qemu

keyval.c (18494B)

---

 /*
  * 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 = qapi-name | index
  *   qapi-name    = '__' / [a-z0-9.-]+ / '_' / [A-Za-z][A-Za-z0-9_-]* /
  *   index        = / [0-9]+ /
  *   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/keyval.h"
 #include "qemu/help_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;
 }