New function heapblocksize()

git-svn-id: svn://svn.cc65.org/cc65/trunk@3157 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/_heapblocksize.s

@@ -0,0 +1,39 @@
+;
+; Ullrich von Bassewitz, 2004-07-17
+;
+; size_t __fastcall__ _heapblocksize (const void* ptr);
+;
+; Return the size of an allocated block.
+;
+
+	.importzp    	ptr1
+       	.export	     	__heapblocksize
+
+        .include        "_heap.inc"
+
+;-----------------------------------------------------------------------------
+; Code
+
+__heapblocksize:
+
+; Decrement the block pointer so it points to the admin data
+
+        sec
+        sbc     #HEAP_ADMIN_SPACE       ; Assume it's less than 256
+        bcs     L1
+        dex
+L1:     sta     ptr1
+        stx     ptr1+1
+
+; Load the size from the given block
+
+        ldy     #1
+        lda     (ptr1),y
+        tax
+        dey
+        lda     (ptr1),y
+
+; Done
+
+        rts
+