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1 #include "util.h"
2 #include "string.h"
3 #include "strfilter.h"
4 
5 /* Operators */
6 static const char *OP_and	= "&";	/* Logical AND */
7 static const char *OP_or	= "|";	/* Logical OR */
8 static const char *OP_not	= "!";	/* Logical NOT */
9 
10 #define is_operator(c)	((c) == '|' || (c) == '&' || (c) == '!')
11 #define is_separator(c)	(is_operator(c) || (c) == '(' || (c) == ')')
12 
strfilter_node__delete(struct strfilter_node * self)13 static void strfilter_node__delete(struct strfilter_node *self)
14 {
15 	if (self) {
16 		if (self->p && !is_operator(*self->p))
17 			free((char *)self->p);
18 		strfilter_node__delete(self->l);
19 		strfilter_node__delete(self->r);
20 		free(self);
21 	}
22 }
23 
strfilter__delete(struct strfilter * self)24 void strfilter__delete(struct strfilter *self)
25 {
26 	if (self) {
27 		strfilter_node__delete(self->root);
28 		free(self);
29 	}
30 }
31 
get_token(const char * s,const char ** e)32 static const char *get_token(const char *s, const char **e)
33 {
34 	const char *p;
35 
36 	while (isspace(*s))	/* Skip spaces */
37 		s++;
38 
39 	if (*s == '\0') {
40 		p = s;
41 		goto end;
42 	}
43 
44 	p = s + 1;
45 	if (!is_separator(*s)) {
46 		/* End search */
47 retry:
48 		while (*p && !is_separator(*p) && !isspace(*p))
49 			p++;
50 		/* Escape and special case: '!' is also used in glob pattern */
51 		if (*(p - 1) == '\\' || (*p == '!' && *(p - 1) == '[')) {
52 			p++;
53 			goto retry;
54 		}
55 	}
56 end:
57 	*e = p;
58 	return s;
59 }
60 
strfilter_node__alloc(const char * op,struct strfilter_node * l,struct strfilter_node * r)61 static struct strfilter_node *strfilter_node__alloc(const char *op,
62 						    struct strfilter_node *l,
63 						    struct strfilter_node *r)
64 {
65 	struct strfilter_node *ret = zalloc(sizeof(struct strfilter_node));
66 
67 	if (ret) {
68 		ret->p = op;
69 		ret->l = l;
70 		ret->r = r;
71 	}
72 
73 	return ret;
74 }
75 
strfilter_node__new(const char * s,const char ** ep)76 static struct strfilter_node *strfilter_node__new(const char *s,
77 						  const char **ep)
78 {
79 	struct strfilter_node root, *cur, *last_op;
80 	const char *e;
81 
82 	if (!s)
83 		return NULL;
84 
85 	memset(&root, 0, sizeof(root));
86 	last_op = cur = &root;
87 
88 	s = get_token(s, &e);
89 	while (*s != '\0' && *s != ')') {
90 		switch (*s) {
91 		case '&':	/* Exchg last OP->r with AND */
92 			if (!cur->r || !last_op->r)
93 				goto error;
94 			cur = strfilter_node__alloc(OP_and, last_op->r, NULL);
95 			if (!cur)
96 				goto nomem;
97 			last_op->r = cur;
98 			last_op = cur;
99 			break;
100 		case '|':	/* Exchg the root with OR */
101 			if (!cur->r || !root.r)
102 				goto error;
103 			cur = strfilter_node__alloc(OP_or, root.r, NULL);
104 			if (!cur)
105 				goto nomem;
106 			root.r = cur;
107 			last_op = cur;
108 			break;
109 		case '!':	/* Add NOT as a leaf node */
110 			if (cur->r)
111 				goto error;
112 			cur->r = strfilter_node__alloc(OP_not, NULL, NULL);
113 			if (!cur->r)
114 				goto nomem;
115 			cur = cur->r;
116 			break;
117 		case '(':	/* Recursively parses inside the parenthesis */
118 			if (cur->r)
119 				goto error;
120 			cur->r = strfilter_node__new(s + 1, &s);
121 			if (!s)
122 				goto nomem;
123 			if (!cur->r || *s != ')')
124 				goto error;
125 			e = s + 1;
126 			break;
127 		default:
128 			if (cur->r)
129 				goto error;
130 			cur->r = strfilter_node__alloc(NULL, NULL, NULL);
131 			if (!cur->r)
132 				goto nomem;
133 			cur->r->p = strndup(s, e - s);
134 			if (!cur->r->p)
135 				goto nomem;
136 		}
137 		s = get_token(e, &e);
138 	}
139 	if (!cur->r)
140 		goto error;
141 	*ep = s;
142 	return root.r;
143 nomem:
144 	s = NULL;
145 error:
146 	*ep = s;
147 	strfilter_node__delete(root.r);
148 	return NULL;
149 }
150 
151 /*
152  * Parse filter rule and return new strfilter.
153  * Return NULL if fail, and *ep == NULL if memory allocation failed.
154  */
strfilter__new(const char * rules,const char ** err)155 struct strfilter *strfilter__new(const char *rules, const char **err)
156 {
157 	struct strfilter *ret = zalloc(sizeof(struct strfilter));
158 	const char *ep = NULL;
159 
160 	if (ret)
161 		ret->root = strfilter_node__new(rules, &ep);
162 
163 	if (!ret || !ret->root || *ep != '\0') {
164 		if (err)
165 			*err = ep;
166 		strfilter__delete(ret);
167 		ret = NULL;
168 	}
169 
170 	return ret;
171 }
172 
strfilter_node__compare(struct strfilter_node * self,const char * str)173 static bool strfilter_node__compare(struct strfilter_node *self,
174 				    const char *str)
175 {
176 	if (!self || !self->p)
177 		return false;
178 
179 	switch (*self->p) {
180 	case '|':	/* OR */
181 		return strfilter_node__compare(self->l, str) ||
182 			strfilter_node__compare(self->r, str);
183 	case '&':	/* AND */
184 		return strfilter_node__compare(self->l, str) &&
185 			strfilter_node__compare(self->r, str);
186 	case '!':	/* NOT */
187 		return !strfilter_node__compare(self->r, str);
188 	default:
189 		return strglobmatch(str, self->p);
190 	}
191 }
192 
193 /* Return true if STR matches the filter rules */
strfilter__compare(struct strfilter * self,const char * str)194 bool strfilter__compare(struct strfilter *self, const char *str)
195 {
196 	if (!self)
197 		return false;
198 	return strfilter_node__compare(self->root, str);
199 }
200