[buffer] Add try_allocate for buffer variables

src/hb-buffer.hh

@@ -132,9 +132,7 @@ struct hb_buffer_t
    * Managed by enter / leave
    */
 
-#ifndef HB_NDEBUG
   uint8_t allocated_var_bits;
-#endif
   uint8_t serial;
   hb_buffer_scratch_flags_t scratch_flags; /* Have space-fallback, etc. */
   unsigned int max_len; /* Maximum allowed len. */
@@ -163,38 +161,40 @@ struct hb_buffer_t
 
   void allocate_var (unsigned int start, unsigned int count)
   {
-#ifndef HB_NDEBUG
     unsigned int end = start + count;
     assert (end <= 8);
     unsigned int bits = (1u<<end) - (1u<<start);
     assert (0 == (allocated_var_bits & bits));
     allocated_var_bits |= bits;
-#endif
+  }
+  bool try_allocate_var (unsigned int start, unsigned int count)
+  {
+    unsigned int end = start + count;
+    assert (end <= 8);
+    unsigned int bits = (1u<<end) - (1u<<start);
+    if (allocated_var_bits & bits)
+      return false;
+    allocated_var_bits |= bits;
+    return true;
   }
   void deallocate_var (unsigned int start, unsigned int count)
   {
-#ifndef HB_NDEBUG
     unsigned int end = start + count;
     assert (end <= 8);
     unsigned int bits = (1u<<end) - (1u<<start);
     assert (bits == (allocated_var_bits & bits));
     allocated_var_bits &= ~bits;
-#endif
   }
   void assert_var (unsigned int start, unsigned int count)
   {
-#ifndef HB_NDEBUG
     unsigned int end = start + count;
     assert (end <= 8);
     HB_UNUSED unsigned int bits = (1u<<end) - (1u<<start);
     assert (bits == (allocated_var_bits & bits));
-#endif
   }
   void deallocate_var_all ()
   {
-#ifndef HB_NDEBUG
     allocated_var_bits = 0;
-#endif
   }
 
   hb_glyph_info_t &cur (unsigned int i = 0) { return info[idx + i]; }
@@ -621,9 +621,10 @@ DECLARE_NULL_INSTANCE (hb_buffer_t);
 #define HB_BUFFER_XALLOCATE_VAR(b, func, var) \
   b->func (offsetof (hb_glyph_info_t, var) - offsetof(hb_glyph_info_t, var1), \
 	   sizeof (b->info[0].var))
-#define HB_BUFFER_ALLOCATE_VAR(b, var)		HB_BUFFER_XALLOCATE_VAR (b, allocate_var,   var ())
-#define HB_BUFFER_DEALLOCATE_VAR(b, var)	HB_BUFFER_XALLOCATE_VAR (b, deallocate_var, var ())
-#define HB_BUFFER_ASSERT_VAR(b, var)		HB_BUFFER_XALLOCATE_VAR (b, assert_var,     var ())
+#define HB_BUFFER_ALLOCATE_VAR(b, var)		HB_BUFFER_XALLOCATE_VAR (b, allocate_var,     var ())
+#define HB_BUFFER_TRY_ALLOCATE_VAR(b, var)	HB_BUFFER_XALLOCATE_VAR (b, try_allocate_var, var ())
+#define HB_BUFFER_DEALLOCATE_VAR(b, var)	HB_BUFFER_XALLOCATE_VAR (b, deallocate_var,   var ())
+#define HB_BUFFER_ASSERT_VAR(b, var)		HB_BUFFER_XALLOCATE_VAR (b, assert_var,       var ())
 
 
 #endif /* HB_BUFFER_HH */