tools/perf/pmu-events/json.c

   1 /* Parse JSON files using the JSMN parser. */
   2
   3 /*
   4  * Copyright (c) 2014, Intel Corporation
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright notice,
  11  * this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  * notice, this list of conditions and the following disclaimer in the
  15  * documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  21  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  22  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  26  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  27  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  28  * OF THE POSSIBILITY OF SUCH DAMAGE.
  29 */
  30
  31 #include <stdlib.h>
  32 #include <string.h>
  33 #include <sys/mman.h>
  34 #include <sys/stat.h>
  35 #include <fcntl.h>
  36 #include <stdio.h>
  37 #include <errno.h>
  38 #include <unistd.h>
  39 #include "jsmn.h"
  40 #include "json.h"
  41 #include <linux/kernel.h>
  42
  43
  44 static char *mapfile(const char *fn, size_t *size)
  45 {
  46         unsigned ps = sysconf(_SC_PAGESIZE);
  47         struct stat st;
  48         char *map = NULL;
  49         int err;
  50         int fd = open(fn, O_RDONLY);
  51
  52         if (fd < 0 && verbose > 0 && fn) {
  53                 pr_err("Error opening events file '%s': %s\n", fn,
  54                                 strerror(errno));
  55         }
  56
  57         if (fd < 0)
  58                 return NULL;
  59         err = fstat(fd, &st);
  60         if (err < 0)
  61                 goto out;
  62         *size = st.st_size;
  63         map = mmap(NULL,
  64                    (st.st_size + ps - 1) & ~(ps - 1),
  65                    PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
  66         if (map == MAP_FAILED)
  67                 map = NULL;
  68 out:
  69         close(fd);
  70         return map;
  71 }
  72
  73 static void unmapfile(char *map, size_t size)
  74 {
  75         unsigned ps = sysconf(_SC_PAGESIZE);
  76         munmap(map, roundup(size, ps));
  77 }
  78
  79 /*
  80  * Parse json file using jsmn. Return array of tokens,
  81  * and mapped file. Caller needs to free array.
  82  */
  83 jsmntok_t *parse_json(const char *fn, char **map, size_t *size, int *len)
  84 {
  85         jsmn_parser parser;
  86         jsmntok_t *tokens;
  87         jsmnerr_t res;
  88         unsigned sz;
  89
  90         *map = mapfile(fn, size);
  91         if (!*map)
  92                 return NULL;
  93         /* Heuristic */
  94         sz = *size * 16;
  95         tokens = malloc(sz);
  96         if (!tokens)
  97                 goto error;
  98         jsmn_init(&parser);
  99         res = jsmn_parse(&parser, *map, *size, tokens,
 100                          sz / sizeof(jsmntok_t));
 101         if (res != JSMN_SUCCESS) {
 102                 pr_err("%s: json error %s\n", fn, jsmn_strerror(res));
 103                 goto error_free;
 104         }
 105         if (len)
 106                 *len = parser.toknext;
 107         return tokens;
 108 error_free:
 109         free(tokens);
 110 error:
 111         unmapfile(*map, *size);
 112         return NULL;
 113 }
 114
 115 void free_json(char *map, size_t size, jsmntok_t *tokens)
 116 {
 117         free(tokens);
 118         unmapfile(map, size);
 119 }
 120
 121 static int countchar(char *map, char c, int end)
 122 {
 123         int i;
 124         int count = 0;
 125         for (i = 0; i < end; i++)
 126                 if (map[i] == c)
 127                         count++;
 128         return count;
 129 }
 130
 131 /* Return line number of a jsmn token */
 132 int json_line(char *map, jsmntok_t *t)
 133 {
 134         return countchar(map, '\n', t->start) + 1;
 135 }
 136
 137 static const char * const jsmn_types[] = {
 138         [JSMN_PRIMITIVE] = "primitive",
 139         [JSMN_ARRAY] = "array",
 140         [JSMN_OBJECT] = "object",
 141         [JSMN_STRING] = "string"
 142 };
 143
 144 #define LOOKUP(a, i) ((i) < (sizeof(a)/sizeof(*(a))) ? ((a)[i]) : "?")
 145
 146 /* Return type name of a jsmn token */
 147 const char *json_name(jsmntok_t *t)
 148 {
 149         return LOOKUP(jsmn_types, t->type);
 150 }
 151
 152 int json_len(jsmntok_t *t)
 153 {
 154         return t->end - t->start;
 155 }
 156
 157 /* Is string t equal to s? */
 158 int json_streq(char *map, jsmntok_t *t, const char *s)
 159 {
 160         unsigned len = json_len(t);
 161         return len == strlen(s) && !strncasecmp(map + t->start, s, len);
 162 }