qapi: introduce OptsVisitor

This visitor supports parsing

  -option [type=]discriminator[,optarg1=val1][,optarg2=val2][,...]

style QemuOpts objects into "native" C structures. After defining the type
tree in the qapi schema (see below), a root type traversal with this
visitor linked to the underlying QemuOpts object will build the "native" C
representation of the option.

The type tree in the schema, corresponding to an option with a
discriminator, must have the following structure:

  struct
    scalar member for non-discriminated optarg 1 [*]
    list for repeating non-discriminated optarg 2 [*]
      wrapper struct
        single scalar member
    union
      struct for discriminator case 1
        scalar member for optarg 3 [*]
        list for repeating optarg 4 [*]
          wrapper struct
            single scalar member
        scalar member for optarg 5 [*]
      struct for discriminator case 2
        ...

The "type" optarg name is fixed for the discriminator role. Its schema
representation is "union of structures", and each discriminator value must
correspond to a member name in the union.

If the option takes no "type" descriminator, then the type subtree rooted
at the union must be absent from the schema (including the union itself).

Optarg values can be of scalar types str / bool / integers / size.

Members marked with [*] may be defined as optional in the schema,
describing an optional optarg.

Repeating an optarg is supported; its schema representation must be "list
of structure with single mandatory scalar member". If an optarg is not
described as repeating in the schema (ie. it is defined as a scalar field
instead of a list), its last occurrence will take effect. Ordering between
differently named optargs is not preserved.

A mandatory list (or an optional one which is reported to be available),
corresponding to a repeating optarg, has at least one element after
successful parsing.

v1->v2:
- Update opts_type_size() prototype to uint64_t.
- Add opts_type_uint64() for options needing the full uint64_t range.
  (Internals could be extracted to "cutils.c".)
- Allow negative values in opts_type_int().
- Rebase to nested Makefiles.

v2->v3:
- Factor opts_visitor_insert() out of opts_start_struct() and call it
  separately for opts_root->id if there's any.
- Don't require non-negative values in opts_type_int()'s error message.
- g_malloc0() may return NULL for zero-sized requests. Support empty
  structures by requesting 1 byte for them instead.

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

qapi/Makefile.objs

@@ -1,3 +1,3 @@
 qapi-obj-y = qapi-visit-core.o qapi-dealloc-visitor.o qmp-input-visitor.o
 qapi-obj-y += qmp-output-visitor.o qmp-registry.o qmp-dispatch.o
-qapi-obj-y += string-input-visitor.o string-output-visitor.o
+qapi-obj-y += string-input-visitor.o string-output-visitor.o opts-visitor.o

qapi/opts-visitor.c

@@ -0,0 +1,427 @@
+/*
+ * Options Visitor
+ *
+ * Copyright Red Hat, Inc. 2012
+ *
+ * Author: Laszlo Ersek <lersek@redhat.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 "opts-visitor.h"
+#include "qemu-queue.h"
+#include "qemu-option-internal.h"
+#include "qapi-visit-impl.h"
+
+
+struct OptsVisitor
+{
+    Visitor visitor;
+
+    /* Ownership remains with opts_visitor_new()'s caller. */
+    const QemuOpts *opts_root;
+
+    unsigned depth;
+
+    /* Non-null iff depth is positive. Each key is a QemuOpt name. Each value
+     * is a non-empty GQueue, enumerating all QemuOpt occurrences with that
+     * name. */
+    GHashTable *unprocessed_opts;
+
+    /* The list currently being traversed with opts_start_list() /
+     * opts_next_list(). The list must have a struct element type in the
+     * schema, with a single mandatory scalar member. */
+    GQueue *repeated_opts;
+    bool repeated_opts_first;
+
+    /* If "opts_root->id" is set, reinstantiate it as a fake QemuOpt for
+     * uniformity. Only its "name" and "str" fields are set. "fake_id_opt" does
+     * not survive or escape the OptsVisitor object.
+     */
+    QemuOpt *fake_id_opt;
+};
+
+
+static void
+destroy_list(gpointer list)
+{
+  g_queue_free(list);
+}
+
+
+static void
+opts_visitor_insert(GHashTable *unprocessed_opts, const QemuOpt *opt)
+{
+    GQueue *list;
+
+    list = g_hash_table_lookup(unprocessed_opts, opt->name);
+    if (list == NULL) {
+        list = g_queue_new();
+
+        /* GHashTable will never try to free the keys -- we supply NULL as
+         * "key_destroy_func" in opts_start_struct(). Thus cast away key
+         * const-ness in order to suppress gcc's warning.
+         */
+        g_hash_table_insert(unprocessed_opts, (gpointer)opt->name, list);
+    }
+
+    /* Similarly, destroy_list() doesn't call g_queue_free_full(). */
+    g_queue_push_tail(list, (gpointer)opt);
+}
+
+
+static void
+opts_start_struct(Visitor *v, void **obj, const char *kind,
+                  const char *name, size_t size, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    const QemuOpt *opt;
+
+    *obj = g_malloc0(size > 0 ? size : 1);
+    if (ov->depth++ > 0) {
+        return;
+    }
+
+    ov->unprocessed_opts = g_hash_table_new_full(&g_str_hash, &g_str_equal,
+                                                 NULL, &destroy_list);
+    QTAILQ_FOREACH(opt, &ov->opts_root->head, next) {
+        /* ensured by qemu-option.c::opts_do_parse() */
+        assert(strcmp(opt->name, "id") != 0);
+
+        opts_visitor_insert(ov->unprocessed_opts, opt);
+    }
+
+    if (ov->opts_root->id != NULL) {
+        ov->fake_id_opt = g_malloc0(sizeof *ov->fake_id_opt);
+
+        ov->fake_id_opt->name = "id";
+        ov->fake_id_opt->str = ov->opts_root->id;
+        opts_visitor_insert(ov->unprocessed_opts, ov->fake_id_opt);
+    }
+}
+
+
+static gboolean
+ghr_true(gpointer ign_key, gpointer ign_value, gpointer ign_user_data)
+{
+    return TRUE;
+}
+
+
+static void
+opts_end_struct(Visitor *v, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    GQueue *any;
+
+    if (--ov->depth > 0) {
+        return;
+    }
+
+    /* we should have processed all (distinct) QemuOpt instances */
+    any = g_hash_table_find(ov->unprocessed_opts, &ghr_true, NULL);
+    if (any) {
+        const QemuOpt *first;
+
+        first = g_queue_peek_head(any);
+        error_set(errp, QERR_INVALID_PARAMETER, first->name);
+    }
+    g_hash_table_destroy(ov->unprocessed_opts);
+    ov->unprocessed_opts = NULL;
+    g_free(ov->fake_id_opt);
+    ov->fake_id_opt = NULL;
+}
+
+
+static GQueue *
+lookup_distinct(const OptsVisitor *ov, const char *name, Error **errp)
+{
+    GQueue *list;
+
+    list = g_hash_table_lookup(ov->unprocessed_opts, name);
+    if (!list) {
+        error_set(errp, QERR_MISSING_PARAMETER, name);
+    }
+    return list;
+}
+
+
+static void
+opts_start_list(Visitor *v, const char *name, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+
+    /* we can't traverse a list in a list */
+    assert(ov->repeated_opts == NULL);
+    ov->repeated_opts = lookup_distinct(ov, name, errp);
+    ov->repeated_opts_first = (ov->repeated_opts != NULL);
+}
+
+
+static GenericList *
+opts_next_list(Visitor *v, GenericList **list, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    GenericList **link;
+
+    if (ov->repeated_opts_first) {
+        ov->repeated_opts_first = false;
+        link = list;
+    } else {
+        const QemuOpt *opt;
+
+        opt = g_queue_pop_head(ov->repeated_opts);
+        if (g_queue_is_empty(ov->repeated_opts)) {
+            g_hash_table_remove(ov->unprocessed_opts, opt->name);
+            return NULL;
+        }
+        link = &(*list)->next;
+    }
+
+    *link = g_malloc0(sizeof **link);
+    return *link;
+}
+
+
+static void
+opts_end_list(Visitor *v, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+
+    ov->repeated_opts = NULL;
+}
+
+
+static const QemuOpt *
+lookup_scalar(const OptsVisitor *ov, const char *name, Error **errp)
+{
+    if (ov->repeated_opts == NULL) {
+        GQueue *list;
+
+        /* the last occurrence of any QemuOpt takes effect when queried by name
+         */
+        list = lookup_distinct(ov, name, errp);
+        return list ? g_queue_peek_tail(list) : NULL;
+    }
+    return g_queue_peek_head(ov->repeated_opts);
+}
+
+
+static void
+processed(OptsVisitor *ov, const char *name)
+{
+    if (ov->repeated_opts == NULL) {
+        g_hash_table_remove(ov->unprocessed_opts, name);
+    }
+}
+
+
+static void
+opts_type_str(Visitor *v, char **obj, const char *name, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    const QemuOpt *opt;
+
+    opt = lookup_scalar(ov, name, errp);
+    if (!opt) {
+        return;
+    }
+    *obj = g_strdup(opt->str ? opt->str : "");
+    processed(ov, name);
+}
+
+
+/* mimics qemu-option.c::parse_option_bool() */
+static void
+opts_type_bool(Visitor *v, bool *obj, const char *name, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    const QemuOpt *opt;
+
+    opt = lookup_scalar(ov, name, errp);
+    if (!opt) {
+        return;
+    }
+
+    if (opt->str) {
+        if (strcmp(opt->str, "on") == 0 ||
+            strcmp(opt->str, "yes") == 0 ||
+            strcmp(opt->str, "y") == 0) {
+            *obj = true;
+        } else if (strcmp(opt->str, "off") == 0 ||
+            strcmp(opt->str, "no") == 0 ||
+            strcmp(opt->str, "n") == 0) {
+            *obj = false;
+        } else {
+            error_set(errp, QERR_INVALID_PARAMETER_VALUE, opt->name,
+                "on|yes|y|off|no|n");
+            return;
+        }
+    } else {
+        *obj = true;
+    }
+
+    processed(ov, name);
+}
+
+
+static void
+opts_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    const QemuOpt *opt;
+    const char *str;
+    long long val;
+    char *endptr;
+
+    opt = lookup_scalar(ov, name, errp);
+    if (!opt) {
+        return;
+    }
+    str = opt->str ? opt->str : "";
+
+    errno = 0;
+    val = strtoll(str, &endptr, 0);
+    if (*str != '\0' && *endptr == '\0' && errno == 0 && INT64_MIN <= val &&
+        val <= INT64_MAX) {
+        *obj = val;
+        processed(ov, name);
+        return;
+    }
+    error_set(errp, QERR_INVALID_PARAMETER_VALUE, opt->name, "an int64 value");
+}
+
+
+static void
+opts_type_uint64(Visitor *v, uint64_t *obj, const char *name, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    const QemuOpt *opt;
+    const char *str;
+
+    opt = lookup_scalar(ov, name, errp);
+    if (!opt) {
+        return;
+    }
+
+    str = opt->str;
+    if (str != NULL) {
+        while (isspace((unsigned char)*str)) {
+            ++str;
+        }
+
+        if (*str != '-' && *str != '\0') {
+            unsigned long long val;
+            char *endptr;
+
+            /* non-empty, non-negative subject sequence */
+            errno = 0;
+            val = strtoull(str, &endptr, 0);
+            if (*endptr == '\0' && errno == 0 && val <= UINT64_MAX) {
+                *obj = val;
+                processed(ov, name);
+                return;
+            }
+        }
+    }
+    error_set(errp, QERR_INVALID_PARAMETER_VALUE, opt->name,
+              "an uint64 value");
+}
+
+
+static void
+opts_type_size(Visitor *v, uint64_t *obj, const char *name, Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    const QemuOpt *opt;
+    int64_t val;
+    char *endptr;
+
+    opt = lookup_scalar(ov, name, errp);
+    if (!opt) {
+        return;
+    }
+
+    val = strtosz_suffix(opt->str ? opt->str : "", &endptr,
+                         STRTOSZ_DEFSUFFIX_B);
+    if (val != -1 && *endptr == '\0') {
+        *obj = val;
+        processed(ov, name);
+        return;
+    }
+    error_set(errp, QERR_INVALID_PARAMETER_VALUE, opt->name,
+              "a size value representible as a non-negative int64");
+}
+
+
+static void
+opts_start_optional(Visitor *v, bool *present, const char *name,
+                       Error **errp)
+{
+    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+
+    /* we only support a single mandatory scalar field in a list node */
+    assert(ov->repeated_opts == NULL);
+    *present = (lookup_distinct(ov, name, NULL) != NULL);
+}
+
+
+OptsVisitor *
+opts_visitor_new(const QemuOpts *opts)
+{
+    OptsVisitor *ov;
+
+    ov = g_malloc0(sizeof *ov);
+
+    ov->visitor.start_struct = &opts_start_struct;
+    ov->visitor.end_struct   = &opts_end_struct;
+
+    ov->visitor.start_list = &opts_start_list;
+    ov->visitor.next_list  = &opts_next_list;
+    ov->visitor.end_list   = &opts_end_list;
+
+    /* input_type_enum() covers both "normal" enums and union discriminators.
+     * The union discriminator field is always generated as "type"; it should
+     * match the "type" QemuOpt child of any QemuOpts.
+     *
+     * input_type_enum() will remove the looked-up key from the
+     * "unprocessed_opts" hash even if the lookup fails, because the removal is
+     * done earlier in opts_type_str(). This should be harmless.
+     */
+    ov->visitor.type_enum = &input_type_enum;
+
+    ov->visitor.type_int    = &opts_type_int;
+    ov->visitor.type_uint64 = &opts_type_uint64;
+    ov->visitor.type_size   = &opts_type_size;
+    ov->visitor.type_bool   = &opts_type_bool;
+    ov->visitor.type_str    = &opts_type_str;
+
+    /* type_number() is not filled in, but this is not the first visitor to
+     * skip some mandatory methods... */
+
+    ov->visitor.start_optional = &opts_start_optional;
+
+    ov->opts_root = opts;
+
+    return ov;
+}
+
+
+void
+opts_visitor_cleanup(OptsVisitor *ov)
+{
+    if (ov->unprocessed_opts != NULL) {
+        g_hash_table_destroy(ov->unprocessed_opts);
+    }
+    g_free(ov->fake_id_opt);
+    memset(ov, '\0', sizeof *ov);
+}
+
+
+Visitor *
+opts_get_visitor(OptsVisitor *ov)
+{
+    return &ov->visitor;
+}

qapi/opts-visitor.h

@@ -0,0 +1,31 @@
+/*
+ * Options Visitor
+ *
+ * Copyright Red Hat, Inc. 2012
+ *
+ * Author: Laszlo Ersek <lersek@redhat.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.
+ *
+ */
+
+#ifndef OPTS_VISITOR_H
+#define OPTS_VISITOR_H
+
+#include "qapi-visit-core.h"
+#include "qemu-option.h"
+
+typedef struct OptsVisitor OptsVisitor;
+
+/* Contrarily to qemu-option.c::parse_option_number(), OptsVisitor's "int"
+ * parser relies on strtoll() instead of strtoull(). Consequences:
+ * - string representations of negative numbers yield negative values,
+ * - values below INT64_MIN or LLONG_MIN are rejected,
+ * - values above INT64_MAX or LLONG_MAX are rejected.
+ */
+OptsVisitor *opts_visitor_new(const QemuOpts *opts);
+void opts_visitor_cleanup(OptsVisitor *nv);
+Visitor *opts_get_visitor(OptsVisitor *nv);
+
+#endif