keyval: New keyval_parse()

keyval_parse() parses KEY=VALUE,... into a QDict.  Works like
qemu_opts_parse(), except:

* Returns a QDict instead of a QemuOpts (d'oh).

* Supports nesting, unlike QemuOpts: a KEY is split into key
  fragments at '.' (dotted key convention; the block layer does
  something similar on top of QemuOpts).  The key fragments are QDict
  keys, and the last one's value is updated to VALUE.

* Each key fragment may be up to 127 bytes long.  qemu_opts_parse()
  limits the entire key to 127 bytes.

* Overlong key fragments are rejected.  qemu_opts_parse() silently
  truncates them.

* Empty key fragments are rejected.  qemu_opts_parse() happily
  accepts empty keys.

* It does not store the returned value.  qemu_opts_parse() stores it
  in the QemuOptsList.

* It does not treat parameter "id" specially.  qemu_opts_parse()
  ignores all but the first "id", and fails when its value isn't
  id_wellformed(), or duplicate (a QemuOpts with the same ID is
  already stored).  It also screws up when a value contains ",id=".

* Implied value is not supported.  qemu_opts_parse() desugars "foo" to
  "foo=on", and "nofoo" to "foo=off".

* An implied key's value can't be empty, and can't contain ','.

I intend to grow this into a saner replacement for QemuOpts.  It'll
take time, though.

Note: keyval_parse() provides no way to do lists, and its key syntax
is incompatible with the __RFQDN_ prefix convention for downstream
extensions, because it blindly splits at '.', even in __RFQDN_.  Both
issues will be addressed later in the series.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1488317230-26248-4-git-send-email-armbru@redhat.com>
This commit is contained in:
Markus Armbruster 2017-02-28 22:26:49 +01:00
parent 112c944655
commit d454dbe0ee
6 changed files with 419 additions and 0 deletions

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@ -141,4 +141,7 @@ void qemu_opts_print_help(QemuOptsList *list);
void qemu_opts_free(QemuOptsList *list);
QemuOptsList *qemu_opts_append(QemuOptsList *dst, QemuOptsList *list);
QDict *keyval_parse(const char *params, const char *implied_key,
Error **errp);
#endif

1
tests/.gitignore vendored
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@ -47,6 +47,7 @@ test-io-channel-file.txt
test-io-channel-socket
test-io-channel-tls
test-io-task
test-keyval
test-logging
test-mul64
test-opts-visitor

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@ -94,6 +94,8 @@ check-unit-y += tests/check-qom-proplist$(EXESUF)
gcov-files-check-qom-proplist-y = qom/object.c
check-unit-y += tests/test-qemu-opts$(EXESUF)
gcov-files-test-qemu-opts-y = util/qemu-option.c
check-unit-y += tests/test-keyval$(EXESUF)
gcov-files-test-keyval-y = util/keyval.c
check-unit-y += tests/test-write-threshold$(EXESUF)
gcov-files-test-write-threshold-y = block/write-threshold.c
check-unit-y += tests/test-crypto-hash$(EXESUF)
@ -720,6 +722,7 @@ tests/vhost-user-test$(EXESUF): tests/vhost-user-test.o $(test-util-obj-y) \
$(chardev-obj-y)
tests/qemu-iotests/socket_scm_helper$(EXESUF): tests/qemu-iotests/socket_scm_helper.o
tests/test-qemu-opts$(EXESUF): tests/test-qemu-opts.o $(test-util-obj-y)
tests/test-keyval$(EXESUF): tests/test-keyval.o $(test-util-obj-y)
tests/test-write-threshold$(EXESUF): tests/test-write-threshold.o $(test-block-obj-y)
tests/test-netfilter$(EXESUF): tests/test-netfilter.o $(qtest-obj-y)
tests/test-filter-mirror$(EXESUF): tests/test-filter-mirror.o $(qtest-obj-y)

180
tests/test-keyval.c Normal file
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@ -0,0 +1,180 @@
/*
* Unit tests for parsing of 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.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/option.h"
static void test_keyval_parse(void)
{
Error *err = NULL;
QDict *qdict, *sub_qdict;
char long_key[129];
char *params;
/* Nothing */
qdict = keyval_parse("", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 0);
QDECREF(qdict);
/* Empty key (qemu_opts_parse() accepts this) */
qdict = keyval_parse("=val", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Empty key fragment */
qdict = keyval_parse(".", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
qdict = keyval_parse("key.", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Overlong key */
memset(long_key, 'a', 127);
long_key[127] = 'z';
long_key[128] = 0;
params = g_strdup_printf("k.%s=v", long_key);
qdict = keyval_parse(params + 2, NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Overlong key fragment */
qdict = keyval_parse(params, NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
g_free(params);
/* Long key (qemu_opts_parse() accepts and truncates silently) */
params = g_strdup_printf("k.%s=v", long_key + 1);
qdict = keyval_parse(params + 2, NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(qdict, long_key + 1), ==, "v");
QDECREF(qdict);
/* Long key fragment */
qdict = keyval_parse(params, NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
sub_qdict = qdict_get_qdict(qdict, "k");
g_assert(sub_qdict);
g_assert_cmpuint(qdict_size(sub_qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(sub_qdict, long_key + 1), ==, "v");
QDECREF(qdict);
g_free(params);
/* Multiple keys, last one wins */
qdict = keyval_parse("a=1,b=2,,x,a=3", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 2);
g_assert_cmpstr(qdict_get_try_str(qdict, "a"), ==, "3");
g_assert_cmpstr(qdict_get_try_str(qdict, "b"), ==, "2,x");
QDECREF(qdict);
/* Even when it doesn't in qemu_opts_parse() */
qdict = keyval_parse("id=foo,id=bar", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(qdict, "id"), ==, "bar");
QDECREF(qdict);
/* Dotted keys */
qdict = keyval_parse("a.b.c=1,a.b.c=2,d=3", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 2);
sub_qdict = qdict_get_qdict(qdict, "a");
g_assert(sub_qdict);
g_assert_cmpuint(qdict_size(sub_qdict), ==, 1);
sub_qdict = qdict_get_qdict(sub_qdict, "b");
g_assert(sub_qdict);
g_assert_cmpuint(qdict_size(sub_qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(sub_qdict, "c"), ==, "2");
g_assert_cmpstr(qdict_get_try_str(qdict, "d"), ==, "3");
QDECREF(qdict);
/* Inconsistent dotted keys */
qdict = keyval_parse("a.b=1,a=2", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
qdict = keyval_parse("a.b=1,a.b.c=2", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Trailing comma is ignored */
qdict = keyval_parse("x=y,", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(qdict, "x"), ==, "y");
QDECREF(qdict);
/* Except when it isn't */
qdict = keyval_parse(",", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Value containing ,id= not misinterpreted as qemu_opts_parse() does */
qdict = keyval_parse("x=,,id=bar", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(qdict, "x"), ==, ",id=bar");
QDECREF(qdict);
/* Anti-social ID is left to caller (qemu_opts_parse() rejects it) */
qdict = keyval_parse("id=666", NULL, &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(qdict, "id"), ==, "666");
QDECREF(qdict);
/* Implied value not supported (unlike qemu_opts_parse()) */
qdict = keyval_parse("an,noaus,noaus=", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Implied value, key "no" (qemu_opts_parse(): negated empty key) */
qdict = keyval_parse("no", NULL, &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Implied key */
qdict = keyval_parse("an,aus=off,noaus=", "implied", &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 3);
g_assert_cmpstr(qdict_get_try_str(qdict, "implied"), ==, "an");
g_assert_cmpstr(qdict_get_try_str(qdict, "aus"), ==, "off");
g_assert_cmpstr(qdict_get_try_str(qdict, "noaus"), ==, "");
QDECREF(qdict);
/* Implied dotted key */
qdict = keyval_parse("val", "eins.zwei", &error_abort);
g_assert_cmpuint(qdict_size(qdict), ==, 1);
sub_qdict = qdict_get_qdict(qdict, "eins");
g_assert(sub_qdict);
g_assert_cmpuint(qdict_size(sub_qdict), ==, 1);
g_assert_cmpstr(qdict_get_try_str(sub_qdict, "zwei"), ==, "val");
QDECREF(qdict);
/* Implied key with empty value (qemu_opts_parse() accepts this) */
qdict = keyval_parse(",", "implied", &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Likewise (qemu_opts_parse(): implied key with comma value) */
qdict = keyval_parse(",,,a=1", "implied", &err);
error_free_or_abort(&err);
g_assert(!qdict);
/* Empty key is not an implied key */
qdict = keyval_parse("=val", "implied", &err);
error_free_or_abort(&err);
g_assert(!qdict);
}
int main(int argc, char *argv[])
{
g_test_init(&argc, &argv, NULL);
g_test_add_func("/keyval/keyval_parse", test_keyval_parse);
g_test_run();
return 0;
}

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@ -24,6 +24,7 @@ util-obj-y += error.o qemu-error.o
util-obj-y += id.o
util-obj-y += iov.o qemu-config.o qemu-sockets.o uri.o notify.o
util-obj-y += qemu-option.o qemu-progress.o
util-obj-y += keyval.o
util-obj-y += hexdump.o
util-obj-y += crc32c.o
util-obj-y += uuid.o

231
util/keyval.c Normal file
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@ -0,0 +1,231 @@
/*
* 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 defines a tree of objects rooted at R
* where for each key-val = key-fragment . ... = val in key-vals
* R op key-fragment op ... = val'
* where (left-associative) op is member reference L.key-fragment
* val' is val with ',,' replaced by ','
* and only R may be empty.
*
* Duplicate keys are permitted; all but the last one are ignored.
*
* 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.
*
* The length of any key-fragment must be between 1 and 127.
*
* Design flaw: there is no way to denote an empty non-root object.
* While interpreting "key absent" as empty object 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 absent", which isn't
* the same as "empty object present".
*
* Additional syntax for use with an implied key:
*
* key-vals-ik = val-no-key [ ',' key-vals ]
* val-no-key = / [^=,]* /
*
* where no-key is syntactic sugar for implied-key=val-no-key.
*
* TODO support lists
* TODO support key-fragment with __RFQDN_ prefix (downstream extensions)
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qmp/qstring.h"
#include "qemu/option.h"
/*
* 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 QINCREF().
* 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);
QDECREF(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;
size_t len;
char key_in_cur[128];
QDict *cur;
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 (;;) {
for (len = 0; s + len < key_end && s[len] != '.'; len++) {
}
if (!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;
}
/*
* 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();
const char *s;
s = params;
while (*s) {
s = keyval_parse_one(qdict, s, implied_key, errp);
if (!s) {
QDECREF(qdict);
return NULL;
}
implied_key = NULL;
}
return qdict;
}