strfilter.c

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// SPDX-License-Identifier: GPL-2.0
#include "util.h"
#include "string2.h"
#include "strfilter.h"

#include <errno.h>
#include "sane_ctype.h"

/* Operators */
static const char *OP_and   = "&";  /* Logical AND */
static const char *OP_or    = "|";  /* Logical OR */
static const char *OP_not   = "!";  /* Logical NOT */

#define is_operator(c)  ((c) == '|' || (c) == '&' || (c) == '!')
#define is_separator(c) (is_operator(c) || (c) == '(' || (c) == ')')

static void strfilter_node__delete(struct strfilter_node *node)
{
    if (node) {
        if (node->p && !is_operator(*node->p))
            zfree((char **)&node->p);
        strfilter_node__delete(node->l);
        strfilter_node__delete(node->r);
        free(node);
    }
}

void strfilter__delete(struct strfilter *filter)
{
    if (filter) {
        strfilter_node__delete(filter->root);
        free(filter);
    }
}

static const char *get_token(const char *s, const char **e)
{
    const char *p;

    while (isspace(*s)) /* Skip spaces */
        s++;

    if (*s == '\0') {
        p = s;
        goto end;
    }

    p = s + 1;
    if (!is_separator(*s)) {
        /* End search */
retry:
        while (*p && !is_separator(*p) && !isspace(*p))
            p++;
        /* Escape and special case: '!' is also used in glob pattern */
        if (*(p - 1) == '\\' || (*p == '!' && *(p - 1) == '[')) {
            p++;
            goto retry;
        }
    }
end:
    *e = p;
    return s;
}

static struct strfilter_node *strfilter_node__alloc(const char *op,
                            struct strfilter_node *l,
                            struct strfilter_node *r)
{
    struct strfilter_node *node = zalloc(sizeof(*node));

    if (node) {
        node->p = op;
        node->l = l;
        node->r = r;
    }

    return node;
}

static struct strfilter_node *strfilter_node__new(const char *s,
                          const char **ep)
{
    struct strfilter_node root, *cur, *last_op;
    const char *e;

    if (!s)
        return NULL;

    memset(&root, 0, sizeof(root));
    last_op = cur = &root;

    s = get_token(s, &e);
    while (*s != '\0' && *s != ')') {
        switch (*s) {
        case '&':   /* Exchg last OP->r with AND */
            if (!cur->r || !last_op->r)
                goto error;
            cur = strfilter_node__alloc(OP_and, last_op->r, NULL);
            if (!cur)
                goto nomem;
            last_op->r = cur;
            last_op = cur;
            break;
        case '|':   /* Exchg the root with OR */
            if (!cur->r || !root.r)
                goto error;
            cur = strfilter_node__alloc(OP_or, root.r, NULL);
            if (!cur)
                goto nomem;
            root.r = cur;
            last_op = cur;
            break;
        case '!':   /* Add NOT as a leaf node */
            if (cur->r)
                goto error;
            cur->r = strfilter_node__alloc(OP_not, NULL, NULL);
            if (!cur->r)
                goto nomem;
            cur = cur->r;
            break;
        case '(':   /* Recursively parses inside the parenthesis */
            if (cur->r)
                goto error;
            cur->r = strfilter_node__new(s + 1, &s);
            if (!s)
                goto nomem;
            if (!cur->r || *s != ')')
                goto error;
            e = s + 1;
            break;
        default:
            if (cur->r)
                goto error;
            cur->r = strfilter_node__alloc(NULL, NULL, NULL);
            if (!cur->r)
                goto nomem;
            cur->r->p = strndup(s, e - s);
            if (!cur->r->p)
                goto nomem;
        }
        s = get_token(e, &e);
    }
    if (!cur->r)
        goto error;
    *ep = s;
    return root.r;
nomem:
    s = NULL;
error:
    *ep = s;
    strfilter_node__delete(root.r);
    return NULL;
}

/*
 * Parse filter rule and return new strfilter.
 * Return NULL if fail, and *ep == NULL if memory allocation failed.
 */
struct strfilter *strfilter__new(const char *rules, const char **err)
{
    struct strfilter *filter = zalloc(sizeof(*filter));
    const char *ep = NULL;

    if (filter)
        filter->root = strfilter_node__new(rules, &ep);

    if (!filter || !filter->root || *ep != '\0') {
        if (err)
            *err = ep;
        strfilter__delete(filter);
        filter = NULL;
    }

    return filter;
}

static int strfilter__append(struct strfilter *filter, bool _or,
                 const char *rules, const char **err)
{
    struct strfilter_node *right, *root;
    const char *ep = NULL;

    if (!filter || !rules)
        return -EINVAL;

    right = strfilter_node__new(rules, &ep);
    if (!right || *ep != '\0') {
        if (err)
            *err = ep;
        goto error;
    }
    root = strfilter_node__alloc(_or ? OP_or : OP_and, filter->root, right);
    if (!root) {
        ep = NULL;
        goto error;
    }

    filter->root = root;
    return 0;

error:
    strfilter_node__delete(right);
    return ep ? -EINVAL : -ENOMEM;
}

int strfilter__or(struct strfilter *filter, const char *rules, const char **err)
{
    return strfilter__append(filter, true, rules, err);
}

int strfilter__and(struct strfilter *filter, const char *rules,
           const char **err)
{
    return strfilter__append(filter, false, rules, err);
}

static bool strfilter_node__compare(struct strfilter_node *node,
                    const char *str)
{
    if (!node || !node->p)
        return false;

    switch (*node->p) {
    case '|':   /* OR */
        return strfilter_node__compare(node->l, str) ||
            strfilter_node__compare(node->r, str);
    case '&':   /* AND */
        return strfilter_node__compare(node->l, str) &&
            strfilter_node__compare(node->r, str);
    case '!':   /* NOT */
        return !strfilter_node__compare(node->r, str);
    default:
        return strglobmatch(str, node->p);
    }
}

/* Return true if STR matches the filter rules */
bool strfilter__compare(struct strfilter *filter, const char *str)
{
    if (!filter)
        return false;
    return strfilter_node__compare(filter->root, str);
}

static int strfilter_node__sprint(struct strfilter_node *node, char *buf);

/* sprint node in parenthesis if needed */
static int strfilter_node__sprint_pt(struct strfilter_node *node, char *buf)
{
    int len;
    int pt = node->r ? 2 : 0;   /* don't need to check node->l */

    if (buf && pt)
        *buf++ = '(';
    len = strfilter_node__sprint(node, buf);
    if (len < 0)
        return len;
    if (buf && pt)
        *(buf + len) = ')';
    return len + pt;
}

static int strfilter_node__sprint(struct strfilter_node *node, char *buf)
{
    int len = 0, rlen;

    if (!node || !node->p)
        return -EINVAL;

    switch (*node->p) {
    case '|':
    case '&':
        len = strfilter_node__sprint_pt(node->l, buf);
        if (len < 0)
            return len;
        __fallthrough;
    case '!':
        if (buf) {
            *(buf + len++) = *node->p;
            buf += len;
        } else
            len++;
        rlen = strfilter_node__sprint_pt(node->r, buf);
        if (rlen < 0)
            return rlen;
        len += rlen;
        break;
    default:
        len = strlen(node->p);
        if (buf)
            strcpy(buf, node->p);
    }

    return len;
}

char *strfilter__string(struct strfilter *filter)
{
    int len;
    char *ret = NULL;

    len = strfilter_node__sprint(filter->root, NULL);
    if (len < 0)
        return NULL;

    ret = malloc(len + 1);
    if (ret)
        strfilter_node__sprint(filter->root, ret);

    return ret;
}