tools/lib/bpf/strset.c

   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
  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
  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
  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
  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
  94 size_t strset__data_size(const struct strset *set)
  95 {
  96         return set->strs_data_len;
  97 }
  98
  99 const char *strset__data(const struct strset *set)
 100 {
 101         return set->strs_data;
 102 }
 103
 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  */
 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  */
 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 }