summaryrefslogtreecommitdiffstats
path: root/misc/json.c
blob: 825251140865be36b5c826ffbdfdab240451bf2c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
/*
 * This file is part of mpv.
 *
 * mpv is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * mpv is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with mpv.  If not, see <http://www.gnu.org/licenses/>.
 */

/* JSON parser:
 *
 * Unlike standard JSON, \u escapes don't allow you to specify UTF-16 surrogate
 * pairs. There may be some differences how numbers are parsed (this parser
 * doesn't verify what's passed to strtod(), and also prefers parsing numbers
 * as integers with stroll() if possible).
 *
 * Does not support extensions like unquoted string literals.
 *
 * Also see: http://tools.ietf.org/html/rfc4627
 *
 * JSON writer:
 *
 * Doesn't insert whitespace. It's literally a waste of space.
 *
 * Can output invalid UTF-8, if input is invalid UTF-8. Consumers are supposed
 * to deal with somehow: either by using byte-strings for JSON, or by running
 * a "fixup" pass on the input data. The latter could for example change
 * invalid UTF-8 sequences to replacement characters.
 *
 * Currently, will insert \u literals for characters 0-31, '"', '\', and write
 * everything else literally.
 */

#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <errno.h>
#include <inttypes.h>
#include <assert.h>

#include "common/common.h"
#include "misc/bstr.h"

#include "json.h"

static bool eat_c(char **s, char c)
{
    if (**s == c) {
        *s += 1;
        return true;
    }
    return false;
}

static void eat_ws(char **src)
{
    while (1) {
        char c = **src;
        if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
            return;
        *src += 1;
    }
}

void json_skip_whitespace(char **src)
{
    eat_ws(src);
}

static int read_str(void *ta_parent, struct mpv_node *dst, char **src)
{
    if (!eat_c(src, '"'))
        return -1; // not a string
    char *str = *src;
    char *cur = str;
    bool has_escapes = false;
    while (cur[0] && cur[0] != '"') {
        if (cur[0] == '\\') {
            has_escapes = true;
            // skip >\"< and >\\< (latter to handle >\\"< correctly)
            if (cur[1] == '"' || cur[1] == '\\')
                cur++;
        }
        cur++;
    }
    if (cur[0] != '"')
        return -1; // invalid termination
    // Mutate input string so we have a null-terminated string to the literal.
    // This is a stupid micro-optimization, so we can avoid allocation.
    cur[0] = '\0';
    *src = cur + 1;
    if (has_escapes) {
        bstr unescaped = {0};
        bstr r = bstr0(str);
        if (!mp_append_escaped_string(ta_parent, &unescaped, &r))
            return -1; // broken escapes
        str = unescaped.start; // the function guarantees null-termination
    }
    dst->format = MPV_FORMAT_STRING;
    dst->u.string = str;
    return 0;
}

static int read_sub(void *ta_parent, struct mpv_node *dst, char **src,
                    int max_depth)
{
    bool is_arr = eat_c(src, '[');
    bool is_obj = !is_arr && eat_c(src, '{');
    if (!is_arr && !is_obj)
        return -1; // not an array or object
    char term = is_obj ? '}' : ']';
    struct mpv_node_list *list = talloc_zero(ta_parent, struct mpv_node_list);
    while (1) {
        eat_ws(src);
        if (eat_c(src, term))
            break;
        if (list->num > 0 && !eat_c(src, ','))
            return -1; // missing ','
        eat_ws(src);
        if (is_obj) {
            struct mpv_node keynode;
            if (read_str(list, &keynode, src) < 0)
                return -1; // key is not a string
            eat_ws(src);
            if (!eat_c(src, ':'))
                return -1; // ':' missing
            eat_ws(src);
            MP_TARRAY_GROW(list, list->keys, list->num);
            list->keys[list->num] = keynode.u.string;
        }
        MP_TARRAY_GROW(list, list->values, list->num);
        if (json_parse(ta_parent, &list->values[list->num], src, max_depth) < 0)
            return -1;
        list->num++;
    }
    dst->format = is_obj ? MPV_FORMAT_NODE_MAP : MPV_FORMAT_NODE_ARRAY;
    dst->u.list = list;
    return 0;
}

/* Parse the string in *src as JSON, and write the result into *dst.
 * max_depth limits the recursion and JSON tree depth.
 * Warning: this overwrites the input string (what *src points to)!
 * Returns:
 *   0: success, *dst is valid, *src points to the end (the caller must check
 *      whether *src really terminates)
 *  -1: failure, *dst is invalid, there may be dead allocs under ta_parent
 *      (ta_free_children(ta_parent) is the only way to free them)
 * The input string can be mutated in both cases. *dst might contain string
 * elements, which point into the (mutated) input string.
 */
int json_parse(void *ta_parent, struct mpv_node *dst, char **src, int max_depth)
{
    max_depth -= 1;
    if (max_depth < 0)
        return -1;

    eat_ws(src);

    char c = **src;
    if (!c)
        return -1; // early EOF
    if (c == 'n' && strncmp(*src, "null", 4) == 0) {
        *src += 4;
        dst->format = MPV_FORMAT_NONE;
        return 0;
    } else if (c == 't' && strncmp(*src, "true", 4) == 0) {
        *src += 4;
        dst->format = MPV_FORMAT_FLAG;
        dst->u.flag = 1;
        return 0;
    } else if (c == 'f' && strncmp(*src, "false", 5) == 0) {
        *src += 5;
        dst->format = MPV_FORMAT_FLAG;
        dst->u.flag = 0;
        return 0;
    } else if (c == '"') {
        return read_str(ta_parent, dst, src);
    } else if (c == '[' || c == '{') {
        return read_sub(ta_parent, dst, src, max_depth);
    } else if (c == '-' || (c >= '0' && c <= '9')) {
        // The number could be either a float or an int. JSON doesn't make a
        // difference, but the client API does.
        char *nsrci = *src, *nsrcf = *src;
        errno = 0;
        long long int numi = strtoll(*src, &nsrci, 0);
        if (errno)
            nsrci = *src;
        errno = 0;
        double numf = strtod(*src, &nsrcf);
        if (errno)
            nsrcf = *src;
        if (nsrci >= nsrcf) {
            *src = nsrci;
            dst->format = MPV_FORMAT_INT64; // long long is usually 64 bits
            dst->u.int64 = numi;
            return 0;
        }
        if (nsrcf > *src && isfinite(numf)) {
            *src = nsrcf;
            dst->format = MPV_FORMAT_DOUBLE;
            dst->u.double_ = numf;
            return 0;
        }
        return -1;
    }
    return -1; // character doesn't start a valid token
}


#define APPEND(b, s) bstr_xappend(NULL, (b), bstr0(s))

static void write_json_str(bstr *b, char *str)
{
    APPEND(b, "\"");
    while (1) {
        char *cur = str;
        while (cur[0] && cur[0] >= 32 && cur[0] != '"' && cur[0] != '\\')
            cur++;
        if (!cur[0])
            break;
        bstr_xappend(NULL, b, (bstr){str, cur - str});
        bstr_xappend_asprintf(NULL, b, "\\u%04x", (unsigned char)cur[0]);
        str = cur + 1;
    }
    APPEND(b, str);
    APPEND(b, "\"");
}

static int json_append(bstr *b, const struct mpv_node *src)
{
    switch (src->format) {
    case MPV_FORMAT_NONE:
        APPEND(b, "null");
        return 0;
    case MPV_FORMAT_FLAG:
        APPEND(b, src->u.flag ? "true" : "false");
        return 0;
    case MPV_FORMAT_INT64:
        bstr_xappend_asprintf(NULL, b, "%"PRId64, src->u.int64);
        return 0;
    case MPV_FORMAT_DOUBLE:
        bstr_xappend_asprintf(NULL, b, "%f", src->u.double_);
        return 0;
    case MPV_FORMAT_STRING:
        write_json_str(b, src->u.string);
        return 0;
    case MPV_FORMAT_NODE_ARRAY:
    case MPV_FORMAT_NODE_MAP: {
        struct mpv_node_list *list = src->u.list;
        bool is_obj = src->format == MPV_FORMAT_NODE_MAP;
        APPEND(b, is_obj ? "{" : "[");
        for (int n = 0; n < list->num; n++) {
            if (n)
                APPEND(b, ",");
            if (is_obj) {
                write_json_str(b, list->keys[n]);
                APPEND(b, ":");
            }
            json_append(b, &list->values[n]);
        }
        APPEND(b, is_obj ? "}" : "]");
        return 0;
    }
    }
    return -1; // unknown format
}

/* Write the contents of *src as JSON, and append the JSON string to *dst.
 * This will use strlen() to determine the start offset, and ta_get_size()
 * and ta_realloc() to extend the memory allocation of *dst.
 * Returns: 0 on success, <0 on failure.
 */
int json_write(char **dst, struct mpv_node *src)
{
    bstr buffer = bstr0(*dst);
    int r = json_append(&buffer, src);
    *dst = buffer.start;
    return r;
}