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
12struct 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
22static 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
30static 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
39struct 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;
79err_out:
80	strset__free(set);
81	return ERR_PTR(err);
82}
83
84void 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
94size_t strset__data_size(const struct strset *set)
95{
96	return set->strs_data_len;
97}
98
99const char *strset__data(const struct strset *set)
100{
101	return set->strs_data;
102}
103
104static 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 */
116int 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 */
142int 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