From f0e63c41139f8982add435536d39aff6f3d4ca98 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Sun, 6 Oct 2019 23:30:35 +0000 Subject: hashmap: use *_entry APIs to wrap container_of Using `container_of' can be verbose and choosing names for intermediate "struct hashmap_entry" pointers is a hard problem. So introduce "*_entry" APIs inspired by similar linked-list APIs in the Linux kernel. Unfortunately, `__typeof__' is not portable C, so we need an extra parameter to specify the type. Signed-off-by: Eric Wong Reviewed-by: Derrick Stolee Signed-off-by: Junio C Hamano --- git-compat-util.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'git-compat-util.h') diff --git a/git-compat-util.h b/git-compat-util.h index 4cc2c8283a..4a23b9090b 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -1322,4 +1322,19 @@ void unleak_memory(const void *ptr, size_t len); #define container_of(ptr, type, member) \ ((type *) ((char *)(ptr) - offsetof(type, member))) +/* + * helper function for `container_of_or_null' to avoid multiple + * evaluation of @ptr + */ +static inline void *container_of_or_null_offset(void *ptr, size_t offset) +{ + return ptr ? (char *)ptr - offset : NULL; +} + +/* + * like `container_of', but allows returned value to be NULL + */ +#define container_of_or_null(ptr, type, member) \ + (type *)container_of_or_null_offset(ptr, offsetof(type, member)) + #endif -- cgit v1.2.3