Re: [Qemu-devel] [RFC PATCH v2 01/16] Visitor: Add methods for migration format use

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 23, 2014 at 05:37:34PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> array types
>     From  https://lists.gnu.org/archive/html/qemu-devel/2011-09/msg02465.html
> 
> str256 type
>     For the upto 256byte strings QEMU commonly uses for IDs
> 
> buffer type
>     For a blob of data that the caller wants to deliver whole (e.g.
>     a page of RAM or block of disk)
> 
> Load/save flags to let a user perform pre-save/post-load checking
> 
> An accessor to get the underlying QEMUFile* (for compatibility)
> 
> compat-sequences
>     Provide enough information for a visitor providing compatibility
> with the old format to generate it's byte stream, while allowing a new
> visitor to do something sensible.
> 
> destroy
>     Allows the caller to destroy a visitor without knowing what type of
>     visitor it is.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  include/qapi/visitor-impl.h | 23 +++++++++++++
>  include/qapi/visitor.h      | 51 +++++++++++++++++++++++++++++
>  qapi/qapi-visit-core.c      | 80 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 154 insertions(+)
> 
> diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
> index f3fa420..10cdbf7 100644
> --- a/include/qapi/visitor-impl.h
> +++ b/include/qapi/visitor-impl.h
> @@ -15,6 +15,9 @@
>  #include "qapi/error.h"
>  #include "qapi/visitor.h"
>  
> +#define VISITOR_SAVING (1<<0)
> +#define VISITOR_LOADING (1<<1)
> +
>  struct Visitor
>  {
>      /* Must be set */
> @@ -29,6 +32,10 @@ struct Visitor
>      void (*start_list)(Visitor *v, const char *name, Error **errp);
>      GenericList *(*next_list)(Visitor *v, GenericList **list, Error **errp);
>      void (*end_list)(Visitor *v, Error **errp);
> +    void (*start_array)(Visitor *v, void **obj, const char *name,
> +                        size_t elem_count, size_t elem_size, Error **errp);
> +    void (*next_array)(Visitor *v, Error **errp);
> +    void (*end_array)(Visitor *v, Error **errp);
>  
>      void (*type_enum)(Visitor *v, int *obj, const char *strings[],
>                        const char *kind, const char *name, Error **errp);
> @@ -38,6 +45,7 @@ struct Visitor
>      void (*type_int)(Visitor *v, int64_t *obj, const char *name, Error **errp);
>      void (*type_bool)(Visitor *v, bool *obj, const char *name, Error **errp);
>      void (*type_str)(Visitor *v, char **obj, const char *name, Error **errp);
> +    void (*type_str256)(Visitor *v, char *obj, const char *name, Error **errp);
>      void (*type_number)(Visitor *v, double *obj, const char *name,
>                          Error **errp);
>  
> @@ -49,6 +57,8 @@ struct Visitor
>      void (*start_handle)(Visitor *v, void **obj, const char *kind,
>                           const char *name, Error **errp);
>      void (*end_handle)(Visitor *v, Error **errp);
> +    void (*type_buffer)(Visitor *v, void *data, size_t len, bool async,
> +                        const char *name, Error **errp);
>      void (*type_uint8)(Visitor *v, uint8_t *obj, const char *name, Error **errp);
>      void (*type_uint16)(Visitor *v, uint16_t *obj, const char *name, Error **errp);
>      void (*type_uint32)(Visitor *v, uint32_t *obj, const char *name, Error **errp);
> @@ -59,6 +69,19 @@ struct Visitor
>      void (*type_int64)(Visitor *v, int64_t *obj, const char *name, Error **errp);
>      /* visit_type_size() falls back to (*type_uint64)() if type_size is unset */
>      void (*type_size)(Visitor *v, uint64_t *obj, const char *name, Error **errp);
> +
> +    void (*destroy)(Visitor *v, Error **errp);
> +
> +    void (*start_sequence_compat)(Visitor *v, const char *name,
> +                                  Visit_seq_compat_mode compat_mode,
> +                                  void *opaque, Error **errp);
> +    void (*end_sequence_compat)(Visitor *v, const char *name,
> +                                Visit_seq_compat_mode compat_mode,
> +                                Error **errp);
> +
> +    QEMUFile* (*get_qemufile)(Visitor *v);
> +
> +    uint64_t flags;
>  };
>  
>  void input_type_enum(Visitor *v, int *obj, const char *strings[],
> diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
> index 29da211..70c20df 100644
> --- a/include/qapi/visitor.h
> +++ b/include/qapi/visitor.h
> @@ -39,11 +39,22 @@ void visit_end_implicit_struct(Visitor *v, Error **errp);
>  void visit_start_list(Visitor *v, const char *name, Error **errp);
>  GenericList *visit_next_list(Visitor *v, GenericList **list, Error **errp);
>  void visit_end_list(Visitor *v, Error **errp);
> +void visit_start_array(Visitor *v, void **obj, const char *name,
> +                       size_t elem_count, size_t elem_size, Error **errp);
> +void visit_next_array(Visitor *v, Error **errp);
> +void visit_end_array(Visitor *v, Error **errp);
> +
>  void visit_start_optional(Visitor *v, bool *present, const char *name,
>                            Error **errp);
>  void visit_end_optional(Visitor *v, Error **errp);
>  void visit_get_next_type(Visitor *v, int *obj, const int *qtypes,
>                           const char *name, Error **errp);
> +/* Blocks of guest memory,disk or otherwise opaque data that there is a lot
> + * of and must be handled efficiently. 'async' true if the write can happen
> + * 'later'
> + */
> +void visit_type_buffer(Visitor *v, void *data, size_t len, bool async,
> +                       const char *name, Error **errp);
>  void visit_type_enum(Visitor *v, int *obj, const char *strings[],
>                       const char *kind, const char *name, Error **errp);
>  void visit_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp);
> @@ -58,6 +69,46 @@ void visit_type_int64(Visitor *v, int64_t *obj, const char *name, Error **errp);
>  void visit_type_size(Visitor *v, uint64_t *obj, const char *name, Error **errp);
>  void visit_type_bool(Visitor *v, bool *obj, const char *name, Error **errp);
>  void visit_type_str(Visitor *v, char **obj, const char *name, Error **errp);
> +/* A string no more than 256 (including term) characters in length */
> +void visit_type_str256(Visitor *v, char *obj, const char *name, Error **errp);
>  void visit_type_number(Visitor *v, double *obj, const char *name, Error **errp);
> +void visit_destroy(Visitor *v, Error **errp);
> +
> +/* Type of visitor, used where actions have to be taken when (de)serializing */
> +bool visitor_loading(Visitor *v);
> +bool visitor_saving(Visitor *v);
> +
> +typedef enum {
> +    VISIT_SEQ_COMPAT_BYTE0TERM,      /* list terminated with a 0 byte */
> +    VISIT_SEQ_COMPAT_FILE,           /* The top level file object */
> +    VISIT_SEQ_COMPAT_SUBSECLIST,     /* list terminated by
> +                                        historical complexity */
> +    VISIT_SEQ_COMPAT_SUBSECTION,     /* One subsection */
> +    VISIT_SEQ_COMPAT_SECTION_HEADER, /* SECTION_FULL/START, header + name */
> +    VISIT_SEQ_COMPAT_SECTION_MIN,    /* SECTION_PART/END - minimal header */
> +    VISIT_SEQ_COMPAT_RAMSECLIST,     /* list terminated by int64 bit
> +                                        RAM_SAVE_FLAG_EOS */
> +    VISIT_SEQ_COMPAT_RAMSECENTRY,    /* Entry in RAM Sec list */
> +    VISIT_SEQ_COMPAT_VMSTATE,        /* One VMState */
> +    VISIT_SEQ_COMPAT_BLOB            /* A binary old-format blob */
> +} Visit_seq_compat_mode;

VisitorSeqCompatMode

We have visit_ for functions but Visitor for types ...

> +
> +/* Start a sequence of items (which may be of unknown length and unknown
> + * mix of some subset of types), specify a compatibility mode that's only
> + * used by an implementation trying to match the existing binary migration
> + * format.
> + * opaque is compat_mode specific
> + */
> +void visit_start_sequence_compat(Visitor *v, const char *name,
> +                                 Visit_seq_compat_mode compat_mode,
> +                                 void *opaque,
> +                                 Error **errp);
> +/* Use visit_get_next_type for each entry including the first */
> +void visit_end_sequence_compat(Visitor *v, const char *name,
> +                                 Visit_seq_compat_mode compat_mode,
> +                                 Error **errp);
> +
> +/* Don't Use! - lets us move forward until we can get rid of all file uses */
> +QEMUFile *visitor_get_qemufile(Visitor *v);
>  
>  #endif
> diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
> index 6451a21..2d20fde 100644
> --- a/qapi/qapi-visit-core.c
> +++ b/qapi/qapi-visit-core.c
> @@ -84,6 +84,28 @@ void visit_end_list(Visitor *v, Error **errp)
>      v->end_list(v, errp);
>  }
>  
> +void visit_start_array(Visitor *v, void **obj, const char *name,
> +                       size_t elem_count, size_t elem_size, Error **errp)
> +{
> +    if (!error_is_set(errp)) {
> +        v->start_array(v, obj, name, elem_count, elem_size, errp);
> +    }
> +}
> +
> +void visit_next_array(Visitor *v, Error **errp)
> +{
> +    if (!error_is_set(errp)) {
> +        v->next_array(v, errp);
> +    }
> +}
> +
> +void visit_end_array(Visitor *v, Error **errp)
> +{
> +    if (!error_is_set(errp)) {
> +        v->end_array(v, errp);
> +    }
> +}
> +
>  void visit_start_optional(Visitor *v, bool *present, const char *name,
>                            Error **errp)
>  {
> @@ -107,6 +129,14 @@ void visit_get_next_type(Visitor *v, int *obj, const int *qtypes,
>      }
>  }
>  
> +void visit_type_buffer(Visitor *v, void *data, size_t len, bool async,
> +                       const char *name, Error **errp)
> +{
> +    if (!error_is_set(errp)) {
> +        v->type_buffer(v, data, len, async, name, errp);
> +    }
> +}
> +
>  void visit_type_enum(Visitor *v, int *obj, const char *strings[],
>                       const char *kind, const char *name, Error **errp)
>  {
> @@ -291,6 +321,13 @@ void visit_type_str(Visitor *v, char **obj, const char *name, Error **errp)
>      }
>  }
>  
> +void visit_type_str256(Visitor *v, char *obj, const char *name, Error **errp)
> +{
> +    if (!error_is_set(errp)) {
> +        v->type_str256(v, obj, name, errp);
> +    }
> +}
> +
>  void visit_type_number(Visitor *v, double *obj, const char *name, Error **errp)
>  {
>      if (!error_is_set(errp)) {
> @@ -347,3 +384,46 @@ void input_type_enum(Visitor *v, int *obj, const char *strings[],
>      g_free(enum_str);
>      *obj = value;
>  }
> +
> +void visit_destroy(Visitor *v, Error **errp)
> +{
> +    v->destroy(v, errp);
> +}
> +
> +void visit_start_sequence_compat(Visitor *v, const char *name,
> +                                 Visit_seq_compat_mode compat_mode,
> +                                 void *opaque, Error **errp)
> +{
> +    if (error_is_set(errp)) {
> +        return;
> +    }
> +
> +    v->start_sequence_compat(v, name, compat_mode, opaque, errp);
> +}
> +
> +void visit_end_sequence_compat(Visitor *v, const char *name,
> +                                 Visit_seq_compat_mode compat_mode,
> +                               Error **errp)
> +{
> +    if (error_is_set(errp)) {
> +        return;
> +    }
> +
> +    v->end_sequence_compat(v, name, compat_mode, errp);
> +}
> +
> +QEMUFile *visitor_get_qemufile(Visitor *v)
> +{
> +    return v->get_qemufile(v);
> +}
> +
> +bool visitor_loading(Visitor *v)
> +{
> +    return v->flags & VISITOR_LOADING;
> +}
> +
> +bool visitor_saving(Visitor *v)
> +{
> +    return v->flags & VISITOR_SAVING;
> +}
> +
> -- 
> 1.9.0