From 9656a581cdb6f505c9adc6b5158b395c21b5c43a Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 30 Oct 2008 10:52:08 -0700 Subject: compiler.h: add offsetof() and container_of() offsetof() is a C99 construct; provided here as an ersatz for older systems. container_of() is a nonstandard but highly useful construct, which allows data structure control items like tree structures to be embedded in larger data structures without the penalty of extra pointers and allocations. Signed-off-by: H. Peter Anvin --- compiler.h | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'compiler.h') diff --git a/compiler.h b/compiler.h index 82b0d7a..5e7e8c4 100644 --- a/compiler.h +++ b/compiler.h @@ -1,6 +1,6 @@ /* ----------------------------------------------------------------------- * * - * Copyright 2007 The NASM Authors - All Rights Reserved + * Copyright 2007-2008 The NASM Authors - All Rights Reserved * * This program is free software; you can redistribute it and/or modify * it under the terms of the license given in the file "LICENSE" @@ -87,6 +87,19 @@ typedef enum bool { false, true } bool; # endif #endif +/* Provide a substitute for offsetof() if we don't have one. This + variant works on most (but not *all*) systems... */ +#ifndef offsetof +# define offsetof(t,m) ((size_t)&(((t *)0)->m)) +#endif + +/* The container_of construct: if p is a pointer to member m of + container class c, then return a pointer to the container of which + *p is a member. */ +#ifndef container_of +# define container_of(p, c, m) ((c *)((char *)(p) - offsetof(c,m))) +#endif + /* Some misguided platforms hide the defs for these */ #if defined(HAVE_STRCASECMP) && !HAVE_DECL_STRCASECMP int strcasecmp(const char *, const char *); -- cgit v1.2.3