/*
* 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
* key = key-fragment { '.' key-fragment }
* key-fragment = / [^=,.]+ /
* val = { / [^,]+ / | ',,' }
*
* 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.
*
* 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 = / [^=,]+ /
*
* 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/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 KEY=VALUE from @params, 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().
* On success, return a pointer to the next KEY=VALUE, or else to '\0'.
* On failure, return NULL.
*/
static const char *keyval_parse_one(QDict *qdict, const char *params,
const char *implied_key,
Error **errp)
{
const char *key, *key_end, *s, *end;
size_t len;
char key_in_cur[128];
QDict *cur;
int ret;
QObject *next;
QString *val;
key = params;
len = strcspn(params, "=,");
if (implied_key && len && key[len] != '=') {
/* Desugar implied key */
key = implied_key;
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);
s = params;
} else {
if (*s != '=') {
error_setg(errp, "Expected '=' after parameter '%.*s'",
(int)(s - key), key);
return NULL;
}
s++;
}
val = qstring_new();
for (;;) {
if (!*s) {
break;
} else if (*s == ',') {
s++;
if (*s != ',') {
break;
}
}
qstring_append_chr(val, *s++);
}
if (!keyval_parse_put(cur, key_in_cur, 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 '='.
* 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,
Error **errp)
{
QDict *qdict = qdict_new();
QObject *listified;
const char *s;
s = params;
while (*s) {
s = keyval_parse_one(qdict, s, implied_key, errp);
if (!s) {
qobject_unref(qdict);
return NULL;
}
implied_key = NULL;
}
listified = keyval_listify(qdict, NULL, errp);
if (!listified) {
qobject_unref(qdict);
return NULL;
}
assert(listified == QOBJECT(qdict));
return qdict;
}
