libsysprof-capture: add mmap()'d ring buffer

This is the start of a ring buffer to coordinate between processes without
the overhead of writing directly to files within the inferior process.
Instead, the parent process can monitor the ring buffer for framing
information and pass that along to the capture writer.

src/tests/test-mapped-ring-buffer.c

@@ -0,0 +1,172 @@
+#include "mapped-ring-buffer.h"
+
+#include <stdint.h>
+
+static gsize real_count;
+
+static gboolean
+drain_nth_cb (gconstpointer data,
+              gsize         len,
+              gpointer      user_data)
+{
+  const gint64 *v64 = data;
+  g_assert_cmpint (len, ==, 8);
+  g_assert_cmpint (*v64, ==, GPOINTER_TO_SIZE (user_data));
+  return G_SOURCE_CONTINUE;
+}
+
+static gboolean
+drain_count_cb (gconstpointer data,
+                gsize         len,
+                gpointer      user_data)
+{
+  const gint64 *v64 = data;
+  g_assert_cmpint (len, ==, 8);
+  ++real_count;
+  g_assert_cmpint (real_count, ==, *v64);
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+test_basic_movements (void)
+{
+  MappedRingBuffer *reader;
+  MappedRingBuffer *writer;
+  gint64 *ptr;
+  guint i;
+  int fd;
+
+  reader = mapped_ring_buffer_new_reader (4096*16);
+  g_assert_nonnull (reader);
+
+  fd = mapped_ring_buffer_get_fd (reader);
+  g_assert_cmpint (fd, >, -1);
+
+  writer = mapped_ring_buffer_new_writer (fd);
+  g_assert_nonnull (writer);
+
+  while ((ptr = mapped_ring_buffer_allocate (writer, sizeof *ptr)))
+    {
+      static gint64 count;
+      g_assert ((GPOINTER_TO_SIZE(ptr) & 0x7) == 0);
+      *ptr = ++count;
+      mapped_ring_buffer_advance (writer, sizeof *ptr);
+    }
+  mapped_ring_buffer_drain (reader, drain_count_cb, NULL);
+
+  ptr = mapped_ring_buffer_allocate (writer, sizeof *ptr);
+  g_assert_nonnull (ptr);
+  *ptr = 1000000;
+  mapped_ring_buffer_advance (writer, sizeof *ptr);
+  mapped_ring_buffer_drain (reader, drain_nth_cb, GSIZE_TO_POINTER (1000000));
+
+  real_count = 0;
+  for (i = 0; i < g_random_int_range (1, 4000); i++)
+    {
+      static gint64 count;
+      g_assert ((GPOINTER_TO_SIZE(ptr) & 0x7) == 0);
+      *ptr = ++count;
+      mapped_ring_buffer_advance (writer, sizeof *ptr);
+    }
+  mapped_ring_buffer_drain (reader, drain_count_cb, NULL);
+
+  real_count = 0;
+  while ((ptr = mapped_ring_buffer_allocate (writer, sizeof *ptr)))
+    {
+      static gint64 count;
+      g_assert ((GPOINTER_TO_SIZE(ptr) & 0x7) == 0);
+      *ptr = ++count;
+      mapped_ring_buffer_advance (writer, sizeof *ptr);
+    }
+  mapped_ring_buffer_drain (reader, drain_count_cb, NULL);
+
+  mapped_ring_buffer_unref (writer);
+  mapped_ring_buffer_unref (reader);
+}
+
+typedef struct
+{
+  gint64 abc;
+  gint64 done;
+} ThreadedMessage;
+
+static gboolean
+handle_msg (gconstpointer data,
+            gsize         length,
+            gpointer      user_data)
+{
+  const ThreadedMessage *msg = data;
+  gboolean *done = user_data;
+  *done = msg->done;
+  return G_SOURCE_CONTINUE;
+}
+
+static void *
+threaded_reader (gpointer data)
+{
+  MappedRingBuffer *reader = data;
+  gboolean done = FALSE;
+
+  while (!done)
+    mapped_ring_buffer_drain (reader, handle_msg, &done);
+
+  return NULL;
+}
+
+static void *
+threaded_writer (gpointer data)
+{
+  MappedRingBuffer *writer = data;
+  ThreadedMessage *msg;
+
+  for (guint i = 0; i < 100000; i++)
+    {
+      while (!(msg = mapped_ring_buffer_allocate (writer, sizeof *msg)))
+        g_usleep (G_USEC_PER_SEC / 10000); /* .1msec */
+
+      msg->done = FALSE;
+      mapped_ring_buffer_advance (writer, sizeof *msg);
+    }
+
+  while (!(msg = mapped_ring_buffer_allocate (writer, sizeof *msg)))
+    g_usleep (G_USEC_PER_SEC / 10000); /* .1msec */
+
+  msg->done = TRUE;
+  mapped_ring_buffer_advance (writer, sizeof *msg);
+
+  return NULL;
+}
+
+static void
+test_threaded_movements (void)
+{
+  GThread *thread1, *thread2;
+  MappedRingBuffer *reader;
+  MappedRingBuffer *writer;
+  int fd;
+
+  reader = mapped_ring_buffer_new_reader (4096*16);
+  g_assert_nonnull (reader);
+
+  fd = mapped_ring_buffer_get_fd (reader);
+  g_assert_cmpint (fd, >, -1);
+
+  writer = mapped_ring_buffer_new_writer (fd);
+  g_assert_nonnull (writer);
+
+  thread1 = g_thread_new ("thread1-reader", threaded_reader, reader);
+  thread2 = g_thread_new ("thread2-writer", threaded_writer, writer);
+
+  g_thread_join (thread1);
+  g_thread_join (thread2);
+}
+
+gint
+main (gint argc,
+      gchar *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+  g_test_add_func ("/MappedRingBuffer/basic_movements", test_basic_movements);
+  g_test_add_func ("/MappedRingBuffer/threaded_movements", test_threaded_movements);
+  return g_test_run ();
+}