp (pspec->pattern, string + (string_length - pspec->pattern_length)) == 0;
        else
            return TRUE;
        case G_MATCH_EXACT:
        if (pspec->pattern_length != string_length)
            return FALSE;
        else
            return strcmp (pspec->pattern, string) == 0;
        default:
        g_return_val_if_fail (pspec->match_type < G_MATCH_LAST, FALSE);
        return FALSE;
    }
}

/**
 * g_pattern_spec_new:
 * @pattern: a zero-terminated UTF-8 encoded string
 *
 * Compiles a pattern to a #GPatternSpec.
 *
 * Returns: a newly-allocated #GPatternSpec
 **/
GPatternSpec* g_pattern_spec_new (const gchar *pattern)
{
    GPatternSpec *pspec;
    gboolean seen_joker = FALSE, seen_wildcard = FALSE, more_wildcards = FALSE;
    gint hw_pos = -1, tw_pos = -1, hj_pos = -1, tj_pos = -1;
    gboolean follows_wildcard = FALSE;
    guint pending_jokers = 0;
    const gchar *s;
    gchar *d;
    guint i;

    g_return_val_if_fail (pattern != NULL, NULL);

    /* canonicalize pattern and collect necessary stats */
    pspec = g_new (GPatternSpec, 1);
    pspec->pattern_length = strlen (pattern);
    pspec->min_length = 0;
    pspec->max_length = 0;
    pspec->pattern = g_new (gchar, pspec->pattern_length + 1);
    d = pspec->pattern;
    for (i = 0, s = pattern; *s != 0; s++)
    {
        switch (*s)
        {
            case '*':
                if (follows_wildcard)	/* compress multiple wildcards */
                {
                    pspec->pattern_length--;
                    continue;
                }
                follows_wildcard = TRUE;
                if (hw_pos < 0)
                    hw_pos = i;
                tw_pos = i;
                break;
            case '?':
                pending_jokers++;
                pspec->min_length++;
                pspec->max_length += 4; /* maximum UTF-8 character length */
                continue;
            default:
                for (; pending_jokers; pending_jokers--, i++) {
                    *d++ = '?';
                    if (hj_pos < 0)
                        hj_pos = i;
                    tj_pos = i;
                }
                follows_wildcard = FALSE;
                pspec->min_length++;
                pspec->max_length++;
                break;
        }
        *d++ = *s;
        i++;
    }
    for (; pending_jokers; pending_jokers--) {
        *d++ = '?';
        if (hj_pos < 0)
            hj_pos = i;
        tj_pos = i;
    }
    *d++ = 0;
    seen_joker = hj_pos >= 0;
    seen_wildcard = hw_pos >= 0;
    more_wildcards = seen_wildcard && hw_pos != tw_pos;
    if (seen_wildcard)
        pspec->max_length = UINT_MAX;

    /* special case sole head/tail wildcard or exact matches */
    if (!seen_joker && !more_wildcards)
    {
        if (pspec->pattern[0] == '*')
        {
            pspec->match_type = G_MATCH_TAIL;
            memmove (pspec->pattern, pspec->pattern + 1, --pspec->pattern_length);
            pspec->pattern[pspec->pattern_length] = 0;
            return pspec;
        }
        if (pspec->pattern_length > 0 &&
                pspec->pattern[pspec->pattern_length - 1] == '*')
        {
            pspec->match_type = G_MATCH_HEAD;
            pspec->pattern[--pspec->pattern_length] = 0;
            return pspec;
        }
        if (!seen_wildcard)
        {
            pspec->match_type = G_MATCH_EXACT;
            return pspec;
        }
    }

    /* now just need to distinguish between head or tail match start */
    tw_pos = pspec->pattern_length - 1 - tw_pos;	/* last pos to tail distance */
    tj_pos = pspec->pattern_length - 1 - tj_pos;	/* last pos to tail distance */
    if (seen_wildcard)
        pspec->match_type = tw_pos > hw_pos ? G_MATCH_ALL_TAIL : G_MATCH_ALL;
    else /* seen_joker */
        pspec->match_type = tj_pos > hj_pos ? G_MATCH_ALL_TAIL : G_MATCH_ALL;
    if (pspec->match_type == G_MATCH_ALL_TAIL) {
        gchar *tmp = pspec->pattern;
        pspec->pattern = string_reverse (pspec->pattern, pspec->pattern_length);
        g_free (tmp);
    }
    return pspec;
}

/**
 * g_pattern_spec_free:
 * @pspec: a #GPatternSpec
 *
 * Frees the memory allocated for the #GPatternSpec.
 **/
void g_pattern_spec_free (GPatternSpec *pspec)
{
    g_return_if_fail (pspec != NULL);

    g_free (pspec->pattern);
    g_free (pspec);
}

/**
 * g_pattern_match_string:
 * @pspec: a #GPatternSpec
 * @string: the UTF-8 encoded string to match
 *
 * Matches a string against a compiled pattern. If the string is to be
 * matched against more than one pattern, consider using
 * g_pattern_match() instead while supplying the reversed string.
 *
 * Returns: %TRUE if @string matches @pspec
 **/
gboolean g_pattern_match_string (GPatternSpec *pspec, const gchar  *string)
{
    g_return_val_if_fail (pspec != NULL, FALSE);
    g_return_val_if_fail (string != NULL, FALSE);

    return g_pattern_match (pspec, strlen (string), string, NULL);
}