aboutsummaryrefslogtreecommitdiff
path: root/util/keyval.c
blob: 904337c8a10e39a1d0fd75df7d037cba1aca6126 (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
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
/*
 * Parsing KEY=VALUE,... strings
 *
 * Copyright (C) 2017 Red Hat Inc.
 *
 * Authors:
 *  Markus Armbruster <armbru@redhat.com>,
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

/*
 * KEY=VALUE,... syntax:
 *
 *   key-vals     = [ key-val { ',' key-val } [ ',' ] ]
 *   key-val      = key '=' val | help
 *   key          = key-fragment { '.' key-fragment }
 *   key-fragment = / [^=,.]+ /
 *   val          = { / [^,]+ / | ',,' }
 *   help         = 'help' | '?'
 *
 * Semantics defined by reduction to JSON:
 *
 *   key-vals specifies a JSON object, i.e. a tree whose root is an
 *   object, inner nodes other than the root are objects or arrays,
 *   and leaves are strings.
 *
 *   Each key-val = key-fragment '.' ... '=' val specifies a path from
 *   root to a leaf (left of '='), and the leaf's value (right of
 *   '=').
 *
 *   A path from the root is defined recursively:
 *       L '.' key-fragment is a child of the node denoted by path L
 *       key-fragment is a child of the tree root
 *   If key-fragment is numeric, the parent is an array and the child
 *   is its key-fragment-th member, counting from zero.
 *   Else, the parent is an object, and the child is its member named
 *   key-fragment.
 *
 *   This constrains inner nodes to be either array or object.  The
 *   constraints must be satisfiable.  Counter-example: a.b=1,a=2 is
 *   not, because root.a must be an object to satisfy a.b=1 and a
 *   string to satisfy a=2.
 *
 *   Array subscripts can occur in any order, but the set of
 *   subscripts must not have gaps.  For instance, a.1=v is not okay,
 *   because root.a[0] is missing.
 *
 *   If multiple key-val denote the same leaf, the last one determines
 *   the value.
 *
 * Key-fragments must be valid QAPI names or consist only of decimal
 * digits.
 *
 * The length of any key-fragment must be between 1 and 127.
 *
 * If any key-val is help, the object is to be treated as a help
 * request.
 *
 * Design flaw: there is no way to denote an empty array or non-root
 * object.  While interpreting "key absent" as empty seems natural
 * (removing a key-val from the input string removes the member when
 * there are more, so why not when it's the last), it doesn't work:
 * "key absent" already means "optional object/array absent", which
 * isn't the same as "empty object/array present".
 *
 * Design flaw: scalar values can only be strings; there is no way to
 * denote numbers, true, false or null.  The special QObject input
 * visitor returned by qobject_input_visitor_new_keyval() mostly hides
 * this by automatically converting strings to the type the visitor
 * expects.  Breaks down for type 'any', where the visitor's
 * expectation isn't clear.  Code visiting 'any' needs to do the
 * conversion itself, but only when using this keyval visitor.
 * Awkward.  Note that we carefully restrict alternate types to avoid
 * similar ambiguity.
 *
 * Alternative syntax for use with an implied key:
 *
 *   key-vals     = [ key-val-1st { ',' key-val } [ ',' ] ]
 *   key-val-1st  = val-no-key | key-val
 *   val-no-key   = / [^=,]+ / - help
 *
 * where val-no-key is syntactic sugar for implied-key=val-no-key.
 *
 * Note that you can't use the sugared form when the value contains
 * '=' or ','.
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qlist.h"
#include "qapi/qmp/qstring.h"
#include "qemu/cutils.h"
#include "qemu/help_option.h"
#include "qemu/option.h"

/*
 * Convert @key to a list index.
 * Convert all leading decimal digits to a (non-negative) number,
 * capped at INT_MAX.
 * If @end is non-null, assign a pointer to the first character after
 * the number to *@end.
 * Else, fail if any characters follow.
 * On success, return the converted number.
 * On failure, return a negative value.
 * Note: since only digits are converted, no two keys can map to the
 * same number, except by overflow to INT_MAX.
 */
static int key_to_index(const char *key, const char **end)
{
    int ret;
    unsigned long index;

    if (*key < '0' || *key > '9') {
        return -EINVAL;
    }
    ret = qemu_strtoul(key, end, 10, &index);
    if (ret) {
        return ret == -ERANGE ? INT_MAX : ret;
    }
    return index <= INT_MAX ? index : INT_MAX;
}

/*
 * Ensure @cur maps @key_in_cur the right way.
 * If @value is null, it needs to map to a QDict, else to this
 * QString.
 * If @cur doesn't have @key_in_cur, put an empty QDict or @value,
 * respectively.
 * Else, if it needs to map to a QDict, and already does, do nothing.
 * Else, if it needs to map to this QString, and already maps to a
 * QString, replace it by @value.
 * Else, fail because we have conflicting needs on how to map
 * @key_in_cur.
 * In any case, take over the reference to @value, i.e. if the caller
 * wants to hold on to a reference, it needs to qobject_ref().
 * Use @key up to @key_cursor to identify the key in error messages.
 * On success, return the mapped value.
 * On failure, store an error through @errp and return NULL.
 */
static QObject *keyval_parse_put(QDict *cur,
                                 const char *key_in_cur, QString *value,
                                 const char *key, const char *key_cursor,
                                 Error **errp)
{
    QObject *old, *new;

    old = qdict_get(cur, key_in_cur);
    if (old) {
        if (qobject_type(old) != (value ? QTYPE_QSTRING : QTYPE_QDICT)) {
            error_setg(errp, "Parameters '%.*s.*' used inconsistently",
                       (int)(key_cursor - key), key);
            qobject_unref(value);
            return NULL;
        }
        if (!value) {
            return old;         /* already QDict, do nothing */
        }
        new = QOBJECT(value);   /* replacement */
    } else {
        new = value ? QOBJECT(value) : QOBJECT(qdict_new());
    }
    qdict_put_obj(cur, key_in_cur, new);
    return new;
}

/*
 * Parse one parameter from @params.
 *
 * If we're looking at KEY=VALUE, store result in @qdict.
 * The first fragment of KEY applies to @qdict.  Subsequent fragments
 * apply to nested QDicts, which are created on demand.  @implied_key
 * is as in keyval_parse().
 *
 * If we're looking at "help" or "?", set *help to true.
 *
 * On success, return a pointer to the next parameter, or else to '\0'.
 * On failure, return NULL.
 */
static const char *keyval_parse_one(QDict *qdict, const char *params,
                                    const char *implied_key, bool *help,
                                    Error **errp)
{
    const char *key, *key_end, *val_end, *s, *end;
    size_t len;
    char key_in_cur[128];
    QDict *cur;
    int ret;
    QObject *next;
    GString *val;

    key = params;
    val_end = NULL;
    len = strcspn(params, "=,");
    if (len && key[len] != '=') {
        if (starts_with_help_option(key) == len) {
            *help = true;
            s = key + len;
            if (*s == ',') {
                s++;
            }
            return s;
        }
        if (implied_key) {
            /* Desugar implied key */
            key = implied_key;
            val_end = params + len;
            len = strlen(implied_key);
        }
    }
    key_end = key + len;

    /*
     * Loop over key fragments: @s points to current fragment, it
     * applies to @cur.  @key_in_cur[] holds the previous fragment.
     */
    cur = qdict;
    s = key;
    for (;;) {
        /* Want a key index (unless it's first) or a QAPI name */
        if (s != key && key_to_index(s, &end) >= 0) {
            len = end - s;
        } else {
            ret = parse_qapi_name(s, false);
            len = ret < 0 ? 0 : ret;
        }
        assert(s + len <= key_end);
        if (!len || (s + len < key_end && s[len] != '.')) {
            assert(key != implied_key);
            error_setg(errp, "Invalid parameter '%.*s'",
                       (int)(key_end - key), key);
            return NULL;
        }
        if (len >= sizeof(key_in_cur)) {
            assert(key != implied_key);
            error_setg(errp, "Parameter%s '%.*s' is too long",
                       s != key || s + len != key_end ? " fragment" : "",
                       (int)len, s);
            return NULL;
        }

        if (s != key) {
            next = keyval_parse_put(cur, key_in_cur, NULL,
                                    key, s - 1, errp);
            if (!next) {
                return NULL;
            }
            cur = qobject_to(QDict, next);
            assert(cur);
        }

        memcpy(key_in_cur, s, len);
        key_in_cur[len] = 0;
        s += len;

        if (*s != '.') {
            break;
        }
        s++;
    }

    if (key == implied_key) {
        assert(!*s);
        val = g_string_new_len(params, val_end - params);
        s = val_end;
        if (*s == ',') {
            s++;
        }
    } else {
        if (*s != '=') {
            error_setg(errp, "Expected '=' after parameter '%.*s'",
                       (int)(s - key), key);
            return NULL;
        }
        s++;

        val = g_string_new(NULL);
        for (;;) {
            if (!*s) {
                break;
            } else if (*s == ',') {
                s++;
                if (*s != ',') {
                    break;
                }
            }
            g_string_append_c(val, *s++);
        }
    }

    if (!keyval_parse_put(cur, key_in_cur, qstring_from_gstring(val),
                          key, key_end, errp)) {
        return NULL;
    }
    return s;
}

static char *reassemble_key(GSList *key)
{
    GString *s = g_string_new("");
    GSList *p;

    for (p = key; p; p = p->next) {
        g_string_prepend_c(s, '.');
        g_string_prepend(s, (char *)p->data);
    }

    return g_string_free(s, FALSE);
}

/*
 * Recursive worker for keyval_merge.
 *
 * @str is the path that led to the * current dictionary (to be used for
 * error messages).  It is modified internally but restored before the
 * function returns.
 */
static void keyval_do_merge(QDict *dest, const QDict *merged, GString *str, Error **errp)
{
    size_t save_len = str->len;
    const QDictEntry *ent;
    QObject *old_value;

    for (ent = qdict_first(merged); ent; ent = qdict_next(merged, ent)) {
        old_value = qdict_get(dest, ent->key);
        if (old_value) {
            if (qobject_type(old_value) != qobject_type(ent->value)) {
                error_setg(errp, "Parameter '%s%s' used inconsistently",
                           str->str, ent->key);
                return;
            } else if (qobject_type(ent->value) == QTYPE_QDICT) {
                /* Merge sub-dictionaries.  */
                g_string_append(str, ent->key);
                g_string_append_c(str, '.');
                keyval_do_merge(qobject_to(QDict, old_value),
                                qobject_to(QDict, ent->value),
                                str, errp);
                g_string_truncate(str, save_len);
                continue;
            } else if (qobject_type(ent->value) == QTYPE_QLIST) {
                /* Append to old list.  */
                QList *old = qobject_to(QList, old_value);
                QList *new = qobject_to(QList, ent->value);
                const QListEntry *item;
                QLIST_FOREACH_ENTRY(new, item) {
                    qobject_ref(item->value);
                    qlist_append_obj(old, item->value);
                }
                continue;
            } else {
                assert(qobject_type(ent->value) == QTYPE_QSTRING);
            }
        }

        qobject_ref(ent->value);
        qdict_put_obj(dest, ent->key, ent->value);
    }
}

/* Merge the @merged dictionary into @dest.
 *
 * The dictionaries are expected to be returned by the keyval parser, and
 * therefore the only expected scalar type is the string.  In case the same
 * path is present in both @dest and @merged, the semantics are as follows:
 *
 * - lists are concatenated
 *
 * - dictionaries are merged recursively
 *
 * - for scalar values, @merged wins
 *
 * In case an error is reported, @dest may already have been modified.
 *
 * This function can be used to implement semantics analogous to QemuOpts's
 * .merge_lists = true case, or to implement -set for options backed by QDicts.
 *
 * Note: while QemuOpts is commonly used so that repeated keys overwrite
 * ("last one wins"), it can also be used so that repeated keys build up
 * a list. keyval_merge() can only be used when the options' semantics are
 * the former, not the latter.
 */
void keyval_merge(QDict *dest, const QDict *merged, Error **errp)
{
    GString *str;

    str = g_string_new("");
    keyval_do_merge(dest, merged, str, errp);
    g_string_free(str, TRUE);
}

/*
 * Listify @cur recursively.
 * Replace QDicts whose keys are all valid list indexes by QLists.
 * @key_of_cur is the list of key fragments leading up to @cur.
 * On success, return either @cur or its replacement.
 * On failure, store an error through @errp and return NULL.
 */
static QObject *keyval_listify(QDict *cur, GSList *key_of_cur, Error **errp)
{
    GSList key_node;
    bool has_index, has_member;
    const QDictEntry *ent;
    QDict *qdict;
    QObject *val;
    char *key;
    size_t nelt;
    QObject **elt;
    int index, max_index, i;
    QList *list;

    key_node.next = key_of_cur;

    /*
     * Recursively listify @cur's members, and figure out whether @cur
     * itself is to be listified.
     */
    has_index = false;
    has_member = false;
    for (ent = qdict_first(cur); ent; ent = qdict_next(cur, ent)) {
        if (key_to_index(ent->key, NULL) >= 0) {
            has_index = true;
        } else {
            has_member = true;
        }

        qdict = qobject_to(QDict, ent->value);
        if (!qdict) {
            continue;
        }

        key_node.data = ent->key;
        val = keyval_listify(qdict, &key_node, errp);
        if (!val) {
            return NULL;
        }
        if (val != ent->value) {
            qdict_put_obj(cur, ent->key, val);
        }
    }

    if (has_index && has_member) {
        key = reassemble_key(key_of_cur);
        error_setg(errp, "Parameters '%s*' used inconsistently", key);
        g_free(key);
        return NULL;
    }
    if (!has_index) {
        return QOBJECT(cur);
    }

    /* Copy @cur's values to @elt[] */
    nelt = qdict_size(cur) + 1; /* one extra, for use as sentinel */
    elt = g_new0(QObject *, nelt);
    max_index = -1;
    for (ent = qdict_first(cur); ent; ent = qdict_next(cur, ent)) {
        index = key_to_index(ent->key, NULL);
        assert(index >= 0);
        if (index > max_index) {
            max_index = index;
        }
        /*
         * We iterate @nelt times.  If we get one exceeding @nelt
         * here, we will put less than @nelt values into @elt[],
         * triggering the error in the next loop.
         */
        if ((size_t)index >= nelt - 1) {
            continue;
        }
        /* Even though dict keys are distinct, indexes need not be */
        elt[index] = ent->value;
    }

    /*
     * Make a list from @elt[], reporting the first missing element,
     * if any.
     * If we dropped an index >= nelt in the previous loop, this loop
     * will run into the sentinel and report index @nelt missing.
     */
    list = qlist_new();
    assert(!elt[nelt-1]);       /* need the sentinel to be null */
    for (i = 0; i < MIN(nelt, max_index + 1); i++) {
        if (!elt[i]) {
            key = reassemble_key(key_of_cur);
            error_setg(errp, "Parameter '%s%d' missing", key, i);
            g_free(key);
            g_free(elt);
            qobject_unref(list);
            return NULL;
        }
        qobject_ref(elt[i]);
        qlist_append_obj(list, elt[i]);
    }

    g_free(elt);
    return QOBJECT(list);
}

/*
 * Parse @params in QEMU's traditional KEY=VALUE,... syntax.
 *
 * If @implied_key, the first KEY= can be omitted.  @implied_key is
 * implied then, and VALUE can't be empty or contain ',' or '='.
 *
 * A parameter "help" or "?" without a value isn't added to the
 * resulting dictionary, but instead is interpreted as help request.
 * All other options are parsed and returned normally so that context
 * specific help can be printed.
 *
 * If @p_help is not NULL, store whether help is requested there.
 * If @p_help is NULL and help is requested, fail.
 *
 * On success, return @dict, now filled with the parsed keys and values.
 *
 * On failure, store an error through @errp and return NULL.  Any keys
 * and values parsed so far will be in @dict nevertheless.
 */
QDict *keyval_parse_into(QDict *qdict, const char *params, const char *implied_key,
                         bool *p_help, Error **errp)
{
    QObject *listified;
    const char *s;
    bool help = false;

    s = params;
    while (*s) {
        s = keyval_parse_one(qdict, s, implied_key, &help, errp);
        if (!s) {
            return NULL;
        }
        implied_key = NULL;
    }

    if (p_help) {
        *p_help = help;
    } else if (help) {
        error_setg(errp, "Help is not available for this option");
        return NULL;
    }

    listified = keyval_listify(qdict, NULL, errp);
    if (!listified) {
        return NULL;
    }
    assert(listified == QOBJECT(qdict));
    return qdict;
}

/*
 * Parse @params in QEMU's traditional KEY=VALUE,... syntax.
 *
 * If @implied_key, the first KEY= can be omitted.  @implied_key is
 * implied then, and VALUE can't be empty or contain ',' or '='.
 *
 * A parameter "help" or "?" without a value isn't added to the
 * resulting dictionary, but instead is interpreted as help request.
 * All other options are parsed and returned normally so that context
 * specific help can be printed.
 *
 * If @p_help is not NULL, store whether help is requested there.
 * If @p_help is NULL and help is requested, fail.
 *
 * On success, return a dictionary of the parsed keys and values.
 * On failure, store an error through @errp and return NULL.
 */
QDict *keyval_parse(const char *params, const char *implied_key,
                    bool *p_help, Error **errp)
{
    QDict *qdict = qdict_new();
    QDict *ret = keyval_parse_into(qdict, params, implied_key, p_help, errp);

    if (!ret) {
        qobject_unref(qdict);
    }
    return ret;
}