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3cf7b6dd3b
By sticking the next pointer first, we don't need a union with
64-bit padding for smaller types. On 32-bit platforms, this
can reduce the size of uint8List from 16 bytes (or 12, depending
on whether 64-bit ints can tolerate 4-byte alignment) down to 8.
It has no effect on 64-bit platforms (where alignment still
dictates a 16-byte struct); but fewer anonymous unions is still
a win in my book.
It requires visit_next_list() to gain a size parameter, to know
what size element to allocate; comparable to the size parameter
of visit_start_struct().
I debated about going one step further, to allow for fewer casts,
by doing:
typedef GenericList GenericList;
struct GenericList {
GenericList *next;
};
struct FooList {
GenericList base;
Foo *value;
};
so that you convert to 'GenericList *' by '&foolist->base', and
back by 'container_of(generic, GenericList, base)' (as opposed to
the existing '(GenericList *)foolist' and '(FooList *)generic').
But doing that would require hoisting the declaration of
GenericList prior to inclusion of qapi-types.h, rather than its
current spot in visitor.h; it also makes iteration a bit more
verbose through 'foolist->base.next' instead of 'foolist->next'.
Note that for lists of objects, the 'value' payload is still
hidden behind a boxed pointer. Someday, it would be nice to do:
struct FooList {
FooList *next;
Foo value;
};
for one less level of malloc for each list element. This patch
is a step in that direction (now that 'next' is no longer at a
fixed non-zero offset within the struct, we can store more than
just a pointer's-worth of data as the value payload), but the
actual conversion would be a task for another series, as it will
touch a lot of code.
Backports commit e65d89bf1a4484e0db0f3dc820a8b209f2fb1e8b from qemu
94 lines
3.7 KiB
C
94 lines
3.7 KiB
C
/*
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* Core Definitions for QAPI Visitor Classes
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#ifndef QAPI_VISITOR_CORE_H
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#define QAPI_VISITOR_CORE_H
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#include "qemu/typedefs.h"
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#include "qapi/qmp/qobject.h"
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#include "qapi/error.h"
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#include <stdlib.h>
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/* This struct is layout-compatible with all other *List structs
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* created by the qapi generator. It is used as a typical
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* singly-linked list. */
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typedef struct GenericList
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{
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struct GenericList *next;
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char padding[];
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} GenericList;
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void visit_start_struct(Visitor *v, const char *name, void **obj,
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size_t size, Error **errp);
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void visit_end_struct(Visitor *v, Error **errp);
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void visit_start_implicit_struct(Visitor *v, void **obj, size_t size,
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Error **errp);
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void visit_end_implicit_struct(Visitor *v);
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void visit_start_list(Visitor *v, const char *name, Error **errp);
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GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size);
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void visit_end_list(Visitor *v);
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/**
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* Check if an optional member @name of an object needs visiting.
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* For input visitors, set *@present according to whether the
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* corresponding visit_type_*() needs calling; for other visitors,
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* leave *@present unchanged. Return *@present for convenience.
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*/
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bool visit_optional(Visitor *v, const char *name, bool *present);
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/**
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* Determine the qtype of the item @name in the current object visit.
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* For input visitors, set *@type to the correct qtype of a qapi
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* alternate type; for other visitors, leave *@type unchanged.
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* If @promote_int, treat integers as QTYPE_FLOAT.
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*/
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void visit_get_next_type(Visitor *v, const char *name, QType *type,
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bool promote_int, Error **errp);
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/*
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* Visit an enum value.
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*
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* @strings expresses the mapping between C enum values and QAPI enum
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* names; it should be the ENUM_lookup array from visit-types.h.
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*
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* May call visit_type_str() under the hood, and the enum visit may
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* fail even if the corresponding string visit succeeded; this implies
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* that visit_type_str() must have no unwelcome side effects.
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*/
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void visit_type_enum(Visitor *v, const char *name, int *obj,
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const char *const strings[], Error **errp);
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void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp);
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void visit_type_uint8(Visitor *v, const char *name, uint8_t *obj,
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Error **errp);
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void visit_type_uint16(Visitor *v, const char *name, uint16_t *obj,
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Error **errp);
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void visit_type_uint32(Visitor *v, const char *name, uint32_t *obj,
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Error **errp);
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void visit_type_uint64(Visitor *v, const char *name, uint64_t *obj,
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Error **errp);
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void visit_type_int8(Visitor *v, const char *name, int8_t *obj, Error **errp);
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void visit_type_int16(Visitor *v, const char *name, int16_t *obj,
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Error **errp);
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void visit_type_int32(Visitor *v, const char *name, int32_t *obj,
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Error **errp);
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void visit_type_int64(Visitor *v, const char *name, int64_t *obj,
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Error **errp);
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void visit_type_size(Visitor *v, const char *name, uint64_t *obj,
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Error **errp);
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void visit_type_bool(Visitor *v, const char *name, bool *obj, Error **errp);
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void visit_type_str(Visitor *v, const char *name, char **obj, Error **errp);
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void visit_type_number(Visitor *v, const char *name, double *obj,
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Error **errp);
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void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp);
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#endif
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