/* * 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); } /* * 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 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(); QObject *listified; const char *s; bool help = false; s = params; while (*s) { s = keyval_parse_one(qdict, s, implied_key, &help, errp); if (!s) { qobject_unref(qdict); return NULL; } implied_key = NULL; } if (p_help) { *p_help = help; } else if (help) { error_setg(errp, "Help is not available for this option"); qobject_unref(qdict); return NULL; } listified = keyval_listify(qdict, NULL, errp); if (!listified) { qobject_unref(qdict); return NULL; } assert(listified == QOBJECT(qdict)); return qdict; }