From fae425d74f20d45a3c0bea4b7403b16f7b659e25 Mon Sep 17 00:00:00 2001 From: Markus Armbruster Date: Mon, 20 Mar 2017 13:55:45 +0100 Subject: keyval: Improve some comments Signed-off-by: Markus Armbruster Message-Id: <1490014548-15083-3-git-send-email-armbru@redhat.com> Reviewed-by: Eric Blake --- util/keyval.c | 47 +++++++++++++++++++++++++++++++---------------- 1 file changed, 31 insertions(+), 16 deletions(-) (limited to 'util') diff --git a/util/keyval.c b/util/keyval.c index f646b36821..46cd540c5a 100644 --- a/util/keyval.c +++ b/util/keyval.c @@ -21,22 +21,36 @@ * * Semantics defined by reduction to JSON: * - * key-vals is a tree of objects and arrays rooted at object R - * where for each key-val = key-fragment . ... = val in key-vals - * R op key-fragment op ... = val' - * where (left-associative) op is - * array subscript L[key-fragment] for numeric key-fragment - * member reference L.key-fragment otherwise - * val' is val with ',,' replaced by ',' - * and only R may be empty. + * 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. * - * Duplicate keys are permitted; all but the last one are ignored. + * Each key-val = key-fragment '.' ... '=' val specifies a path from + * root to a leaf (left of '='), and the leaf's value (right of + * '='). * - * The equations must have a solution. Counter-example: a.b=1,a=2 - * doesn't have one, because R.a must be an object to satisfy a.b=1 - * and a string to satisfy a=2. + * 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. * - * Key-fragments must be valid QAPI names or consist only of digits. + * 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. * @@ -64,8 +78,8 @@ /* * Convert @key to a list index. - * Convert all leading digits to a (non-negative) number, capped at - * INT_MAX. + * 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. @@ -337,7 +351,8 @@ static QObject *keyval_listify(QDict *cur, GSList *key_of_cur, Error **errp) } /* - * Make a list from @elt[], reporting any missing elements. + * 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. */ -- cgit v1.2.1