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qemu/qapi/qapi-visit-core.c
Eric Blake a15fcc3cf6 qapi: Add new clone visitor 
We have a couple places in the code base that want to deep-clone
one QAPI object into another, and they were resorting to serializing
the struct out to QObject then reparsing it.  A much more efficient
version can be done by adding a new clone visitor.

Since cloning is still relatively uncommon, expose the use of the
new visitor via a QAPI_CLONE() macro that takes care of type-punning
the underlying function pointer, rather than generating lots of
unused functions for types that won't be cloned.  And yes, we're
relying on the compiler treating all pointers equally, even though
a strict C program cannot portably do so - but we're not the first
one in the qemu code base to expect it to work (hello, glib!).

The choice of adding a fourth visitor type deserves some explanation.
On the surface, the clone visitor is mostly an input visitor (it
takes arbitrary input - in this case, another QAPI object - and
creates a new QAPI object during the course of the visit).  But
ever since commit da72ab0 consolidated enum visits based on the
visitor type, using VISITOR_INPUT would cause us to run
visit_type_str(), even though for cloning there is nothing to do
(we just copy the enum value across, without regards to its mapping
to strings).   Also, since our input happens to be a QAPI object,
we can also satisfy the internal checks for VISITOR_OUTPUT.  So in
the end, I settled with a new VISITOR_CLONE, and chose its value
such that many internal checks can use 'v->type & mask', sticking
to 'v->type == value' where the difference matters.

Note that we can only clone objects (including alternates) and lists,
not built-ins or enums.  The visitor core hides integer width from
the actual visitor (since commit 04e070d), and as long as that's the
case, we can't clone top-level integers.  Then again, those can
always be cloned by direct copy, since they are not objects with
deep pointers, so it's no real loss.  And restricting cloning to
just objects and lists is cleaner than restricting it to non-integers.
As such, I documented that the clone visitor is for direct use only
by code internal to QAPI, and should not be used on incomplete objects
(other than a hack to work around the fact that we allow NULL in place
of "" in visit_type_str() in other output visitors).  Note that as
written, the clone visitor will never fail on a complete object.

Scalars (including enums) not at the root of the clone copy just fine
with no additional effort while visiting the scalar, by virtue of a
g_memdup() each time we push another struct onto the stack.  Cloning
a string requires deduplication of a pointer, which means it can also
provide the guarantee of an input visitor of never producing NULL
even when still accepting NULL in place of "" the way the QMP output
visitor does.

Cloning an 'any' type could be possible by incrementing the QObject
refcnt, but it's not obvious whether that is better than implementing
a QObject deep clone.  So for now, we document it as unsupported,
and intentionally omit the .type_any() callback to let a developer
know their usage needs implementation.

Add testsuite coverage for several different clone situations, to
ensure that the code is working.  I also tested that valgrind was
happy with the test.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-14-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-07-06 10:52:04 +02:00

354 lines
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/*
* Core Definitions for QAPI Visitor Classes
*
* Copyright (C) 2012-2016 Red Hat, Inc.
* Copyright IBM, Corp. 2011
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu-common.h"
#include "qapi/qmp/qobject.h"
#include "qapi/qmp/qerror.h"
#include "qapi/visitor.h"
#include "qapi/visitor-impl.h"
void visit_complete(Visitor *v, void *opaque)
{
assert(v->type != VISITOR_OUTPUT || v->complete);
if (v->complete) {
v->complete(v, opaque);
}
}
void visit_free(Visitor *v)
{
if (v) {
v->free(v);
}
}
void visit_start_struct(Visitor *v, const char *name, void **obj,
size_t size, Error **errp)
{
Error *err = NULL;
if (obj) {
assert(size);
assert(!(v->type & VISITOR_OUTPUT) || *obj);
}
v->start_struct(v, name, obj, size, &err);
if (obj && (v->type & VISITOR_INPUT)) {
assert(!err != !*obj);
}
error_propagate(errp, err);
}
void visit_check_struct(Visitor *v, Error **errp)
{
if (v->check_struct) {
v->check_struct(v, errp);
}
}
void visit_end_struct(Visitor *v, void **obj)
{
v->end_struct(v, obj);
}
void visit_start_list(Visitor *v, const char *name, GenericList **list,
size_t size, Error **errp)
{
Error *err = NULL;
assert(!list || size >= sizeof(GenericList));
v->start_list(v, name, list, size, &err);
if (list && (v->type & VISITOR_INPUT)) {
assert(!(err && *list));
}
error_propagate(errp, err);
}
GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size)
{
assert(tail && size >= sizeof(GenericList));
return v->next_list(v, tail, size);
}
void visit_end_list(Visitor *v, void **obj)
{
v->end_list(v, obj);
}
void visit_start_alternate(Visitor *v, const char *name,
GenericAlternate **obj, size_t size,
bool promote_int, Error **errp)
{
Error *err = NULL;
assert(obj && size >= sizeof(GenericAlternate));
assert(!(v->type & VISITOR_OUTPUT) || *obj);
if (v->start_alternate) {
v->start_alternate(v, name, obj, size, promote_int, &err);
}
if (v->type & VISITOR_INPUT) {
assert(v->start_alternate && !err != !*obj);
}
error_propagate(errp, err);
}
void visit_end_alternate(Visitor *v, void **obj)
{
if (v->end_alternate) {
v->end_alternate(v, obj);
}
}
bool visit_optional(Visitor *v, const char *name, bool *present)
{
if (v->optional) {
v->optional(v, name, present);
}
return *present;
}
bool visit_is_input(Visitor *v)
{
return v->type == VISITOR_INPUT;
}
void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp)
{
assert(obj);
v->type_int64(v, name, obj, errp);
}
static void visit_type_uintN(Visitor *v, uint64_t *obj, const char *name,
uint64_t max, const char *type, Error **errp)
{
Error *err = NULL;
uint64_t value = *obj;
v->type_uint64(v, name, &value, &err);
if (err) {
error_propagate(errp, err);
} else if (value > max) {
error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
name ? name : "null", type);
} else {
*obj = value;
}
}
void visit_type_uint8(Visitor *v, const char *name, uint8_t *obj,
Error **errp)
{
uint64_t value = *obj;
visit_type_uintN(v, &value, name, UINT8_MAX, "uint8_t", errp);
*obj = value;
}
void visit_type_uint16(Visitor *v, const char *name, uint16_t *obj,
Error **errp)
{
uint64_t value = *obj;
visit_type_uintN(v, &value, name, UINT16_MAX, "uint16_t", errp);
*obj = value;
}
void visit_type_uint32(Visitor *v, const char *name, uint32_t *obj,
Error **errp)
{
uint64_t value = *obj;
visit_type_uintN(v, &value, name, UINT32_MAX, "uint32_t", errp);
*obj = value;
}
void visit_type_uint64(Visitor *v, const char *name, uint64_t *obj,
Error **errp)
{
assert(obj);
v->type_uint64(v, name, obj, errp);
}
static void visit_type_intN(Visitor *v, int64_t *obj, const char *name,
int64_t min, int64_t max, const char *type,
Error **errp)
{
Error *err = NULL;
int64_t value = *obj;
v->type_int64(v, name, &value, &err);
if (err) {
error_propagate(errp, err);
} else if (value < min || value > max) {
error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
name ? name : "null", type);
} else {
*obj = value;
}
}
void visit_type_int8(Visitor *v, const char *name, int8_t *obj, Error **errp)
{
int64_t value = *obj;
visit_type_intN(v, &value, name, INT8_MIN, INT8_MAX, "int8_t", errp);
*obj = value;
}
void visit_type_int16(Visitor *v, const char *name, int16_t *obj,
Error **errp)
{
int64_t value = *obj;
visit_type_intN(v, &value, name, INT16_MIN, INT16_MAX, "int16_t", errp);
*obj = value;
}
void visit_type_int32(Visitor *v, const char *name, int32_t *obj,
Error **errp)
{
int64_t value = *obj;
visit_type_intN(v, &value, name, INT32_MIN, INT32_MAX, "int32_t", errp);
*obj = value;
}
void visit_type_int64(Visitor *v, const char *name, int64_t *obj,
Error **errp)
{
assert(obj);
v->type_int64(v, name, obj, errp);
}
void visit_type_size(Visitor *v, const char *name, uint64_t *obj,
Error **errp)
{
assert(obj);
if (v->type_size) {
v->type_size(v, name, obj, errp);
} else {
v->type_uint64(v, name, obj, errp);
}
}
void visit_type_bool(Visitor *v, const char *name, bool *obj, Error **errp)
{
assert(obj);
v->type_bool(v, name, obj, errp);
}
void visit_type_str(Visitor *v, const char *name, char **obj, Error **errp)
{
Error *err = NULL;
assert(obj);
/* TODO: Fix callers to not pass NULL when they mean "", so that we
* can enable:
assert(!(v->type & VISITOR_OUTPUT) || *obj);
*/
v->type_str(v, name, obj, &err);
if (v->type & VISITOR_INPUT) {
assert(!err != !*obj);
}
error_propagate(errp, err);
}
void visit_type_number(Visitor *v, const char *name, double *obj,
Error **errp)
{
assert(obj);
v->type_number(v, name, obj, errp);
}
void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp)
{
Error *err = NULL;
assert(obj);
assert(v->type != VISITOR_OUTPUT || *obj);
v->type_any(v, name, obj, &err);
if (v->type == VISITOR_INPUT) {
assert(!err != !*obj);
}
error_propagate(errp, err);
}
void visit_type_null(Visitor *v, const char *name, Error **errp)
{
v->type_null(v, name, errp);
}
static void output_type_enum(Visitor *v, const char *name, int *obj,
const char *const strings[], Error **errp)
{
int i = 0;
int value = *obj;
char *enum_str;
while (strings[i++] != NULL);
if (value < 0 || value >= i - 1) {
error_setg(errp, QERR_INVALID_PARAMETER, name ? name : "null");
return;
}
enum_str = (char *)strings[value];
visit_type_str(v, name, &enum_str, errp);
}
static void input_type_enum(Visitor *v, const char *name, int *obj,
const char *const strings[], Error **errp)
{
Error *local_err = NULL;
int64_t value = 0;
char *enum_str;
visit_type_str(v, name, &enum_str, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
while (strings[value] != NULL) {
if (strcmp(strings[value], enum_str) == 0) {
break;
}
value++;
}
if (strings[value] == NULL) {
error_setg(errp, QERR_INVALID_PARAMETER, enum_str);
g_free(enum_str);
return;
}
g_free(enum_str);
*obj = value;
}
void visit_type_enum(Visitor *v, const char *name, int *obj,
const char *const strings[], Error **errp)
{
assert(obj && strings);
switch (v->type) {
case VISITOR_INPUT:
input_type_enum(v, name, obj, strings, errp);
break;
case VISITOR_OUTPUT:
output_type_enum(v, name, obj, strings, errp);
break;
case VISITOR_CLONE:
/* nothing further to do, scalar value was already copied by
* g_memdup() during visit_start_*() */
break;
case VISITOR_DEALLOC:
/* nothing to deallocate for a scalar */
break;
}
}
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