libsysprof-capture: Add SysprofCaptureJitmapIter to replace GHashTable

Change `sysprof_capture_reader_read_jitmap()` to return a `const
SysprofCaptureJitmap *` (like the other `read` functions), and add a new
`SysprofCaptureJitmapIter` type to allow easy iteration over the jitmap.

This allows a use of `GHashTable` to be removed from the API. It breaks
the libsysprof-capture API and ABI.

All the callers iterate over the jitmap rather than looking up elements
by key. If that functionality is needed in future, additional API can be
added to allow it on `SysprofCaptureJitmap`.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Helps: #40

src/libsysprof-capture/sysprof-capture-reader.c

@@ -758,10 +758,9 @@ sysprof_capture_reader_read_process (SysprofCaptureReader *self)
   return process;
 }
 
-GHashTable *
+const SysprofCaptureJitmap *
 sysprof_capture_reader_read_jitmap (SysprofCaptureReader *self)
 {
-  g_autoptr(GHashTable) ret = NULL;
   SysprofCaptureJitmap *jitmap;
   uint8_t *buf;
   uint8_t *endptr;
@@ -787,17 +786,15 @@ sysprof_capture_reader_read_jitmap (SysprofCaptureReader *self)
   if (!sysprof_capture_reader_ensure_space_for (self, jitmap->frame.len))
     return NULL;
 
-  jitmap = (SysprofCaptureJitmap *)(gpointer)&self->buf[self->pos];
-
-  ret = g_hash_table_new_full (NULL, NULL, NULL, g_free);
+  jitmap = (SysprofCaptureJitmap *)(void *)&self->buf[self->pos];
 
   buf = jitmap->data;
   endptr = &self->buf[self->pos + jitmap->frame.len];
 
+  /* Check the strings are all nul-terminated. */
   for (i = 0; i < jitmap->n_jitmaps; i++)
     {
       SysprofCaptureAddress addr;
-      const char *str;
 
       if (buf + sizeof addr >= endptr)
         return NULL;
@@ -805,23 +802,19 @@ sysprof_capture_reader_read_jitmap (SysprofCaptureReader *self)
       memcpy (&addr, buf, sizeof addr);
       buf += sizeof addr;
 
-      str = (char *)buf;
-
       buf = memchr (buf, '\0', (endptr - buf));
 
       if (buf == NULL)
         return NULL;
 
       buf++;
-
-      g_hash_table_insert (ret, GSIZE_TO_POINTER (addr), g_strdup (str));
     }
 
   sysprof_capture_reader_bswap_jitmap (self, jitmap);
 
   self->pos += jitmap->frame.len;
 
-  return sysprof_steal_pointer (&ret);
+  return jitmap;
 }
 
 const SysprofCaptureSample *
@@ -1512,3 +1505,53 @@ sysprof_capture_reader_read_allocation (SysprofCaptureReader *self)
 
   return ma;
 }
+
+typedef struct {
+  const SysprofCaptureJitmap *jitmap;
+  const uint8_t *buf;
+  unsigned int i;
+
+  void *padding1;
+  void *padding2;
+} RealSysprofCaptureJitmapIter;
+
+void
+sysprof_capture_jitmap_iter_init (SysprofCaptureJitmapIter   *iter,
+                                  const SysprofCaptureJitmap *jitmap)
+{
+  RealSysprofCaptureJitmapIter *real_iter = (RealSysprofCaptureJitmapIter *) iter;
+
+  assert (iter != NULL);
+  assert (jitmap != NULL);
+
+  real_iter->jitmap = jitmap;
+  real_iter->buf = jitmap->data;
+  real_iter->i = 0;
+}
+
+bool
+sysprof_capture_jitmap_iter_next (SysprofCaptureJitmapIter  *iter,
+                                  SysprofCaptureAddress     *addr,
+                                  const char               **name)
+{
+  RealSysprofCaptureJitmapIter *real_iter = (RealSysprofCaptureJitmapIter *) iter;
+  const char *_name;
+
+  assert (iter != NULL);
+
+  if (real_iter->i >= real_iter->jitmap->n_jitmaps)
+    return false;
+
+  if (addr != NULL)
+    memcpy (addr, real_iter->buf, sizeof (*addr));
+  real_iter->buf += sizeof (*addr);
+
+  _name = (const char *) real_iter->buf;
+  if (name != NULL)
+    *name = _name;
+  real_iter->buf += strlen (_name) + 1;
+
+  real_iter->i++;
+
+  return true;
+}