projects/linux·blob master · refs

197 lines · 4.8 KiB

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
110static long strset_str_append(struct strset *set, const char *s)
111{
112 uintptr_t old_data = (uintptr_t)set->strs_data;
113 size_t old_data_len = set->strs_data_len;
114 uintptr_t old_s = (uintptr_t)s;
115 long len = strlen(s) + 1;
116 void *p;
117
118 /*
119 * Hashmap keys are always offsets within set->strs_data, so to even
120 * look up some string from the "outside", we need to first append it
121 * at the end, so that it can be addressed with an offset. Luckily,
122 * until set->strs_data_len is incremented, that string is just a piece
123 * of garbage for the rest of the code, so no harm, no foul. On the
124 * other hand, if the string is unique, it's already appended and
125 * ready to be used, only a simple set->strs_data_len increment away.
126 */
127 p = strset_add_str_mem(set, len);
128 if (!p)
129 return -ENOMEM;
130
131 /*
132 * The set->strs_data might have reallocated and if 's' pointed
133 * to an internal string within the old buffer, then it became
134 * dangling and needs to be reconstructed before the copy.
135 */
136 if (old_data && old_data != (uintptr_t)set->strs_data &&
137 old_s >= old_data && old_s < old_data + old_data_len)
138 s = set->strs_data + (old_s - old_data);
139
140 memcpy(p, s, len);
141
142 return len;
143}
144
145/* Find string offset that corresponds to a given string *s*.
146 * Returns:
147 * - >0 offset into string data, if string is found;
148 * - -ENOENT, if string is not in the string data;
149 * - <0, on any other error.
150 */
151int strset__find_str(struct strset *set, const char *s)
152{
153 long old_off, new_off, len;
154
155 len = strset_str_append(set, s);
156 if (len < 0)
157 return len;
158
159 new_off = set->strs_data_len;
160
161 if (hashmap__find(set->strs_hash, new_off, &old_off))
162 return old_off;
163
164 return -ENOENT;
165}
166
167/* Add a string s to the string data. If the string already exists, return its
168 * offset within string data.
169 * Returns:
170 * - > 0 offset into string data, on success;
171 * - < 0, on error.
172 */
173int strset__add_str(struct strset *set, const char *s)
174{
175 long old_off, new_off, len;
176 int err;
177
178 len = strset_str_append(set, s);
179 if (len < 0)
180 return len;
181
182 new_off = set->strs_data_len;
183
184 /* Now attempt to add the string, but only if the string with the same
185 * contents doesn't exist already (HASHMAP_ADD strategy). If such
186 * string exists, we'll get its offset in old_off (that's old_key).
187 */
188 err = hashmap__insert(set->strs_hash, new_off, new_off,
189 HASHMAP_ADD, &old_off, NULL);
190 if (err == -EEXIST)
191 return old_off; /* duplicated string, return existing offset */
192 if (err)
193 return err;
194
195 set->strs_data_len += len; /* new unique string, adjust data length */
196 return new_off;
197}