trace: Provide a detailed event control interface

This interface decouples event obtaining from interaction.

Events can be obtained through three different methods:

* identifier
* name
* simple wildcard pattern

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

trace/control.h

@@ -1,41 +1,193 @@
 /*
  * Interface for configuring and controlling the state of tracing events.
  *
- * Copyright (C) 2011 Lluís Vilanova <vilanova@ac.upc.edu>
+ * Copyright (C) 2011-2012 Lluís Vilanova <vilanova@ac.upc.edu>
  *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
  */
 
-#ifndef TRACE_CONTROL_H
-#define TRACE_CONTROL_H
+#ifndef TRACE__CONTROL_H
+#define TRACE__CONTROL_H
 
 #include "qemu-common.h"
+#include "trace/generated-events.h"
 
 
-/** Print the state of all events. */
-void trace_print_events(FILE *stream, fprintf_function stream_printf);
-/** Set the state of an event.
+/**
+ * TraceEventID:
  *
- * @return Whether the state changed.
+ * Unique tracing event identifier.
+ *
+ * These are named as 'TRACE_${EVENT_NAME}'.
+ *
+ * See also: "trace/generated-events.h"
  */
-bool trace_event_set_state(const char *name, bool state);
+enum TraceEventID;
 
-
-/** Initialize the tracing backend.
+/**
+ * trace_event_id:
+ * @id: Event identifier.
  *
- * @events Name of file with events to be enabled at startup; may be NULL.
- *         Corresponds to commandline option "-trace events=...".
- * @file   Name of trace output file; may be NULL.
- *         Corresponds to commandline option "-trace file=...".
- * @return Whether the backend could be successfully initialized.
+ * Get an event by its identifier.
+ *
+ * This routine has a constant cost, as opposed to trace_event_name and
+ * trace_event_pattern.
+ *
+ * Pre-conditions: The identifier is valid.
+ *
+ * Returns: pointer to #TraceEvent.
+ *
+ */
+static TraceEvent *trace_event_id(TraceEventID id);
+
+/**
+ * trace_event_name:
+ * @id: Event name.
+ *
+ * Search an event by its name.
+ *
+ * Returns: pointer to #TraceEvent or NULL if not found.
+ */
+TraceEvent *trace_event_name(const char *name);
+
+/**
+ * trace_event_pattern:
+ * @pat: Event name pattern.
+ * @ev: Event to start searching from (not included).
+ *
+ * Get all events with a given name pattern.
+ *
+ * Returns: pointer to #TraceEvent or NULL if not found.
+ */
+TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev);
+
+/**
+ * trace_event_is_pattern:
+ *
+ * Whether the given string is an event name pattern.
+ */
+static bool trace_event_is_pattern(const char *str);
+
+/**
+ * trace_event_count:
+ *
+ * Return the number of events.
+ */
+static TraceEventID trace_event_count(void);
+
+
+
+/**
+ * trace_event_get_id:
+ *
+ * Get the identifier of an event.
+ */
+static TraceEventID trace_event_get_id(TraceEvent *ev);
+
+/**
+ * trace_event_get_name:
+ *
+ * Get the name of an event.
+ */
+static const char * trace_event_get_name(TraceEvent *ev);
+
+/**
+ * trace_event_get_state:
+ * @id: Event identifier.
+ *
+ * Get the tracing state of an event (both static and dynamic).
+ *
+ * If the event has the disabled property, the check will have no performance
+ * impact.
+ *
+ * As a down side, you must always use an immediate #TraceEventID value.
+ */
+#define trace_event_get_state(id)                       \
+    ((id ##_ENABLED) && trace_event_get_state_dynamic(trace_event_id(id)))
+
+/**
+ * trace_event_get_state_static:
+ * @id: Event identifier.
+ *
+ * Get the static tracing state of an event.
+ *
+ * Use the define 'TRACE_${EVENT_NAME}_ENABLED' for compile-time checks (it will
+ * be set to 1 or 0 according to the presence of the disabled property).
+ */
+static bool trace_event_get_state_static(TraceEvent *ev);
+
+/**
+ * trace_event_get_state_dynamic:
+ *
+ * Get the dynamic tracing state of an event.
+ */
+static bool trace_event_get_state_dynamic(TraceEvent *ev);
+
+/**
+ * trace_event_set_state:
+ *
+ * Set the tracing state of an event (only if possible).
+ */
+#define trace_event_set_state(id, state)                \
+    do {                                                \
+        if ((id ##_ENABLED)) {                          \
+            TraceEvent *_e = trace_event_id(id);        \
+            trace_event_set_state_dynamic(_e, state);   \
+        }                                               \
+    } while (0)
+
+/**
+ * trace_event_set_state_dynamic:
+ *
+ * Set the dynamic tracing state of an event.
+ *
+ * Pre-condition: trace_event_get_state_static(ev) == true
+ */
+static void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
+
+/**
+ * trace_event_set_state_dynamic_backend:
+ *
+ * Warning: This function must be implemented by each tracing backend.
+ */
+void trace_event_set_state_dynamic_backend(TraceEvent *ev, bool state);
+
+
+
+/**
+ * trace_print_events:
+ *
+ * Print the state of all events.
+ *
+ * Warning: This function must be implemented by each tracing backend.
+ */
+void trace_print_events(FILE *stream, fprintf_function stream_printf);
+
+/**
+ * trace_backend_init:
+ * @events: Name of file with events to be enabled at startup; may be NULL.
+ *          Corresponds to commandline option "-trace events=...".
+ * @file:   Name of trace output file; may be NULL.
+ *          Corresponds to commandline option "-trace file=...".
+ *
+ * Initialize the tracing backend.
+ *
+ * Warning: This function must be implemented by each tracing backend.
+ *
+ * Returns: Whether the backend could be successfully initialized.
  */
 bool trace_backend_init(const char *events, const char *file);
 
-/** Generic function to initialize the state of events.
+/**
+ * trace_backend_init_events:
+ * @fname: Name of file with events to enable; may be NULL.
  *
- * @fname Name of file with events to enable; may be NULL.
+ * Generic function to initialize the state of events.
  */
 void trace_backend_init_events(const char *fname);
 
-#endif  /* TRACE_CONTROL_H */
+
+#include "trace/control-internal.h"
+
+#endif  /* TRACE__CONTROL_H */