xref: /openbmc/linux/tools/lib/bpf/strset.c (revision c302378b)
1 // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
2 /* Copyright (c) 2021 Facebook */
3 #include <stdint.h>
4 #include <stdlib.h>
5 #include <stdio.h>
6 #include <errno.h>
7 #include <linux/err.h>
8 #include "hashmap.h"
9 #include "libbpf_internal.h"
10 #include "strset.h"
11 
12 struct strset {
13 	void *strs_data;
14 	size_t strs_data_len;
15 	size_t strs_data_cap;
16 	size_t strs_data_max_len;
17 
18 	/* lookup index for each unique string in strings set */
19 	struct hashmap *strs_hash;
20 };
21 
strset_hash_fn(long key,void * ctx)22 static size_t strset_hash_fn(long key, void *ctx)
23 {
24 	const struct strset *s = ctx;
25 	const char *str = s->strs_data + key;
26 
27 	return str_hash(str);
28 }
29 
strset_equal_fn(long key1,long key2,void * ctx)30 static bool strset_equal_fn(long key1, long key2, void *ctx)
31 {
32 	const struct strset *s = ctx;
33 	const char *str1 = s->strs_data + key1;
34 	const char *str2 = s->strs_data + key2;
35 
36 	return strcmp(str1, str2) == 0;
37 }
38 
strset__new(size_t max_data_sz,const char * init_data,size_t init_data_sz)39 struct strset *strset__new(size_t max_data_sz, const char *init_data, size_t init_data_sz)
40 {
41 	struct strset *set = calloc(1, sizeof(*set));
42 	struct hashmap *hash;
43 	int err = -ENOMEM;
44 
45 	if (!set)
46 		return ERR_PTR(-ENOMEM);
47 
48 	hash = hashmap__new(strset_hash_fn, strset_equal_fn, set);
49 	if (IS_ERR(hash))
50 		goto err_out;
51 
52 	set->strs_data_max_len = max_data_sz;
53 	set->strs_hash = hash;
54 
55 	if (init_data) {
56 		long off;
57 
58 		set->strs_data = malloc(init_data_sz);
59 		if (!set->strs_data)
60 			goto err_out;
61 
62 		memcpy(set->strs_data, init_data, init_data_sz);
63 		set->strs_data_len = init_data_sz;
64 		set->strs_data_cap = init_data_sz;
65 
66 		for (off = 0; off < set->strs_data_len; off += strlen(set->strs_data + off) + 1) {
67 			/* hashmap__add() returns EEXIST if string with the same
68 			 * content already is in the hash map
69 			 */
70 			err = hashmap__add(hash, off, off);
71 			if (err == -EEXIST)
72 				continue; /* duplicate */
73 			if (err)
74 				goto err_out;
75 		}
76 	}
77 
78 	return set;
79 err_out:
80 	strset__free(set);
81 	return ERR_PTR(err);
82 }
83 
strset__free(struct strset * set)84 void strset__free(struct strset *set)
85 {
86 	if (IS_ERR_OR_NULL(set))
87 		return;
88 
89 	hashmap__free(set->strs_hash);
90 	free(set->strs_data);
91 	free(set);
92 }
93 
strset__data_size(const struct strset * set)94 size_t strset__data_size(const struct strset *set)
95 {
96 	return set->strs_data_len;
97 }
98 
strset__data(const struct strset * set)99 const char *strset__data(const struct strset *set)
100 {
101 	return set->strs_data;
102 }
103 
strset_add_str_mem(struct strset * set,size_t add_sz)104 static void *strset_add_str_mem(struct strset *set, size_t add_sz)
105 {
106 	return libbpf_add_mem(&set->strs_data, &set->strs_data_cap, 1,
107 			      set->strs_data_len, set->strs_data_max_len, add_sz);
108 }
109 
110 /* Find string offset that corresponds to a given string *s*.
111  * Returns:
112  *   - >0 offset into string data, if string is found;
113  *   - -ENOENT, if string is not in the string data;
114  *   - <0, on any other error.
115  */
strset__find_str(struct strset * set,const char * s)116 int strset__find_str(struct strset *set, const char *s)
117 {
118 	long old_off, new_off, len;
119 	void *p;
120 
121 	/* see strset__add_str() for why we do this */
122 	len = strlen(s) + 1;
123 	p = strset_add_str_mem(set, len);
124 	if (!p)
125 		return -ENOMEM;
126 
127 	new_off = set->strs_data_len;
128 	memcpy(p, s, len);
129 
130 	if (hashmap__find(set->strs_hash, new_off, &old_off))
131 		return old_off;
132 
133 	return -ENOENT;
134 }
135 
136 /* Add a string s to the string data. If the string already exists, return its
137  * offset within string data.
138  * Returns:
139  *   - > 0 offset into string data, on success;
140  *   - < 0, on error.
141  */
strset__add_str(struct strset * set,const char * s)142 int strset__add_str(struct strset *set, const char *s)
143 {
144 	long old_off, new_off, len;
145 	void *p;
146 	int err;
147 
148 	/* Hashmap keys are always offsets within set->strs_data, so to even
149 	 * look up some string from the "outside", we need to first append it
150 	 * at the end, so that it can be addressed with an offset. Luckily,
151 	 * until set->strs_data_len is incremented, that string is just a piece
152 	 * of garbage for the rest of the code, so no harm, no foul. On the
153 	 * other hand, if the string is unique, it's already appended and
154 	 * ready to be used, only a simple set->strs_data_len increment away.
155 	 */
156 	len = strlen(s) + 1;
157 	p = strset_add_str_mem(set, len);
158 	if (!p)
159 		return -ENOMEM;
160 
161 	new_off = set->strs_data_len;
162 	memcpy(p, s, len);
163 
164 	/* Now attempt to add the string, but only if the string with the same
165 	 * contents doesn't exist already (HASHMAP_ADD strategy). If such
166 	 * string exists, we'll get its offset in old_off (that's old_key).
167 	 */
168 	err = hashmap__insert(set->strs_hash, new_off, new_off,
169 			      HASHMAP_ADD, &old_off, NULL);
170 	if (err == -EEXIST)
171 		return old_off; /* duplicated string, return existing offset */
172 	if (err)
173 		return err;
174 
175 	set->strs_data_len += len; /* new unique string, adjust data length */
176 	return new_off;
177 }
178