From 983f52d4b3f86fb9dc9f8b142132feb5a8723016 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 28 Apr 2016 15:45:09 -0600 Subject: qapi-visit: Add visitor.type classification We have three classes of QAPI visitors: input, output, and dealloc. Currently, all implementations of these visitors have one thing in common based on their visitor type: the implementation used for the visit_type_enum() callback. But since we plan to add more such common behavior, in relation to documenting and further refining the semantics, it makes more sense to have the visitor implementations advertise which class they belong to, so the common qapi-visit-core code can use that information in multiple places. A later patch will better document the types of visitors directly in visitor.h. For this patch, knowing the class of a visitor implementation lets us make input_type_enum() and output_type_enum() become static functions, by replacing the callback function Visitor.type_enum() with the simpler enum member Visitor.type. Share a common assertion in qapi-visit-core as part of the refactoring. Move comments in opts-visitor.c to match the refactored layout. Signed-off-by: Eric Blake Message-Id: <1461879932-9020-2-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- qapi/string-output-visitor.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'qapi/string-output-visitor.c') diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c index c2e5c5b..0d44d7e 100644 --- a/qapi/string-output-visitor.c +++ b/qapi/string-output-visitor.c @@ -351,7 +351,7 @@ StringOutputVisitor *string_output_visitor_new(bool human) v->string = g_string_new(NULL); v->human = human; - v->visitor.type_enum = output_type_enum; + v->visitor.type = VISITOR_OUTPUT; v->visitor.type_int64 = print_type_int64; v->visitor.type_uint64 = print_type_uint64; v->visitor.type_size = print_type_size; -- cgit v1.1 From d9f62dde1303286b24ac8ce88be27e2b9b9c5f46 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 28 Apr 2016 15:45:31 -0600 Subject: qapi: Simplify semantics of visit_next_list() The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- qapi/string-output-visitor.c | 41 ++++++++++++++--------------------------- 1 file changed, 14 insertions(+), 27 deletions(-) (limited to 'qapi/string-output-visitor.c') diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c index 0d44d7e..d013196 100644 --- a/qapi/string-output-visitor.c +++ b/qapi/string-output-visitor.c @@ -20,7 +20,7 @@ enum ListMode { LM_NONE, /* not traversing a list of repeated options */ - LM_STARTED, /* start_list() succeeded */ + LM_STARTED, /* next_list() ready to be called */ LM_IN_PROGRESS, /* next_list() has been called. * @@ -48,7 +48,7 @@ enum ListMode { LM_UNSIGNED_INTERVAL,/* Same as above, only for an unsigned interval. */ - LM_END + LM_END, /* next_list() called, about to see last element. */ }; typedef enum ListMode ListMode; @@ -58,7 +58,6 @@ struct StringOutputVisitor Visitor visitor; bool human; GString *string; - bool head; ListMode list_mode; union { int64_t s; @@ -266,39 +265,29 @@ static void print_type_number(Visitor *v, const char *name, double *obj, } static void -start_list(Visitor *v, const char *name, Error **errp) +start_list(Visitor *v, const char *name, GenericList **list, size_t size, + Error **errp) { StringOutputVisitor *sov = to_sov(v); /* we can't traverse a list in a list */ assert(sov->list_mode == LM_NONE); - sov->list_mode = LM_STARTED; - sov->head = true; + /* We don't support visits without a list */ + assert(list); + /* List handling is only needed if there are at least two elements */ + if (*list && (*list)->next) { + sov->list_mode = LM_STARTED; + } } -static GenericList *next_list(Visitor *v, GenericList **list, size_t size) +static GenericList *next_list(Visitor *v, GenericList *tail, size_t size) { StringOutputVisitor *sov = to_sov(v); - GenericList *ret = NULL; - if (*list) { - if (sov->head) { - ret = *list; - } else { - ret = (*list)->next; - } + GenericList *ret = tail->next; - if (sov->head) { - if (ret && ret->next == NULL) { - sov->list_mode = LM_NONE; - } - sov->head = false; - } else { - if (ret && ret->next == NULL) { - sov->list_mode = LM_END; - } - } + if (ret && !ret->next) { + sov->list_mode = LM_END; } - return ret; } @@ -311,8 +300,6 @@ static void end_list(Visitor *v) sov->list_mode == LM_NONE || sov->list_mode == LM_IN_PROGRESS); sov->list_mode = LM_NONE; - sov->head = true; - } char *string_output_get_string(StringOutputVisitor *sov) -- cgit v1.1