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

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

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;
+
+/* 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;
+}
+
-- 
1.8.5.3